conducting remedial investigations/feasibility … · epa/540/p-91/001 oswer directive 9355.3-11...

United States Office of Emergency EPA/540/P-91/001Environmental Protection Remedial Response February 1991Agency Washington, DC 20460

Superfund

Conducting RemedialInvestigations/FeasibilityStudies for CERCLAMunicipal Landfill Sites

Word-searchable Version – Not a true copy

EPA/540/P-91/001OSWER Directive 9355.3-11

February 1991

Conducting Remedial Investigations/Feasibility Studies for CERCLA

Municipal Landfill Sites

Office of Emergency and Remedial ResponseU.S. Environmental Protection Agency

Washington, D.C. 20460


NOTICE

Development of this document was funded by the United States Environmental ProtectionAgency. It has been subjected to the Agency’s review process and approved for publicationas an EPA document.

The policies and procedures set out in this document are intended solely for the guidanceof response personnel. They are not intended, nor can they be relied upon, to create anyrights, substantive or procedural, enforceable by any party in litigation with the UnitedStates. EPA officials may decide to follow this guidance, or to act variance with thesepolicies and procedures based on an analysis of specific site circumstances, and to changethem at any time without public notice.


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GLOSSARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii

ES EXECUTIVE SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ES-1

1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-11.1 Background on Municipal Landfills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-21.2 Document Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3

2 SCOPING THE RI/FS FOR MUNICIPAL LANDFILL SITES . . . . . . . . . . . . . . . . . . . . . 2-12.1 Evaluation of Existing Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

2.1.1 Sources of Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-22.1.2 Types of Data and Data Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-32.1.3 Presentation of Available Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4

2.2 Existing Data Evaluation Results and Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-42.2.1 Site Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-62.2.2 Site History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-72.2.3 Regional and Site Geology and Hydrogeology . . . . . . . . . . . . . . . . . . . . . . . . 2-72.2.4 Hydrology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9

2.2.4.1 Surface Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-92.2.4.2 Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9

2.2.5 Waste Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-92.2.6 Sampling Activities and Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10

2.3 Site Visit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-102.4 Limited Field Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-122.5 Conceptual Site Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-152.6 Risk Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-182.7 Preliminary Remedial Action Objectives and Goals . . . . . . . . . . . . . . . . . . . . . . . . . 2-192.8 Preliminary Remedial Technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-20

2.8.1 Development of Preliminary RemedialAction Alternatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-20

2.8.2 Review of Remedial Technologies inCERCLA Landfill RODs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-21

2.9 Objectives of the RI/FS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-232.10 Development of DQOs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-312.11 Section 2 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-39

3 SITE CHARACTERIZATION STRATEGIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-13.1 Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2

3.1.1 Groundwater Investigations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-23.1.1.1 Phase I Site Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-23.1.1.2 Phase II Site Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4

3.1.2 Data Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-43.1.3 Placement of Monitoring Wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5

3.1.3.1 Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-53.1.3.2 Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-53.1.3.3 Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7

3.1.4 Groundwater Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7


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3.2 Leachate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-73.2.1 Leachate, Investigations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-10

3.2.1.1 Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-103.2.1.2 Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-103.2.1.3 Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12

3.2.2 Data Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-123.2.3 Leachate Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-13

3.3 Landfill Contents/Hot Spots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-133.3.1 Landfill Contents/Hot Spot Investigations . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-13


3.3.2 Data Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-253.3.3 Landfill Contents/Hot Spots Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-25

3.4 Landfill Gas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-253.4.1 Landfill Gas Investigations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-25


3.4.2 Data Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-283.4.3 Landfill Gas Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-29

3.5 Wetlands and Sensitive Environments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-293.5.1 Wetlands and Sensitive Environment Evaluation . . . . . . . . . . . . . . . . . . . . . . 3-29


3.5.2 Data Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-323.5.3 Wetlands Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-32

3.6. Surface Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-343.6.1 Surface Water Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-34


3.6.2 Data Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-363.6.3 Surface Water Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-36

3.7 Baseline Risk Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-373.7.1 Components of the Baseline Risk Assessment . . . . . . . . . . . . . . . . . . . . . . . 3-37

3.7.1.1 Contaminant Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-373.7.1.2 Exposure Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-393.7.1.3 Toxicity Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-393.7.1.4 Risk Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-39

3.7.2 Using the Baseline Risk Assessment to StreamlineRemedial Action Decisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-39

3.8 Section 3 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-40

4 DETAILED DESCRIPTION OF TECHNOLOGIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-14.1 Remedial Action Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-14.2 Landfill Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2

4.2.1 Access Restrictions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-24.2.1.1 Deed Restrictions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-34.2.1.2 Fencing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3


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4.2.2 Containment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-34.2.2.1 Surface Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-34.2.2.2 Cap (Landfill Cover) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6

4.2.3 Removal/Disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-124.2.3.1 Excavation (Hot Spots) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-124.2.3.2 Consolidation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-144.2.3.3 Disposal Offsite (Hot Spots) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-14

4.2.4 Hot Spots Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-154.2.4.1 Thermal Treatment (Onsite) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-164.2.4.2 Stabilization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-17

4.2.5 Innovative Treatment Technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-184.2.5.1 Description of Technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-18

4.2.6 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-194.3 Leachate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-21

4.3.1 Collection of Leachate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-214.3.1.1 Subsurface Drains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-214.3.1.2 Vertical Extraction Wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-21

4.3.2 Treatment of Leachate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-224.3.2.1 Onsite Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-234.3.2.2 Offsite Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-25

4.3.3 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-274.4 Landfill Gas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-28

4.4.1 Collection of Landfill Gas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-284.4.1.1 Passive Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-284.4.1.2 Active Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-29

4.4.2 Treatment of Landfill Gas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-304.4.2.1 Thermal Treatment (Enclosed Ground Flares) . . . . . . . . . . . . . . . . 4-30

4.4.3 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-324.5 Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-32

4.5.1 Collection, Treatment, and Disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-324.5.2 Containment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-32

4.5.2.1 Vertical Barriers (Slurry Walls) . . . . . . . . . . . . . . . . . . . . . . . . . . 4-324.5.3 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-34

4.6 Wetlands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-354.6.1 Removal or Management of Wetlands Sediments . . . . . . . . . . . . . . . . . . . . . 4-354.6.2 Mitigating Wetlands Losses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-354.6.3 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-36

4.7 Surface Water and Sediments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-364.7.1 Treatment of Surface Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-364.7.2 Removal and Management of Sediments . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-364.7.3 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-37

4.8 Section 4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-37

5 EVALUATION CRITERIA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-15.1 Overall Protection of Human Health and the Environment . . . . . . . . . . . . . . . . . . . . . 5-25.2 Compliance with ARARs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-6

5.2.1 Federal ARARs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-65.2.1.1 Chemical-Specific ARARs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-65.2.1.2 Location-Specific ARARs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-235.2.1.3 Action-Specific ARARs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-24


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5.2.2 State ARARs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-255.2.2.1 Chemical-Specific ARARs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-265.2.2.2 Location-Specific ARARs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-265.2.2.3 Action-Specific ARARs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-26

5.3 Long-Term Effectiveness and Permanence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-275.4 Reduction of TMV Through Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-275.5 Short-Term Effectiveness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-275.6 Implementability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-275.7 Cost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-285.8 State Acceptance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-285.9 Community Acceptacne . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-285.10 Section 5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-28

6 DEVELOPMENT AND EVALUATION OF ALTERNATIVES FOR THEEXAMPLE SITE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-16.1 Example Site ARARs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-8

6.1.1 Chemical-Specific ARARs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-86.1.1.1 Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-86.1.1.2 Surface Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-8

6.1.2 Location-Specific ARARs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-86.1.3 Action-Specific ARARs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-8

6.1.3.1 Soils/Landfill Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-86.2 Development of Alternatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-8

6.2.1 Alternative 1--No Action Alternative . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-96.2.2 Alternative 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-96.2.3 Alternative 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-106.2.4 Alternative 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-11

6.3 Comparative Analysis of Alternatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-126.3.1 Overall Protection of Human Health and the Environment . . . . . . . . . . . . . . 6-126.3.2 Compliance with ARARs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-126.3.3 Short-Term Effectiveness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-126.3.4 Long-Term Effectiveness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-136.3.5 Reduction of Toxicity, Mobility, and Volume Through Treatment . . . . . . . . . . 6-136.3.6 Implementability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-146.3.7 Costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-14

6.4 Section 6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-14

7 BIBLIOGRAPHY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1

Appendix A Site Characterization Strategy for an Example Site

Appendix B Remedial Technologies Used at Landfill Sites


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TABLESPage

2-1 Limited Field Investigation Options for Municipal Landfill Sites . . . . . . . . . . . . . . . . . . . . . 2-132-2 Preliminary Identification of Remedial Action Objectives for

Media of Concern at Municipal Landfill Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-202-3 Remedial Actions Used at Landfill Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-242-4 Phase I Remedial Investigation Objectives for Municipal

Landfill Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-322-5 Phase II Remedial Investigation Objectives for Municipal

Landfill Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-36

3-1 Conditions That Determine Monitoring Well Location and Numbers . . . . . . . . . . . . . . . . . . . 3-83-2 Range of Typical Domestic Refuse Leachate Constituent

Concentrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-113-3 Leachate Sampling Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-133-4 Summary of Sampling Requirements for Soil and Landfill Contents . . . . . . . . . . . . . . . . . . 3-273-5 Landfill Gas Sampling Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-293-6 Summary of Sampling Requirements for Environmental Evaluation . . . . . . . . . . . . . . . . . . . 3-323-7 Sampling and Monitoring Rationale for Surface Water and

Sediments Near Municipal Landfill Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-36

5-1 Evaluation of Technologies Frequently Used at Municipal Landfills . . . . . . . . . . . . . . . . . . . 5-35-2 Potential Federal Location-Specific ARARs for Municipal Landfill Sites . . . . . . . . . . . . . . . . 5-75-3 Potential Federal Action-Specific ARARs for Municipal Landfill Sites . . . . . . . . . . . . . . . . . 5-9

6-1 Recommended Alternatives: Summary of Detailed Analysis (Example Site) . . . . . . . . . . . . . 6-2

B-1 RODs Reviewed for Municipal Landfill Study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-1B-2 Remedial Technologies Used at Landfill Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-6B-3 Breakdown by Region of Remedial Technologies Used at Landfill Sites . . . . . . . . . . . . . . . B-36

FIGURES

2-1 Flow Diagram for Data Evaluation and Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-52-2 Typical Soil/Geologic Cross Section of Municipal Landfill

and Adjacent Areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-82-3 Schematic of Conceptual Landfill Site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-162-4 Potential Conceptual Site Model for Municipal Landfills . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-172-5 Identification of Remedial Technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-22

3-1 Logic Diagram for Monitoring Well and Screen Placement . . . . . . . . . . . . . . . . . . . . . . . . . 3-93-2 Logic Diagram for Leachate Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-143-3 Logic Diagram for Soils/Landfill Contents Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-263-4 Logic Diagram for Landfill Gas Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-303-5 Logic Diagram for Environmental Assessment Near Municipal Landfills . . . . . . . . . . . . . . 3-333-6 Logic Diagram for Surface Water/Sediment Sampling Near Municipal Landfill . . . . . . . . . . 3-38

4-1 Landfill Cover Selection Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7


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GLOSSARY OF ACRONYMS AND ABBREVIATIONS

ARAR Applicable or relevant and appropriate requirementBOD Biochemical oxygen demandBTU British thermal unitCAA Clean Air ActCERCLA Comprehensive Environmental Response, Compensation and Liability ActCLP Contract laboratory programCOD Chemical oxygen demandCRP Community relations planCWA Clean Water ActDNAPL Dense, nonaqueous-phase liquidDQO Data quality objectiveEMSL Environmental Monitoring Systems LaboratoryEPA U.S. Environmental Protection AgencyFIT Field Investigation TeamFML Flexible membrane linerFS Feasibility studyFSP Field Sampling PlanFWQC Federal Water Quality CriteriaGAC Granular activated carbonGC Gas chromatographyGPR Ground penetrating radarHDPE High density polyetheleneHRS Hazard ranking systemHSP Health and safety planLDR Land Disposal RestrictionsLFG Landfill gasLFI Limited field investigationMCL Maximum contaminant levelsMCLG Maximum contaminant level goalsNCC National Climatic CenterNCP National Contingency PlanNPDES National Pollutant Discharge Elimination SystemNPL National Priorities ListO&M Operations and maintenanceOVA Organic vapor analyzerPARCC Precision, accuracy, representativeness, completeness, comparabilityPA/SI Preliminary assessment/site inspectionPCB Polychlorinated byphenylPIC Products of incomplete combustionPID Photoionization detectorPOTW Publicly owned treatment works


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ppb Parts per billionppm Parts per millionPRP Potentially responsible partyPVC Poly vinyl chlorideQAPP Quality assurance project planQA/QC Quality assurance/quality controlRCRA Resource Conservation and Recovery ActRD/RA Remedial design/remedial actionRI Remedial investigationROD Record of decisionRPM Remedial project managerSAP Sampling and analysis planSDWA Safe Drinking Water ActSOW Scope of workSVE Soil vapor extractionTAL Target analyte list TBC To be consideredTCE TrichloroetheneTCL Target compound listTCPL Toxicity characteristic leaching procedureTDS Total dissolved solidsTMV Toxicity, mobility, and volumeTOC Total organic carbonTSDF Treatment, storage, and disposal facilityTSS Total suspended solidsUSGS U.S. Geological SurveyVC Vinyl chlorideVOC Volatile organic compound


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ACKNOWLEDGEMENTS

This document was developed by EPA’s Office of Emergency and Remedial Response withassistance provided by CH2M HILL in partial fulfillment of Contract No. 68-W8-0098. SusanCange served as EPA project manager. The CH2M HILL project team was headed by JohnRendall and included Amelia Janisz, Sadia Kissoon, Dave Bunte, Fouad Arbid, Gayle Lytle, andPat Trate.

In addition to the many EPA Headquarters personnel who assisted in this effort, the followingregional, state, and contractor representatives provided significant contributions to thepreparation of this document:

Wayne Robinson EPA, Region I

Edward Als EPA, Region IISherrel HenryCaroline Kwan

Fran Costanzi EPA, Region IIIMindi Snoparsky

Fred Bartman EPA, Region VDion NovakRobert Swale

Steve Veale EPA, Region VI

Gwen Hooten EPA, Region VIII

Brian Ullensvang EPA, Region IX

Mary Jane Nearman EPA, Region XDebbie Yamamoto

Thomas J. Cozzi State of New JerseyDepartment of Environment Protection

Peter Kmet State of WashingtonDepartment of Ecology

Celia VanDerloop State of WisconsinDepartment of Natural Reaouces

Alan Felser Ebasco

Phil Smith CH2M HILL

Bill Swanson CDM/FPC


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EXECUTIVE SUMMARY

A broad framework for the RemedialInvestigation/Feasibility Study (RI/FS) and selectionof remedy process has been created through theNational Contingency Plan (NCP) and the U.S.EPA RI/FS Guidance (U.S. EPA, 1988d). Withthis framework now in place, the Office ofEmergency and Remedial Response’s efforts arebeing focused on streamlining the RI/FS andselection of remedy process for specific classes ofsites with similar characteristics. One such class ofsites is the municipal landfills which composeapproximately 20 percent of the sites on theSuperfund Program’s National Priorities List(NPL). Landfill sites currently on the NPL typicallycontain a combination of principally municipal andto a lesser extent hazardous waste and range in sizefrom 1 acre to 640 acres. Potential threats tohuman health and the environment resulting frommunicipal landfills may include:

• Leachate generation and groundwatercontamination

• Soil contamination

• Landfill contents

• Landfill gas

• Contamination of surface waters,sediments, and adjacent wetlands

Because these sites share similar characteristics,they lend themselves to remediation by similartechnologies. The NCP contains the expectationthat containment technologies will generally beappropriate remedies for wastes that pose arelatively low low-level threat or where treatmentis impracticable. Containment has been identified asthe most likely response action at these sitesbecause (1) CERCLA municipal landfills areprimarily composed of municipal, and to a lesserextent hazardous wastes; therefore, they often posea low-level threat rather than a principal threat; and(2) the volume and heterogeneity of waste withinCERCLA municipal landfills will often maketreatment impractical. The NCP also contains anexpectation that treatment should be

considered for identifiable areas of highly toxicand/or mobile material (hot spots) that posepotential principal threats. Treatment of hot spotswithin a landfill will therefore be considered andevaluated.

With these expectations in mind, a study ofmunicipal landfills was conducted with the intent ofdeveloping methodologies and tools to assist instreamlining the RI/FS and selection of remedyprocess. Streamlining may be viewed as amechanism to enhance the efficiency andeffectiveness of decision-making at these sites. Thegoals of this study to meet this objective include: (1)developing tools to assist in scoping the RI/FS formunicipal landfill sites, (2) defining strategies forcharacterizing municipal landfill sites that are on theNPL, and (3) identifying practicable remedial actionalternatives for addressing these types of sites.

Streamlining Scoping

The primary purpose of scoping an RI/FS is todivide the broad project goals into manageable tasksthat can be performed within a reasonable period oftime. The broad project goals of any Superfund siteare to provide the information necessary tocharacterize the site, define site dynamics, definerisks, and develop a remedial program to mitigatecurrent and potential threats to human health andthe environment. Scoping of municipal landfill sitescan be streamlined by focusing the RI/FS tasks onjust the data required to evaluate alternatives thatare most practicable for municipal landfill sites.Section 2 of this document describes the activitiesthat must take place to plan an RI/FS and providesguidelines for establishing a project’s scope. Tosummarize, scoping of the RI/FS tasks can bestreamlined by:

• Developing preliminary remedial objectivesand alternatives based on the NCPexpectations and focusing on alternativessuccessfully implemented at other sites

• Using a conceptual site model (see Figure2-4 for a generic model devel-


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• oped for municipal landfill sites based ontheir similarities) to help define siteconditions and to scope future field tasks

• Conducting limited field investigations toassist in targeting future fieldwork

• Identifying clear, concise RI objectives inthe form of field tasks to ensure sufficientdata are collected to adequatelycharacterize the site, perform thenecessary risk assessment(s), and evaluatethe practicable remedial action alternatives

• Identifying data quality objectives (DQOs)that result in a well-defined sampling andanalysis plan, ensure the quality of the datacollected, and integrate the informationrequired in the RI/FS process

• Limiting the scope of the baseline riskassessment as discussed below

Streamlining the Baseline Risk Assessment

The baseline risk assessment may be used todetermine whether a site poses risks to humanhealth and the environment that are significantenough to warrant remedial action. Because optionsfor remedial action at municipal landfill sites arelimited, it may be possible to streamline or limit thescope of the baseline risk assessment by (1) usingthe conceptual site model and RI-generated data toperform a qualitative risk assessment that identifiesthe contaminants of concern in the affected media,their concentrations, and their hazardous propertiesthat may pose a risk through the various routes ofexposure and (2) identifying pathways that are anobvious threat to human health or the environmentby comparing RI-derived contaminantconcentration levels to standards that are potentialchemical-specific applicable or relevant andappropriate requirements (ARARs) for the action.(When potential ARARs do not exist for a specificcontaminant, risk-based chemical concentrationsshould be used.)

Where established standards for one or morecontaminants in a given medium are clearlyexceeded, the basis for taking remedial action is

generally warranted (quantitative assessments thatconsider all chemicals, their potential additiveeffects, or additivity of multiple exposure pathwaysare not necessary to initiate remedial action). Incases where standards are not clearly exceeded, amore thorough risk assessment may be necessarybefore initiating remedial action.

This streamlined approach may facilitate earlyaction on the most obvious landfill problems(groundwater and leachate, landfill gas, and thelandfill contents) while analysis continues on otherproblems such as affected wetlands and streamsediments. Dividing a site into operable units andperforming early or interim actions is often desirablefor these types of sites. This is because performingcertain early actions (e.g., capping a landfill) canreduce the impact to other parts of a site while theRI/FS continues. Additionally, early actions must beconsistent with the site’s final remedy and thereforehelp to speed up the clean-up process.

Ultimately, it will be necessary to demonstrate thatthe final remedy, once implemented, will in factaddress all pathways and contaminants of concern,not just those that triggered the remedial action. Theapproach outlined above facilitates rapidimplementation of protective remedial measures forthe major problems at a municipal landfill site.

Streamlining Site Characterization

Site characterization for municipal landfills can beexpedited by focusing field activities on theinformation needed to sufficiently assess risksposed by the site, and to evaluate practicableremedial actions. Recommendations to helpstreamline site characterization of media typicallyaffected by landfills are discussed in Section 3 ofthis report. A summary of the site characterizationstrategies is presented below.

Leachate/Groundwater Contamination

Characterization of a site’s geology andhydrogeology will affect decisions on cappingoptions as well as on extraction and treatmentsystems for leachate and groundwater. Datagathered during the hydrogeologic investigation aresimilar to those gathered during investigations at


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other types of NPL sites. Groundwatercontamination at municipal landfill sites may,however, vary in composition from that at othertypes of sites in that it often contains high levels oforganic matter and metals.

Leachate generation is of special concern whencharacterizing municipal landfill sites. The mainfactors contributing to leachate quantity areprecipitation and recharge from groundwater andsurface water. Leachate is characteristically highin organic matter as measured by chemical oxygendemand (COD) or biochemical oxygen demand(BOD). In many landfills, leachate is perchedwithin the landfill contents, above the water table.Placing a limited number of leachate wells in thelandfill is an efficient means of gatheringinformation regarding the depth, thickness, andtypes of the waste; the moisture content and degreeof decomposition of the waste; leachate head levelsand the composition of landfill leachate; and theelevation of the underlying natural soil layer.Additionally, leachate wells provide good locationsfor landfill gas sampling. It should be noted,however, that without the proper precautions,placing wells into the landfill contents may createhealth and safety risks. Also, installation of wellsthrough the landfill base may create conduitsthrough which leachate can migrate to lowergeologic strata, and the installation of wells intolandfill contents may make it difficult to ensure thereliability of the sampling locations.

Landfill Contents

Characterization of a landfill’s contents is generallynot necessary because containment of the landfillcontents, which is often the most practicabletechnology, does not require such information.Certain data, however, are necessary to evaluatecapping alternatives and should be collected in thefield. For instance, certain landfill properties suchas the fill thickness, lateral extent, and age willinfluence landfill settlement and gas generationrates, which will thereby have an influence on thecover type at a site. Also, characterization of alandfill’s contents may provide valuable informationfor PRP determination. A records review can alsobe valuable in gathering data concerning disposalhistory, thus reducing the need for field sampling ofcontents.

Hot Spots

More extensive characterization activities anddevelopment of remedial alternatives (such asthermal treatment or stabilization) may beappropriate for hot spots. Hot spots consist of highlytoxic and/or highly mobile material and present apotential principal threat to human health or theenvironment. Excavation or treatment of hot spotsis generally practicable where the waste type ormixture of wastes is in a discrete, accessiblelocation of a landfill. A hot spot should be largeenough that its remediation would significantlyreduce the risk posed by the overall site, but smallenough that it is reasonable to consider removal ortreatment. It may generally be appropriate toconsider excavation and/or treatment of thecontents of a landfill where a low to moderatevolume of toxic/mobile waste (for example, 100,000cubic yards or less) poses a principal threat tohuman health and the environment.

Hot spots should be characterized if documentationand/or physical evidence exists to indicate thepresence and approximate location of the hot spots.Hot spots may be delineated using geophysicaltechniques or soil gas surveys and typically areconfirmed by excavating test pits or drillingexploratory borings. When characterizing hot spots,soil samples should be collected to determine thewaste characteristics; treatability or pilot testingmay be required to evaluate treatment alternatives.

Landfill Gas

Several gases typically are generated bydecomposition of organic materials in a landfill. Thecomposition, quantity, and generation rates of thegases depend on such factors as refuse quantityand composition, placement characteristics, landfilldepth, refuse moisture content, and amount ofoxygen present. The principal gases generated (byvolume) are carbon dioxide, methane, trace thiols,and occasionally, hydrogen sulfide. Volatile organiccompounds may also be present in landfill gases,particularly at co-disposal facilities. Data generatedduring the site characterization of landfill gas shouldinclude landfill gas characteristics as well as therole of onsite and offsite surface emissions, and thegeologic and hydrogeologic conditions of the site.


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Streamlining the Development of Alternatives

Section 4 of this document describes the remedialtechnologies that are generally appropriate toCERCLA landfill sites. Inclusion of thesetechnologies is based on experience at landfill sitesand expectations inherent in the NCP. Tostreamline the development of remedial actionalternatives for landfill contents, hot spots, landfillgas, contaminated groundwater, and leachate, thefollowing points should be considered:

• The most practicable remedial alternativefor landfills is containment. Suchcontainment may be achieved by installinga cap to prevent vertical infiltration ofsurface water. Lateral infiltration of wateror gases into the landfill can be preventedby a perimeter trench-type barrier. Capsand perimeter barriers sometimes are usedin combination. The type of cap wouldlikely be either a native soil cover,single-barrier cap, or composite-barriercap. The appropriate type of cap to beconsidered will be based on remedialobjectives for the site. For example, a soilcover may be sufficient if the primaryobjective is to prevent direct contact andminimize erosion. A single barrier orcomposite cap may be necessary whereinfiltration is also a significant concern.Similarly, the type of trench will bedependent on the nature of the contaminantto be contained. Impermeable trenchesmay be constructed to contain liquids whilepermeable trenches may be used to collectgases. Compliance with ARARs may alsoaffect the type of containment system tobe considered.

• Treatment of soils and wastes may bepracticable for hot spots. Consolidation ofhot spot materials under a landfill cap is apotential alternative in cases whentreatment is not practicable or necessary.Consolidation-related differentialsettlements may be large enough to requireplacement of an interim cap during theconsolidation phase. Once the rate ofsettlement is observed to decrease, then a

final cap can be placed over the waste.

• Extraction and treatment of contaminatedgroundwater and leachate may be requiredto control offsite migration of wastes.Additionally, extraction and treatment ofleachate from landfill contents may berequired. Collection and treatment may benecessary indefinitely because of continuedcontaminant loadings from the landfill.

• Constructing an active landfill gascollection and treatment system should beconsidered where (1) existing or plannedhomes or buildings may be adverselyaffected through either explosion orinhalation hazards, (2) final use of the siteincludes allowing public access, (3) thelandfill produces excessive odors, or (4) itis necessary to comply with ARARs. Mostlandfills will require at least a passive gascollection system (that is, venting) toprevent buildup of pressure below the capand to prevent damage to the vegetativecover.

Conclusions

Evaluation and selection of appropriate remedialaction alternatives for CERCLA municipal landfillsites is a function of a number of factors including:

• Sources and pathways of potential risks tohuman health and the environment

• Potential ARARs for the site (SignificantARARs might include RCRA and/or stateclosure requirements, and federal or staterequirements pertaining to landfill gasemissions.)

• Waste characteristics

• Site characteristics (including surroundingarea)

• Regional surface water (includingwetlands) and groundwater characteristicsand potential uses


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Because these factors are similar for manyCERCLA municipal landfill sites, it is possible tofocus the RI/FS and selection of remedy process.In general, the remedial actions implemented atmost CERCLA municipal landfill sites include:

• Containment of landfill contents (i.e., landfillcap)

• Remediation of hot spots

• Control and treatment of contaminatedgroundwater and leachate

• Control and treatment of landfill gas

Other areas that may require remediation includesurface waters, sediments, and adjacent wetlands.


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Section 1INTRODUCTION

Approximately 20 percent of the sites on theNational Priorities List (NPL) are landfills where acombination of principally municipal and to a lesserextent hazardous wastes have been co-disposed.Because these sites typically share similarcharacteristics, the Superfund Program anticipatesthat their remediation will involve similar wastemanagement approaches.

EPA has established a number of expectationspertaining to the remediation of CERCLA sites andhas listed them in the National Contingency Plan(NCP). One of these expectations, which isparticularly relevant to municipal landfills, states thatengineering controls such as containment will beused for waste that poses a relatively low long-termthreat or for sites where treatment is impracticable.The preamble to the NCP identifies municipallandfills as a type of site where treatment may beimpracticable due to the size and heterogeneity ofthe contents of many landfills. Because of thisexpectation, the containment alternative should bedeveloped in the detailed analysis, and will often bethe appropriate response action for CERCLAmunicipal landfill sites based on the nine criteria.However, other alternatives such as leachaterecirculation or “flushing” of landfill contents maybe appropriate for certain situations and ifdetermined to be practicable should not bediscounted.

A second NCP expectation states that principalthreats (e.g., highly mobile and/or highly toxicwaste) will be treated, if practicable. Treatment ofhot spots within a landfill may be consideredpracticable when: (1) wastes are in discrete,accessible locations of a landfill and present apotential principal threat to human health and theenvironment and (2) a hot spot is large enough thatits remediation will significantly reduce the riskposed by the site, but small enough that it isreasonable to consider removal and/or treatment.Characterization of hot spots to determine iftreatment is practicable should be performed whenthere is either documentation or physical evidence(e.g., aerial photographs) indicating the approximatelocation of hot spots.

Other expectations in the NCP that may be relevantto the remediation of municipal landfills aresummarized below.

• A combination of engineering controls andtreatment will be used as appropriate toachieve protection of human health and theenvironment. An example would includetreatment of hot spots in conjunction withcontainment (capping) of the landfillcontents.

• Institutional controls such as access anddeed restrictions will be used to supplementengineering controls as appropriate, toprevent exposure to hazardous wastes.

• Groundwaters will be returned to beneficialuses whenever practical, within areasonable time, given the particularcircumstances of the site.

• Innovative technologies will be considcredwhen such technologies offer the potentialfor superior treatment performance orlower costs for performance similar to thatof demonstrated technologies.

The similarity in landfill characteristics and the NCPexpectations make it possible to streamline theRI/FS process for municipal landfills. Bystreamlining the RI/FS process EPA will (1)improve the efficiency and effectiveness of decisionmaking at these sites; (2) provide for consistencyamong the Regions in their approach to conductingan RI/FS and selecting remedial actions, and (3)facilitate more effective remedial designs.

In direct response to the need to develop tools andmethodologies to streamline the RI/FSprocess for different site types (Recommenda-tion No. 23 in the Superfund ManagementReview Implementation Plan), the Office ofEmergency and Remedial Response has devel-oped this document which (1) provides informa-tion and tools to assist in scoping an RI/FS,


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(2) defines appropriate strategies for characterizingmedia typically impacted by municipal landfills, (3)identifies a strategy for simplifying the baseline riskassessment (thereby allowing for early action atthese sites), and (4) identifies the most practicableremedial action alternatives for addressing thesetypes of sites.

1.1 Background On MunicipalLandfills

CERCLA municipal landfill sites are unique in boththeir size and composition. The landfills currently onthe NPL range in size from 1 acre to 640 acres,while most are facilities where a combination ofprincipally municipal and to a lesser extenthazardous wastes have been codisposed of.Municipal wastes disposed of in these landfillstypically includes a heterogeneous mixture ofmaterials primarily composed of household refusesuch as yard and food wastes and paper, andcommercial waste such as plastics, inert mineralwaste, glass, and metals. There are four ways inwhich hazardous wastes may have been disposedof in municipal landfills. First, landfills that operatedbefore the implementation of RCRA on November19, 1980, typically accepted and co-disposed of bothliquid and solid hazardous waste. Second, smallquantity generators contribute varying quantities ofhazardous wastes to municipal landfills. Smallquantity generators are those that produce no morethan one kilogram per month of designated acutehazardous waste or no more than 100 kilograms permonth of all other hazardous wastes combined (see40 CFR 261.5). Third, some household wastes suchas batteries and paints are hazardous. And fourth,biodegradation of wastes within the landfill cancreate new compounds that are hazardous.

The dynamics within a landfill create an unknownand changing environment. Microbial degradation ofthe municipal solid waste occurs, in addition tovarious unknown interactions between hazardousand municipal solid wastes. Microbial degradationof municipal solid waste is a dynamic process thatoccurs for an indefinite period of time after wastehas been placed within a landfill. Microorganismsnaturally occurring in the soil and refuse biodegradethe wastes in distinct stages; each stage of

degradation creates different byproducts.

Landfills can react with the environment in anumber of ways. One type of interaction occurswhen precipitation and/or liquid wastes disposed ofwithin the landfill percolate through the landfilledmass to form a liquid called leachate. Leachate mayenter the subsurface soils and groundwater or bedischarged to nearby surface waters and wetlandsfrom groundwater or seeps. The amount ofleachate formed from a landfill is a function of (1)the amount of precipitation in the area, (2) the typesof materials disposed of in the landfill, (3) thedesign, size, age, and initial moisture content of thelandfill, and (4) the permeability and porosity oflandfilled materials and the soil used to cover thelandfill. The characteristics of landfill leachatedepend upon factors such as initial concentrationsof compounds, solubilities, and vapor pressures,rates at which compounds are transformed bymicrobial and chemical processes within the landfill,and the physical characteristics of the landfilledmaterials. The transport and fate of leachate in thesubsurface environment is a function of the landfilldesign and the characteristics of the underlying soiltypes.

A second way in which landfills can interact withthe environment is through discharge to nearbysurface waters and wetlands. As mentionedpreviously, leachate may be discharged from seepsto local surface waters and wetlands orcontaminated groundwaters may recharge thesemedia. The most direct contribution however, isoften through stormwater runoff. Runoff from alandfill may be voluminous but the contact time withthe landfill materials is often limited.

A third type of interaction between landfills and theenvironment is through airborne emissions of gasesand vapors. Some of the volatile compounds emittedfrom landfills are those present in the landfill as it isbeing filled, while others are generated bymicroorganisms as they degrade the wastes in thelandfill. The principal airborne emissions(by volume) associated with landfills aremethane and carbon dioxide. These gasesare the result of anaerobic microbialdegradation of municipal solid wastes. Othervolatile compounds often emitted from


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CERCLA landfills include halogenatedhydrocarbons, simple alkanes, vinyl chloride,benzene and other aromatic compounds, andmerceptons. The principal factors affecting the typeof air emissions include (1) the type of materialsdisposed of in the landfill, (2) the age of thelandfilled refuse, (3) the type of cover overlayingthe landfilled wastes, (4) the presence or absenceof a gas extraction and treatment system, (5)subsurface gas migration, and (6) the presence ofunderground/subsurface fires. Barometric pressureand wind speed and direction also play an importantrole in the affects to potential receptors.

1.2 Document Organization

This document is organized into six sections. Thefirst section is this introduction, which includes thegoals and objectives of this project as well as asummary of municipal landfill characteristics andtheir potential impact on the environment. Section 2describes the activities necessary to adequatelyscope an RI/FS for a landfill site and provides anumber of tools to assist in scoping. The thirdsection describes site characterization strategies forco-disposal facilities that either have or do not have

suspected hot spots. Section 4 of this reportdescribes the remedial technologies that areappropriate for CERCLA landfills, including thedata requirements to adequately evaluate them.Section 5 includes an analysis of the nine criteriaused to evaluate practicable technologies andsummarizes basic conclusions that can be made foreach technology in light of each of the evaluationcriteria. The final section describes appropriateremedial alternatives that have been developed foran example municipal landfill site and presents anevaluation of these alternatives. The purpose of thissection is to illustrate how technologies might becombined to form alternatives typically developedfor landfill sites and how these are evaluated usingthe nine criteria.

Additionally, scoping activities, and an appropriatesite characterization strategy, have been identifiedfor the example site and included as Appendix A tobetter illustrate some of the concepts presented inthis document. Appendix B of this documentcontains an historical record of the remedial actionsselected for CERCLA municipal landfill sitesthrough FY 1989.


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Section 2 SCOPING THE RI/FS FOR MUNICIPAL LANDFILL SITES

Developing a work plan is the first step inconducting an RI/FS at a municipal landfill site. Theprocess of developing a comprehensive scope ofwork to be defined in the work plan is known asscoping, and has several functions. It identifies thepreliminary remedial action alternatives, summarizesthe RI/FS objectives, and outlines the tasksnecessary to meet these objectives. Because thework plan is the foundation of the RI/FS, theremedial project manager (RPM) should devoteconsiderable attention to preparing it and theindividual tasks. Without a definition of a properwork plan, it is unlikely that the RI/FS or the projectobjectives will be met because it is difficult toachieve loosely defined RI/FS or project objectivesthat extend over a long time. It should also berecognized that adjustments should be made to thework plan as work on the RI/FS progresses andmore is learned about the site.

A primary purpose of scoping an RI/FS, therefore,is to divide the broad project goals into manageabletasks that can be performed within a reasonableperiod of time. Proper planning also provides theRPM with a mechanism for measuring progressand controlling the project.

The broad project goals for an RI/FS at anySuperfund site are to provide the informationnecessary to characterize the site, define sitedynamics, define risks, and develop a remedialprogram to mitigate or eliminate potential adversehuman health and environmental impacts. The tasksthat should be performed to achieve these goalsinclude the following:

• Evaluate existing site data (Section 2.1)

• Conduct a site visit (Section 2.3)

• Conduct a limited site investigation, asnecessary (Section 2.4)

• Define the conceptual site model (Section2.5)

• Scope the risk assessment (Section 2.6)

• Identify preliminary applicable or relevantand appropriate requirements (ARARs)

• Develop preliminary remedial actionobjectives and goals (Section 2.7)

• Develop preliminary remedial technologies(Section 2.8)

• Develop objectives of the RI/FS (Section2.9)

• Develop data quality objectives (DQOs)(Section 2.10)

• Prepare an RI/FS work plan and samplingand analysis plan

• Prepare a health and safety plan

• Prepare a community relations plan

• Conduct Phase I site investigations

• Evaluate Phase I data

• Refine remedial action alternatives

• Conduct Phase II site investigations, ifnecessary

• Evaluate remedial action alternatives

The scope of work for a municipal landfill site maybe different from the scopes for other types of sites,such as surface impoundments, waste piles, andtank farms. Because waste in municipal landfills isa heterogeneous mixture of materials and maycontain liquid and solid hazardous wastes, thenumber of remedial action alternatives is limited.Therefore, site-characterization strategies that canbe used at municipal landfill sites are limited. Thespecific strategies for characterizing different typesof landfill sites are presented in Section 3 of thisreport. This section focuses on the components ofscoping an RI/FS for municipal landfill sites.


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2.1 Evaluation of Existing Data

Existing data should be reviewed and evaluatedbefore any other activities are performed, so thatthe site dynamics can be understood and the scopeof the RI can be adequately prepared. Thoroughdata evaluation is important because it affects boththe timing and cost of the RI/FS. The evaluationalso identifies the needs and objectives of anylimited field investigation, the selection ofpreliminary remedial action alternatives, the RI/FSobjectives, and the development of the DQOs.

To begin understanding site dynamics and scopingthe RI, sources of existing data should be identifiedand the data should be compiled. Information on thearea’s hydrology and geology should be collected sothat contaminant pathways can be identified. Typesand sources of hazardous materials in the landfillshould be determined, where possible. In addition,regulatory activities should be reviewed, includinginformation on any existing landfill cover. Finally,the results of past sampling and analysis effortsshould be evaluated for their usefulness.

If, after existing data are evaluated, it is determinedthat there is insufficient information to define sitedynamics and to develop the conceptual site model,limited field investigations should be conducted.Limited field investigations are performed duringscoping, and should be limited to easily obtainabledata for which results can be received in a shortperiod of time. The existing data, together with theresults of any limited field investigations, should thenbe used to construct the conceptual site model andto develop the preliminary remedial actionalternatives and the RI/FS objectives.

2.1.1 Sources of Information

Federal, state, and local agencies may havepertinent information for evaluating a site. Althoughsome of this information may be general, it still canbe used to establish a baseline. As an example,records of previous ownership may indicate thatthere were manufacturing operations at a site.Exact locations of buildings may not be available,but the materials used in manufacturing operationscould suggest that additional analytical parametersbe tested. In addition to government sources, other

data sources that may be particularly useful inobtaining more specific information on a siteinclude:

• Preliminary assessment/site inspection data

• HRS scoring package

• Potentially responsible party (PRP) searchreport

• Aerial photographs

• State files, including inspection reports,permit applications, and well data bases

• Interviews with state inspectors, localgovernment bodies, and local residents

• Site history, ownership, operation/disposalpractices (past and present, from pastowners, operators, or generators)

• Weight tickets/logs

• Data from original siting studies orengineering designs

• Closure plans

Information available from other agencies and thetypes of information generally available from otherpotential data sources are summarized in Table 2-1of Guidance for Conducting RemedialInvestigations and Feasibility Studies UnderCERCLA (U.S. EPA, 1988d). Appendix B of thisdocument provides information on technologiesmost frequently implemented at municipal landfillsites based on a review of RODs signed through1989.

Existing data should be evaluated and summarizedin formats that are easily reviewed by individualsnot involved in the collection process. Reviewingand evaluating the available data will lead to anunderstanding of the site conditionsand identification of evident data gaps.During this activity, the quality (that is,accuracy and precision) of the data and theirconformance with the quality control (QC)


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protocols under which they were collected shouldbe assessed. If possible, preliminary data (e.g.,condition of cap) should be confirmed by onsiteobservations.

2.1.2 Types of Data and Data Quality

At this early stage, it is important to focus oncompiling as much information as possible about thesite’s characteristics and hydrogeological setting.Although the complete set of desired information isnot always available or of good quality, it isimportant to gather all that is available. Thisinformation includes:

• The landfill’s condition, especially its slopestability, the presence of underground fires,levels of methane gas, and amount of cover

• Areas of suspected contamination, unusualsurface patterns, or unusual surfacefeatures (for example, mines)

• Boundaries of areas of suspectedcontamination

• Depth to groundwater and seasonalfluctuations

• Existing site conditions, such as recentconstruction of neighboring houses

• Site and property boundaries and landfilldepth

• Existing residential, municipal, and industrialwells, including construction and analyticaldata

• Details of landfill construction, such asdrainage channels, clay liners, capconstruction (full or partial), facility basegrades, present engineering controls (ifany), and any current landfill gas venting

• Evidence of leachate seeps, contaminatedsurface water runoff, or other spread ofcontamination

• Nature of the soils around and under thelandfill (for example, permeability,composition, clay, organic content)

• Nature and characteristics of material inthe landfill, particularly chemicalcomposition of hazardous waste

• Nature of disposal practices (If wasteswere segregated, locate potential hot spotareas).

As part of this compilation, data quality should beevaluated to determine the uncertainty associatedwith the conclusions drawn from existing data andtheir usability. Uncertainty about the adequacy ofexisting data can arise from two sources: therepresentativeness or the specificity of the samplingtechniques used to collect the data, and the validityof the analytical methods used. Therepresentativeness of data can be assessed byreviewing their sources. The rationale and methodof sample collection should be determined. Theanalytical methods should be reviewed to determineif the analyses are appropriate to the RI/FSobjectives. Data validation identifies invalid data andqualifies the usability of the remaining data. Formaldata validation procedures are used to identify datathat are the result of improper analyticalprocedures. QC information, if available, can bereviewed to assess the validity of the analyses. Theusability of data without QC information cansometimes be assessed by using statisticaltechniques or by using professional judgment.Statistical techniques can be used to judge whetherthe data are consistent by examining theirdistribution. Data values that are exceptional maybe suspect and should be verified with additionalsamples of known quality. Additional information onthe statistical evaluation of data can be found inStatistical Methods for Evaluating theAttainment of Superfund Cleanup Standards,Volume I: Soils and Solid Media (U.S. EPA,1989a).

Other information that is not classed as validbecause of QC restrictions can be used inestablishing a hypothesis about contaminantbehavior over time. These data generally should notbe used in making final decisions about the need forcleanup, but they can help in developing anunderstanding of site dynamics, sampling strategiesfor the RI, and preliminary remedial actionalternatives. Factors that must be considered inevaluating the data for their usefulness are:


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• The age and comparability of the data sets.Standard methods of sample collection andanalysis may change over time; thus,sample results may not be directlycomparable.

• The existence of replicate sample data forestimating precision.

• The sampling design used to collect thesamples (for example, were bothupgradient and downgradient wells locatedat the landfill for the collection of thegroundwater samples?).

• The methods used to collect, preserve,handle, and transport the samples.

• The analytical methods used to estimatepollutant concentrations (for example, doesthe analytical method provide results thatcan be used for risk assessment, or is itsusefulness limited to site characterization?).

• The length of time samples were heldbefore analysis (for example, volatileorganic analysis has a 14-day allowableholding time or a 7-day holding time whennot preserved with acid).

• The published sensitivity or detection limitof the analytical methods (for example, isthe detection limit higher or lower than thechemical-specific ARAR?). The detectionlimit should be lower than both thechemical-specific ARARs and appropriaterisk-based concentrations.

• The quality control measures used by fieldand laboratory teams (for example, wereblank samples used to determine if sampleswere contaminated during collection oranalysis?).

The assessment of data reliability should alsoextend to the entire site investigation process. Therationale for selecting the sampling locations and fordetermining the completeness of the samplingshould be evaluated. The sampling plans andmethods, if available, should be reviewed foraspects of the site useful for determining the RI/FSobjectives.

An important part of reviewing and evaluating theavailable data is assessing their reliability, that is, theextent to which the data represent site conditions.The dates of maps, drawings, and plans should bechecked. Sampling locations should be evaluated forrepresentativeness. Analytical data should bechecked against internal laboratory and source QCcriteria (blanks, duplicates, spike/recovery), and themethods of sample collection, preservation,handling, and sampler decontamination should beexamined for potential irregularities. If more thanone laboratory tested samples from the same areaon the site, the results should be assessed forconsistency, and variations in methodology shouldbe identified.

The level of effort to review the data quality maybe significant if large amounts of potentially highquality data are available. More typical, however, isthe case where some analytical data are low orunknown quality and will be used only in thedevelopment of the initial site conceptual model andinitial sampling planning activities. In this case, dataquality review may not require a significant level ofeffort.

2.1.3 Presentation of Available Data

Whenever possible, the available data should besummarized in graphs, tables, or matrices. Data canalso be presented as isoconcentration maps forparameters that depict the degree and extent ofcontamination for the various media orhydrogeologic units. These compact formats allowfor efficient presentation, comparison, and use oflarge amounts of data. A written summary is alsovaluable for conveying data trends and generalconditions. All summaries, whether graphic, tabular,or written, should identify both what is known(conditions at the site) and what is not known(evident data gaps).

2.2 Existing Data EvaluationResults and Report

The evaluation of existing data should result in thepreparation of a preliminary base map, geologiccross sections, a hydrology summary, preliminarywaste characterizations, and a summaryof sampling activities and results. Figure2-1 presents a flow diagram for gathering


2-5Word-searchable Version – Not a true copy

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evaluating, and preparing data for an RI/FS at amunicipal landfill site.

Inadequate data review during this stage of theRI/FS can result in a misdirected focus of the study,which may cause the collection of unnecessarysamples, an escalation of field investigation costs,and/or project delays. As an example, inadequatedata review during scoping to determine the needfor treatability studies for leachate/groundwater orlandfill hot spots may result in project delays andincreased costs.

2.2.1 Site Description

The site description should provide accurate,detailed, and current information on the site. Aphysical description of the site and its surroundingsand a preliminary base map should be prepared.Data in the hazard ranking system (HRS) scoringpackage and the preliminary assessment/siteinspection (PA/SI) should provide some of the basicinformation. The base map should include:

• Surface water drainage patterns and sitedischarge locations

• Locations of existing residential, municipal,and industrial wells, and surface waterintakes

• Presence of wetlands/floodplains, wildlifehabitats, scenic rivers, and historicalarcheological resources

• Onsite and offsite buildings, structures, andpiping, including existing landfill gasextraction equipment

• Area and site topography and vegetation

• Underground and overhead utilities in thevicinity of the site (All utilities that couldpossibly impact geophysical surveys shouldbe identified during scoping.)

• Availability of water, sewer, phone, andelectrical hookups for the site

• Nearby structures, residences, and otherland uses

• Previous sample locations

• Known or suspected hot spots

• Locations of potential hazards (forexample, hazards due to falls, heavy-equipment operation areas, electrical powerlines)

• Areas of active landfilling operations

• Property lines, facility and refuseboundaries

• Access and security (for example, roads,fences, gates)

The site map should differentiate between the siteboundary (the area of the landfill) and the propertyboundaries (total area of the property may notnecessarily be used as a landfill). The preliminarybase map can be developed from existing site maps,aerial photographs, or a topographic survey. EPA’sEnvironmental Photographic Interpretation Center(EPIC) in Warrenton, Virginia, can provide a widerange of information on a site, such as:

• Aerial photographs and analysis for a singledate

• Aerial photographs and analysis over timeeither for the site itself or for a wider area(historical analysis)

• Topographic mapping at 1-foot to 5-footcontour intervals

• Orthographic mapping, which is a rectifiedphotoimage with a superimposedtopographic map

Existing figures, photographs, and maps may beuseful sources of historical information but shouldnot be relied on for information on current siteconditions. A fly-over of the site may be necessaryto obtain current aerial photos and/or to conduct atopographic survey. If a subcontractor must beprocured for this activity, it may have to be delayeduntil the RI fieldwork is conducted.


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As mentioned above, the site description shouldinclude the areas, if any, of active landfillingoperations; locations selected for sampling or wellinstallation should consider the impact on the site’snormal operation and maintenance. Meteorologicdata should also be collected and considered duringthe development of the work plan. Meteorologicdata can be used to determine appropriate times forsite visits, to direct sampling efforts, and to evaluateremedial action alternatives, such as incineration,capping, or grading. Barometric pressure data arealso useful for interpreting landfill gas volumecollection data.

2.2.2 Site History

The site history section should detail, inchronological order, the history of previousregulatory actions, disposal activities, types andquantities of wastes, previous owners or operators,site uses, and site engineering studies. Significanteffort should be expended in detailing the specificsof disposal activities and of types and quantities ofwastes. Site records and interviews with nearbyresidents and former site operators are valuablesources of this information.

The history of previous disposal activities at amunicipal landfill often directly affects the RIobjectives, specifically the need to determinewhether hot spots may be present and worthy ofinvestigation. In addition to investigating a potentialprincipal threat, the contents of hot spots areimportant for associating PRPs with the site.Identifying the chemical components may aid inidentifying the sources of the waste in the hot spots.

A brief history of operations at adjoining or nearbyfacilities and other relevant environmentalcontamination at or near the site should also beincluded. These potential offsite sources ofcontamination should be considered during thedevelopment of the work plan. They may affect thechoice of sampling and monitoring well locationsand may contribute contamination to various media.Multiple sources of contaminants in the vicinity canmake it difficult to identify all PRPs.

2.2.3 Regional and Site Geology andHydrogeology

In addition to the preliminary site base map,preliminary geologic cross sections should bedeveloped, if possible, to provide a threedimensional overview of soils and geology and thepossible extent of soil and groundwatercontamination at the site. The purpose of this effortis to identify any changes or correlations in the typeand movement of contamination and soil types andstructure. This information will be used to:

• Estimate the depth of the landfill

• Estimate the depth to groundwater

• Identify the limits of subsurface samplingprograms

• Select appropriate soil sampling and drillingmethods

The preliminary soil/geologic cross-section can bedeveloped from existing site maps, soil and geologicpublications, reports on soil borings and monitoringwell installation, and analytical results of soilsampling and groundwater sampling, if available. Asuggested type of cross-section is shown in Figure2-2. Features shown on a cross section of this typeshould include:

• Ground surface features (for example,buildings, above-ground tanks, roads)

• Soil horizons (for example, clay lenses orother soil layers with differingcharacteristics)

• Major geologic units

• Locations of domestic and/or public supplywells

• Locations of existing borings, wells, andtest pits

• Existing sample locations, including thelocation of offsite sampling locations to


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determine whether offsite contamination isa problem in the area

• Depth to groundwater

If no soil borings, test pits, or monitoring wells havebeen installed at the site, it may not be possible toconstruct a detailed preliminary cross section.However, geologic and soil publications--such asUnited States Geological Survey (USGS) reports,Soil Conservation Service data, state geologicalsurvey reports, state well databases, logs of publicsupply companies, and information from local welldrillers--should be available to give an estimate ofthe thickness of unconsolidated material, the depthto the groundwater table, and current aquifer uses(e.g., agricultural, drinking water).

If sufficient information from these sources isavailable, this section should also identify the origin,texture, and distribution of unconsolidated materials;the origin, texture, nature, and distribution ofbedrock units; and the texture and classification ofsurficial soils. In addition, if available, this sectionshould identify rock type, porosity (primary andsecondary), areal extent of geologic units, andstructural geology. This information can helpidentify complex hydrogeological units and definerecharge and discharge zones and flow systems.The regional and site-specific geology are describedin this section to help identify contaminant pathwaysand develop a conceptual site model.

2.2.4 Hydrology

Collection and evaluation of hydrologic data shouldinclude both surface water and groundwatercomponents.

2.2.4.1 Surface Water

Surface water bodies near the site should beidentified to (1) evaluate the potential impact of thelandfill on the body of water, (2) understand therelationship, if any, between the surface water andgroundwater flow at the site, and (3) determinetheir potential to be discharge locations for treatedleachate and surface runoff from the cappedlandfill.

Groundwater flow may be affected by seasonalsurface water fluctuations and may either discharge

to surface water or be recharged by surface waterat different times of the year. This information maybe identified by comparing concurrent groundwaterand surface water level measurements takenseasonally. Preliminary information for groundwatercan be obtained from USGS hydrogeologic atlases,state aquifer maps or water resource overlays, thelocal board of health, water control board, planningcommission, or the local Department of PublicWorks.

2.2.4.2 Groundwater

A groundwater assessment should be performed atand near the site to determine depth togroundwater, local and regional groundwater flowdirections, gradients, recharge areas, dischargeareas, and to identify aquifers used by private andpublic water supply wells in the area. Thisinformation may be determined by evaluating thedata gathered for the section on regional andsite-specific geology (Section 2.2.3). If nomonitoring wells have been installed at the site, itmay not be possible to assess specific groundwaterlevels or local flow directions at the site. However,geologic publications, as mentioned in Section 2.2.3,should be able to give an estimate for the region ofthe depth to the groundwater table.

If possible, a well survey should also be initiatedduring scoping. This survey can serve a number ofpurposes, including evaluating the “usability” ofexisting wells for future field activities andaccounting for pumping influences when selectingadditional sampling locations for monitoring wells.This survey would also be useful for identifyingpotentially contaminated wells being used asdomestic, municipal, or industrial supplies. Wellinstallation logs, if available, may be useful inpreparing geologic cross sections.

2.2.5 Waste Characterization

The types and quantities of wastes within thelandfill are estimated during waste characterization.This information can be developed from landfilldisposal records; county, state, and EPA records;interviews with current/previous employeesof the landfill; aerial photographs; resultsof sampling landfill contents; and interviewswith state inspectors. If available, the


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periods of disposal should also be estimated to helpidentify the likelihood that contaminants will be inthe landfill (for example, volatile organicssometimes migrate quickly and may not be present)and to establish PRP responsibility. Althoughinterviews and records searches aretime-consuming, the information gathered is veryuseful in directing the RI/FS process and theselection of remedial action alternatives.

2.2.6 Sampling Activities and Results

A summary of the chemical analytical datacollected at or near the site may provide extensiveinformation about the potential effects of the site onthe surrounding media and about future data needs.This section addresses the affected media at thesite, not the sources, which are addressed under“Waste Characterization” (Section 2.2.5). Thesummary of sampling activities and results shouldinclude the date of the study, the name of the firmresponsible for the study, the name and address ofthe laboratory that performed the analysis, themedia sampled, the analytes, and the analyticalmethods used.

The usability of the data should be evaluated asdiscussed in Section 2.1.2, bearing in mind thatthere are several data uses (for example, sitecharacterization, evaluation of alternatives, PRPdetermination) that require different qualities ofdata. The existing chemical analysis information(including QC information) should be included in anappendix of the work plan.

2.3 Site Visit

A site visit by the RPM and other appropriatepersonnel (e.g., state and Federal agencyrepresentatives) is necessary during the scopingprocess to:

• Verify existing data (for example, conditionof cap, amount of soil cover, extent ofslope erosion)

• Identify existing site remediation systems(for example, landfill gas or leachatecollection systems)

• Identify critical areas (for example,possible equipment-staging areas, accessroadways, residential areas)

• Visually characterize wastes (for example,leachate seeps, exposed drums, stainedsoils)

• Gather additional data to support furthersite evaluation (for example, wetlands,floodplains, biota)

• Evaluate the practicability of geophysicalsurveys

Detailed examination of a municipal landfill duringa site visit is important for several reasons.Observation of slope instability or explosive levelsof gas may indicate the need to mitigate animmediate hazard. Details of cap construction mayaffect the feasibility of remedial technologies.Remedial technologies that use heavy equipmentcan also be removed from consideration by softground surfaces or other conditions limiting accessto the landfill.

Characterization of waste materials by visualobservation is also important. Visual identification ofhot spots or the physical characteristics of thewastes (sludge-like or solid) is necessary forsampling preparation and for ensuring therepresentativeness of sampling. The physical andchemical characteristics of the waste are keyvariables in defining alternative technologies forremedial actions and in identifying the mostcost-effective actions. Special wastes (radioactive,laboratory packs, etc.) not normally associated withmunicipal landfills may also be at the site and shouldbe noted during the site visit. However, thecertainty of information gathered by visualobservation during the site visit is limited. Ideally, asite should be visited when vegetation is minimal.Potential sampling locations should be identifiedcarefully, because later plant growth may coverthem. It is sometimes useful to visit a site after aheavy rainfall, if possible, to observe runoff andleachate seepages that may not be visible at othertimes. A follow-up visit during a dry period may beuseful in evaluating the potential for dust generation.


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The time needed to complete a site visit will dependon the size and complexity of the site and whetherinterviews will be conducted. On average, a sitevisit may take between 1 to 2 days (not includinginterviews).

The following activities may be performed duringthe site visit:

• Identification of unusual features, including

S Spill areas and stained soils

S Evidence of environmental stress toflora or fauna and adjacent wetlands

S Presence of waste requiring specialhandling or precautions

S Presence of surface impoundmentsand aboveground tanks

S Presence of underground storagetanks, aboveground vents, or fill pipes

• Examination of landfills, including

S Evidence of slope instability, leachateseeps, soil erosion

S Details of cap construction, stability,areas of cover cracking, erosion, orsubsidence

S Evidence of gas release through cap

S Approximate perimeter of the landfill

S Evidence of partially buried drums orother hazardous materials

S Localized areas of stressed vegetationor detection on explosimeter

S Factors affecting the accessibility ofthe landfill to heavy equipment, such asmoisture content of the soil, width ofbenches/access roads

S Identification of site features that mayinterfere with the performance ofgeophysical surveys

• Field characterization of wastes, including

S G e n e r a l n a t u r e o f t h ewastes--residential, industrial, sludges,or a mixture

S Physical state of the wastes--dry, wet,very compressible, firm, free liquids

S Physical properties of exposedwastes--odor, gas generation, state ofdecomposition

S Preliminary measurements in hot areaswith an organic vapor analyzer (OVA)

• Identification of:

S Site utilities, facilities, and structures

S Unusual wastes (laboratory packs,cylinders)

S Drainage patterns

S Possible offsite sources ofcontamination

S Recent construction, including housingdevelopments

• Division of site into grids to facilitateidentification of target areas and futureremedial activities (a cartesian grid iseffective)

• Identification of access, egress, staging,and security points

• Interviews with local residents (opportunityto confirm well survey and also necessaryfor preparation of community relations plan[CRP])


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• Identification and confirmation of featureson the preliminary base map andsoil/geologic cross-section

• Preparation of photographs of site features

• Performance of air quality monitoring forhigh levels of volatiles or methane

A health and safety plan (HSP) should be preparedfor the initial site visit unless an HSP was developedfor previous site work, in which case this plan maybe adequate. If no plan exists, a limited HSP shouldbe developed on the basis of existing data. TheRPM should coordinate with the Regional Healthand Safety Officer on the need for the HSP andcontents. Requirements for an HSP can be found inOccupational Safety and Health GuidanceManual for Superfund Activities (NationalInstitute of Occupational Safety and Health, 1984),Guidance on Remedial Investigations UnderCERCLA (U.S. EPA, 1985e), and StandardOperating Safety Guides (U.S. EPA, 1984c).

2.4 Limited Field Investigation

After existing data have been evaluated and a sitevisit has been conducted, a preliminary conceptualsite model depicting the site's dynamics should bedeveloped. If the information required to developthis model is incomplete, a limited field investigation(LFI) should be conducted. (See Section 2.5 forinformation on the conceptual site model.) The LFIshould be restricted to the collection of easilyobtainable data, which can be gathered quickly. Itspurpose is to define the scope of work as preciselyas possible, given the available information. The LFItypically involves field measurements but mayinclude chemical analysis of groundwater fromexisting wells or samples from other easilyaccessible sample locations. The limited fieldinvestigation is normally performed during thepreparation of the work plan and before extensivesampling begins for the RI.

Table 2-1 is a list of the possible activities that couldbe performed during an LFI at a municipal landfillsite. This table should not be interpreted to meanthat all of these objectives (and actions to meet the

objectives) should be met to adequately scope anRI/FS for a municipal landfill site. Rather, the datarequirements for adequately scoping the projectshould be determined on a site-by-site basis. Dataneeds will differ for each site and will depend onfactors such as the results of the existing-dataevaluation, the number and type of potentialcontaminant pathways and receptors, and the RIobjectives.

RI reports for municipal landfills were reviewed todetermine the usual activities performed duringlimited field investigations at landfills. Theseactivities are shown in Table 2-1 and can include:

• Property surveys

• Topographic surveys

• Surveys of location, elevation, accessibilityof monitoring wells

• Well surveys for all residential wells withinthe current or potentially affected area

• Collection and analysis of samples fromexisting monitoring and residential wells

• Surface and volatile emissions survey

• Water level measurements taken fromexisting monitoring wells

• Survey of gas levels in nearby residencesto determine if they are near the explosiverange (also in onsite buildings and confinedspaces)

Most of this information requires fieldmeasurements, which would not be gathered duringthe site visit. General investigation Table 2-1continued activities that could be done during thesite visit are described in Section 2.3 and notrepeated here.

Well installation and other activities requiringsubcontracting should be avoided during the LFI.Sampling is also typically not performed; however,sampling of existing and residential


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Table 2-1LIMITED FIELD INVESTIGATION OPTIONS FOR

MUNICIPAL LANDFILL SITES

Page 1 of 2

Activity Objectives Action

General Investigation Identify previous siteowner/operators and delineatesite boundaries. Estimateuncertainties in boundaries.

Conduct property survey orperform a title search or identifyproperty ownership from taxrecords, or plat maps.

Locate existing monitoringwells.

Perform location and elevationsurvey of existing monitoringwells.

Evaluate site drainage patterns. Review topographic maps andperform hydrologic survey.

Evaluate site-cover conditionsand surface water drainage.

Perform visual surfaceinspection with topographicmaps. Conduct surfaceemissions survey.

Evaluate gas migration,potential, if applicable.

Measure explosive gas levels innearby residences, or onsitebuildings, if present. Alsomeasure in water meter boxesand utility corridors, if landfillgas poses a threat.

Locate sampling locations. Survey a grid for the site andcross-reference to samplelocations.

Determine landfill subsidence, ifsurvey is otherwise required.

Measure elevations along crownof fill or install benchmarks inareas of potential subsidence(requires repeat visits bysurveyor).

Geotechnical Investigation Describe geologic features,classify soil.

Conduct visual observation ofmechanical erosion, slopeinstability, differentialsettlement, and ponding caused by subsidences and cracking.


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Table 2-1LIMITED FIELD INVESTIGATION OPTIONS FOR

MUNICIPAL LANDFILL SITES

Page 2 of 2


Hydrogeologic Investigation Evaluate usefulness of existingmonitoring well network.

Conduct a well survey for allwells (residential, commercial,industrial). Determine local usesof groundwater and accessibilityof existing wells. Obtainpermission for use.

Determine if existing wells areobstructed (e.g., by sounding tothe bottom of the well).

Review preliminary locations fornew monitoring wells.

Perform fracture-trace analysisin areas with fractured bedrock(can be done through EPICstudy).

Determine location of residentialwells and their construction.

Perform well survey for allresidential wells adjacent to, anddowngradient from, the landfill.Obtain well logs from federal,state, local utilities, or municipalagencies.

Determine direction ofgroundwater flow and estimategradients.

Record water levelmeasurements from existingwells (at least quarterly, todetermine seasonal variations).

Determine rate of groundwaterflow in strata and bedrockfractures .

Perform hydraulic conductivity tests on existing wells.

Confirm previous sampling resultsfor both existing monitoring andresidential wells and collectadditional data as necessary.Identify areas of groundwatercontamination and types ofcontaminants.

Collect and analyze* samplesfrom monitoring and residentialwells. Record qualityparameters for the samplesanalyzed. Compare new resultswith values from previousstudies.

Determine if residential wellsadjacent to, and downgradientfrom, the landfill arecontaminated.

Collect and analyze* tap watersamples before any filtration unitand conduct preliminary riskassessment.

*Sample collection and analysis is not usually performed as a part of an LFI but is an option that couldprovide valuable information for scoping future fieldwork.


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wells has been included in this table because thisinformation, if obtainable, will greatly assist inscoping the RI/FS.

The tasks required to perform a limited fieldinvestigation may be included in the statement ofwork for an EPA contractor if the site is designatedas a fund-lead site, or they may be attached to theconsent order for a PRP-lead RI/FS. Performing anLFI during the development of the work plan oftensaves both time and money. This is because it takesless time and is less costly to scope the RI/FScorrectly the first time than to rescope certainaspects of the project at a later date.

2.5 Conceptual Site Model

The conceptual site model is developed so that anunderstanding of the site dynamics can be obtained.Its purpose is to describe the site and its environsand to present hypotheses regarding the suspectedsources and types of contaminants present,contaminant release and transport mechanisms, rateof contaminant release and transport (wherepossible), affected media, known and potentialroutes of migration, and known and potential humanand environmental receptors. In general,quantitative data should be incorporated whereverpossible. Hypotheses presented by the model aretested, refined, and modified throughout the RI.

Generally, a conceptual site model is based on theexisting data evaluation and is developed before anyfield activities, including those performed as part ofan LFI. If insufficient information is available todevelop a conceptual site model, the LFI providesthe information needed to develop a sufficientmodel for scoping further investigations.

The conceptual site model is a tool that can assistthe site manager in determining the scope of theproject, identifying data needs, and establishingpreliminary remedial action objectives. For example,if residential areas are upwind of the site andexisting data indicate no volatile emissions ofconcern, then air may be considered an unaffectedmedium in the model and no further data should becollected during the RI. On the other hand, ifresidential wells near the landfill are contaminated

and existing groundwater data are limited, then thesite model will indicate that groundwater is anaffected medium and the collection and analysis ofsamples from this medium should be included in theRI.

A generic conceptual site model for municipallandfills was developed so that a basis for projectscoping could be established. The conceptual sitemodel was developed for municipal landfill siteswith data collected from review of 71 municipallandfill RODs. Figure 2-3 presents a schematicdiagram of this model, and Figure 2-4 depicts theinformation as a flow diagram. This generic modelmay be utilized to develop a site-specific model.After evaluating the data and completing a site visit,the RPM should determine which contaminantrelease and transport mechanisms are appropriatefor the municipal landfill site in question. Forexample, if hospital wastes or radionuclides are inthe landfill, then they should be added as acontaminant source, and the release mechanism,affected media, exposure pathways, and rcceptorsshould be identified. Likewise, contaminant releaseand transport mechanisms and media that are notaffected by the landfill should be deleted fromFigure 2-4. For example, if the landfill is in adepressed area and surface runoff flows into thelandfill area and not away from it, then the twoassociated release mechanisms, runoff and erosion,can be eliminated from the model. However, ifthere is uncertainty about the existence of specificcontaminant release and transport mechanisms, itshould be retained.

The key element in the development of theconceptual site model is to identify those aspects ofthe model that require more information to make adecision about remediation. For example, if it is notpossible to decide whether removal or containmentof a known hot spot is the most cost-effectivealternative because of uncertainty about volume,early field efforts should include measures toestimate the volume of the material within the hotspot. Or, suppose that existing data show that onlyvolatile organics are of concern in the residentialwells. For streamlining the analytical program,chemical analysis of groundwater samples shouldthen be focused on the target compound list


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parameters (U.S. EPA, 1988a), with some analysisof the target analytes list parameters (U.S. EPA,1987g) to confirm their absence.

The site model will also indicate the potential humanand environmental receptors affected by the site. Ifquantitative information is developed as part of theconceptual model, it may be possible to develop apreliminary evaluation of potential risks toreceptors. Experience and judgment can be used tofocus on the contamination that causes the greatestrisk or, if standards are available [such as maximumcontaminant levels (MCLs)], they can be used toidentify potentially affected receptors and the needto initiate remedial action (see Section 2.6).

The site model can also help identify preliminaryremedial action alternatives. For example, ifcontaminated groundwater from the landfill is beingused for residential water supply, then preliminaryremedial action alternatives could include any of thefollowing, depending on the site conditions:alternative water supply, online water treatmentssystems for each household, capping to preventdownward percolation of precipitation andassociated transport of the contaminants from thelandfill to the groundwater, and a slurry wall toprevent additional horizontal movement of thecontaminated groundwater.

2.6 Risk Assessment

The risk assessment is initiated to help to determinewhether the contaminants of concern at the sitepose a current or potential risk to human health orthe environment and to help determine whetherremedial action is warranted. The assessments aresite-specific and may vary in the exent to whichqualitative and quantitative analyses are utilized,depending on the complexity and particulars of thesite, as well as the availability of pertinent ARARs,and other criteria and guidance.

The Risk Assessment Guidance for Superfund:Human Health Evaluation Manual (U.S. EPA,1989k) describes a preliminary identification ofpotential human exposure that is included in thedevelopment of the work plan and the Sampling andAnalysis Plan. This assessment is based on existingdata and information and on the conceptual site

model and is designed to identify data gaps, providea focus for the RI/FS, and provide support forremediation to proceed, if appropriate.

The baseline risk assessment is a quantitative,chemical-oriented evaluation of the potential threatsto human health and the environment that would beposed by a site in the absence of any remedialaction, i.e., the no-action alternative. The baselinerisk assessment is usually quantitative, althoughqualitative analysis may be appropriate andsufficient. A baseline risk assessment identifies andcharacterizes the toxicity of contaminants ofconcern, potential exposure pathways, potentialhuman and environmental receptors, and the extentof expected impact or threat under the conditionsdefined for the site. The baseline risk assessmentcan be used as a tool to streamline remedial actiondecisions by identifying areas where remediationshould proceed immediately (see Section 3.7). Therisk assessment for comparison of remedialalternatives is designed to identify potential threatsto human health or the environment that may arisefrom the execution of various types of remediationactivities. Section 6.3 presents a comparativeanalysis of alternatives for an example municipallandfill site.

The preliminary identification of exposures isconducted during the scoping of the RI/FS and isbased on information from the PA/SI and possiblyother previous investigations. This exercise uses thisexisting information to identify the potential area ofcontamination, chemicals of concern, routes ofcontaminant transport, and potential exposurepathways to identify data needs and to focus theRI/FS. Because options for remedial action atmunicipal landfill sites are limited, it may be possibleto use this preliminary information, with the additionof toxicity information or ARARs to initiateremedial action, if appropriate. Specifically, earlyaction may be warranted when human health orenvironmental standards for one or morecontaminants in a given media are clearlyexceeded. However, because there isoften not a lot of data available at thisstage, or because data is of questionable quality, itmay not be possible to justify an early or interimremedial action at this stage. However, if the


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need for an interim or early action is suspected(e.g., temporary landfill cover, groundwaterremediation, respectively) but insufficient data areavailable, these data needs should be identified andthe corresponding data should be collected early inthe RI process. This may allow for decisions onpotential early or interim remedial actions to bemade during the baseline risk assessment (Section3.7). Detailed information can be found on scopingrisk assessments in the documents Risk AssessmentGuidance for Superfund--Human HealthEvaluation Manual (U.S. EPA, 1989j), and RiskAssessment Guidance for Superfund--Environmental Evaluation Manual (U.S. EPA,1989c).

2.7 Preliminary Remedial ActionObjectives and Goals

Preliminary remedial action objectives and goals aredeveloped during the scoping of the RI/FS to assistin identifying preliminary remedial actionalternatives and RI data requirements. Remedialaction objectives are general descriptions of whatthe remedial action is expected to accomplish. Thepreliminary remedial action objectives are based onthe existing data for the site and the conceptual sitemodel. Remedial action objectives are aimed atprotecting human health and the environment andshould specify:

• The contaminant(s) of concern

• The exposure rate(s) and receptor(s)

• An acceptable contaminant level or rangeof contaminant levels for each exposureroute

Examples of general remedial action objectives formedia of concern at municipal landfill sites arepresented in Table 2-2.

Remedial action goals are a subset of the remedialaction objective; the remedial action goals consist ofchemical concentrations that are protective andserve as specific numeric goals for the remedialaction. Preliminary remedial action goals should bedeveloped with the preliminary ARARs andexposure assessment. An example of a preliminaryremedial action goal would be to prevent ingestionof groundwater containing TCE above 5

micrograms per liter. In this example, thepreliminary remedial action goal is based on theMCL for TCE.

It is necessary that both the preliminary riskassessment and preliminary ARARs be used indeveloping the preliminary remedial action goals. Adescription of the preliminary risk assessment ispresented in Section 2.6.

As part of identifying remedial action goals,ARARs that typically apply to municipal landfillsites are divided into three types:

• Chemical-specific ARARs (MCLs,MCLGs, etc.)

• Location-specific ARARs (floodplains,wetlands)

• Action-specific ARARs (performancedesign standards)

Potential federal ARARs that may affect municipallandfill sites are discussed in Section 5 of thisreport.

To assist in developing preliminary remedial actiongoals, an ARARs table should be developed andshould include identifiable contaminants of concern,affected media, regulatory agencies concerned withthe media (federal, state, or local), potentialremedial action alternatives (see Section 2.8), andregulatory agencies concerned with that action. Amore detailed list of chemical concentrations will begenerated during development of the DQOs.

Promulgated state ARARs that are more stringentthan federal requirements and have been identifiedin a timely manner must also be included (althoughthey may later be waived if they have not beenconsistently applied). In particular, the stateARARs for landfill cap design, extracting andmonitoring landfill gas, or discharging contaminatedgroundwater should be incorporated. It is importantthat care be used in identifying andeliminating potential ARARs at this stageof the scoping process. In developingremedial action goals, "to-be-considered"(TBC) material such as proposed MCLsshould also be evaluated. TBC material


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Table 2-2PRELIMINARY IDENTIFICATION OF REMEDIAL ACTION OBJECTIVES

FOR MEDIA OF CONCERN AT MUNICIPAL LANDFILL SITES

Environmental Media Remedial Action Objective

Soils/Landfill Contents (Primarilyfrom hot spots)

Prevent direct and dermal contact with, and ingestionof contaminated soil/landfill contents

Air/Dust Prevent inhalation

Landfill gas Prevent inhalation and explosion

Surface water Prevent ingestion, adsorption, and bioconcentration

Sediment Prevent ingestion, adsorption, and bioconcentration

Groundwater Prevent ingestion and dermal adsorption

Prevent migration to surface waters

Leachate Seeps Prevent onsite inhalation and dermal adsorption

Prevent migration to surface waters

includes nonpromulgated advisories and guidanceissued by the federal or state government, and oftenreflects the latest scientific information on healtheffects, detection limits, and technical feasibility.

2.8 Preliminary Remedial Technologies

2.8.1 Development of Preliminary RemedialAction Alternatives

Preliminary identification of remedial actionalternatives for each medium of interest shouldbegin after the identification of the preliminaryremedial action objectives. Developing thepreliminary remedial action alternatives at this timeand before determining the RI scope has severaladvantages:

• Defining the degree of detail necessary indelineating the extent of groundwater orsoil contamination

• Identifying data needed for evaluatingremedial action technologies

• Identifying action-specific ARARs thatmay influence the scope of RI activities

The number of practicable remedial actionsavailable for municipal landfills is limited. They arebased on previous experience, engineeringjudgment, and the NCP expectations. As stated inthe NCP, EPA expects that containmenttechnologies will generally be appropriate for wastethat poses a relatively low long-term threat orwhere treatment is impracticable (40 CFR Sec.300.430(a)(iii)(A)). In addition, U.S. EPA expectstreatment to be considered for identifiable areas ofhighly toxic and/or mobile material that constitutethe principal threat(s) posed by the site (40 CFRSec. 300.430(A)(iii)(C)). Remedial actions whichare most practicable for municipal landfill sites arediscussed in more detail in Section 4.

The remedial action alternatives developed at thistime will be refined throughout the RI/FS. Althoughthese alternatives will direct the sitecharacterization activities and will form the basis forthe FS, they do not necessarily have to limit thealternatives considered later in the FS. However, ifalternatives that are not identified here are laterconsidered in the FS, it may be necessaryto collect additional site data in a


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second phase of the RI. This approach maycontradict the goal of streamlining the RI/FS formunicipal landfill sites, and it is therefore importantthat potentially viable alternatives are not eliminatedtoo early in the process. On the other hand,alternatives should be ruled out at this stage if theyare clearly unsuited for the site (that is, technicallyinfeasible or inappropriate for the site and wastecharacteristics) or if the costs are grosslyexcessive. An example of an impracticablealternative might be excavation and incineration ofthe contents of a landfill that contains more than100,000 cubic yards of waste.

As stated previously, remedial action objectives aredeveloped as a first step in identifying remedialaction alternatives. General response actions (forexample, treatment or containment) are thenidentified to satisfy the remedial action objectivesfor each medium of concern. Technology types (forexample, chemical treatment) necessary forachieving each remedial action objective areidentified, followed by the identification andevaluation of technology process options for eachtechnology. Uncertainties about existing siteconditions that preclude choosing a remedial actionalternative should be highlighted to focus sampledesign, collection, and analytical methods.

The site characterization proposed at municipallandfill sites (see Section 3 of this report) reflectsthe number of remedial alternatives available.Several technologies or alternatives are unlikely tosurvive screening in the FS for effectiveness,implementability, or cost reasons. These alternativesshould be eliminated in the preliminary screeningstage or as potential alternatives are beingdeveloped. As an example, complete excavation ofa large landfill with subsequent treatment ordisposal is not generally feasible because the costswould be grossly excessive for the effectivenessthey provide. Additionally, excavation of a landfillmay cause greater risks than it prevents. Likewise,treatment or offsite disposal is not typicallyconsidered for landfill contents because most of thewaste within landfills is a heterogeneous mixture ofmaterials.

Remedial action alternatives for landfill sites arepractically limited to source control by capping andpossibly removal or treatment of hot

spots, groundwater extraction and treatment, andlandfill-gas control. Onsite surface water,sediments, and wetlands are typically addressed byeither source control or groundwater treatment.These alternatives are often combined withinstitutional controls, alternative water supply, orfencing for a complete remedial action. As with allSuperfund sites, the no-action alternative must alsobe evaluated for all media. This alternative involvesno additional activities by EPA, thereby providing abaseline for evaluating other alternatives.

Figure 2-5 portrays a conceptual model foridentifying technologies that will lead toachievement of specific remedial action objectivesat municipal landfill sites.

2.8.2 Review of Remedial Technologies inCERCLA Landfill RODs

To identify the most viable remedial technologiesfor use at municipal landfill sites on the NPL,CERCLA landfill RODs through 1989 werereviewed. Table B-1, in Appendix B of thisdocument, lists RODs that were reviewed. Asource control ROD has not yet been completed forsome of the sites, and a footnote in Table B-1indicates those sites where partial remedies havebeen implemented to date (for example, remediesfor groundwater contamination). The informationpresented in this section is based on the NCPexpectations and the remedies outlined in the RODdocuments. Since the ROD precedes the remedialdesign and remedial action (RD/RA) phase, someof the remedies indicated may not have beenimplemented yet. However, the information is stillvaluable for remedy selection purposes. Additionalinformation on the status of specific remedialactions can be gathered by contacting the EPARegional office in which a specific ROD waswritten.

A comprehensive list of the technologies used atspecific sites in each of the EPA Regions is alsopresented in Appendix B (Table B-2). Whenconducting a feasibility study for a specific site, anEPA RPM could use this list to identify sites withinhis or her region for which the same technologieswere considered. Additional information could thenbe gathered on those sites to help in the FS process.Table B-3, also included in Appendix B, presents a


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summary by EPA Region of the frequency withwhich specific technologies were implemented atthe CERCLA municipal landfill sites. Thisinformation was used to determine whichtechnologies appear to be most practicable forCERCLA municipal landfill sites based on pastexperience.

Table 2-3 presents brief descriptions of remedialtechnologies that could be applied to variousenvironmental media at municipal landfill sites.These technologies were identified on the basis ofthe ROD review mentioned above. Also included inthis table are comments that can assist the RPMduring development of remedial action alternatives.The evaluation comments identify situations wherea technology may be practicable, and therefore,worthy of consideration. A detailed description ofthe most practicable technologies, including the datarequirements to evaluate these technologies, can befound in Section 4 of this report.

The need for treatability testing to evaluate remedialtechnologies should be identified during projectscoping. During scoping, a literature survey shouldbe conducted to gather information on atechnology's applicability, performance,implementability, relative costs, and operation andmaintenance requirements. If practical candidatetechnologies have not been sufficientlydemonstrated or cannot be adequately evaluated onthe basis of available information (e.g.,characterization of a waste alone is insufficient topredict treatment performance or the size and costof treatment units), then treatability testing shouldbe performed. The treatability testing programshould be designed and implemented during the RI,while other field activities are underway. Additionalinformation on treatability studies can be found inthe documents titled, Guide for ConductingTreatability Studies under CERCLA (U.S. EPA,1989i) and Summary of Treatment TechnologyEffectiveness for Contaminated Soil (U.S. EPA,1989k).

2.9 Objectives of the RI/FS

The overall objectives of the RI/FS are to:

• Complete a field program for collectingdata of known and acceptable quality to

evaluate the type, extent, and magnitude ofcontamination in the surface andsubsurface soils, landfill gas, groundwater,surface water, and sediment of ponds andwetlands

• Determine the present and future risks tohuman health and the environment fromexisting contamination

• Develop and evaluate remedial actionalternatives where unacceptable risks areidentified

If a risk to human health or to the environmentexists and remedial action is necessary, theobjective of the RI/FS is to select a cost-effectiveremedial action that minimizes or eliminatesexposure to contaminants from the landfill.Achieving this objective requires a series ofdecisions involving several interrelated activities.These activities are based on the work plan, whichspecifies the information necessary for developinga cost-effective data-collection program and forsupporting subsequent decisions.

During scoping, decisions are made to identify theremedial action alternatives that could beimplemented if certain site conditions were met.Information about a site is gathered to determinewhether the site meets the conditions that wouldallow a particular alternative to be implemented.The objectives of the RI are therefore tocharacterize the site to assess if risks to humanhealth or to the environment are present and toprovide sufficient information to develop andevaluate remedial action alternatives. Physicalinformation about the site is necessary todifferentiate among the technologies available foreach remedial action alternative. This information isobtained during the RI. In addition to specific fieldtasks, the RI objectives should address the broadproject goals. If this information has not beenpreviously collected during the initial site scoping, itmust be collected during the RI. This informationincludes characterizing the landfill for theenvironmental setting, the proximity and size ofhuman population, the nature of the problem(s), thetreatability testing for contaminated groundwaterand leachate (and possibly for hot spots), and thepotential remedial actions.


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Table 2-3REMEDIAL ACTIONS USED AT LANDFILL SITES

Page 1 of 7

Environmental MediaGeneral Response

Actions Remedial Technologies Process Options Description Evaluation Comments

Soils/Landfill Contents No Action No action. Required by NCP to be carried throughdetailed analysis of alternatives.

Access Restriction Deed Restrictions All deeds for property within potentiallycontaminated areas would includerestrictions on use of property.

Potentially viable.

GroundwaterRestrictions

Permits All deeds for property with potentiallycontaminated areas would includerestrictions on development and domesticuse of groundwater.

Potentially viable.

Fencing Security fences installed around potentiallycontaminated areas to limit access.

Potentially viable.

Containment Surface Controls Grading Reshaping of topography to manageinfiltration and run-off to control erosion.

Potentially viable.

Revegetation Seeding, fertilizing, and watering until astrand of vegetation has established itself.

Potentially viable.

Cap Native Soil Uncontaminated native soil placed overlandfill.

Viable in cases where direct contact/erosionare prime threats. Also may be viable incases where majority of source is belowwater table and leaching is not a significantrelease mechanism. Unless engineered todo so, will not result in reduction ininfiltration.

Single barrier FML liner or compacted clay over site.Usually protected with additional fill above,and topsoil. Clay cap is normally 2 feetthick.

Potentially viable in situations where it isnot necessary to comply with RCRASubtitle C.

Double barrier Compacted clay covered with a syntheticmembrane (20 millimeter minimum)followed by 1 foot of sand and 1.5 feet offill and 6 inches of topsoil to provideerosion and moisture control and freeze-thaw protection.

Potentially viable. Provides maximumprotection from exposure due to directcontact. Also, this is the most effectivecapping option for reducing infiltration incompliance with RCRA guidance.


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Page 2 of 7



Soils/Hot Spots Removal Excavation MechanicalExcavation

Use of mechanical excavation equipment toremove and load landfill wastes fordisposal.

Potentially viable for hot spot areas. Mayrelease VOCs to the atmosphere posing athreat to nearby residents. Although VOCrelease are usually controllable, potential forfires and explosions from methane gaspresent.

Drum Removal Excavation of subsurface drums applies tohot spots areas. A drum grappler, a drumcradle, or a sling attached to a backhoe orcrane, or a front-end loader can be usedfrom drum removal.

Potentially viable for hot spot areas.Potential for fires and explosions fromflammable material.

Consolidation Refers to consolidation under a landfill capof excavated material from hot spot areas.

Potentially viable for hot spot areas.

Disposal Onsite RCRA Type Landfill Permanent storage facility onsite, doublelined with clay and a synthetic membraneliner and containing a leachate collection/detection system.

RCRA landfills are usually not constructedonsite because of typically poor sitecharacteristics and great expense.

Disposal Offsite RCRA Landfill Transport of excavated soil to a RCRApermitted landfill.

Potentially viable for hot spot areas. RCRALand Disposal Regulations may requiretreatment of waste prior to disposal.

Soil Treatment Thermal Treatment Onsite Incineration Landfill wastes are thermally destroyed in acontrolled oxygen sufficient environment.

Potentially viable for hot spot areas. Highconcentration of inorganics would inhibitefficiency. May require pretreatment fordebris.

Low TemperatureThermalVolatilization

VOCs removed from soil in a drying unit. Potentially viable for VOC hot spot areas.However, it is rarely effective by itselfbecause of mixed nature of waste materialincluding inorganics and nonvolatilefraction of organics, and may requirepretreatment of debris.


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Page 3 of 7



Soil/Hot Spots(Continued)

In Situ Treatment Biological Treatment Biodegradation Soils seeded with microorganisms andnutrients to allow biological degradation.

Potentially viable for hot spot areas. Pilottesting is required to design thebiodegradation process. Effectiveness isuncertain since results have not beendemonstrated with diverse mixed wastestypically present at municipal landfill sites.

Physical Treatment Vapor Extraction Volatile organics stripped from soil andrecovered in vapor form through extractionwells.

Potentially viable--applicable for removal ofVOCs; inorganic and semivolatilecontamination would remain..

Solidification/Stabilization

Soil mixed with an pozzolanic/cementmaterial which can solidify and reducemobility of contaminants.

Potentially viable for hot spot areas.Effective for soils contaminated withinorganics and low concentrations oforganics.

Offsite Treatment RCRA Incinerator Incineration of contaminated soils at aRCRA-permitted facilities.

Rarely viable due to unavailability andexpense.

Air/Dust Containment Dust Controls Cover/Cap Uncontaminated native soil placed overlandfill.

Potentially viable for dust control.

Groundwater andLeachate

No Action No Action. Required by NCP to be carried throughdetailed analysis of alternatives.

InstitutionalControls

Alternate Water Supply Public Water Supply Residents will be connected to public watersupply.

Potentially viable.

Containment Vertical Barriers Slurry Wall Trench around site or hot spot is excavatedwhile filled with a bentonite slurry. Trenchis backfilled with a soil- (or cement)bentonite mixture.

Potentially viable--effectiveness depends onsite characteristics. Slurry wall should bekeyed into aquitard or bedrock.

Horizontal Barriers Bottom Sealing Controlled injection of slurry in notchedinjection holes to produce horizontal barrierbeneath site.

Potentially viable--however, very rarelyused because of ineffectiveness inachieving an adequate seal.

Collection Extraction Extraction Wells Series of wells to extract contaminatedgroundwater.

Potentially viable. May include perimeterwells to collect leachate as well asdowngradient wells to capture offsitemigration of contaminated groundwater.


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Page 4 of 7



Groundwater andLeachate (continued)

Treatment (may alsoapply to surfacewater)

Leachate Collection Leachate Drains/Collection Trench

System of perforated pipe laid in trenchesonsite to collect contaminated groundwaterand lower water table.

Potentially viable.

Biological Treatment Aerobic The use of aerobic microbes to biodegradeorganic wastes.

Potentially viable for organics. Sludgeproduced.

Anaerobic The use of anaerobic microbes tobiodegrade organic wastes.

Potentially viable for organics. Sludgeproduced.

Chemical Treatment Ion Exchange Contaminated water passed through a bedor resin material where exchange of ionsoccurs between the bed and water.

Potentially viable.

Oxidation Oxidizing agents added to waste foroxidation of heavy metals, unsaturatedorganics, sulfides, phenolics, and aromatichydrocarbons to less toxic oxidation states.

Potentially viable.

Metals Precipitation Inorganic constituents altered to reduce thesolubility of heavy metals through theaddition of a substance that reacts with themetals or changes the pH.

Potentially viable.

pH Adjustment Neutralizing agents (such as lime) added toadjust the pH. This may be done toneutralize a waste stream or to reduce thesolubility of inorganic constituents as partof the metals precipitation process.

Potentially viable.

Physical Treatment Granular ActivatedCarbon (GAC)Adsorption

Passage of contaminated water through abed of adsorbent so contaminants adsorb onthe surface.

Potentially viable.

Air Stripping Mixing of large volumes of air with waterin a packed column or through diffusedaeration to promote transfer of VOCs fromliquid to air.

Potentially viable.

Sedimentation Suspended particles are settled out as apretreatment or primary treatment step.

Potentially viable.


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Page 5 of 7



Groundwater andLeachate (continued)

Treatment(continued)

Physical Treatment(continued)

Sand Filtration Used to filter out suspended particles. Maybe preceded by coagulation/flocculationstep to increase the effectiveness of sandfiltration.

Potentially viable.

Disposal Onsite Discharge Aquifer Reinjection Extracted, treated groundwater is reinjectedinto the aquifer to accelerate the cleanup

May not be viable due to state ARARs.

Offsite Discharge POTW Extracted groundwater discharged to localPOTW for further treatment.

Potentially viable. Requires extensivenegotiations with POTW.

Groundwater Monitoring Groundwater monitoring of existing or newwells to detect changes in groundwatermovement or contamination.

Potentially viable.

Landfill Gas (LFG) Collection Passive Vents Pipe Vents Atmospheric vents are used for ventingLFG at points where it is collecting andbuilding up pressure. Vents are often usedin conjunction with flares.

Potentially viable.

Trench Vents Constructed by excavating a deep narrowtrench surrounding the waste site orspanning a section of the area perimeter.The trench is backfilled with gravel,forming a path of least resistance throughwhich gases migrate upward to theatmosphere. Trenches are most successfullyused where the depth of LFG migration islimited by groundwater or an imperviousformation.

Potentially viable.

Interceptor Trenches Used when a landfill contains saturatedrefuse near the surface. Constructed byexcavating a deep, narrow trenchsurrounding the waste site or along asection of the perimeter. Backfilled withgravel to form a path of least resistance.

Potentially viable.


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Page 6 of 7



Landfill Gas (LFG)(Continued)

Collection(Continued)

Active Systems Extraction Wells Applied extraction vacuum will serve towithdraw LFG in both the horizontal andvertical directions. Wells are connected by acollection header which leads to ablower/burner facility. Vacuum blowersserve to extract the LFG from the wells andpush the collected gas through a free ventor waste gas burner.

Potentially viable.

Air Injection System Wells are constructed in the natural soilbetween the landfill and threatenedstructures. A blower pumps air into thewells, creating a pressurized zone whichboth retards LFG flow and dilutessubsurface methane concentrations.

Potentially viable. Application of thistechnology is site specific. Injection wellsmust be located a sufficient distance fromthe landfill to prevent forcing air into therefuse. Spacing and depth of wells are alsoimportant.

Treatment Thermal Destruction Enclosed GroundFlares

Enclosed ground flare systems consist of arefactory-lined flame enclosure. Waste issometimes mixed with a supplemental fueland fed through a vertical, open-ended pipe.Pilot burners next to the end of the pipeignite the waste.

Potentially viable--however, could producesecondary air pollutants from the process.

Monitoring Monitoring Wells Potentially viable.

Surface Water andWetlands Sediments

Removal Excavation MechanicalExcavation

Use of mechanical excavation equipment toremove and load contaminated sedimentsfor disposal.

Potentially viable. Potential for secondarymigration of contaminants via surface waterduring excavation.

Dewatering Wells or Trenches Temporary lowering of water table. Usuallydone in conjunction with sediment removal.

Potentially viable way to reduce the risk ofsecondary migration of contaminants duringexcavation.

Disposal Offsite Disposal/Discharge

RCRA Landfill Transport of excavated sediment to aRCRA permitted landfill.

Potentially viable. Treatment may be basedon land disposal restrictions.

Treatment Physical Stabilization Soil mixed with stabilizing reagents (e.g.,lime, fly ash) which can stabilizecontaminants.

Potentially viable for sedimentscontaminated with inorganics and lowconcentrations of organics.

Thermal Treatment Contaminated sediments are thermallydestroyed in a controlled oxygen-sufficientenvironment.

Potentially viable. Ash may requireadditional treatment for inorganics.


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Page 7 of 7



Surface Water Detention andSedimentation

Stormwater Controls GradingRevegegation

Reshaping of topography to manageinfiltration and run-off to control erosion.

Potentially viable. Usually implementedwith the construction of a cap.

Collection Surface Controls Pumping, Diversion,or Collection

Collection of surface water for removal,rerouting, or treatment.

Potentially viable.

Treatment Physical, Chemical, andBiological Treatment

See Grondwater andLeachate ProcessOptions

Treatment of surface water using biological,chemical, or physical treatment to removeorganic or inorganic contaminants. Seedescriptions of process options undergroundwater and leachate treatment.

Potentially viable for small ponds orlagoons. Will usually be done inconjunction with treatment of groundwateror leachate.

Monitoring Gaging Stations Surface water monitoring to measure flowand containment concentration.

Potentially viable.


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Tables 2-4 and 2-5 present more specific RIobjectives for both Phase I and Phase II fieldwork.A phase is defined as a time period whereadditional sample collection may be necessary tocharacterize a site more completely. Activities suchas recontracting for services or remobilizing onto asite would be considered a separate “phase” offieldwork. Ideally, site characterization of bothsources (landfill and hot spots) and other affectedmedia should be conducted in one phase. In somecases, however, because of the site’s complexity,Phase II sampling may be required. Phase I andPhase II sampling are often, but not necessarily,sequential. These investigations can take place onslightly different schedules or take placesimultaneously, depending on the analyticalturnaround time and field observations.

If sufficient information is not collected in a singlephase to characterize a site adequately, it may benecessary to conduct a Phase II investigation.Phase II investigations are more frequently requiredfor potential or existing groundwater contaminationor at landfill sites with nearby wetlands and/orsurface water. Phase I groundwater investigationstypically estimate the plume location and may besufficient to initiate remedial actions for plumecontainment. Phase II groundwater investigationstypically further refine the extent of groundwatercontamination and are typically used to aid in thedesign and implementation of the final responseactions. Similarly, Phase I wetland and/or surfacewater investigations determine if the wetlands orsurface waters are affected, while Phase II wetlands and/or surface water investigations determinethe magnitude and extent of the impact. Phase IIinvestigations for landfill contents and landfill gasare not typically done, because adequateinformation for characterizing these media is usuallyobtained from the Phase I investigation.

2.10 Development of DQOs

DQOs are qualitative and quantitative statementsspecifying the required quality of the data for eachspecific use. DQOs are based on the concept thatdifferent data uses often require data of varyingquality. An example of different data uses for the

RI/FS include site characterization, risk assessment,and alternatives evaluation.

DQO development is begun during generation ofthe conceptual site model and further refined duringdefinition of the preliminary remediation goals.DQOs, however, are not made final or documenteduntil after the RI objectives have been established.There are three objectives in developing DQOs.One is to obtain a well-defined sampling andanalysis plan (SAP). The SAP consists of a fieldsampling plan (FSP) and a quality assurance projectplan (QAPP). The SAP identifies the number andtypes of samples to be collected, the appropriatemethod of analysis, and the reason the informationfrom these samples is necessary to make necessaryremedial decisions. The second objective indeveloping DQOs is to identify the required QA/QCprocedures to ensure the quality of the data beingcollected. The third objective is to integrate theinformation required by the decision makers, datausers, and technical specialists associated with theRI/FS process. This integrated approach allows fora cost-effective RI/FS implementation program.

The DQO process includes three stages foridentifying the data quality needed to characterizea site adequately. The stages are:

• Stage 1. Identify decision types

- Identify and involve decision makers,technical specialists, and other datausers

- Evaluate available information foruncertainty or adequacy for makingdecisions

- Specify the RI/FS objectives and thecritical decisions that would affectpotential remedial actions

• Stage 2. Identify data uses and needs

- Identify data uses and types

- Identify data quality and quantity needs

- Evaluate sampling and analysis options


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Table 2-4PHASE I REMEDIAL INVESTIGATION OBJECTIVES FOR

MUNICIPAL LANDFILL SITES*Page 1 of 4

Activity

Phase I Objectives(Activities Generally Performed After Work Plan is Approved)

Objectives Action

Site Mapping/Site Dynamics Map site and determine topography;determine site boundaries, drainage patterns,and other geophysical features.

Use photogrammetric methods fromaerial photography; conduct fly-over, if necessary.

Geophysical Investigation Investigate presence of buried ferromagneticmaterials (drums) where documentation and/orphysical evidence indicates their presence.

Determine waste fill locations and determinegeologic strata.

Conduct magnetometer and/orground-penetrating radar survey.

Conduct electromagneticconductivity survey.

Geotechnical Investigation Evaluate the physical properties of geologicunit governing transport of contaminants.

Collect data on permeability,porosity, hydraulic head, percentorganic carbon, etc.

Collect data on soil characteristics todetermine if onsite soil can be used as fillmaterial and to determine placement of apotential cap or

Measure soil characteristics such asplasticity index, moisture content,porosity, and permeability.

Identify offsite borrow-source for capconstruction

Survey local area for appropriatematerial.

Evaluate existing cap to determine physicalproperties.

1) Collect data on permeability,porosity, and measure thickness.

2) Determine Atterberg limits.

3) Determine extent of vegetationcover, any vegetative stress, anderosion.

4) Monitor landfill settlement (e.g.,topographic survey and benchmarkinstallation and survey).

Hydrogeologic Investigation Determine depth of wells and screen intervalsfor existing shallow and deep wells.

Obtain soil classification or geologicdata.

Identify and characterize hydrogeologic units. 1) Drill borings around landfill fordevelopment of boring logs to betterdefine the aquifers and confininglayers; drilling through landfillcontents may be conducted afterevaluating health, safety, and otherrisks.

2) Perform down-hole geophysicalsurveys.


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Activity


Objectives Action

Hydrogeologic Investigation(Continued)

Determine direction of groundwater flow andestimate vertical and horizontal gradients.

1) Install monitoring wells and takewater level measurements from newand existing wells.

2) Investigate yield of private andpublic wells.

Determine rate of groundwater flow andevaluate the feasibility of groundwaterextraction.

Install monitoring wells and performhydraulic conductivity tests on newand existing wells; check waterlevels at a maximum of once amonth during the RI.

Meteorological Investigation Determine prevailing wind direction and airspeed to evaluate remedial actions.

Collect and analyze wind speed anddirection data.

Chemical Investigation

Groundwater Identify extent and type of groundwatercontamination to perform an assessment ofhuman health risks.

Install monitoring well in aquifers ofconcern; design monitoring wellnetwork to determine the extent ofthe plume (wells should also belocated in “clean” area to confirmthat the end of the plume is locatedboth vertically and horizontally);collect and analyze samples.

Identify upgradient water quality for eachgeologic unit. Install upgradient monitoring wells

in aquifers of concern.

Determine upgradient concentration. Install monitoring wells upgradientof the landfill and collect andanalyze samples.

Determine source of groundwatercontamination.

Collect and analyze groundwatersamples and compare results to thelandfill waste characteristics andbackground levels.

Determine whether seasonal fluctuationsoccur in contaminant concentrations in thegroundwater and in hydraulic characteristics.

Sample and analyze groundwaterduring different seasons.

Evaluate feasibility of groundwater treatmentsystems.

Obtain COD, BOD, metals, andother conventional water qualitydata.


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Activity


Objectives Action

Leachate Identify extent and type of leachate toevaluate feasibility of groundwater treatmentsystem.

Collect ana analyze leachate data.

Estimate amount of leachate production fromlandfill.

Install leachate wells in or aroundlandfill and measure leachate head.

Perform water balance calculationon landfill.

Surface Water and Sediment Determine viability of treatment technologies. Collect field measurements onRedox and DO.

Determine groundwater and surface waterinteractions during several periods during theRI.

Install staff gauges onsite, surveygauges, measure surface water levelsand groundwater levelsconcurrently.

Determine background concentration ofsurface water and sediment.

Collect and analyze upstream waterand sediment samples.

Collect and compare up- anddowngradient surface water todowngradient groundwater samples;also collect up- and downgradientsediment samples.

Determine surface runoff impact on surfacewater quality; determine the type and extentof contamination in nearby surface waters andsediments.

1) Collect and analyze samples fromnearest leachate seeps and compareto stream water quality.

2) Collect and analyze surface waterand sediment samples at increasingdistances away from the landfill andcompare results to landfill wasteand background levels.

Determine the absence or presence ofcontamination in onsite ponds.

1) Collect and analyze surface waterand sediment samples for onsiteponds.

2) Conduct toxicity testing(bioassay).


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Activity


Objectives Action

Landfill Gas/Air Identify areas within the landfill containinghigh concentrations of explosive of toxiclandfill gas to perform an assessment ofhuman health risks due to air toxics andexplosive hazards, to evaluate the feasibilityof gas collection and treatment, to evaluateneed for immediate action, and to evaluateother remedial actions.

1) Obtain flow-related data fromexisting and newly installed gasvents, estimate emission rates, andperform air modeling.

2) Obtain samples of landfill gasfrom within the landfill using theleachate headwell.

Estimate concentrations of selected VOCsbeing emitted to the atmosphere.

Collect and analyze ambient airsamples.

Landfill Gas/Groundwater Identify areas within the landfill containinghigh concentrations of explosives or toxiclandfill gas to determine if VOCs act or mayact as a source of groundwater contamination.

Obtain flow-related data fromexisting and newly installed gasvents, estimate emission rates, andperform air modeling.

Hot Spots Investigate areal extent, depth, andconcentration of contaminants at hot spots inthe landfill’s contents.

Collect and analyze samples frompotential hot spot areas(documentation and/or physicalevidence must exist to qualify hotspot as “potential”), with moreextensive sampling within confirmedhot spot areas.

Environmental Evaluation Delineate wetlands. Conduct wetlands delineationsurvey.

Determine impact of landfill on nearbywetlands.

Collect and analyze surface waterand sediment from nearby wetlands.

Describe aquatic and terrestrial community invicinity of site and aquatic communitydownstream of site.

Collect or observe aquatic orterrestrial organisms in the vicinityof the site; conduct sensitivereceptor survey.

Determine impact of remedial action onwetlands/flood plains.

Delineate wetlands/flood plain areasin vicinity of site.

*Refer to Section 2, Site Characterization Strategies, for an explanation of when these activities are appropriate.


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Table 2-5PHASE II REMEDIAL INVESTIGATION OBJECTIVES FOR


Activity

Phase II Objectives(Activities Generally Performed After Work Plan is Approved)

Objectives Action

Geophysical Investigation Further investigate probable presence ofburied ferromagnetic materials (drums).

Excavate probable drum burial area.

Geotechnical Investigation Further evaluate the physical propertiesgoverning transport of contaminants throughidentified pathways.

Collect additional data onpermeability, porosity, hydraulichead, percent organic carbon, etc.;model pathways.

Hydrogeologic Investigation Determine depth of wells and screen intervalsfor existing shallow and deep wells.

Obtain additional soil classificationor geologic data; review Phase I RIresults.

Further identify and characterizehydrogeologic units.

1) Drill additional boringsthroughout site for development ofboring logs to better define theaquifers and configuring layers(health, safety, and long-term riskassociated with drilling into thelandfill should be weighed againstthe potential usefulness of the datafor evaluating alternatives).

2) Perform down-hole geophysicalsurveys, as appropriate.

Further determine direction of groundwaterflow and estimate gradients.

Install additional monitoring wellsand take water level measurementsfrom new and existing wells.


Install monitoring wells and performhydraulic conductivity and pumpingtests on new and existing wells;check water levels at a maximum ofonce a month during the RI.


Groundwater Identify extent and type of groundwatercontamination to delineate plume.

Install additional monitoring wells inaquifers of concern; collect andanalyze samples.

Redetermine upgradient concentration if PhaseI results inconclusive

Install additional monitoring wellsupgradient of the landfill and collectand analyze samples.

Further determine whether seasonalfluctuations occur in contaminantconcentrations in the groundwater and inhydraulic characteristics.

Sample and analyze groundwaterwith additional rounds of samplingfrom the same location(s).

Further evaluate feasibility of groundwatertreatment systems.

Obtain additional COD, BOD, andother conventional water qualitydata; initiate treatability studies, asnecessary.


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Table 2-5PHASE II REMEDIAL INVESTIGATION OBJECTIVES FOR


Activity

Phase II Objectives(Activities Generally Performed After Work Plan is Approved)

Objectives Action

Surface Water and Sediment Further determine effect of groundwater onsurface water.

Collect and compare additional up-and downgradient surface water andsediment samples to downgradientgroundwater samples.

Compare additional stream and water levelsduring several periods during the RI.

Install additional staff gauges onsite,survey gauges, measure surfacewater levels and groundwater levelsconcurrently.

Landfill Gas/Air If initial results are inconclusive, identifyadditional areas within the landfill containinghigh concentrations of explosives or toxiclandfill gas to perform an assessment ofhuman health risks due to air toxics andexplosive hazards, to evaluate the feasibilityof gas collection and treatment, and toevaluate other remedial actions.

Obtain additional flow-related datafrom existing and newly installedgas vents, estimate emission rates,and perform air modeling.

Landfill Gas/Groundwater If initial results are inconclusive, identifyadditional areas within the landfill containinghigh concentrations of explosives or toxiclandfill gas to determine if VOCs act or mayact as a source of groundwater contamination.

Obtain additional flow-related datafrom existing and newly installedgas vents, estimate emission rates,and perform air modeling.

Environmental Evaluation Describe aquatic and terrestrial community invicinity of site and aquatic communitydownstream of site on a seasonal basis.

Collect or observe aquatic orterrestrial organisms in the vicinityof the site on a seasonal basis.

*Refer to Section 2, site Characterization Strategies, for an explanation of when these activities are appropriate.


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- Review precis ion , accuracy,representatives, completeness, andcomparability (PARCC) parameters

• Stage 3. Design data collection program

- Assemble data - Design program

Although the elements of Stage 1 can be thought ofas distinct steps, they are continuous, incorporatingadditional information as it becomes available.DQOs should be undertaken in an interactive anditerative manner; DQO elements are continuallyreviewed and evaluated as data are compiled.

The output of the DQO process is a well-definedSAP, with summary information provided in theproject work plan. Documentation is supplied,detailing the type of samples believed to benecessary for each matrix to obtain sufficientrepresentation of site conditions. The desiredPARCC of the chemical analyses are alsodocumented.

Before the DQOs are developed, a detailed list ofpotential ARARs specifying the required chemicalconcentrations should be prepared. In addition, apreliminary risk assessment may be conducted andchemical concentrations relating to a 10-4 to 10-6

risk range should be determined. The purpose of theARARs and risk assessment information is todetermine the contaminants of concern and therequired analytical detection limits. These ARARsshould include both federal and state requirements,because some states may have their own morestringent standards. The detection limits notedduring the assembly of the ARARs should beincorporated in the DQOs.

A combination of laboratory services may be usedto achieve the DQOs so that time and money areused efficiently. There are five levels of datamethodologies and associated quality control thatcan be used during an RI:

• Level I is the lowest quality data butprovides the fastest results. Field screeningor analysis provides Level I data. It can beused for health and safety monitoring andpreliminary screening of samples to identify

those requiring confirmation sampling(Level IV). The generated data canindicate the presence or absence of certainconstituents and is generally qualitativerather than quantitative. It is the leastcostly of the analytical options.

• Level II data are generated by fieldlaboratory analysis using more-sophisticated portable analyticalinstruments or a mobile laboratory onsite.This provides fast results and better-qualitydata than in Level I. The analyses can beused to direct a removal action in an area,reevaluate sampling locations, or directinstallation of a monitoring well network.

• Level III data may be obtained by acommercial laboratory with or without CLPprocedures. (The laboratory may or maynot participate in the CLP.) The analysesdo not usually use the validation ordocumentation procedures required of CLPLevel IV analysis. The analyzedparameters are relevant to the design ofthe remedial action.

• Level IV data are used for riskassessment, engineering design, and cost-recovery documentation. All analyses areperformed in a CLP analytical laboratoryand follow CLP procedures. Level IV ischaracterized by rigorous QC protocols,documentation, and validation.

• Level V data are those obtained bynonstandard analytical procedures. Methoddevelopment or modification may berequired for specific constituents ordetection limits.

• Other. This category includes data obtainedfrom analyses of the physical properties ofsoil, such as Atterberg limits and soilmoisture.

Tables 6-1 through 6-3 in Appendix A of thisreport present an example of a DQO summaryfor an example landfill site. The analyticallevels are mixed to provide an optimalanalytical program. For example, in the case of


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groundwater, Level I data can consist of screeningfor volatile organic compounds (VOCs) using aphotoionization detector, and Level III can beobtained from analyzing for parameters needed fortreatment such as iron and manganese. Level IIdata can consist of analysis of the groundwater byan onsite mobile laboratory. Placement of themonitoring wells can then be readjusted in the field,if necessary. Level IV data would provide theresults of site characterization and risk assessment.Level V data would be obtained for chemicals suchas vinyl chloride (for vinyl chloride, the detectionlimit required for risk assessment, based on a 10-6

cancer risk, is lower than the detection limitestablished in CLP methodology).

The first phase of DQO development is completeonce the field program has been defined. The RItasks necessary to achieve the DQOs must bespecified in the work plan and may be altered orredefined, depending on the results of fieldwork.Additional information on DQOs can be found in

the documents titled Data Quality Objectives forRemedial Response Activities, Volumes I and II(U.S. EPA, 1987b and U.S. EPA, 1987c).

2.11 Section 2 Summary

This section illustrates the key components ofscoping an RI/FS for a CERCLA municipal landfillsite. The primary purpose of scoping an RI/FS is todivide the broad project goals into manageable tasksthat can be performed within a reasonable period oftime. The broad project goals for an RI/FS at anySuperfund site are to provide the informationnecessary to characterize the site, define sitedynamics, define risks, and develop a remedialprogram to mitigate potential adverse public healthand environmental impacts. To obtain the necessarydata to achieve these goals, Section 3 presentsvarious site-characterization strategies and theassociated field tasks for municipal landfill sites.


3-1

Section 3SITE CHARACTERIZATION STRATEGIES

Once a work plan has been developed, fieldactivities are undertaken to further characterize thesite. The purpose of site characterization is toassess the risks to human health and theenvironment posed by the site and to develop aremediation strategy to mitigate these current andpotential threats.

As described in Section 2, site characterizationbegins with an evaluation of previous data andanalytical results. This information is combined withfield investigations to fill in data gaps and to testhypotheses about the site developed during scoping.In this section, characterization activities aredescribed by the different media that might becontaminated by a municipal landfill site, anddifferent site characterization strategies for twotypes of municipal landfill sites are discussed.

Most municipal landfill sites on the NPL areco-disposal facilities that may or may not haveknown or suspected hot spots. Hot spots consist ofhighly toxic and/or highly mobile material andpresent a potential principal threat to human healthor the environment (see 40 CFR Sec.300.430(a)(1)(iii)(C)). Excavation or treatment ofhot spots is generally practicable where the wastetype or mixture of wastes is in a discrete, accessiblelocation of a landfill. A hot spot should be largeenough that its remediation will significantly reducethe risk posed by the overall site, but small enoughthat it is reasonable to consider removal and/ortreatment.

The two principal types of municipal landfills are asfollows:

• Landfill Type I. This is a co-disposalfacility where records or some other formof evidence indicate that hazardous wasteswere disposed of with municipal solidwastes. There are no known or suspectedhot spot areas, and historical records andphysical evidence, such as aerialphotographs and the site visit, do notdocument any discrete subsurface disposalareas.

• Landfill Type II. This is a co-disposalfacility where approximate locations of hotspots are known or suspected, eitherthrough documentation, physical evidence,or consistent employee/resident interviews.Small- to moderate-sized landfills (forexample, less than 100,000 cubic yards)that pose a principal threat to human healthand the environment are included in thisgroup because it may be appropriate toconsider excavating and/or treatment of thecontents of these landfills.

Placing municipal landfill sites into these twocategories allows more efficient characterizationthrough avoidance of extensive and unnecessarysampling, and streamlines the RI/FS process. Itshould be noted that the distinction between theselandfill types will not always be clear. Therefore,the application of the approaches described belowshould be flexible and adapted to the specific sitecharacteristics.

In general, categorizing landfills into different typesallows the site characterization to focus ondetecting and then characterizing hot spots.Because there are no known or suspected hotspots, the feasibility study for Landfill Type I canfocus on capping alternatives as part of an operableunit. This focused feasibility study could precede orbe conducted concurrently with the groundwaterinvestigation, particularly at sites where leachate isnot a problem. At Landfill Type II, more effort canbe expended on characterizing and remediating thehot spots. At these sites, the feasibility studies canfocus on the operable units and remedial actionalternatives for these units.

Site characterization strategies for the landfill typesare described below by medium. The focus of thedescriptions is primarily on those media most oftenrequiring remediation at municipal landfill sites (e.g.,groundwater, leachate, landfill contents/hot spots, and landfill gas). Other areassuch as wetlands, surface water, and sedimentsare also discussed, but in less detail,since the nature of contamination is not unique


3-2

to municipal landfill sites and information is readilyavailable from other sources. The descriptions wereprepared as if the site investigations were done inonly one medium. However, at most sites, this willnot be the case. The user should read alldescriptions applicable to the site, and coordinatesampling and investigation efforts as described inSection 2.10, Development of DQOs. Samplerequirements should be reviewed in all media ofconcern to determine the most efficient and concisemethod of obtaining data.

Site characterization efforts may generate a largeamount of data. Organization of the data is essentialto proper interpretation. During planning of surveysor well installations, consideration should be given todata organization--mapping, geologic cross sections,grid points, etc.--as well as to organization of resultsfrom field instrument analyses.

3.1 Groundwater

Characterizing a site’s geology and hydrogeology aswell as developing an understanding of the regionalgeology and hydrogeology is paramount to the sitecharacterization process. Data gathered for sitecharacterization of geology and hydrogeologysignificantly affect the selection of an appropriateremedial action strategy. The type of cap selected,the location of the groundwater extraction systemand amount of groundwater extracted, and thenecessity for collecting and treating landfill gas areall affected by the geology and hydrogeology of thesite. General procedures for Phase I and Phase IIsite characterizations of regional and site-specificgeology and hydrogeology are described below.More specific information on placement ofmonitoring wells by landfill type is given in Section3.1.3.

All Phase I and Phase II characterization activitiescan be done at both types of landfill sites.Depending on the type and quality of data gatheredboth before and during development of the RI/FSwork plan, some of these activities may have beenperformed. Further information on characterizingsite hydrogeology is available in Guidance onRemedial Actions for ContaminatedGroundwater at Superfund Sites (U.S. EPA,

1988e).

3.1.1 Groundwater Investigations

The characterization of the groundwater beneathand near a site is often completed in two phases.The initial site characterization study is based on areview of existing literature describing the regionaland local geology and site history. This literatureincludes local government records and aerialphotographs. The second phase is based on thereview of existing literature and is used to design asampling and monitoring program to answerquestions developed during the first phase.

The initial characterization of the hydrogeology andthe groundwater conditions (done before or duringthe limited field investigation) depends on anunderstanding of the relationship of the site geologyand groundwater flow characteristics. At aminimum, a description of the site geology shouldinclude the lithology of geologic units underlying thesite that are contaminated or used as Class I or IIaquifers, and the relationship among the units.

3.1.1.1 Phase I Site Characterization

In Phase I, geological information about the area,gathered during the limited field investigation, andintrusive activities such as drilling and geophysicalsurveys (described in further detail in Section 3.2)is reviewed. The data gathered for the Phase I sitecharacterization should be sufficient to provide ageneral understanding of the hydrogeological regimeof the region and its relationship to the landfill. Theinformation should give a general picture of thelocal stratigraphy, depositional environments of thestrata, the tectonic history as it relates to tilting,folding, or fracturing of the strata present,groundwater depth and flow direction, the units thatare contaminated or used as Class I or II aquifers,and local groundwater uses, including the effects ofpumping (withdrawal). After this information hasbeen gathered and reviewed, a regional conceptualmodel of the Hydrogeology should be developed(see Section 2.5). Future field investigations arebased on this model and are developed to fill in thedata gaps and to answer hypotheses presented bythe model.


3-3

This conceptual model is revised as newinformation is developed from the field investigation.

A limited number of boreholes with wells andpiezometers monitoring discrete water-bearingzones should be installed during the Phase I sitecharacterization. For characterization purposes, itmay be useful if at least one borehole is drilled intothe first confining layer beneath the uppermostaquifer (water table or unconfined aquifer).Boreholes and monitoring wells should be drilled atthe site in numbers and locations sufficient tocharacterize the geology, water levels, andgroundwater flow beneath the site. Sufficientborings and wells should be installed to permit theconstruction of meaningful geologic cross sections.The density of data points should describe therelationships between geologic and hydrologicconditions. For example, if groundwater flow iscontrolled by fractures in tilted strata, a sufficientnumber of wells should intersect or cross thefractured strata.

Information derived from the borings should besufficient to:

• Correlate stratigraphic units

• Identify zones of possible high hydraulicconductivity

• Identify confining layers

• Identify any unusual or unexpectedgeological features such as faults,fractures, facies changes, solutionchannels, etc.

In some cases, samples should be collected to testfor geotechnical and geochemical parameters.Tests could include cation exchange capacity ifmetals contamination is expected, bulk density andmoisture content for treatment characteristics,permeability and porosity for containment orextraction effectiveness, and analytical parameters(e.g., TAL metals, TCL organics) for contaminantfate and transport.

Each boring should be documented with a boring logthat describes:

• Soil classifications or rock types

• Structural features such as fractures anddiscontinuities

• Depth to water

• Depth of boring and reason for termination

• Development of soil zones and verticalextent

• Any evidence of contamination

• Geotechnical information such as blowcounts, color, grain-size distributions, andplasticity

• Well construction details (if boring isfinished as a monitoring well)

At least the first borehole should be sampledcontinuously to determine if the subsurfacematerials are variable. Samples should be collectedfrom every significant stratigraphic contact andformation, especially the confining layers.Subsequent borings may be sampled atpredetermined intervals that are justified based onthe subsurface characteristics. All boreholes inwhich piezometers or monitoring wells are notinstalled must be properly abandoned. Soil samplesshould be described by a qualified geologist,geotechnical engineer, or soil scientist.

Groundwater quality samples that identify the extentand type of contamination should be collected in theaquifer of concern. The aquifer of concern is theunit where contamination is known or suspected orone that is used as a Class I or II aquifer.Upgradient water quality for the aquifers ofconcern should also be established. Seasonalfluctuations in contaminant concentrations should bedetermined. Well pairs may be required todetermine the vertical direction of flow between thewater table and a lower aquifer. The deep well ofthe pair can also determine if the contamination hasentered a lower aquifer. Wells penetrating loweraquifers must be constructed with care so that theydo not become conduits for contamination. If suchwells are intended only to determine the hydraulicrelationship between two aquifers, theyshould not be placed downgradient from apotential contaminant source. They should only


3-4

be placed downgradient from a source if thehydraulic relationships of that area may be differentthan at other locations or if contamination issuspected or documented.

The Phase I site characterization should be flexibleto accommodate revisions to the scope asinformation becomes available. For example,groundwater sampling results may be obtained witha fast turnaround time during the Phase I fieldactivities. This would allow refining the investigationprogram in the field to delineate contamination andpossibly limit the need or extent of a Phase IIinvestigation.

3.1.1.2 Phase II Site Characterization

Phase II site characterization is warranted if thedata obtained in Phase I are insufficient to assessrisks to human health and the environment and todevelop and evaluate remedial action alternatives.If the information obtained in Phase I cannotanswer questions on the direction and rate ofgroundwater flow, effectiveness of an observed orpresumed aquiclude, extent of observedcontamination, or location of known or presumedcontamination, a Phase II site characterization isnecessary. For instance, descriptions from theboring logs may indicate that a confining layer ispossibly continuous across the site, but aquifer testsor analytical data indicate that the confining layer isdiscontinuous. In this case, additional borings, wells,and aquifer tests may be necessary to resolve theconflicting data.

Phase II site characterizations are also necessaryif previously unknown hot spots are detected duringthe Phase I site activities and additional borings orwells are beyond the capability of the driller. Datashould be obtained during Phase II sitecharacterization activities to place the hydrogeologyof known and newly discovered hot spots in contextwith the geology of the site and region.

During this phase, the compatibility of the naturallyoccurring clay minerals and other rock andsoil-forming materials with any known chemicals inthe landfill should be examined. Soil and rocks witha high carbonate content will be attacked by acids,increasing their permeability. Clays similar tobentonite can be ineffective barriers to themigration of some organic compounds. Laboratory

determination (X-ray diffraction) of the clay typesmay be necessary.

Data gathered during Phase II site characterizationactivities should primarily be directed towardsidentifying potential targets and optimizing theanalytical program. Additional monitoring wellsshould be installed, and groundwater and leachatesamples should be collected from areas wherePhase I activities indicate that contamination hasspread or is spreading. Sampling in “clean” areasshould be minimized unless Phase I activities did notadequately define these areas. Monitoring wells areneeded to identify the limits of the plume, and assuch, would be at the end of the plume in areasconsidered “clean.” Additional piezometers can beinstalled if groundwater and leachate rate and flowdirection need to be clarified for modeling anddescriptive purposes.

If the necessary characterization is largely doneduring Phase I activities, then fewer boreholes andless additional indirect investigation will benecessary during Phase II activities, Placement ofboreholes, piezometers, and monitoring wells shouldbe carefully reviewed so that essential informationon leachate and groundwater is collected. Drillingan excessive number of boreholes will notnecessarily provide useful information on the site’shydrogeology. Additional information on placementof monitoring wells is provided in Section 3.1.3.

3.1.2 Data Requirements

A detailed description of groundwater remedialaction alternatives for municipal landfill sites can befound in Section 4.5. To evaluate the variousremedial action alternatives, data gathered before orduring the site characterization of groundwatershould include:

• The regional geologic regime and regionalgroundwater flow direction

• A hydrogeologic investigation tocharacterize the groundwater aquiferincluding the depth to water, flow direction,flow rate, the extent and nature ofconfining layers, fractures, and anypotential pathways for contaminantmigration at the site


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• Location of site-specific items of interestsuch as outcrops, springs, seeps, leachateoutbreaks, and surface drainage features

• The compatibility of the suspectedcontaminants with naturally occurringmaterials at the site

• Identification of actual or potentiallyuseable aquifers (e.g., Class I and Class IIaquifers) and water-bearing units and theirphysical properties (including linkagebetween aquifers)

• Climatic and topographic conditionsaffecting groundwater recharge anddischarge, erosion, flooding, and surfacewater conditions of interest

• Identification of potential pathways forcontaminant migration

• Geologic conditions, hazards, or constraintsthat could contribute to offsite contaminantmigration or that might preclude certainremedial alternatives

• Site-specific analysis such as BOD andCOD (see Section 4.5)

3.1.3 Placement of Monitoring Wells

3.1.3.1 Objectives

The objective of installing monitoring wells is todetermine if the landfill has affected thegroundwater system. Monitoring wells are used to:

• Determine subsurface conditions, includingconfining layers and zones of highpermeability

• Determine background (upgradient) waterquality

• Locate contaminant plumes

• Characterize groundwater contaminants

• Characterize hot spots

Because there are many uses for monitoring wellsat municipal landfill sites, there are no simpleprocedures for determining appropriate placement.Simple geology characterized by horizontal, thick,homogeneous, unfractured strata tends to reducethe number of soil borings and monitoring wells.More complicated geology, including fractured,tilted, folded, thin, or heterogeneous geologic stratatends to increase the number of soil borings andmonitoring wells necessary to adequatelycharacterize a site. Landfill conditions that lead tomore detailed investigations include known locationsof the disposal of hazardous wastes and loss ofcontainment (liner or slurry wall) integrity.

3.1.3.2 Procedures

Landfill Type I. This is a municipal landfill whereco-disposal of hazardous and municipal wastesoccurred, but the disposal in a discrete, accessiblelocation of highly toxic and/or highly mobile materialthat presents a potential principal threat to humanhealth or the environment, is not known. Thepresence of hazardous constituents in thegroundwater is a concern at this type of landfill.The number of wells should be determined on asite-specific basis.

Upgradient Monitoring Wells . The number ofwells increases with the complexity of site geologyand landfill design or history. Upgradient monitoringwells should be in a “clean” area so that they mayprovide representative background groundwaterquality in the aquifer of concern. They should bescreened in the same strata as the downgradientmonitoring wells unless the bedrock dips steeply orrock types change rapidly across the site. Locationof the monitoring wells should also considergroundwater and contaminant velocity at the site.Groundwater that moves slowly and where thecontaminants are widely dispersed will requirecareful location of upgradient wells to avoid theplume. The location of upgradient monitoring wellsshould consider surface water or agricultural andindustrial activities that may be affecting thegroundwater quality upgradient of the landfill. Apreliminary estimate of contaminant travel distancesshould be determined so initial well installationapproaches can be determined.


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Downgradient Monitoring Wells. Downgradientmonitoring wells should be near the landfillboundary and in the saturated zone. If the landfilllies above the saturated zone, the leachate migrationpathway to the groundwater should be consideredbefore monitoring well placement is determined. Incases where complex interbedding, especially ofalluvial deposits, underlie the landfill, additionalmonitoring wells may be required. It should also berecognized that glacial stratigraphy can also be verycomplex.

Downgradient monitoring wells should be locatedalong any zone that may offer preferentialgroundwater movement. Geologic features such assolution channels, faults, or permeable linear sandlenses should also be considered in downgradientmonitoring well placement, since these features canact as groundwater conduits. Other features thataffect the placement of downgradient monitoringwells include fill areas, buried pipes and utilitytrenches, areas with high hydraulic gradients, andareas with high groundwater velocities. Placementof downgradient monitoring wells should alsoconsider low-permeability zones associated withsuch features as clay lenses, dense bedrock, andglacial till that can differentially retard groundwaterflow.

The use of field data or rapid turnaround data froma nearby laboratory can provide useful informationin the placement of monitoring wells. For example,an onsite laboratory could be used during wellinstallation to provide analytical results that wouldbe used to reevaluate the proposed monitoring wellnetwork. Groundwater samples could be analyzedfor selected VOCs and inorganic anions to aid indetermining the extent of the groundwater plume.Inorganic anions such as chloride and sulfate arepersistent chemicals that can be used as indicatorsof contaminant transport. Therefore, mappingelevated levels of these indicator chemicals relativeto upgradient concentrations can give a moreaccurate picture of the extent of the groundwaterplume than just VOC analysis. Because ofvolatization, adsorption, and degradation, VOCsmay diminish in concentrations more rapidly thanthe inorganic ions.

Other Monitoring Wells. Additional monitoringwells need to be installed and sampled to determinethe integrity of any confining layers and todetermine whether the confining layer is continuousor breached. Where a confining layer exists,monitoring wells should be installed in the area inorder to assess vertical flow between the upper andlower aquifer, and the groundwater flow in thelower aquifer. In general, numerous boreholes orwells through confining layers should be avoidedwhen the site conceptual model indicates a very lowpotential for contamination of the underlyingaquifer.

Monitoring Well Screen Placement. Monitoringwells should be completed in the first aquiferencountered beneath the landfill and other discretezones beneath. That aquifer will usually beunconfined at the landfill location. The nature of thesuspected contaminants should be used todetermine the ideal screen location in the aquifer.Most typical landfill contaminants are solubleenough to be detected by laboratory instruments, soscreening in the upper portion of the aquifer shoulddetect any contamination present.

If a highly variable geology exists at the site, eachscreen should be open only to one stratum. If ascreen is open to more than one stratum,contaminants may move to uncontaminated zones,and the actual zone of contamination will beimpossible to determine. A typical screen length is5 feet, but longer screen lengths are required inzones of very low permeability or where waterlevels are known to change over great intervals.Generally, screens should be no longer than 20 feet.

If the contaminant is a dense, non-aqueous phaseliquid (DNAPL), the screens must monitor thebottom of the first aquifer. If this distance isexcessive, several monitoring wells with overlappingscreens are typically installed. DNAPL migration isgenerally controlled by the top surface of theconfining layer, and is little affected by the hydraulicgradient. Additional monitoring wells and boreholesmay be required to define this surface. A DNAPLwill enter deeper aquifers if breaches in theconfining layer are encountered. DNAPLs maymove through clays at order-of-magnitude greatervelocities than water. Monitoring wells should


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be placed in the lower aquifer to determine thehydraulic gradient between the two aquifers, and todetermine if contamination has reached the loweraquifer. DNAPLs can migrate to the bottom of thelower aquifer, but often this distance is great andthe nature and topography of the underlyingaquitard are difficult to define.

The viscosity and dispersivity of the contaminantshould also be considered during monitoring wellscreen placement. A highly viscous liquid willmigrate very slowly in the subsurface. Itsmovement may be affected more by capillaryattraction than by normal factors of gradient andhydraulic conductivity. A highly dispersivecompound, on the other hand, can migrate quicklyby dispersion and extend downgradient much fasterthan the gradient and hydraulic conductivityindicate.

Organic contaminants that are less dense thanwater may be detected with screens that extendfrom at least 5 feet above the saturated zone toabout 15 feet into the saturated zone. This detectsany floating, non-aqueous phase contaminants.Screen openings should be confined to a singlestratum.

Landfill Type II. The principal concern at this typeof landfill is the known or suspected hot spots.Monitoring well and screen placement described forLandfill Type I can be employed, but additionalmonitoring wells should be placed downgradient ofall confirmed hot spots. (The presence of hot spotsis confirmed using the geophysical surveyprocedures described in Section 3.2.)

Hot spots should be treated as unique sites withinthe landfill. The hot spot may be isolated with up-and downgradient monitoring wells within thelandfill. Test pits should be installed in such areas toinvestigate the subsurface materials. This willrestrict remediation to a smaller area. Care must beexercised because drilling through the landfill toinstall the monitoring wells could compromise theintegrity of any liners, puncture isolated drums, orpenetrate a gas pocket, causing an explosionhazard. Also, because of the nature of landfillmaterial, the integrity (or quality) of samplinglocations within the landfill is unknown.

3.1.3.3 Guidelines

The summary documents presenting the data shouldcontain concise, narrative descriptions of the databut must rely on clear, detailed figures to presentthe spatial relationships of groundwater, geology,and the landfill. Geologic cross sections based onthe boring logs must depict all significant soil androck units, geological structures, zones of highpermeability and confining layers present, and thedepth to water and the unconfined and confinedwater levels. The locations of all borings should bedisplayed on an appropriate map. The lines of thecross sections should be shown, and surfacefeatures should be located on the cross sections.

A map showing the monitoring well locations shouldalso be prepared. The map can display water levelsand develop water level contours and showgroundwater flow direction, groundwater divides,recharge, and discharge areas. In cases wheremore than one aquifer exists, the map can also beused to show the direction of vertical groundwaterflow.

3.1.4 Groundwater Summary

Table 3-1 summarizes the conditions that determinemonitoring well locations and numbers. A flowchartsummarizing the decisions necessary to determinesampling and monitoring locations is presented inFigure 3-1. The decision points illustrated across thetop of the figure must be considered separately indetermining monitoring well placement. Forinstance, a determination of where to placeupgradient monitoring wells does not eliminatedecisions on where to place wells to characterizezones of permeability.

The Phase I and Phase II site characterizationsapply to both landfill types as well as other NPLsites. Placement and number of monitoring wellsvary according to the size of the site, the geology ofthe area, and the type of landfill.

3.2 Leachate

The main factor contributing to leachate quan-tity is infiltration. However, other factors--


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Table 3-1CONDITIONS THAT DETERMINE MONITORING WELL LOCATION AND NUMBERS

Conditions Monitoring Well LocationNumber of Monitoring

Wells

Landfill in saturated zone Downgradient near landfill boundary butalong zones of high hydraulicconductivity, including hot spots.

High.

ORIf no zones of high permeability, neardowngradient boundary of landfill ornear confirmed hot spot.

Moderate.

Landfill above saturatedzone

Possibly at some distance fromdowngradient landfill boundary or hotspot--depends on subsurface featurescontrolling fluid movement in vadose orsaturated zone.

High.

ORIf homogeneous geology, downgradientin uniform array.

Moderate to high.

Landfill in vadose zone Intercept leachate downgradient. Moderate.

Interlayered confining layers Top of each confining layerdowngradient.

At least one per confininglayer.

Breached or continuousconfining layer

Top of confining layer and in next loweraquifer downgradient.

At least two.

No upgradient contaminantsource

Upgradient of landfill boundary–distancedepends on groundwater velocity andcontaminant dispersivity–in same strataas monitoring wells on downgradient sideof landfill or as required by geology.

Relatively few–at least one,probably more.

Upgradient contaminantsources

Near potential source and upgradient oflandfill and downgradient of source–insame strata as monitoring wells ondowngradient side of landfill or asrequired by geology.

One per source and perstrata.


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including groundwater and surface water rechargeand the water generated as part of refusedecomposition--all contribute to the quantity ofleachate generated. Leachate production generallyfollows a cyclic pattern depending on local rainfall,runoff, and evapo-transpiration rates. Leachatetypically carries many suspended and dissolvedmaterials; the specific nature and concentrationdepend on the landfill history as well as itsdegradation stage. Typical leachate concentrationranges are presented in Table 3-2. The large rangespresented may be due in part to analysis of leachatediluted by groundwater. Additional information onleachate composition and contaminantconcentrations in leachate can be found inCharacterization of MWC Ashes and Leachatesfrom MSW Landfills, Monofills and Co-DisposalSites (U.S. EPA, 1987f).

Leaching is a contaminant release mechanism,potentially transporting contamination to onsite andoffsite groundwater through groundwatermovement, or to onsite surface water, sediments,and nearby wetlands by recharging due to leachateseeps. Leaching is usually the contaminant releasemethod of greatest concern at landfill sites.

3.2.1 Leachate Investigations

3.2.1.1 Objectives

The objectives of leachate investigations are to:

• Determine location of leachate seeps

• Determine chemical characteristics ofleachate

• Locate potential source areas (in situationswhere there are no known or suspected hotspots, the entire landfill may be considereda source)

• Determine leachate impact on groundwater

Leachate samples may be analyzed to confirm orcomplement data obtained from analysis ofgroundwater and soil samples.

3.2.1.2 Procedures

Landfill Type I. Type I landfills include thoselandfills where a combination of municipal andhazardous wastes have been co-disposed. At thesetypes of landfills, discrete hot spot locations areneither known nor suspected. At these sites, awater balance identifying water sources anddischarges should be performed for the entire siteto estimate annual leachate production. Leachatecollection locations should be identified forsampling. The location where leachate dischargesultimately depends on the site’s physical andgeological characteristics. In most cases, at leastpart of the leachate that discharges from the landfillmigrates into the underlying groundwater system. Inthis case, leachate acts as groundwater rechargeand its detection and collection can become verydifficult. The actual zone depends on thepermeabilities of the materials involved and in theirspecific gravities, mixing (turbulent versus laminarflow), and diffusion. Where underlying refuse, soil,or rock strata are impervious, leachate willdischarge on the surface either at the landfill toe orsomewhere on the slopes.

At both landfill types, it may be necessary to samplethe surface waters. Leachate can move laterallybelow ground toward a creek or stream, affectingthe water quality. Samples should be collected bothupstream and downstream of the site to monitor thissituation properly. At other sites in which the refuseis deposited on impervious clays and in areas ofhigh precipitation, the leachate can outcrop at thetop and sides of the fill and flow with the surfacerunoff directly to a receiving water body. Samplesshould be collected at the leachate seep andupstream of the seep.

When a number of seeps are present in the samearea, compositing of samples from these seeps maybe appropriate in some limited cases. Theadvantage of compositing is that the costs ofanalysis, data validation, and database activities arelowered while not eliminating sampling of any of theseeps. The disadvantage is that information on theindividual seeps is not available. Compositing wouldnot be appropriate if significant differences inleachate composition are expected.


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Table 3-2*RANGE OF TYPICAL DOMESTIC REFUSE

LEACHATE CONSTITUENT CONCENTRATIONS

ConstituentConcentration Range Per Liter

(mg)

Iron 200 - 1,700

Zinc 1 - 135

Arsenic 0 - 70

Lead 0 - 14

Phosphate 5 - 130

Sulfate 25 - 500

Chloride 100 - 2,400

Sodium 100 - 3,800

Nitrogen (Kjeldahl) 20 - 500

Hardness (as CaCO3) 200 - 5,250

COD 0 - 750,000

BOD 9 - 55,000

TOC 5 - 30,000

TDS 0 - 51,000

TSS 2 - 140,000

Total Residue 1,000 - 45,000

Nickel 0.01 - 0.8

Copper 0.10 - 9.0

pH 4.00 - 8.5

*From Characterization of MWC Ashes and Leachates fromMSW Landfills, Monofills, and Co-Disposal Sites (EPA, 1987f)


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When collecting samples, field observations can beused to determine if samples from adjacentlocations can be composited into one representativesample. Samples from leachate seeps that are neareach other can be composited if they 1) aresimilarly colored, 2) have similar liquid phases, and3) appear similar when scanned with fieldinstruments. Samples from opposite sides of thelandfill should not be composited. Furtherinformation on leachate sampling methods isavailable in Volumes I and II of EPA’s ACompendium of Superfund Field OperationsMethods (EPA, 1987h).

If available, samples should also be collected fromleachate collection drains and/or extraction wellsusing pumping or bailing, except for VOCs, whichmust be collected using a bailer. Samples should beanalyzed for priority pollutant organics and metalsand cyanide. Other parameters, such as BOD,COD, pH, TDS, TSS, oil and grease, TOC,chlorides, nitrite, nitrate, ammonia, total phosphorus,and sulfides should be analyzed to provide data fordesign of a leachate treatment system.

In many landfills, leachate is perched within thelandfill contents, above the water table. In theabsence of leachate collection systems at LandfillTypes I and II, leachate wells installed into thelandfill, as part of the site characterization, mayprovide good hydrologic information on the site.That is, placing a limited number of leachate wellsin the landfill is an efficient means of gatheringinformation regarding the depth, thickness, andtypes of the waste; the moisture content and degreeof decomposition of the waste; leachate head levelsand the composition of landfill leachate; and theelevation of the underlying natural soil layer.Additionally, leachate wells provide good locationsfor landfill gas sampling. Leachate wells should notbe placed where there are existing leachatecollection systems, to prevent possible damage tothese structures. In addition, it should be noted that,without the proper precautions, placing wells intothe landfill contents may create health and safetyrisks. Also, installation of wells through the landfillbase may create conduits through which leachatecan migrate to lower geologic strata. And finally,the installation of wells into landfill contents maymake it difficult to ensure the reliability of the

sampling locations.

The number of leachate wells will vary for eachlandfill. In cases where the refuse is fairly thick,clusters or nested wells may be appropriate todetermine if leachate composition varies with depth.Samples should be analyzed for parameterspreviously described.

Landfill Type II. Type II landfills differ from TypeI landfills in that there is evidence of hot spot areas.In these cases, treatment of hot spots may be away of reducing the amount and concentration ofleachate generated. As with Landfill Type I, awater balance for the entire site should beperformed to estimate annual leachate production.

At landfills that are suspected or known to containhot spots, leachate wells should not be used as asubstitute for test pits and actual waste sampling.However, chemical analyses of the leachate maydemonstrate a principal threat to the groundwater orsurface water systems not observed from analysisof environmental samples showing lowerconcentrations.

For any sample collection method used, more thanone round of sampling is recommended tocharacterize the leachate properly. A minimum oftwo sampling events, one during a dry period andthe second during or immediately after precipitation,should be performed to determine variability inleachate composition.

3.2.1.3 Guidelines

Field screening techniques described in Section3.3.1.3 may be useful in determining which samplesare amenable to compositing or forwarding to theanalytical laboratory. Visual observations, sitetopography, and surface drainage patterns are alsoimportant in determining the appropriate leachatesampling locations.


A detailed description of leachate remedial actionalternatives can be found in Section 4.3. Toevaluate the various remedial action alternatives,data gathered before or during characterization ofleachate should include:


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• A contour map to define surface waterdrainage pattern

• Soil characteristics including permeability,grain size distribution, and moisture contentto determine the physical propertiesgoverning contaminant transport

• Climatological characteristics includingtemperature and precipitation to helpdetermine approximate leachate volumesfor the site

• Waste characteristics, including BOD,COD, pH, TDS, TSS, oil and grease,chlorides, nitrite, nitrate, ammonia, totalphosphorus, sulfides, and metals, todetermine a suitable leachate treatmentsystem

• Depth to groundwater and groundwaterflow direction and velocity to evaluate thefeasibility of leachate or groundwaterextraction and treatment

3.2.3 Leachate Summary

Leachate sampling at seeps and streams isrecommended for both landfill types. Leachate canmove laterally below ground toward a creek orstream, affecting the water quality. Samplingstreams and leachate seeps can provide informationon actual or potential water quality impacts.Installation of leachate wells at landfill Types I andII can provide information such as depth, thickness,and types of waste; leachate head levels and thecomposition of landfill leachate; and the elevation ofthe underlying natural soil layer. Table 3-3summarizes the recommended leachate samplinglocations.

Figure 3-2 presents a logic flow diagram forleachate sampling.

3.3 Landfill Contents/Hot Spots

Containment has generally been identified as themost practicable remedial technology for municipallandfills because the volume and heterogeneity oflandfill contents often makes treatmentimpracticable. Characterization of municipal landfillcontents therefore is generally not necessarybecause containment of the landfill contents do notrequire such information. More extensivecharacterization activities and development ofremedial alternatives (such as thermal treatment orstabilization) may be appropriate for hot spots. Thefollowing subsections discuss site characterizationstrategies for landfill Types I and II for surficialsoils, caps and liners, and landfill contents (includinghot spots).

3.3.1 Landf i l l Contents /Hot SpotInvestigations

Typically, investigations at municipal landfills areseparated into four areas:

• Surficial soils• Caps• Liners• Landfill contents

Surficial investigations are undertaken if there iseither physical evidence or data that suggest thepresence of substantially contaminated surficialsoil in the general area of the landfill.Surficial sampling investigations should belimited if surface soils are planned to be

Table 3-3LEACHATE SAMPLING PROGRAM

Location Minimum Sampling Events

Collection drain Two–collect one during dryer and oneduring wetter period of the year.

Surface locations–steam, seeps Same as above.


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covered with a cap. Cap and liner investigations areundertaken when previous engineering studies orfield observations indicate their presence at a site,while landfill content investigations are undertakento characterize known or suspected hazardouswaste disposal areas (potential hot spots). Small tomoderate-sized landfills (e.g., less than 100,000cubic yards) may also undergo subsurfaceinvestigations if the landfill poses either an existingor potential threat to human health or theenvironment and if it is appropriate to considerremediation of the entire contents of these landfillsthrough excavation, treatment, or disposal.

It should be noted that investigations into landfillcontents are rarely implemented at municipallandfills. This is due primarily to problems inexcavating through refuse and the heterogeneousnature of the refuse, which makes characterizationdifficult. Sampling of landfill contents may,however, be useful for enforcement purposes (e.g.,identifying PRPs). Drilling through the base of thelandfill is not recommended due to the potential formigration of leachate to lower geologic strata.However, in general, drilling into refuse forinstallation of various extraction systems (forexample, leachate and landfill gas) is commonlyimplemented (see Sections 4.2 and 4.4).

3.3.1.1 Objectives

The general purpose of characterizing soils and hotspots is to define the risks posed by thesemedia/contaminants and select the appropriateremedial action alternatives for further evaluation.However, the specific objectives, and therefore, thesampling procedures, vary for each type ofinvestigation. The objectives of each type of soilsinvestigation are described below:

Topographic Surveys . The objectives ofperforming topographic surveys at municipal landfillsites are to:

• Establish a basis for determining the totaland differential settlement of the existingcap

• Document erosion gullies and otherrelevant topographic features that mightaffect the remediation scheme or point to

anomalies that require further investigation

Surficial Soil Investigation. Surficial soilinvestigations are performed to:

• Determine the distribution andconcentration of contamination in surficialsoils

• Document erosion patterns

• Determine if the surficial soils, either inwhole or just in hot spots, should beincluded in the source control actions forthe landfill.

Investigations of surficial soils should be limited ifthere are plans to place a new cover system overthe existing surficial soils. However, if surficial soilsare significantly contaminated, particularly in hotspots, then separate source-control remediation ofthe contaminated soils may be considered; aninvestigation of contamination in the topsoil isappropriate, even if there are plans to place a finalcover over most of the existing surficial soils.

Surficial soil investigations are normally focused onanomalies observed at the surface, such as:

• Leachate seeps

• Stains or other discoloration in the surficialsoils

• Stressed vegetation

Analysis of surficial soil and sediment samples mayconfirm or complement data from analysis ofsurface waters. While the presence or absence ofcontamination of surficial soils may have norelationship to groundwater contamination, theremay be contamination of surficial soils and nogroundwater contamination, or vice versa.

Cap Investigation. A cap investigation isintended to determine if a new cover systemwould be required to reduce infiltration ofwater, to collect gas, to minimize erosion, or tomeet ARARs. Another purpose is to definetotal and differential settlement that might


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occur if a new cover system is placed on thelandfill. If excessive settlement is predicted, thewaste will probably require stabilization before finalclosure with an engineered cover system.

Existing caps may either be engineered or not. Thedegree of sophistication employed in theinvestigation of an existing cap will depend to agreat extent on whether it is planned to use all orpart of the existing cap in a new, engineered coversystem. If none of the existing cap will beincorporated into the new cover system (e.g., if theexisting cap will be buried beneath a new cover),detailed investigations of the existing cap are usuallynot necessary. If an existing cap was not properlydesigned and constructed, it will usually not bepossible to incorporate the existing cap within theprofile of a new, engineered cover system, althoughthe existing cap may serve as foundation supportfor the new cover system. In many cases, a cursoryinvestigation of the existing cap will verify that itwas not constructed to engineering standards. Inthis situation, more detailed characterization of theexisting cap is not necessary.

If it is suspected that an existing cap wasengineered, and information on the design andconstruction of the cap is not available, thenpreliminary work should be performed to verify thatthe cap was properly designed and constructed. Forexample, suppose excavation of several test pitsreveals that the cap consists of 12 inches of topsoilunderlain by 2 feet of low-permeability soil thatappears to have been compacted. This informationsuggests that the existing cap was engineered withthe intention of including a layer of topsoil above ahydraulic barrier layer. If preliminary informationindicates that the cap was engineered, and if it isdesired to investigate the feasibility of incorporatingall or part of the existing cap in the final coversystem, then detailed characterization tests areneeded to confirm the properties of the existing cap.

The objectives of a cap investigation are to:

• Determine the approximate thickness,composition, and horizontal extent of theexisting cap (a greater level of detail isneeded if the existing cap is engineered andwill be incorporated in the final coversystem)

• Determine if any hot spots of soil

contamination are present in the existingcap and characterize these hot spots to theextent necessary to determine whether thesoils can be covered and left in the landfillor whether the hot spots need to beexcavated and separately remediated forsource control

• Document the integrity of the existing cap(e.g., determine if roots have penetratedthrough the cap) and determine thegeotechnical and other relevant propertiesof the existing cap if the existing cap wasengineered and will be an integral part ofthe final cover system

• Evaluate potential settlement (total anddifferential) of the landfill and the finalcover system that will be placed on thelandfill

• Evaluate the stability of any slopes and thecapacity of the waste to support the finalcover systems and any surficial loadingssuch as those from surface traffic orconstruction equipment

Liner Investigation. Liner investigations arerarely performed, even if there is evidence of aliner, since the liner could be punctured during theinvestigation and contribute to groundwaterdegradation. If a liner investigation is going to beperformed, then the objectives may include:

• Confirming the existence of a liner

• Determining its permeability

• Evaluating, if possible, its susceptibility tochemical damage

A liner investigation could also be undertaken todetermine the probability that contaminants willmigrate to the groundwater.

Subsurface Soil and Landfill ContentsInvestigation. The purpose of subsurfacesampling is to obtain a portion of soil (disturbed orundisturbed) or landfilled materials for chemical andgeotechnical analysis. This can be done by drillingand taking samples of the subsurface soils andlandfill contents or by excavating test


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pits or trenches. As previously described,subsurface investigations may only be used atmunicipal landfills where documentation or physicalevidence exists to indicate the presence of hotspots.

The objectives of subsurface testing, using test pitsor trenches, are to:

• Evaluate the integrity of any buried drums

• Determine the degree of contamination ofany unsaturated soil

Surface geophysical surveys are performed toidentify areas of buried metal and other areas ofconcern. Based on the results, test pit locations canthen be selected to investigate areas where drumsor tanks are suspected. Magnetometer surveys(total field and vertical gradient), electromagneticsurveys, and soil gas surveys can be used to identifytest pit sites. It should be noted, however, thatlandfills contain many products other than metaldrums. Therefore, magnetometers andelectromagnetic surveys are used only when thereis evidence to suggest large, discrete areas of drumdisposal. Trenching, test pitting, and boringinstallation are used to characterize hot spot areas.Test pits and trenches allow a larger, morerepresentative area to be observed and permitselection of specific samples from relatively shallowsubsurface materials (biased grab sampling). Testpits and trenches are typically dug to confirm theresults of surface geophysical investigations, whileborings are typically used to investigate deepercontamination. Also, soil gas surveys can be used toidentify hot spots if the suspected contaminantsinclude VOCs. The soil gas survey may be able toidentify areas of higher VOC concentrations thatcan later be investigated with test pits or borings.

3.3.1.2 Procedures

Landfill Type I

A Type I municipal landfill is one in whichco-disposal of hazardous and municipal wasteoccurred, but the location of highly toxic and/orhighly mobile material, which presents a potentialprincipal threat to human health or the environment(hot spots), is not known.

Topographic Surveys . Topographic data are oftenrequired to document erosional features, to identifytopographic anomalies that might be related todeteriorated drums or other hot spots, and toprovide a basis for evaluating the potential total anddifferential settlement resulting, from decompositionof waste or compression of waste from the weightof the final cover system. The survey should bedesigned to define areas with a differentialsettlement as small as 6 inches over horizontaldistances of 10 feet. To document settlement overtime, a series of settlement markers should beestablished on a grid pattern of approximately 100feet (more in areas with known settlementproblems).

Surficial Soils. Surficial soils are investigated todetermine the distribution and concentration ofcontamination, to document erosion patterns, and todetermine if surficial soils should be included insource control actions. Before the sampling isinitiated, the soils exposed at the surface should beexamined visually for evidence of staining; fieldpersonnel should also look for signs of vegetationstress. Geophysical techniques such aselectromagnetics or ground-probing radar may behelpful in identifying anomalies, hot spots, or otherzones of surficial soil that warrant investigation. Ifit is anticipated that an engineered cover system willbe constructed over the area of concern, samplingof surficial soils may not be necessary or samplingefforts may be limited. If there is an engineered capon the landfill, surficial soil samples for analysis ofcontaminant concentration may not be neededunless surficial soil is likely to remain as is, and thehistory of the soil used for the cap is unknown.

To sample surficial soils, a grid often issuperimposed on each area suspected ofcontamination, e.g., stained areas orvegetation-stressed areas. Soil samples can becollected at alternate nodes on the grid. The nodesamples can be composited to reduce the number ofanalyses. The analyses from at least twobackground samples should be available forcomparison. Background samples should beobtained from areas with a similar soil compositionon the site, but outside the influence of thesite. Previous activities at any offsite locationsshould be considered before collecting back-


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ground samples, since these offsite activities couldintroduce contamination.

The depths of the surficial soil sample and theanalytical parameters vary from site to site but, ingeneral, should be specified as follows:

• Samples for priority pollutant metals andcyanide analyses should be collected from the0- to 6-inch depth to characterize directexposure risks (i.e., contact and ingestion).

• Samples for VOC analyses should be collectedfrom the 18- to 24-inch depth because thesecompounds tend to evaporate from the soil atshallower depths.

Other sampling depths may be appropriate based onsite-specific circumstances (e.g., depth togroundwater, soil structure). While samples fromdifferent nodes may be composited horizontally,vertical compositing is not recommended, exceptover short intervals, because compositing willobscure analytical results. Additionally, compositingsamples for VOC analysis is not recommendedbecause of losses during mixing of samples.Additional analyses can be performed, depending onthe results of the site history and previous wastecharacterization studies. Additional analyticalparameters could include RCRA hazardous wastecharacteristics, total BTU content, and bulk weightof the material.

The frequency of surficial soil sampling depends onthe characteristics of the soil and waste, andrequires professional judgment. For example,contaminant migration from uniformly depositedwaste in a relatively uniform soil will be morepredictable than migration from random placementof wastes in a heterogeneous environment such asa landfill. Sampling will, therefore, be required at ahigher frequency near the landfill area, sincecontaminants can be expected to migrateirregularly.

Surficial soil samples can be collected usingstainless steel trowels or shovels, hand augers, orsoil sampling tubes. Samples containing volatilecompounds must be scaled to prevent losses.Special techniques may be required to preserve soilsamples so that levels of contami-

nation do not change between sampling andanalysis.

Cap Investigation. The cap investigation must becarefully planned to maximize the value of datacollected and to ensure that unnecessary data arenot collected. First, it must be determined whetherthe existing cap is likely to have been engineered. Inmost cases, the existing cap will not have beenengineered, and since it is recommended that thesetype cover systems are not used as part of a newengineered cover system (except as a foundation)detailed assessment of the geotechnical propertiesof the cap materials is usually not necessary.However, basic information concerning theapproximate thickness and lateral extent of theexisting cap, composition of the cap, andcharacteristics of the soils that make up the cap willneed to be developed. There are many techniquesthat may be used in determining the thickness andlateral extent of the cap, including surfacegeophysical techniques such as ground-penetratingradar. However, drilling of holes or excavation oftest pits will generally be needed either alone or asa means to calibrate surface geophysicaltechniques. Sampling at a frequency ofapproximately one exploratory boring or trench peracre is suggested. Samples should be analyzed todetermine the liquid and plastic limits of the soils,percentage of fines, percentage of gravel, moisturecontent, shear strength, and any other relevantparameters.

For more detailed investigations, an appropriatelysized grid can be superimposed on several areas ofthe existing cap. Samples can be collected either atalternate nodes on the grid or randomly. Areasselected for sampling should include bothrepresentative locations and those areas whereerosion, cracking, or fracturing has occurred.

Shallow test pits can be dug to expose a crosssection of the cap. Test pits can be dug by hand orwith a backhoe. Test pits are usually excavated nomore than 1 foot below the thickness of thecap. Exploratory borings, drilled with a handauger or truck-mounted equipment, can alsoyield information on the materials that makeup the existing cap. Sampling tubes can bepushed or driven into the cap materials ifthe characteristics of the in situ material need


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to be identified. Otherwise, disturbed samples ofmaterials generally are collected for later use in thelaboratory. Procedures described in ASTMStandard D420, Standard Guide for Investigatingand Sampling Soil and Rock , should be followed.

If undisturbed samples are to be obtained, athin-walled sampling tube (often called “Shelbytube”) should be used. Shelby tubes are pushed intothe cap using a drill rig, hydraulic ram, or otherdevice that provides a straight, steady push. It is notrecommended that the sampling tube be pusheddirectly with a backhoe because that usually tilts thetube. Also, the sampling tube should never be driveninto the soil if an undisturbed sample is sought. Thesampling tube usually is not pushed more than about18 inches into the soil; a push of 6 inches or less isrecommended for very stiff or hard, cohesive soils.Once a sample has been obtained, it is classified inthe field, extruded from the sampling tube, andsealed in a sample-holding device or sealed directlyin the tube. Samples then are placed in speciallydesigned boxes that hold the samples in position andprevent their disturbance during transport back tothe laboratory. Collection of undisturbed samplesshould be in accordance with ASTM StandardD1587, Standard Practice for Thin-Walled TubeSampling of Soils. Transport and storage ofsamples should be in accord with ASTM StandardD4220, Standard Practices for Preserving andTransporting Soil Samples.

Undisturbed samples are tested routinely todetermine the moisture content and density of thesoil and are subjected to relevant tests to define thesoil property of interest, e.g., shear strength.Undisturbed soil samples are sometimes tested formore routine properties, such as liquid and plasticlimit, to develop a basis for comparing the results ofvarious laboratory tests.

Tests to determine compaction characteristics areusually performed on large, bulk samples of thematerials obtained from soil borings or test pits.However, unless the existing materials in the capwill be excavated and recompacted, there is usuallyno need for compaction tests other than to verifythat the existing materials are well or poorlycompacted. (In most cases, the existing cover

materials are assumed to be poorly compacted.)

Sometimes the permeability (to air or water) ofexisting cap materials will require evaluation. If theexisting cap, or a layer within the existing cap, isexpected to have a low permeability, a combinationof laboratory permeability tests on undisturbedsamples and field (in situ) permeability tests isrecommended. However, field tests are timeconsuming and difficult; they are usuallyrecommended only when the use of the existing capmaterials for a low-permeability barrier in the finalcover system is being considered. Laboratorypermeability tests usually are performed at afrequency of 1 per acre per lift on modern,engineered, low-permeability barriers of compactedsoil. A similar frequency would be appropriate forevaluation of a pre-existing barrier that is thought tohave been engineered or otherwise constructed toachieve a low permeability. The recommendedmethod for laboratory permeability testing is ASTMD5084, Hydraulic Conductivity of SaturatedPorous Materials Using a Flexible WallPermeameter.

In some circumstances, the existing cap may havea high permeability, and the material could be usedas a gas collection layer within the final coversystem. Accurate measurement of extremely highgas permeability is difficult; accepted methods of insitu testing do not exist. The permeability to air isprobably best evaluated on the basis of grain sizeand permeability to water, as measured in thelaboratory. With an existing material that issuspected of having a high permeability, the mainissue to be investigated is whether the material hassufficiently high permeability over the full arealextent of the site. Thus, testing of many samples (atleast three tests per acre) to establish consistencyof high permeability would be appropriate.

After the initial stage of geotechnical investigationand sampling is completed, the results are evaluatedto determine whether more field work is needed.Additional tests may be necessary toevaluate various issues. For example, itmay be necessary to construct test patchesof the proposed cover material over the landfillto determine the feasibility of constructing and


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compacting materials for the final cover system onweak, compressible waste materials.

Waste Investigation. The physical and biologicalproperties of the landfill contents have an influenceon the feasibility of placing a final cover on a site.Some wastes are so compressible or biologicallyunstable that technical problems can arise inconstructing and maintaining a final, engineeredcover because of excessive settlement. In suchcases, it may be necessary to physically orbiologically stabilize the waste prior to placement ofa final cover. The need to stabilize the waste priorto construction of a final cover may be a criticalissue in the feasibility study of closure of the site.

The depth of waste must be accurately defined sothat settlement patterns can be calculated. Surfacegeophysical techniques, such as seismic refraction,can be useful in defining the depth of waste in somecircumstances. Drilling soil borings is the mostreliable way to determine the depth of the waste;however, in some cases, this may poseunacceptable health and safety risks. Particularattention should be given to evaluating the variabilityof thickness of the waste because a variablethickness can cause significant and harmfuldifferential settlement of the final cover.

It may be advantageous to initiate a program tomeasure settlement of the landfill. This wouldinclude the installation of one or more benchmarksoutside the fill area and periodic surveying ofsettlement markers placed on the surface of theexisting cap. The measurement of settlement mayneed to extend through the RI/FS and into theremedial design in order to monitor for a sufficienttime. Differential settlement is often more critical tothe performance of a final cover system than istotal settlement. The magnitude of differentialsettlement, expressed as the amount of settlementover a specified horizontal distance, that exists in acap can be a useful indicator of future problemswith differential settlement. Sometimes moreextensive testing may be needed to quantifydifferential settlement and to define the need forstabilizing the underlying waste. Examples of thesetypes of studies include:

• Passage of a heavy, vibratory compactor

over the surface of the site andmeasurement of the resulting settlement

• Prototype deep, dynamic compaction(which involves dropping a large weight onthe surface to compact underlyingmaterials)

• Construction of a test fill on the existingcap

The degree of decomposition of the landfill is oftenrelevant to issues such as potential for futuresettlement and generation of gas. Knowledge of theamount of organic materials, volatile solids, ashcontent, and moisture content usually helps inunderstanding the condition and stability of theburied waste.

Geotechnical tests such as shear strength andconsolidation tests often are impractical for solidwastes because large fragments of solid wastecannot be small laboratory test specimens.However, if the waste is homogeneous and free oflarge fragments, such tests are practical and shouldbe performed to characterize the strength andcompressibility of the waste.

When laboratory testing of samples from municipallandfills is impractical (as is usually the case), theengineering team generally will be forced to relyupon published data on the geotechnical propertiesof waste. These properties are sensitive to the bulkdensity and moisture content of the waste. Anattempt to quantify bulk density (even ifapproximate) and moisture content of the wastemay yield valuable data for purposes of estimatingother characteristics of the waste material.

The potential for the waste to produce gases fromvolatilization or decomposition should be evaluated.Analysis of gas from venting wells usually isdefinitive.

Liner Investigations . Liner investigations shouldbe performed only if previous engineering studiesindicate the presence of a liner and the liner iseasily accessible. In general, soil borings shouldnot be taken through any liner becausecontamination may be spread by puncturingthe confining layers. However, in prac-


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tice, it is impossible to confirm that a liner existswithout drilling to the liner and sampling it; this willusually require some penetrations. The penetrationsmust be carefully sealed using techniques similar tothose for sealing monitoring wells.

If the liner extends to the sides of the municipallandfill, then samples may be collected at the edgeof the liner. For low-permeability soil liners, tests todefine permeability, as described for caps, should beperformed. For geomembranes, the liner samplesshould be collected where leachate seeps areevident, if possible, and examined for deterioration.

Favorable results (e.g., low permeability), from thetests do not necessarily mean that the unexaminedportion of the liner is preventing groundwatercontamination. Rips, tears, or uneven distribution ofliner materials could exist. Hydrogeological studiesalso should provide more information on thecondition of any liner, although these studies mayprovide inconclusive data.

Landfill Type II

Landfill contents are generally only sampled wherehot spots are suspected from either physicalevidence or record searches or when the landfill issmaller than 100,000 cubic yards and it has beendetermined that (1) the landfill poses an actual orpotential risk to human health or the environment,and (2) it is practicable to consider excavationand/or treatment of the contents. Landfill samplingis not normally performed under othercircumstances, since it can be assumed that landfillcontents are heterogeneous. The horizontal extentof hot spots should be delineated usingmagnetometer, electromagnetic (terrainconductivity), or soil gas surveys. Electromagneticsurveys are used principally to detect drum clustersburied near the surface (e.g., approximately onehalf times the coil spacing); magnetometer surveysare used to detect drums buried as deep as 15 feetbeneath the surface; and soil gas surveys are usedto detect leaking drums containing VOCs.Confirmation and contaminant quantification in hotspot areas are done by excavating test pits ordrilling soil borings.

These survey methods develop numerous datapoints. Reduction, processing, and presentation aremajor concerns in proper interpretation andanalyses of the data. If available, data taken in thefield should be electronically recorded anddownloaded to a computer system for processing.Additional information on the use of these methodsmay be found in Quantitative Magnetic Analysisof Landfills (Bevan, 1983) and Magnetic SurveyMethods Used in the Initial Assessment of aWaste Disposal Site (Fowler, date unknown).

Magnetometer Survey. A magnetometermeasures the total magnetic field of the earth andits localized perturbations. A metal mass such assteel drums or other ferrous materials distorts thismagnetic field and is indicated on the readout.Magnetometer surveys are used at municipal landfillsites to determine the extent, location, and relativemagnitude of drum disposal areas and may provideuseful information in determining the extent of thelandfill boundary. A magnetometer survey may beconducted rapidly with minimal labor and field time.

Before conducting a magnetometer survey, anappropriate-sized grid is laid out over the portion ofthe landfill suspected to contain the buried drums.The lines should be generally oriented in anorth-south fashion, and should be plotted andlabeled on a site topographic map. Data intervals(points on the line) should be greater than 10 feet,and space between traverse lines should be at least25 feet. In situations where the size andapproximate mass of a suspected object is known,the characteristics of the suspected object woulddictate the line intervals and points. A fixed pointshould be established where base data can becollected at various times during the day. Thisinformation can be used for correction purposes.

During the magnetometer survey, the field teamshould note any potential interference. These mayinclude any steel on the surface, construction debristhat may contain steel rebar, fences, power lines,and other buildings. Some of the local interferenceswith the magnetometer sensor can be minimized byincreasing the distance between the ground and thesensor.


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Total field and vertical gradient measurements arecollected using the magnetometer. Vertical gradientdata have higher resolution than the total field dataand minimize potential noise problems (e.g.,interference from miscellaneous ferrous materialssuch as wire). The total field and vertical gradientdata are collected simultaneously. At the completionof the magnetometer survey, data can be correctedfor the effects of the diurnal changes in the localmagnetic field. Once this is done, a magneticcontour map is prepared to interpret magneticanomalies.

Electromagnetic (Terrain Conductivity)Survey. An electromagnetic survey measures theconductivity variations between landfill soils andsuspected drum disposal areas. These surveysindicate where buried drums may be located. Depthestimates can be generalized by incorporatingmagnetometer components and both the horizontaland vertical components of the electromagneticsurvey data. Magnetometer data is dependent onthe amount of ferrous mass and the depth of whichit is buried. A large mass that is buried very deepwill look the same as a small mass buried near thesurface. By combining the vertical and horizontalelectromagnetic survey data, one can determinehow deeply a particular mass is buried.

The objective of an electromagnetic survey is tolocate buried metallic and/or conductive massessuch as discrete drum disposal areas. However,conductivity variations in soils or landfill materialsoften limit the survey’s ability to distinguish thedisposal areas. An electromagnetic survey can beused for rapid data collection with minimal sitepreparation.

Before conducting an electromagnetic survey, anappropriate-sized grid is laid out over the portion ofthe landfill suspected to contain the subsurfacematerials. Data are often collected at 3-meter coilseparations but can be extended to 10, 20, and40-meter spacings, depending on the depth ofinvestigation required. If soil conditions permit (i.e.,thin or non-existent clay layers), ground penetratingradar can also be used. The different coilseparations and orientations (vertical and horizontal)help identify whether conductivity variations arecaused by shallow or deep sources. The data are

plotted and contoured to describe the sourcedisposal area.

Soil Gas Survey. If a magnetometer orelectromagnetic survey does not accurately definethe boundaries of subsurface drum disposal areasand the contaminants of concern are VOCs, soilgas surveys can be conducted. Also, if the hot spotis an area of open dumping of hazardoussubstances, including VOCs, a soil gas survey maybe useful in delineating the area extent. As part ofthe soil gas survey, ground probes are driven toplanned depths, and a vacuum pump is used to drawthe samples from the probe. Soil gas samples arecollected in Tedlar bags or stainless steel bombs, orare adsorbed onto carbon or analyzed in the fieldwith an OVA. Initially, vertical profiles of organicgases in the soil pore spaces are measured andplotted at several locations. Based on these verticalprofiles and the particular organic gases present, thesampling depth for more soil gas samples isselected.

Once a constant sampling depth is established, soilgas samples are collected on an appropriate-sizedgrid laid out over the suspected disposal area. Oncethe location is better delineated, additional samplingon a smaller grid may be conducted to refine thelimits of the area. If results from the initial verticalprofiles do not provide sufficient data to find asolvent plume, the soil gas survey may bediscontinued. The sampling depth may be limited bythe presence of buried drums, and extreme careshould be exercised when driving probes intolandfills.

Analyses of the samples can delineate theboundaries of contaminated subsurface areas.These surveys can also be used to minimize thenumber of test pits, geotechnical borings ormonitoring wells that must be drilled or installed.Soil gas surveys can save the time and expenseincluded in drilling additional geotechnical boringsand monitoring wells; however, they are moretime-consuming and expensive than magnetometerand electromagnetic surveys.

Test Pits or Trenches. Depending on the resultsof the geophysical surveys and soil gas surveys, testpits or trenches may be excavated.


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OSHA requires that some type of investigativemethod such as test pitting be used prior to anyexcavation. Test pits or trenches are typicallyexcavated by backhoes due to the anticipatedhazardous nature of any subsurface materials. Thesize of the excavation depends primarily on thefollowing:

• Approximate area of the buried materials

• Space required for efficient excavation

• Economics and efficiency of availableequipment

Test pits normally have a cross section that is 4 to10 feet square; test trenches are usually 3 to 6 feetwide and may extended for any length to revealconditions along a specific line. Further informationon test pits is available in EPA’s A Compendium ofSuperfund Field Operations Methods (EPA,1987h).

Trenches or pits should not be excavated tooclosely together. Sufficient space should bemaintained between excavations to put soils thatwill be stockpiled for cover, and to allow access andfree movements by haul vehicles and operatingequipment. Excavated soil should be stockpiled toone side in one location. If possible, it should bedownwind of the excavation and away from theedge of the pit to reduce pressure on the walls.Soils should be placed on a sheet of heavy plastic toprevent additional contamination of surface soils.

If the excavation uncovers drums, they should becarefully examined for identifying markings.Information stenciled on drums can sometimes beused to identify PRPs. Any labels on the outside ofthe drums should also be used to specify additionalanalytical parameters for soil testing. Samples areselected by depth, visual observations (e.g., soilstaining), the concentration or types of VOCsdetected during the screening process, andstratigraphic relationships.

The field supervisor selects the depth intervals afterconsultation with the project hydrogeologist andchemist. At least one sample is collected from eachwall and the bottom of the excavation for field

screening. If visual observations and the fieldscreening procedures indicate that the samples aresimilar, they may be composited before laboratoryanalysis. If visual observations, field screening, orstratigraphic relationships indicate that the samplesare different, then they should be analyzedseparately by the laboratory. Samples of possiblewaste materials (e.g., leaks from buried drums ortanks) should not be composited.

Test pits excavated into fill are generally moreunstable than pits dug into natural in-place soils.Any required samples should be gathered withoutentering the test pit or trench. Samples of leachate,groundwater, and sidewall soils can be taken withtelescoping poles, etc., or if necessary, from thebucket of the backhoe. If intact or crushed drumsare encountered, they should not be removed.Drummed materials should not be tested unless thedrums are degraded and leaking, as evidenced bythe presence of liquids in the test pits around them.

Dewatering may be required to assure the stabilityof the side walls. This is an important considerationfor excavations in landfill material. Liquids removedas a result of dewatering operations must behandled as potentially contaminated materials. Thewater from any excavated saturated soils anderosion or sedimentation of these soils should becontrolled. A temporary detention basin and adrainage system should be considered, if necessary,to prevent contaminated wastes from spreading.

Following completion of sampling and test pitlogging, test pits are backfilled to grade. If excessmaterial shows evidence of gross organiccontamination or photoionization detector (PID)readings above background, it should be drummed.Otherwise, the excavated materials should beevenly spread over the test pit area and coveredwith uncontaminated soil.

The analytical results are compared with thegroundwater plume data to identify groundwatercontaminant source areas. This information is usedto identify the potential for future contaminantreleases to the groundwater; to evaluatecontainment, treatment, and disposal alternatives forthe hot spots; and to identify PRPs.


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Soil Borings . In some cases it may be appropriateto drill soil borings within the landfill contents tocharacterize known hot spots. The number anddepth of borings should be based on site specificconditions such as the suspected size and depth ofthe hot spot, and potential variability in contaminantlevels within the hot spot. Prior to drilling soilborings into a hot spot, a geophysical survey shouldbe completed as well as a review of any existinginformation (such as disposal records) on the natureof contamination in the hot spot.

Care must be exercised when sampling landfillcontents because drilling through the landfill couldcompromise the integrity of any liners (particularlysynthetic membrane liners), or penetrate a gaspocket causing an explosion hazard or release ofVOCs. Sampling landfill contents can also bedifficult, as garbage bags, baling wire, etc., cling tothe augers. Sampling should be extended to thebottom of the landfill only in situations where thedepth of the landfill is known and where it is knownthat there is no liner. Sampling should not penetratethe base of the landfill.

Landfill content samples are usually taken atintervals approved by the field engineer or geologist.Samples are typically taken at each change inmaterial type and are based on sampling using fieldmonitoring instruments. Where sampling is difficultor a larger volume of material is needed, alarger-diameter split-spoon sampler (3-inch), aShelby tube, a pitcher-type sampler, or a piston-typesampler might be required.

3.3.1.3 Guidelines

Determining the extent of soil contamination can bevery time consuming and costly. It is important tokeep the principal focus for conducting any soilsampling in the proper perspective, that is, defininggrossly contaminated soil that will be addressed byremedial action alternatives developed for thelandfill contents or hot spots. Characterization oflandfill contents is not necessary when capping isthe only practicable remedial action alternative.

A combination of field instruments and appropriatelaboratory samples can be used to preliminarilydetermine the type and extent of contamination

while minimizing cost and time. However, fieldanalytical techniques have certain limitations:

• OVA or PID. If VOCs are in the soil, theuse of an organic vapor analyzer (OVA) orphotoionization detector (PID) may indicatethe presence of VOCs. However, the headspace reading from a sample will dependon time delay after sampling, temperature,seal of lid on sample container, and wind.The results of the head space readingindicate VOC contamination, but usually donot produce quantitative results. It shouldbe noted, when selecting an instrument,that an OVA will detect methane where aPID will not.

• Mobile Laboratory Gas Chromatograph.The use of a field gas chromatographrequires the availability of a power supplyor battery packs with a clean area. Thisallows the analysis of samples for manycontaminants depending on the columnused, but does not provide totalcontaminant levels.

• Metals Analyses. Field instruments formetals analyses are limited to detection ofcertain indicator compounds, such ascopper, mercury, and chromium, but do notdetect levels below 10 ppm.

• Mobile Laboratory PCB Analysis,Polychlorinated byphenyls (PCBs) in thesoils can be detected in the field using theproper extraction solvent and gaschromatograph (GC). These surveys canprovide immediate information on thelateral extent of soil contamination.However, this usually requires the use of afield lab set up at the site and generally is alarge expense for timely turnaround (PCBscan be analyzed on a field portable GC,with the right column).

• Acids or Bases. Soil pH can be measuredby mixing standard volumes of soil anddeionizcd water and measuring theresulting pH of the slurry with a pH meter.


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To evaluate the various remedial action alternativesfor landfill contents and hot spots, data gatheredbefore or during the site characterization of landfillcontents/hot spots should include:

• 1-foot contour maps on an appropriatescale (e.g., 1 inch equals 50 feet) so thatslope length and gradients can be assessedfor capping alternatives

• Soil characteristics, including permeability,grain size, Atterberg limits, and erosionrates, for grading, capping, and thermaltreatment alternatives

• Waste characteristics of hot spot areasincluding TAL metals, TCL organics,RCRA waste characteristics (e.g.,ignitability, corrosivity, reactivity), totalBTU content, bulk weight of the material,and results of any pilot testing (ifnecessary) for thermal treatmentalternatives

• Climatic conditions including the 25-year,24-hour storm, frost depth, and surfacewater runoff velocity for cap design

• Existing cap characteristics

• Geologic characteristics and groundwaterdepth for capping and hot spot excavationalternatives

• Future uses of the site

3.3.3 Landfill Contents/Hot Spots Summary

Table 3-4 summarizes the sampling requirementsfor soils and landfill contents. Figure 3-3 shows alogic diagram for the decisions necessary tocharacterize soils and landfill contents by landfilltype. For Landfill Type I, the following sitecharacterization is necessary:

• Soils at leachate seeps• Areas with stressed vegetation • Stained soils • Existing caps and liners, if accessible

Geophysical surveys and test pits are not required.

For Landfill Type II, the following sitecharacterization steps are necessary:

• Soils at leachate seeps

• Areas with stressed vegetation

• Stained soils

• Existing caps and liners, if accessible

• Hot spot areas involving geophysical andsoil gas surveys, test pits and borings

3.4 Landfill Gas

Several gases are typically generated bydecomposition of organic materials in a landfill. Thecomposition, quantity, and generation rates of thegases depend on such factors as refuse quantityand composition, refuse placement characteristics,landfill depth, refuse moisture content, and amountof oxygen present. The principal gases generatedare carbon dioxide, methane, nitrogen, andoccasionally, hydrogen sulfide. Vinyl chloride,toluene, benzene, hydrogen cyanide, and other toxiccontaminants may also be present.

During a landfill’s early stages the refuse undergoesaerobic decomposition, and the principal gasgenerated is carbon dioxide. Once all the freeoxygen is depleted, the refuse decompositionbecomes anaerobic, and the principal gases becomecarbon dioxide and methane. Migration of landfillgas can pose onsite and offsite fire and explosionhazards. In addition, landfill gas can be an inhalationhazard and can become soluble in groundwater.

3.4.1 Landfill Gas Investigations

3.4.1.1 Objectives

The goal of landfill gas characterization is to identifyareas in the landfill containing high concentrationsof explosive or toxic landfill gas to:

• Perform an assessment of human healthrisks due to air toxics and explosivehazards


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Table 3-4SUMMARY OF SAMPLING REQUIREMENTS FOR SOIL AND LANDFILL CONTENTS

Medium To BeInvestigated Sample Location Considerations

Surficial soil--stained orstressed areas, leachateseeps

Horizontal composites fromalternate grid nodes or randomlocations on the grid.

Metals and cyanide at 0-6 inches.Volatile organics at 18-24 inches.

Existing Cap Representative random areasand areas where erosion,cracking, fracturing occurs.

Permeability, compaction tests.Test pits to determine cap depth.

Existing liners, ifaccessible

Accessible edges of liner. Clay and soil--permeability, compaction.Geotextile--suspectibility to chemicaldamage.

Landfill contents Randome areas in landfill of lessthan 100,000 yds 3.*

Stratigraphic changes, analyses forcontaminants indicated by recordsearch.

Hot spots Grids for surface geophysicalmethods, one sample from eachwall and bottom of test pit--composite or discrete.

Use surface geophysical methods first,excavate test pits.

*Sampling of landfills of small to moderate volume is dependent on (1) whether the landfill poses apotential principal threat to human health or environment, and (2) whether it is practicable to considerexcavation, disposal, or treatment of the landfill contents.

• Evaluate the feasibility of gas collectionand treatment

• Evaluate other remedial actions

The landfill gas investigation can be focused tocollect data specific to the remedial alternativesavailable for landfill gas. These remedialalternatives typically include active or passivelandfill gas collection systems which are describedin Section 4.4. The following subsections discussthe objectives, the procedures, and generalguidelines for site characterization of landfill gas.

3.4.1.2 Procedures

Various landfill gas collection methods can be used,depending on the type of landfill, and are describedbelow.

Landfill Type I. Methane gas as well as otherpotential toxic gases are of concern at this type oflandfill where disposal of hazardous wastes withmunicipal wastes has occurred, but there are noknown or suspected hot spots. Grid sampling forlandfill gas at random areas is the recommendedapproach for this type of landfill. Landfill gassamples should be collected from areas of thelandfill where methane production is suspected,such as for sites where a passive venting systemalready exists. Field screening may be used toidentify these areas if they are not already known.However, note that any field screening instrumentemploying a PID will not respond to methane due tomethane’s high ionization potential. Flame ionizationdetectors such as the OVA can be used to screenfor methane. Methane-specific Draeger tubes canalso provide a qualitative measure of the presenceof methane in landfill gas. Analysis


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should include VOC analysis to identify thepresence of toxic organics. If specific contaminantsof concern have been iden t i f i ed ,contaminant-specific Draeger tubes can be used. Ifspecific contaminants have not been identified, GCanalysis for target compound list (TCL) VOCsshould be performed.

Soil gas probes are commonly used to collect landfillgas samples due to the relative ease of samplecollection using this process. An appropriately sizedgrid can be superimposed on a target area, and thenodes sampled (grid sampling). A grid size of 100feet by 100 feet is often used. Grids can betightened to address smaller target areas of knownmethane production. The use of soil gas probes canalso be helpful in evaluating potential offsitemigration.

Samples are analyzed using a gas chromatograph.Sampling equipment should be decontaminatedbetween sampling points to prevent anycross-contamination. Using the OVA with acharcoal pre-filter can help improve the qualitativemeasure of methane concentration in landfill gas.The charcoal filter adsorbs most of thenon-methane gases, which results in an OVAreading closer to the actual methane concentrationin the gas sample.

Samples can be collected from existing gas vents orfrom test pits. A typical test pit can be 1 cubic footin size (e.g., approx. 1 foot deep). It is covered witha board with a small opening on top. Gas samplescan be pumped using a small electric or batteryoperated pump from this opening into a Tedlar bag(or stainless steel canister). The Tedlar bag samplescan be analyzed using the OVA or by onsiteanalysis using a mobile GC, and is typically used forfast-turn-around results. Samples can be collectedusing existing extraction wells following this sameprocedure. Stainless steel canisters are state-of-the-art air/gas collection devices that can beshipped for offsite analysis more readily than theother collection devices, but are expensive andrequire elaborate decontamination proceduresbefore they can be reused. Special care should alsobe taken with the field and trip blanks for airsamples due to possible cross-contamination orlaboratory problems.

Landfill Type II. Like landfill Type I, methane gasas well as other potential toxic gases are of concernat this type of landfill where disposal of hazardouswastes with the municipal wastes occurred, andthere are known or suspected hot spots. Gridsampling of random areas for methane sampling isrecommended if no known methane productionareas have been identified. Known hot spots can besampled for toxic contaminants (such as VOCssuspected to be present) on a tighter grid, based onthe size of the hot spot area. Sample collectionprocedures described for Landfill Type I can beemployed; VOC analysis should definitely beperformed to identify the presence of toxicorganics. If specific contaminants of concern havebeen identified, contaminant- specific Draeger tubescan be used; followup of laboratory analysis ofthese specific contaminants should be conducted. Ifspecific contaminants have not been identified, GCanalysis for TCL VOCs should be performed.

Further information on landfill gas sampling methodsis available in EPAs A Compendium of SuperfundField Operations Methods (EPA, 1987h).

3.4.1.3 Guidelines

A gas monitoring program is difficult to establishbecause of the difficulty in predicting where the gaswill migrate. If the cover material for a landfill hasa high clay content, is well compacted, or is wet orfrozen, it is not too likely that the gas will diffuseuniformly up through the cover. Plots ofisoconcentration lines of gas concentrationsdetermined from field monitoring may assist indetermining migration patterns. Monitoring forlandfill gas around the perimeter of the landfill mayalso be useful in determining lateral migrationpatterns.

A landfill gas monitoring program may also includesome sampling in residential areas. This mayinclude sampling for landfill gas in nearbybasements of residential or commercial buildings.


A detailed description of landfill gas remedial actionalternatives can be found in Section 4.4.


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To evaluate the various remedial action alternatives,data gathered before or during the sitecharacterization of landfill gas should include:

• Contour maps to determine possiblemigration patterns

• Geologic, hydrogeologic, and soilcharacteristics including permeability,moisture content, geologic strata, pH, anddepth to bedrock and groundwater todetermine potential gas migration patterns

• Landfill gas characteristics includingcomposition, moisture content, quantity, andheat and methane content to determinetreatment alternatives

• Types of microorganisms present in wasteto determine biodegradation stages (forestimating gas production)

3.4.3 Landfill Gas Summary

Table 3-5 summarizes the recommended samplinglocations for landfill gas. Figure 3-4 illustrates thedecision process required to determine theappropriate sampling approach to be implemented.

For Landfill Type I, soil gas probes and grids overa 100- by 100-foot area with sampling for methaneand VOCs is recommended. For Landfill Type II,the same sampling locations are recommended, with

the exception that a tighter grid (based on the sizeof the hot spot) is used in hot spot areas, and thatsampling for methane, VOCs, and specificcontaminants associated with the hot spots isrecommended.

3.5 Wetlands and Sensitive Environments

Many municipal landfills have been built on or next tonatural wetlands or other sensitive environments.Sensitive environments next to municipal landfillsmay be contaminated by inflows of leachate throughthe surface water or groundwater pathways. Inaddition, contaminated sediments in wetlands mayadsorb heavy metals or complex organics in leachateand source material from municipal landfills. Thefollowing subsections broadly discuss the objectives,procedures, and guidelines for characterizing nearbywetlands and sensitive environments.

3.5.1 Wetlands and Sensitive EnvironmentEvaluation

Data gathered before or during the environmentalevaluation will be used to characterize thecontamination and its extent (e.g., sediment volume)and to assess the impact of contamination onindigenous biota. Wetlands should be delineated inaccordance with the Federal Manual for Identifyingand Delineating Jurisdictional Wetlands (U.S. Fishand Wildlife Service, et al., 1989).

Table 3-5LANDFILL GAS SAMPLING PROGRAM

Landfill Type Sampling Locations Analysis

I Soil gas probes at node of 100- by 100-foot grid over random areas.

Methane and VOCs.

II Soil gas probes at nodes of 100- by100-foot grid over random areas andtighter grid over hot spots (based onsize of hot spot area).

Methane, VOCs, andspecific contaminants.



Figure 3-4LOGIC DIAGRAM FORLANDFILL GAS SAMPLING

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3.5.1.1 Objectives

The objectives of the environmental evaluation areto:

• Determine the impact of the site onsensitive environments (e.g., habitats,wildlife)

• Determine the impact of remedial actionon wetlands or floodplains

These environmental evaluations are normallyperformed, if the municipal landfill is built on or nextto wetlands or other sensitive environments. Theprincipal focus of these investigations is thesediments. However, other media of concern mayinclude surface water and aquatic species. Theenvironmental evaluation should provide informationregarding compliance with other environmentalstatutes, such as the Endangered Species Act, theCoastal Zone Management Act, and the ExecutiveOrder on Floodplains and Wetlands. Additionalinformation on conducting environmentalevaluations can be found in Risk AssessmentG u i d a n c e f o r S u p e r f u n d , VolumeII--Environmental Evaluation Manual (U.S.EPA, 1989c).

3.5.1.2 Procedures

Landfill Type I. The approach to theenvironmental evaluation will be the same for bothlandfill types. A review of the data from theleachate investigation (Section 3.2.1) and the landfillcontent/hot spot investigation (Section 3.3.1) maybe useful in determining contaminants that mayaffect wetland areas.

If surface water drainage patterns indicate possibledeposition of contaminated sediment in a wetlandsarea, a minimum of one composite sediment samplefrom the major drainage channel and at least twobackground sediment samples from the wetlandsarea should be collected. If the composite sample iscontaminated, then additional grab samples shouldbe collected to delineate the areal extent ofcontamination. The number of additional samples tobe collected should be determined on a case-by-case basis, depending on the potential extent ofcontamination.

In areas where vegetation stress is visible,composite sediment samples should be collectednear the affected flora. Two background samples,if not already collected for comparison purposes,should be collected. These samples will indicate ifcontamination from the landfill is present that mayrequire that biota sampling be done.

Data from other media investigations should bereviewed, because additional pathways could beidentified. For example, where leachate seeps intogroundwater and discharges into a wetlands area,background samples and samples of the potentiallycontaminated area, both sediment and groundwater,should be collected at the point of groundwaterrecharge.

A qualified field biologist should survey the area andnote plant and animal species, if the area isindicated as a sensitive environment during therecords searches or the site visit. Any remedialaction alternatives considered for the site shouldinclude mitigation procedures for these sensitiveenvironments.

Landfill Type II. The environmental evaluationwill be the same for Type II landfills as for a TypeI landfill. However, the investigation andremediation of hot spot areas may be a viablemeans of reducing or eliminating the source ofwetlands contamination.

3.5.1.3 Guidelines

After data from the environmental evaluation andother media investigations are collected, anexposure assessment should be performed. Theexposure assessment should particularly reviewpotential biota targets and the probability that theywill be affected by the site. If contamination ispresent and will harm the sensitive environments,then aquatic and terrestrial tissue sampling or acuteor chronic toxicity testing should be considered tofurther assess the impact of the site. Biota samplingcould include:

• Sampling of visibly affected plant life

• Invertebrate sampling in riverbeds

• Fish shocking, if recreational fishing area


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• Capture and sampling of native wildlife, ifit is known to be consumed by humans

Terrestrial and aquatic tissue sampling is laborintensive and expensive and should only beconducted if warranted by the exposureassessment. These types of studies are very rarelyperformed during an RI/FS. A more detaileddescription of collection of biota sampling isdescribed in the documents titled Guidance forConducting Remedial Investigations andFeasibility Studies Under CERCLA (U.S. EPA,1988d), and EPA’s A Compendium of SuperfundField Operation Methods (EPA, 1987h).


A description of remedial action alternatives forwetlands contamination can be found in Section 4.6.To evaluate remedial action alternatives, datagathered before or during the environmental sitecharacterization should include:

• Contaminants and concentrations in thesediments and volume of contaminatedsediments to assess remedial action

alternatives

• Species of flora and fauna that may beaffected by contaminants and remedialaction alternatives (Fauna should includebirds, terrestrial wildlife, and aquaticwildlife.)

A coordinated approach should be used whenconducting an environmental evaluation, becausegroundwater and surface water investigations(Sections 3.1 and 3.6) often overlap environmentalevaluations. For example, leachate from a municipallandfill can seep into groundwater, which rechargesto a wetlands area. The groundwater investigationwould identify the contamination pathway and couldprovide additional information on potentialcontamination in the wetlands. Both mediacharacterization efforts, therefore, should beintegrated.

3.5.3 Wetlands Summary

Table 3-6 summarizes the sampling rationale for anenvironmental evaluation, while Figure 3-5

Table 3-6SUMMARY OF SAMPLING REQUIREMENTS

FOR ENVIRONMENTAL EVALUATION

Media to Be Investigated Sample Locations

Minimum Number of Samples

Wetlands Collected sediment sample fromaffected area and background samples.

One composite sample per majordrainage channel; twobackground.

Collect additional sediment samples toconfirm extent of contamination.

Depends on size of potentiallycontaminated area.

SensitiveEnvironments

Observe sample aquatic/terrestrial lifein affected area.

Depends upon biota in affectedarea.

Collect aquatic/terrestrial life for tissuestudies.

Depends upon biota in affectedarea.

Collect sediment sample from stressedarea.

One composite sample per area.

Groundwater(Section 3.1)

Collect surface water sediment andgroundwater samples.

(See Section 3.1)


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shows a typical flow chart to determine samplinglocations. The sampling and monitoring locationsapply equally to both types of landfills.

3.6 Surface Water

Many municipal landfills are near surface waterbodies, including rivers, intermittent streams, ponds,and lakes. Surface water may be contaminated by:

• Site surface water runoff

• Surface seepage of leachate

• Leachate seepage to groundwater, whichrecharges to a surface water body

3.6.1 Surface Water Investigation

The surface water investigation must becoordinated with the groundwater, leachate, andlandfill contents/hot spots investigations (Sections3.1, 3.2, and 3.3, respectively). The rationale for thelocation of surface water sampling and monitoringpoints is often derived from the investigation ofother media.

3.6.1.1 Objectives

The objectives of the surface water investigationare as follows:

• Determine the impact of the site onsurface water and sediments (e.g., fromlandfill runoff and leachate seeps)

• Determine contaminant concentration inupstream samples

• Evaluate surface water hydrology,including drainage patterns, flow, andsurface water/groundwater relationships,as necessary

• Determine the waste characteristics ofsurface water and sediments

• Determine the extent of contaminationand sediment volumes

• Determine the tidal or seasonal effects ofthe surface water on the landfill

• Determine impact of flooding on capdesign and potential erosion

Much of the above information can be obtainedthrough record searches, initial site investigations,and agencies such as the USGS, Soil ConservationService, and other public agencies. Fieldinvestigations of water level measurements andsampling should be conducted to supplement thisinformation (see Guidance for ConductingRemedial Investigations and Feasibility StudiesUnder CERCLA (U.S. EPA, 1988d)).

3.6.1.2 Procedures

Landfill Type I. Contamination of surface waterand sediment is primarily of concern at Type IIlandfills. However, since unknown amounts ofhazardous wastes may be commingled withmunicipal wastes, migration of contaminants tosurface waters via leachate and runoff may also beof concern at some Type I landfill sites. Theapproach to both investigating surface water andsediment contamination will be similar for bothlandfill types. The types of surface waters that mayneed to be investigated at municipal landfill sitesinclude rivers, streams, lakes, ponds, or lagoons.

Many municipal landfills are located near rivers orstreams. Surface water and sediment samplesshould be collected upgradient (i.e., upstream) ofthe site, far enough to avoid any tidal influences,and downgradient of any known drainage/leachateseeps. In areas where tidal influence is aconsideration, samples should be composited fromseveral locations in both the upgradient anddowngradient areas. Care should be taken so thatcross-contamination of these samples by otherindustries or other adjacent landfills is avoided.Sediment and surface water samples should becollected upgradient and downgradient in eachadjacent river or stream. Additional samplinglocations might be added depending upon the size ofthe site, the number of rivers or streams near thelandfill, and the location of drainage or leachateseeps to the river or stream.


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Typical analytical parameters for surface water andsediment samples include pH, temperature, TSS,salinity, and specific contaminant concentrations.These data provide capacity of the water to carrycontaminants and water/sediment partitioning(Guidance for Conducting RemedialInvestigations and Feasibility Studies UnderCERCLA (U.S. EPA, 1988d)). Specific samplingtechniques are described in EPA’s Compendium ofSuperfund Field Operations Methods (EPA,1987h).

If contamination of a river is suspected ordocumented, river water levels and correspondingflows should be monitored upgradient from the siteand downgradient from any leachate seeps orrunoff. This information can be used to assessdilution effects and potential seasonal variations incontaminant concentrations due to changing waterlevels. Care should be taken when choosing riverflow monitoring locations so that impacts frompermitted or nonpermitted discharges fromindustries or adjacent landfills are avoided. Often,USGS and various state agencies monitor river flowat various points along major rivers or streams.These data bases can be used for water level, flowrate, and drainage data needs. The locations maynot be ideal, but a water balance can provide areasonable estimate for site characterization. If theriver is not monitored, a minimum of two waterlevel staff gauges should be installed, oneupgradient from the site and one downgradient fromthe site in each adjacent river or stream.Precipitation data can be acquired from localweather bureaus or the National Climatic DataCenter in Asheville, North Carolina.

Water level measurement frequency will dependupon the data needs of the site. At a minimum,measurements should be conducted during thesurface water sampling. More frequentmeasurements are required to determine tidal orseasonal influences.

Some municipal landfills are located nearintermittent streams. These streams often transportcontamination from landfills as a result of surfacewater runoff during or after periods of heavyrainfall. Contamination can also be the result of anaccidental release of contaminants such as

overflow of a surface impoundment. Ifcontamination is suspected as a result of seasonallandfill runoff, surface water and sediment samplesshould be collected during or immediately followingperiods of heavy rainfall. An evaluation of thedrainage patterns of the site should indicate optimalsampling locations. One sample should be collectedwhere runoff or overflow enters the streamchannel, and one sample should be collectedupgradient of the site, if possible. Additional surfacewater samples may be collected to assess theimpact of contamination from the intermittentstream on the water quality of any rivers or lakesdownstream.

Intermittent streams are not usually monitored byother agencies. The stream depth, width, and flowrate during or after periods of heavy rainfall shouldbe measured. The USGS can be consulted forestimates of water drainage in a particular area.Local weather bureaus should be contacted forprecipitation data.

Many municipal landfills are situated near lakes andponds or have small ponds on the site. Lakes andponds are often contaminated by surface waterrunoff and leachate seeps from the landfill. Inaddition, groundwater contaminated from leachateseeps could recharge to nearby lakes and ponds.

Surface water and sediment samples should becollected near the drainage or leachate seeps andbackground samples should be collected upgradientof leachate seeps. Care should be taken to preventcross-contamination from industrial dischargers andother landfills. Additional sampling may be requiredto assess seasonal/tidal fluctuations and multiplepoint discharges.

Larger surface water bodies should be monitored todetermine tidal and seasonal fluctuations that affectthe extent of contamination and groundwater flows.As mentioned above, the USGS and other agenciesmay already monitor water levels and flows tolakes. These data bases should be used. USGS datacan be found in their WATSTORE files, and U.S.EPA data can be found in their STORET files.Precipitation data can be obtained from localweather bureaus or the National Climatic DataCenter in Asheville, North Carolina.


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Landfill Type II. For landfills that are suspected orknown to have hot spot areas, investigation andremediation of hot spot areas may be a viablemeans of reducing or eliminating the source ofcontamination of surface water and sedimentcontamination. In some situations, hot spots mayextend into surface water sediment. Information oncharacterizing hot spots can be found in Section 3.3.

3.6.1.3 Guidelines

Data to be collected should include sampling ofpotentially affected surface waters and sedimentsfrom ponds, lakes, rivers, and streams (upgradientand downgradient).

At a minimum, surface water and sediment samplesshould be collected near drainage or leachate seeps.Background samples should also be collectedupgradient of leachate seeps and upstream of thelandfill site for streams and rivers.

The determination of analytical parameters forsediment and surface water samples shouldcorrelate with leachate analysis and hot spotanalysis. A review of the data generated from

the landfill contents/hot spot investigation (Section3.3.1) and the leachate investigation (Section 3.2.1)should indicate contaminants of concern for thesurface water investigation.


Surface waters are generally not treated atmunicipal landfill sites. However, removal andmanagement of contaminated sediments fromsurface water may be required. A description ofremedial action alternatives for surface water andsediments can be found in Section 4.7. Data needsfor evaluating surface water and sediment remedialalternatives can be quite extensive depending on theextent of potentially contaminated surface water ata specific site. Since surface water data needs arelargely dependent on the investigation of othermedia, they are discussed under the surface waterinvestigation (Section 3.6.1).

3.6.3 Surface Water Summary

Table 3-7 summarizes the recommended samplinglocations for surface waters. A flowchartsummarizing the decisions necessary to

Table 3-7SAMPLING AND MONITORING RATIONALE FOR SURFACE WATER

AND SEDIMENTS NEAR MUNICIPAL LANDFILL SITES

LocationSampling/HydrologicalMonitoring Location Considerations

Rivers Upgradient of site, down gradientof site.

Background samples.

Tidal influence, seasonal influence,leachate seeps, groundwater recharge,number of rivers/streams bordering thesite.

IntermittentStreams

Upgradient and downgradient fromleachate seep/surface water run-off/seep.

Seasonal influence.

Ponds Points of known run-off/seep andbackground samples.

Seasonal influence, groundwaterrelationships, other related rivers orstreams.

Lakes Points of known run-off/seep andbackground samples.

Tidal influence, seasonal influence,leachate seeps, groundwater relationships,other related rivers or streams.


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determine sampling and monitoring location ispresented in Figure 3-6. The sampling andmonitoring locations are equally applicable to bothtypes of landfills.

3.7 Baseline Risk Assessment

Baseline risk assessments evaluate the potentialthreat to human health and the environment in theabsence of any remedial action. They often providethe basis for determining if remedial action isnecessary and the justification for performingremedial actions. The baseline risk assessment canalso be used to support a finding of imminent andsubstantial endangerment if such a finding isrequired as part of an enforcement action. It shouldbe noted that the risk assessment is performed byEPA regardless of whether it is anenforcement-lead site or not. Detailed guidance forconducting risk assessments is provided in the RiskAssessment Guidance for Superfund, VolumeI--Human Health Evaluation Manual (U.S. EPA,1989j); and the Risk Assessment Guidance forSuperfund--Environmental Evaluation Manual(U.S. EPA, 1989c).

In general, the objectives of a baseline riskassessment may be attained by identifying andcharacterizing the following:

• Toxicity and levels of hazardoussubstances in relevant media (forexample, air, groundwater, soil, surfacewater, sediment, and biota)

• Environmental fate and transportmechanisms, such as physical, chemical,and biological degradation processes andhydrogeological conditions

• Potential human and environmentalreceptors

• Extent of expected impact or threat; andthe likelihood of such impact or threatoccurring (that is, risk characterization)

• Levels of uncertainty associated with theabove items

The level of effort required to conduct a baseline

risk assessment depends largely on the complexityof the site. The goal is to gather sufficientinformation to characterize the potential risk from asite adequately and accurately, while at the sametime conduct this assessment as efficiently aspossible. Use of the conceptual site modeldeveloped and refined previously will help focusinvestigation efforts and, therefore, streamline thiseffort. Factors that may affect the level of effortrequired include:

• Number, concentration, and types ofchemicals present

• Extent of contamination

• Quality and quantity of availablemonitoring data

• Number and complexity of exposurepathways (including the complexity ofrelease sources and transport media)

• Required precision of sample analyses,which in turn depends on site conditionssuch as the extent of contaminantmigration and the proximity,characteristics, and size of potentiallyexposed population(s)

• Availability of appropriate standardsand/or toxicity data

3.7.1 Components of the Baseline RiskAssessment

The baseline risk assessment process can bedivided into four components:

• Contaminant identification• Exposure assessment• Toxicity assessment• Risk characterization

A brief overview of each component follows.

3.7.1.1 Contaminant Identification

The objective of contaminant identification is toscreen the information that is available onhazardous substances or wastes present at the siteand to identify contaminants of concern to


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focus subsequent efforts in the risk assessmentprocess. Contaminants of concern may be selectedbecause of their intrinsic toxicological properties,because they are present in large quantities, orbecause they are presently in or potentially maymove into critical exposure pathways (for example,drinking water supply).

3.7.1.2 Exposure Assessment

The objectives of an exposure assessment are toidentify actual or potential exposure pathways, tocharacterize the potentially exposed populations,and to determine the extent of the exposure.Detailed guidance on conducting exposureassessments is provided in the Exposure FactorsHandbook (U.S. EPA, 1989dd), and in theSuperfund Exposure Assessment Manual (U.S.EPA, 1988aa).

3.7.1.3 Toxicity Assessment

Toxicity assessment, as part of the Superfundbaseline risk assessment process, considers (1) thetypes of adverse health or environmental effectsassociated with individual and multiple chemicalexposures; (2) the relationship between magnitudeof exposures and adverse effects; and (3) relateduncertainties such as the weight of evidence for achemical’s potential carcinogenicity in humans.

3.7.1.4 Risk Characterization

In the final component of the risk assessmentprocess, the potential risks of adverse health orenvironmental effects for each of the exposurescenarios derived in the exposure assessment, arecharacterized and summarized. Estimates of risksare obtained by integrating information developedduring the exposure and toxicity assessments tocharacterize the potential or actual risk, includingcarcinogenic risks, noncarcinogenic risks, andenvironmental risks. The final analysis shouldinclude a summary of the risks associated with asite including each projected exposure route forcontaminants of concern and the distribution of riskacross various sectors of the population. In addition,such factors as the weight-of-evidence associatedwith toxicity information, and any uncertaintiesassociated with exposure assumptions should bediscussed.

3.7.2 Using the Baseline Risk Assessmentto Streamline Remedial Action Decisions

The baseline risk assessment often providesjustification for performing remedial action at a site.Once a potential risk to human health or theenvironment has been demonstrated, an evaluationof the appropriate remedial measures to mitigate therisk must be performed. The results of the baselinerisk assessment are used in combination withchemical-specific ARARs to determine clean-uplevels, which in turn help to direct appropriateremedial measures. Options for remedial action atmunicipal landfill sites, however, are often limited.Therefore, in many cases, it may be possible tostreamline or limit the scope of the baseline riskassessment in order to initiate remedial action onthe most obvious landfill problems(groundwater/leachate, landfill contents, and landfillgas). Ultimately, it will be necessary to demonstratethat the final remedy, once implemented, willaddress all pathways and contaminants of concern,not just those that triggered the need for remedialaction.

Rapid implementation of protective measures forthe major problems at a landfill site may beaccomplished by:

1. Using the conceptual site model and RI-generated data to perform a qualitative riskassessment that identifies contaminants ofconcern in the affected media, contaminantconcentrations, and their hazardous propertiesthat may pose a risk through the various routesof exposure.

2. Identifying pathways that are an obvious threatto human health or the environment bycomparing RI-derived contaminantconcentration levels to standards that arepotential chemical-specific applicable orrelevant and appropriate requirements(ARARs) for the action. These may include:

• Non-zero maximum contaminant levelgoals (MCLGs) and MCLs forgroundwater and leachate (40 CFR300.430(e))

• State air quality standards for landfill gas


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When potential ARARs do not exist for a specificcontaminant, risk-based chemical concentrationsshould be used.

Where established standards for one or morecontaminants in a given medium are clearlyexceeded, remedial action is generally warranted(quantitative assessments that consider allchemicals, their potential additive effects, oradditivity of multiple exposure pathways are notnecessary). In cases where standards are notclearly exceeded, a more thorough risk assessmentmay be advisable before deciding whether or not totake remedial action.

The benefits of performing early or interim actionsat a landfill site include speeding up the clean-upprocess and reducing the impact on other affectedmedia (e.g., wetlands) at a site while the RI/FScontinues. The effect of early action at a landfillshould be factored into any ongoing riskassessment. For example, if leachate seepage thathad been contaminating surface water and wetlandsis stopped as a result of an early action, then therisk assessment developed subsequently for thestream sediments and wetlands should assume nofurther loading. Any early actions also need to bedesigned for flexibility so that they will be consistent

with subsequent actions. For example, it may benecessary to adjust a groundwater pump-and-treatearly action designed to attain MCLs to achieveeven lower levels, determined to be necessaryunder a subsequent risk assessment, in the interestof protecting environmental receptors in thewetlands into which the groundwater discharges.

Although this process allows for earlyimplementation of remedial measures, a riskassessment will be required to demonstrate that thefinal remedy at the site is protective of humanhealth and the environment.


This section provides information on how tocharacterize CERCLA municipal landfill sites sothat site dynamics and site risks can be defined.Also included in this section is a description of thebaseline risk assessment for municipal landfills.Section 4 describes technologies most practicablefor remediating CERCLA municipal landfill sites.The information in these two sections can then beused to assist in the development of appropriateremedial action alternatives to mitigate potentialadverse human health and environmental impacts ofmunicipal landfill sites.


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Section 4DETAILED DESCRIPTION OF TECHNOLOGIES

4.1 Remedial Action Objectives

Because many CERCLA municipal landfill sitesshare similar characteristics, they lend themselvesto remediation by similar technologies. EPA hasestablished a number of expectations as to thetypes of remedial alternatives that should bedeveloped during the detailed analysis stage; theyare listed in the National Contingency Plan (40CFR 300.430(a)(1)). For municipal landfill sites, itis expected that:

• The principal threats posed by a site willbe treated wherever practical, such as inthe case of remediation of a hot spot.

• Engineering controls such as containmentwill be used for waste that poses arelatively low long-term threat or wheretreatment is impractical.

• A combination of methods will be used asappropriate to achieve protection ofhuman health and the environment. Anexample of combined methods formunicipal landfill sites would be treatmentof hot spots in conjunction withcontainment (capping) of the landfillcontents.

• Institutional controls such as deedrestrictions will be used to supplementengineering controls, as appropriate, toprevent exposure to hazardous wastes.

• Innovative technologies will be consideredwhen such technologies offer the potentialfor superior treatment performance orlower costs for performance similar tothat of demonstrated technologies.

• Groundwater will be returned to beneficialuses whenever practical, within areasonable time, given the particularcircumstances of the site.

As a first step in developing remedial actionalternatives, remedial action objectives need to bedeveloped. Typically, the primary remedial actionobjectives for remediating municipal landfill sitesinclude:

• Preventing direct contact with landfillcontents

• Reducing contaminant leaching togroundwater

• Controlling surface water runoff anderosion

• Remediating hot spots

• Collecting and treating contaminatedgroundwater and leachate

• Controlling and treating landfill gas

• Remediating contaminated surface waterand sediments

• Remediating contaminated wetland areas

Based on the above remedial action objectives forCERCLA municipal landfill sites and the EPAexpectations outlined in the NCP, the followingpoints should be considered in order to streamlinethe development of remedial action alternatives:


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• Generally, the most practicable remedialalternative for landfills is containment(capping). Depending on sitecharacteristics, containment could rangefrom a soil cover to a multi-componentimpermeable cap.

• Treatment of soils and wastes may bepracticable for hot spots. Consolidation ofhot spot materials under a landfill cap is apotential alternative in cases whentreatment is not practicable or necessary.

• Extraction and treatment of contaminatedgroundwater and leachate may berequired to control offsite migration ofwastes. Additionally, extraction andtreatment of leachate from landfillcontents may be required. Collection andtreatment may be necessary indefinitelybecause of continued contaminantloadings from the landfill.

• Constructing an active landfill gascollection and treatment system should beconsidered where (1) existing or plannedhomes or buildings may be adverselyaffected through either explosion orinhalation hazards, (2) final use of the siteincludes allowing public access, (3) thelandfill produces excessive odors, or (4) itis necessary to comply with ARARs.Most landfills will require at least apassive gas collection system (that is,venting) to prevent buildup of pressurebelow the cap and to prevent damage tothe vegetative cover.

A review of the selected remedies in the recordsof decision (RODs) EPA has signed through FY1989 for CERCLA municipal landfill sitesindicates that certain technologies areimplemented more often than others (AppendixB). Based on this review of technologies usedmost frequently at CERCLA municipal landfillsites and, based on the NCP expectations, a list oftechnologies has been developed. The descriptionsin this section of these technologies is intended tostreamline the RI/FS process by making availablea list of technologies practical for use at CERCLAmunicipal landfills. The list of technologiesdescribed in this section is not intended to alleviate

the responsibility of the feasibility study team toconsider other, possibly appropriate technologies.Design considerations and data needs have alsobeen included to help guide the data-gatheringtasks associated with remedial investigations.

The technology discussions have been grouped bymedia for organizational reasons. However, theinteractions between media should be consideredwhen assembling technologies into alternatives.For example, leachate, contaminated groundwater,and landfill gas condensate may all requiretreatment using some or all of the same processes.

While the descriptions focus primarily ontechnologies used at landfill sites, brief descriptionsof surface water and groundwater remediation areincluded. Often, contamination of these mediamust be addressed, although the nature of theremedial alternatives is not necessarily unique tolandfill sites. Likewise, mitigation of wetlands isaddressed because a significant number ofmunicipal landfill sites are located within or closeto wetlands.

4.2 Landfill Contents

4.2.1 Access Restrictions

Access restrictions at municipal landfill sites areintended to prevent or reduce exposure to onsitecontamination. They include actions such asfencing, signage, and restrictive covenants on theproperty deed to prevent development of the siteor use of groundwater below the site. Accessrestrictions may also be imposed to reducerequired maintenance and to protect the integrityof a remedial alternative such as a landfill cap.Some of the conditions at a municipal landfill sitethat may warrant access restrictions include:

• Landfills where no cap has beenconstructed

• Landfills where passive venting of landfill gas is being used or cases

where no landfill gas controls havebeen implemented and gas emissionsmay be a hea l th hazard


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• Landfills where erosion of the cover maybe of concern (limit all-terrain vehicles,vehicular traffic, creation of foot paths,etc.)

• Landfills where liability concerns maywarrant limiting access

Situations where access restrictions such as fencingmay not be necessary include:

• Rural areas where heavy use is unlikelyand where occasional trespassing, such asfor hunting, does not present a risk

• Urban areas in situations where the landfillis capped and landfill gas does not presenta significant risk and where the localcommunity may desire that the land beused for an appropriate purpose such as apark area. In cases where fencing is notnecessary, it may still be prudent to postsigns to warn trespassers of potential risks.

The two types of access restrictions most used atmunicipal landfill sites include deed restrictions andfencing. Conditions in the area of the site should beevaluated in the 5-year reviews to assess thecontinuing or future need for access restriction.

4.2.1.1 Deed Restrictions

Restrictive covenants on deeds to the landfillproperty are intended to prevent or limit site use anddevelopment. Restrictive covenants, written into thelandfill property deed, notify any potential purchaserof the landfill property that the land was used forwaste disposal and that the land use must berestricted in order to ensure the integrity of thewaste containment system. The effectiveness ofdeed restrictions depends on state and local laws,continued enforcement, and maintenance. Mostrestrictions are subject to changes in politicaljurisdiction, legal interpretation, and level ofenforcement. Some, such as aquifer userestrictions, are voluntary and are not enforceable.In addition, some states do not allow deedrestrictions to be placed on properties due toinherent problems associated with enforcement.

Because deed restrictions are generally used inconjunction with other remedial actions, the specificprohibitions outlined in the restrictive covenant arebased on the type of remedial action implementedat the site and how the effectiveness of thatremedial action can be improved through deedrestrictions. For municipal landfill sites, the majorpurpose of deed restrictions is to protect theintegrity of the cap. The restrictive covenant shouldlimit subsurface development (excavation),excessive vehicular traffic (including off-roadvehicles and dirt bikes), and groundwater use.Additional deed restrictions may be required foreffective implementation of other technologies. Thepermissible uses/limitations for the specific landfillproperty should be identified based on the risk thesite poses and the remedial actions likely to beimplemented.

4.2.1.2 Fencing

When necessary, fencing is used to physically limitaccess to the landfill site. Signs may be posted tomake clear to potential trespassers that there maybe a health threat associated with going on the site.Signs typically are posted at equal intervals alongthe perimeter of the site and along roads leading tothe site. The most common type of fence used tolimit access is a chain-link fence about eight feethigh. Barbed wire on top of the fence may also berequired to deter trespassing. Gates alone may besufficient if only vehicular traffic needs to belimited. The primary data needed for fenceevaluation is a determination of the area to befenced. First, however, the location and potentialrisks of the landfill site, along with local land userestrictions, should be identified to determinewhether fencing is necessary at all.

4.2.2. Containment

Containment refers to technologies that isolate thelandfill contents and mitigate offsite migrationthrough the use of engineering controls.Containment technologies include surface controlsand capping.

4.2.2.1 Surface Controls

Surface control technologies are designed tocontrol and direct site runoff (potentially for


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treatment) and to prevent offsite surface waterfrom running onto the site. These technologiesreduce water infiltration into the waste andassociated leachate generation, and slow down therate of cap erosion. Surface controls to divertrun-on and minimize infiltration at municipal landfillsites often are implemented in conjunction with siteclosure. Such controls are almost always employedin concert with other technologies such asinstallation of a landfill cap. Landfill covers, like anyother disturbed soils, are prone to erosion, whichcan result in exposing and eventually mobilizingcontaminated materials. Therefore, if necessary,erosion and sediment controls should be considered,including space requirements for sedimentationbasins and erosion control structures. Surfacecontrols most commonly used at municipal landfillsites are grading and revegetation.

Grading. Grading modifies topography in order topromote positive drainage and control the flow ofsurface water. A properly graded surface willchannel uncontaminated surface water around thelandfill, thereby minimizing infiltration through thelandfill cap.

Grading is also the general term for techniques thatreshape the surface of landfills in order to controlerosion and to manage surface water infiltration,run-on, and runoff. Designing proper slope lengthsand gradients, and creating berms and swales arecommon grading techniques used to control androute surface water. Earth fill, typically from offsiteborrow sources, may be required to change slopegradients and to construct earthen berms.Regrading existing fill material is recommended insituations where there is a significant quantity of fill,if analysis shows the fill is acceptable to reuse.Significant cost savings could be made by usingexisting fill and thereby minimizing the cost oftransporting fill material from an offsite source.

Generally, slopes on top of the landfill range from 3percent to 8 percent in order to promote runoff andcontrol erosion. Sideslopes can be as steep as3H:1V (33 percent) as long as benches (horizontalsteps) are provided to interrupt the slopes and thuscontrol soil erosion and maintain slope stability.Steeper slopes can exist under certain slopeconditions.

However, the use of slopes less steep than 3H:1Vis recommended.

Municipal solid wastes usually settle during the lifeof a landfill due to decomposition of organic wastesand the weight of superimposed loads of refuse andsoil. The settlement may be significant, especially inthe deepest points of the landfill which typically arelocated at the center of the landfill. Settlement canresult in changing surface slopes and possiblyflattening some of these slopes. A well preparedgrading plan will take settlement into account byrecommending slopes that will still be effective aftersettlement. Potential settlement problems can beidentified by placing benchmarks that can besurveyed at various times throughout the RI/FSprocess. Continued operations and maintenance(O&M) will also be required to maintain adequatesurface slopes.

Grading techniques are well developed andcommonly used in landfills around the U.S. Theyare often performed in conjunction with capping andrevegetation and have a considerable impact byreducing leachate generated due to infiltration.

Some implementation and O&M considerationsconcerning an adequate grading plan include thefollowing:

• A well designed grading plan should resultin runoff from the site being controlled.Also, water that would otherwise run ontothe site will be diverted.

• A properly graded site will reduce thecontact time of runoff water on the landfill,thus reducing the rate of infiltration ofsurface water into the landfill.

• Erosion of cover soil can be controlledthrough grading, and soil retention willencourage the growth of beneficialvegetation.

• The cost of earth fill may be high,especially when the borrow source isremote. Free fill may be available fromlarge construction projects.


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• There will be a need for ongoingmaintenance because soil erosion andsettlement of waste can change the slopegradient.

• Some of the benefits such as reducedinfiltration rate or reduced volume ofleachate can be hard to quantify in landfillswhere there is no leachate collectionsystem.

In order to develop an adequate grading plan, thefollowing data should be gathered:

• Likely distance to borrow source

• The extent to which the existing fill couldbe used as part of the grading plan

• Existing topography and boundary ofproject earthworks (area to be graded)

• Climatological data (for example,precipitation)

• Stormwater retention and sedimentationboring requirements

• Soil data for the grading soil (for example,runoff curve number, permeability, grainsize distribution)

• Slope length and gradient limits--forexample, maximum and minimum lengthand gradient. (Top slopes range from 3percent to 8 percent; sideslopes, if lined,typically are not steeper than 3H:1V, witha bench for every 25-foot rise in elevation.)

• Maximum allowable erosion per acre--typically, 2 tons per acre per year (U.S.EPA, 1989d).

• Maximum stormwater flow velocity andtype of material available for ditch lining.Ditch or channel protection depends mainlyon the type of soil where the channel isbeing excavated (for example, grass,gravel, gabions, grouted gabions, concrete,plastic lining, etc.). For example, channels

excavated in fine gravel will require liningwhen flow velocity exceeds 2.5 feet persecond, while alluvial silts can withstandvelocities up to 2.7 feet per second withoutlining.

Revegetation. Revegetation is a method used tostabilize the soil surface of a landfill site andpromote evapotranspiration. Revegetationdecreases erosion of the soil by wind and water,reduces sedimentation in stormwater runoff, andcontributes to the development of a naturally stablesurface. It is also used to improve the aesthetics ofthe landfill, which is especially important when thesite is being considered for use as recreational land.

Revegetation is used as a temporary measure tostabilize the soil surface or as a permanent featurewhen the closed landfill site is being reclaimed forother uses. A systematic revegetation plan includesselection of a suitable plant species, seedbedpreparation, seeding/planting, mulching and/orchemical stabilization, fertilization, and maintenance.

Revegetation is used most in concert with othercontainment technologies such as caps. Since mostcaps include an impermeable layer, revegetationmay require a drainage layer over the impermeablelayer to avoid rotting of the plant roots. In dryclimates, irrigation may be necessary at times tomaintain strong plants. Trees and shrubs with deeproots that might penetrate the impermeable coverlayer should be prevented from growing on landfillcovers.

Some implementation and O&M considerationsconcerning revegetation include the following:

• Revegetation will reduce soil erosion bywind and water, improve site aesthetics,and increase evapotranspiration due toplants.

• The requirement for periodic maintenance(such as mowing) should be considered.

• The potential need for irrigation, which iscostly and may conflict with objectives ofreduced infiltration, should be considered.


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Some plant species commonly used for revegetationinclude Kentucky bluegrass, tall fescue, meadowfescue, redtop bentgrass, smooth bromegrass, fieldbromegrass, orchard grass, annual ryegrass,timothy, and red canary grass. Revegetationtypically includes grass and legume mixtures.Revegetation species can be selected using thestate’s Soil Conservation Service guidelines. Also,the EPA Office of Research and Development hasdeveloped a computer model, titled Veg Cover,which can be used to provide information on theselection of revegetation species. Additionally, thetype of plant species to be used in different climatesand conditions can be found in Design andConstruction of Covers for Solid Waste Landfills(U.S. EPA, 1979a).

The type of plant species selected for revegetationdepends on a number of factors. Primary dataneeds for determining an appropriate plant speciesfor revegetation are:

• Type of seeding--temporary or permanent

• Time of year when the seeding is to beperformed

• Type of climate at the landfill (annualprecipitation, low/high temperatures)

• Topographic characteristics (for example,slope steepness, drainage patterns)

• Soil characteristics (for example, nutrients,pH, moisture content, organic content, grainsize distribution)

Other factors that should be considered in selectinga plant species include:

• Minimizing the level of maintenancerequired after seeding

• Effects of increased surface soilpermeability due to root system andpossible increased infiltration through thecover

4.2.2.2 Cap (Landfill Cover)

The selection of an appropriate cap design willdepend not only on the technical objectives but alsoon risk factors and the identified ARARs for thelandfill site. A discussion and some examples ofpotential ARARs for municipal landfill sites arepresented in Section 5. Additional guidance fordetermining requirements to CERCLA sites can befound in the CERCLA Compliance with OtherLaws Manual: Part I (U.S. EPA, 1988c).

A determination should be made on which RCRAclosure requirements are relevant and appropriatefor the specific site of concern. RCRA Subtitle Dclosure requirements are generally applicable unlessa determination is made that Subtitle C is applicableor relevant and appropriate. In general, RCRASubtitle C would be applicable if the waste is alisted or characteristic waste under RCRA, and thewaste was disposed of after November 19, 1980(effective date of RCRA) or the response actionconstitutes treatment, storage, or disposal, asdefined by RCRA. The decision about whether aRCRA requirement is relevant and appropriate isbased on consideration of a variety of factors,including the nature of the waste and its hazardousproperties, and the nature of the requirement itself.State closure requirements that are more stringentthan the Federal requirements must be used indetermining a final cover design. These regulatoryrequirements should be integrated with the technicalobjectives for the site, based on site characteristics,to determine the best capping alternatives to beevaluated in detail.

Capping technologies may be designed to reducesurface water infiltration, control emissions of gasand odors, reduce erosion, and improve aesthetics.Capping technologies also provide a stable outsidesurface that prevents direct contact with wastes.The different types of capping technologies typicallyused at landfills include:

• Native soil cover• Single barrier (e.g., clay)• Composite barrier (e.g., clay plus FML)

Figure 4-1 is a simplified decision tree fordetermining an appropriate profile cap based on siteand waste characteristics.


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The primary data needed for designing a capsystem include:

• Depth to groundwater beneath waste (capsmay be of limited benefit in areas of highgroundwater if they are the only remedialaction used)

• Availability of cover materials (caps maybe high in cost if the desirable material isnot locally available)

• Rate or magnitude of waste settlementunder the cap (changes in waste thickness,degree of decomposition, and potentialpresence of large, near-surface voidsshould be known)

• Steepness of slopes

• Cover soil characteristics

- Proctor compaction Properties- Permeability- Grain size gradation- Shear Strength- Atterberg limits- Field moisture capacity

• Maximum frost depth at the location of thesite

• Anticipated weather conditions at the site(for example, temperature, precipitation,wind)

• Proximity to residential, commercial, orindustrial units

• Future land use of the site

The efficiency of the covers may be calculatedusing EPA’s computer model, HELP (hydrologicevaluation of landfill performance). HELP is aquasi-two-dimensional hydrologic model of verticalwater movement through the landfill cap. Themodel accounts for the effects of surface waterrunoff, evapotranspiration, soil moisture storage, andlateral flow through drainage layers to predict therate of water infiltration through covers. The HELPmodel is available from EPA’s Risk Reduction andEngineering Laboratory (RREL) in Cincinnati, Ohio.

Soil Cover. The use of native soil (nonclays) ascover for containment of wastes may beappropriate in arid climates where surface waterinfiltration (and subsequent leachate generation) isnot a controlling factor. Native soil caps are usedwhen the primary objective is to control erosion andprevent direct contact. However, in regions havingmore evapotranspiration potential than rainfall,native soil covers can be engineered to also reduceinfiltration. This is accomplished by incorporatingfield storage capacity within the cap sufficient tostore the largest seasonal inflow event. Such waterbalance designs can be performed and verifiedusing the HELP model. Native soil covers may alsobe appropriate on stabilized or solidified wastes, oras temporary caps to prevent direct contact withwastes. A temporary cap as an interim action maybe warranted in situations where the settlement rateof the landfill contents has not stabilized.

Native soils used to reduce the rate of infiltration inarid regions typically have high field storagecapacities (for example, 0.3 vol/vol). Soils with highfield storage capacity have a high percentage offine material (passing U.S. No. 200 sieve; forexample, silts and sandy silts). Also, native soils canbe mixed with additives and mechanicallycompacted to lower their permeability and makethem more suitable for reducing infiltration. Therequired field storage capacity and permeability ofsoil that is used to reduce infiltration depends on thefollowing factors:

• Climatological data for the region wherethe landfill is located (for example,precipitation for the design storm event,temperature, and depth of evaporativezone)

• Characteristics related to the type andcondition of vegetation that is expected tob e p l a n t e d ( f o r e x a m p l e ,evapotranspiration)

• Physical characteristics of the site (forexample, slope gradient and thickness ofnative soil layer)

Unless a water balance analysis is performed aspart of the design of a native soil cover, the


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native soil cover provides only separation,protection, and/or a vegetative layer. Generally,native soils are suitable for vegetation due to theirhigh organic content. A typical native soil cover thatprovides these limited functions is 18 to 24 inchesdeep, has a permeability less than or equal to 1 x10-5 cm/sec, and a field storage capacity less than0.3 vol/vol.

Implementation and O&M considerationsconcerning native soil covers include the following:

• Soil covers are generally low in initial cost.

• Construction materials generally are readilyavailable from local sources.

• Soil covers usually should be vegetated tominimize erosion.

• Unless designed to do so, soil covers arenot very effective in reducing infiltration.(If reduced infiltration is the design goal,field permeability testing should beperformed prior to construction to verifythat the expected low permeability can beachieved.)

• Erosion can expose waste if cover is notadequately maintained through continuedO&M.

• Native soil may not be naturally useful as abarrier layer in many cases and mayrequire processing.

• Native soil may not be stable on steepslopes (greater than 33 percent); therefore,constructibility may limit the slope to lessthan 25 percent.

Single Barrier. The main functions of a singlebarrier landfill cap are to reduce surface infiltration,prevent direct contact, limit gas emissions, andcontrol erosion. The two most commonly usedbarrier layers are clay soils and FMLs. Both serveas low-permeability barrier layers that reducesurface water infiltration into the landfill. Thebarrier layer is usually overlain by a drainage layerand/or a vegetative/ protective layer. A waterbalance analysis must be performed if a drainage

layer is incorporated into the cap. The claymaterials generally used are natural clays but alsocan be processed clay minerals such as bentonitemixed with native soils. The clay barrier must havea permeability less than 1 x 10-7 to be effective asa barrier. If bentonite is used, the high shrink-swellpotential needs to be considered.

Clay materials can achieve very low permeabilities(e.g., 1 x 10-7 cm/sec) if they are well compactedand if their moisture content is optimum, asdetermined in the laboratory. Upon surface drying,clayey soils form desiccation cracks that can allowsurface water to infiltrate. Also, in cold climates,clay may be damaged by freeze-thaw action unlessit is buried below the frost depth. In order toprevent surface drying, a layer of cover soil shouldbe placed over the clay layer to aid in maintainingthe clay’s moisture and to provide a base forrevegetation. Also, a soil cover layer can preventfreeze-thaw damage to the clay if the cover layeris of a depth equal to or greater than the localmaximum frost depth.

FMLs, on the other hand, are synthetic materialsthat, if punctured, can allow surface water topermeate into the landfill. A cover of soil over theFML, as well as a bedding layer under the FML, isnecessary to protect the integrity of the liner and toallow for revegetation.

Recently, bentonite panels have been marketed foruse as liners for municipal landfill sites. Previously,these panels have been used for liningimpoundments and lagoons, waterproofingstructures, lining spill containment areas, and similaruses. The panels consists of a dry granular sodiumbentonite layer approximately 1/4 inch thick with awoven geotextile on each side which allows somebentonite, upon hydration, to seep through the meshto facilitate a seal between overlapping panels.When hydrated, the bentonite is capable ofexpanding up to 15 times its former volume ifunconfined. This characteristic provides a sealwhen the material is confined and provides someself-healing at small holes or penetrations. Severallandfill sites are presently using these panels withapparent success. However, use of these panelsmay require demonstration to the appropriateregulatory agencies that the preferred


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liner system will meet the performance objectivesof the applicable regulations, even if the regulations,as written, are not met. Care must be used inapplications of bentonite board barriers on slopes.As the bentonite hydrates, its shear strengthdecreases and slope failures may result.

Weather conditions must be considered whenconstructing a landfill cap. If clay is used, dry,windy climates make moisture control difficult.Freezing temperatures, rain, and excessive naturalmoisture make proper placement of clay difficult.FML installation is not affected as much by hot, dry,or wet weather, but wind and cold temperature cancause problems. Caution must be used in wetweather, however, to ensure the integrity of FMLseams. The FML must be dry for proper seaming.

Subgrades for both clay and FML barrier layersmust be prepared to provide a sound foundation forthe barrier layer. This may require stripping existingvegetation, scarifying and compacting existing coversoils, or placing and compacting a layer of fill. Theintegrity of the foundation layer should be verifiedby proof rolling, when possible. Visible soft zonesshould be excavated and recompacted. A smoothsteel roller should be used to dress the surface ofthe subgrade before placement of an FML.

A typical cross section of a single-barrier capconsists of the following layers (from visible top totop of waste):

• Vegetative and protective layer--24 inchesof native soil

• Optional drainage layer--12 inches of sand(permeability $ 1 x 10-2 cm/sec) or acomposite drainage net

• Barrier layer--24 inches of clay(permeability ≤ 1 x 10-7 cm/sec) or a 30-mil(minimum) FML

• Bedding layer--12 to 24 inches ofcompacted select native soil or sandsubgrade

Regulations of individual states or specificapplications may require a different cross section;however, the function of the above-describedsystem would meet the intent of most requirementsof a single-barrier cap.

Some implementation and O&M considerationsconcerning single-barrier caps include the following:

• Either a clay or FML cap should result inlow permeability and reduction ofinfiltration.

• There is a known history of operating andplacement experience for both clay andsynthetic liners.

• A single barrier clay cap can be relativelylow in cost if clay is locally available.However, it may be very expensive if theborrow source is remote.

• Several choices of materials are used tomanufacture FMLs (e.g., PVC, HDPE,etc.) depending on the specific application.The selection of material is usually madeduring design.

• An FML cap may be more difficult torepair than a clay cap.

• A clay cap may be made less permeableby increasing bentonite admixture.

• A clay cap and an FML require carefulplacement with strict QA/QC, especiallyaround any gas vents.

• Both FMLs and clays may react tochemical attack and become morepermeable.

• Clay caps require careful design and strictQA/QC. Field permeability tests should beconducted before construction to verifythat the desired low permeability criterioncan be achieved using the specifiedmaterial and equipment.


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• Clay caps may be subject to damage byweather elements (freeze-thaw andsurface drying).

• Problems may rise with clay or FML capsand/or drainage layers in cases wheresubstantial landfill settlement is expected.

• In some cases, it may be useful toconstruct a temporary cover until the rateof settlement subsides and then construct afinal cap.

Composite Barrier. A composite-barrier capprovides an additional barrier layer, which reducesthe rate of infiltration more than a single-barrier capdoes. A composite barrier consists of a compactedclay layer overlain by a synthetic liner (FML). Thecomposite barrier, in turn, is overlain by an optionaldrainage layer and by a top vegetative/protectivelayer.

• The vegetative/protective layer providesstability and erosion control. It alsoprovides protection for the synthetic linerand for the drainage layer.

• The synthetic or natural drainage layerprovides drainage of infiltration water inorder to maintain a hydraulic head of nomore than 1 foot on top of the syntheticliner barrier.

• The synthetic and clay barrier layersprovide maximum infiltration protection.

• The subgrades under the bottom barrierlayer and overtop of the waste provide abedding layer and can act as a gascollection layer, if required.

A composite-barrier cap is to be used when thelandfill contains RCRA listed wastes, wastesufficiently similar to RCRA listed waste, or RCRAcharacteristic waste. The need for acomposite-barrier cap in cases where landfillscontain much lower concentrations of hazardouscontaminants than that of RCRA characteristic orlisted wastes must be judged on a site-specific basisand may depend on factors such as site

characteristics and potential receptors.Composite-barrier caps are also required in somestates (New York 6NYCRR Part 360) for closureof municipal solid waste facilities.

RCRA provides technical guidance (U.S. EPA, July1989d) that defines the types of layers EPAconsiders to be appropriate for a cap for newRCRA landfill cells. This guidance is a TBC (to beconsidered) and is intended to meet the RCRAregulations requiring a cap of equal or lowerpermeability than underlying liners or native soils.The minimum thicknesses for the layers in a RCRAcap (from visible top to top of waste) are asfollows:

• Vegetative and protective layer--24 inchesof native soil

• Drainage layer--12 inches of sand(permeability $ 1 x 10-2 cm/sec) or geonet(transmissivity $ 3 x 10-5 m2/sec)

• First barrier layer component--FML (20-milminimum)

• Second barrier layer component--24 inchesof clay (permeability ≤ 1 x 10-7 cm/sec)

• Bedding layer (optional)--12 inches ofnative soil or sand subgrade

The final design profile of a typical composite capwill also include geotextiles as a filter between theprotective cover and the drainage layer and as aprotective layer over the synthetic barrier if a layerof natural drainage stone is used. A geosyntheticmust not be placed between the two barrier layersor the effectiveness of the composite will becompromised. Multilayer caps pose a stabilityproblem on slopes. Laboratory direct shear testsmust be performed to measure the interface frictionangles between the various layers. To ensurestability, a slope stability analysis should beperformed for each interface.

Some implementation and O&M considerationsconcerning composite-barrier caps include thefollowing:


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• A composite barrier provides enhancedprotection against infiltration.

• Onsite material potentially can be used forsome of the layers.

• A composite-barrier cap will meet RCRArequirements for new landfill cells.

• Construction requires strict QA/QC.

• Stability problems may occur on sideslopesgreater than 10 percent.

• Problems may arise with clay layers,synthetic barriers, and/or drainage layers incases where substantial landfill settlementis expected.

• Lysimeters may be useful to monitor thecover performance (leak detection) wherecover stability is uncertain.

• In some cases, it may be useful toconstruct a temporary cover until the rateof settlement subsides and then construct afinal composite-barrier cap.

4.2.3 Removal/Disposal

Removal of contaminated soils at municipal landfillsites is generally limited to hot spots or, whenpracticable, to landfills with a low to moderatevolume of waste (e.g., less than 100,000 cubicyards). Complete excavation of the municipallandfill contents is often not considered practicablebecause of the large volume of waste typicallyfound at CERCLA municipal landfill sites. Noexamples of complete excavation were found in thereview of remedial actions outlined in the RODslisted in Appendix B.

As previously stated, hot spots that are appropriatefor excavation and removal should be indiscrete,accessible locations of a landfill where a waste typeor mixture of wastes presents a principal threat tohuman health or the environment. The area shouldbe large enough so that remediation will significantlyreduce the risk posed by the overall site and smallenough to be reasonably practicable for removal

and/or treatment. Hot spots will not be investigatedand characterized unless some form ofdocumentation or physical evidence (for example,aerial photography) exists to support their existence.In cases where it is not clear whether a hot spotposes a principal threat and it is practicable toexcavate, at least one alternative should bedeveloped for removal/treatment of that area. Thisalternative will be considered during detailedanalysis of remedial action alternatives.

4.2.3.1 Excavation (Hot Spots)

Excavation of hot spots will be required prior toconsolidation, treatment (except in situ treatment) ordisposal offsite. Excavation of hot spots to removecontaminated soils will require the use of standardconstruction equipment or special equipmentadapted to minimize disturbance of the deposit orsecondary migration. Also, any excavations must beperformed in accordance with OSHA. Typically,mechanical equipment such as backhoes, bulldozers,and front-end loaders is used for excavation. Theuse of scrapers and draglines usually makes itdifficult to adequately control site dispersion. Whilethe selection of specific equipment normally isbased on contractor preference, the selection alsodepends on the water table location, the watercontent, and consistency and strength of thecontaminated soils to be excavated. It is almostalways cost-effective to excavate contaminated soilin thin, 4- to-12-inch layers to minimize the volumeto be managed.

In many cases, due to landfilling practicesand the weight of overlying material, drumsmay be crushed and empty. Isolated drumslocated throughout the landfill may notbe identifiable nor represent a principal threat.In the event that buried, full drums,are encountered, the hazards associated withthe drums must be evaluated. Evaluationmay be accomplished by staging, opening,sampling and analysis followed by transport anddisposal. Ambient air should be monitoredcontinuously during drum removal activities. A drumgrappler, a drum cradle or sling attached to abackhoe or crane, or a front-end loader can be usedfor drum removal. Drums may be opened by bungremovers or drum cutters. Depending on their


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condition, removed drums may need to be over-packed into salvage drums prior to transport.

Some implementation and O&M considerationsconcerning excavation include the following:

• Excavation of hot spots is a conventional,demonstrated technology that can becost-effective, particularly when areas areconsolidated with other landfill materialprior to capping.

• Solid material above the water table can beexcavated with very little secondarymigration and good control of depth of cut.By using the proper excavation equipmentand sediment control devices, the effect ofsurface runoff can be minimized.

• Waste disposal may require handling,stockpiling, and truck hauling of largevolumes of material.

• Good control of depth of excavation can bedifficult under water. In some cases,excavation would require the constructionof impermeable barriers and sitedewatering.

• In situations where excavation extendsbelow the water table, dewatering is likelyto be required. Consideration should begiven to seasonal fluctuations in thegroundwater table. Significant shoring anddewatering costs may be eliminated byexcavating at times when the water table islow.

• Site accessibility to heavy equipment shouldbe evaluated to determine whether trackvehicles may be required.

• The distance over which excavatedmaterial must be hauled should beevaluated to determine whether separatemoving equipment (such as dump trucks) isrequired.

• Seasonal (climate) constraints onexcavation activities may affect theschedule for excavation. Depending on the

size of the area, temporary enclosures andportable heating devices may be used ifexcavation occurs during winter months.

• Enclosure of the excavation area may benecessary if volatile organic compound(VOC) emissions are high.

• Potential exposure to workers and nearbycommunities during excavation must beconsidered. Enclosed cabs may benecessary to minimize operator exposure.

The primary data needs for preparing an excavationplan for removal of contaminated materials include:

• Waste characteristics--Excavation is notsuited for materials with a low solidscontent (dewatering may be required).Total suspended solids (TSS), totaldissolved solids (TDS), volume-weight(percentage of moisture) analysis may benecessary to determine the solids content ifcontamination extends below the watertable. Other data such as particle size,viscosity, and pH may also assist inmaterial handling needs. Analysis forhazardous waste parameters (for example,TAL metals, TCL organics) andgeophysical testing (for example,magnatometry or ground penetrating radar)may be warranted if the presence of burieddrums is suspected.

• Water table levels (and seasonalfluctuations, if data exists)

• Volume of contaminated material

• Geologic characteristics from geologicmaps and boring logs to assess difficulty ofexcavation

• Climate information from National ClimaticCenter (NCC) or local weather bureau toassess frequency of rains, seasonalvariations in temperature


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4.2.3.2 Consolidation

A common disposal option for outlying hot spots atmunicipal landfill sites is consolidation with otherlandfill material followed by capping. Consolidationmay also be a practicable alternative for disposal ofwastes in undesirable locations (for example,wetlands) or contaminated sediments. The objectiveof consolidation is to relocate contaminated materialfrom outlying areas into the landfill contents tominimize the required size of a landfill cap.

Since consolidation within the area of contaminationis not considered management of the material, LandDisposal Restrictions (LDR) requirements do notapply. Therefore, material can be consolidatedwithout being treated first. In situations wherecontamination has spread to eroding sideslopes,contaminated soil can be excavated andconsolidated within the landfill, thereby reducing therequired area of the cap. Consolidated material canalso be used as fill under the cap as called for bythe grading plan.

Some implementation and O&M considerationsconcerning consolidation include the following:

• Consolidation is usually implemented inconjunction with capping, and the capdesign may be influenced by the volumeand nature of the material beingconsolidated.

• Consolidation may require handling,stockpiling, and truck hauling of largevolumes of material.

• Considerations and data needs listed underexcavation should also be reviewed.

• Potential exposure to workers and nearbycommunities during consolidation activitiesmust be considered.

The primary data needs to evaluate consolidationare basically covered under the data needs forpreparation of an excavation plan. The mostimportant information to coordinate with theselection and design of a landfill cap will include:

• Waste characteristics of hots p o t - - d e t e r m i n e d d u r i n g s i t echaracterization

• Volume of contaminated material

4.2.3.3 Disposal Offsite (Hot Spots)

Offsite land disposal is generally considered theleast desirable alternative for remediation.However, offsite disposal may be employed ifonsite treatment followed by disposal under thelandfill cap is not feasible. Onsite disposal may notbe feasible or practical if the waste is regulatedunder RCRA and must be disposed of in a RCRAlandfill.

The requirements for offsite disposal ofcontaminated soils will be based largely on theRCRA LDRs. The LDRs may be applicable to thecontaminated soils if it is determined that the soilshave been contaminated by a restricted listedRCRA waste or if the contaminated soils exhibit aRCRA hazardous waste characteristic. Aspreviously stated, LDRs do not apply if the hotspots are to be consolidated (only) under the landfillcap.

If it is determined that the contaminated soils are aRCRA waste, the LDRs may require that a specificconcentration level be achieved prior to landdisposal in a RCRA landfill or that a specifiedtechnology be used for treatment prior to disposal ina RCRA landfill. If a concentration is specified andthe soils are below these concentrations, the soils donot have to be treated prior to offsite disposal in aRCRA landfill. It is possible that treated soils,particularly if incinerated, could be delisted anddisposed of onsite or in a solid waste landfill.

If the soils are a RCRA waste, offsite land disposalmust be at a permitted RCRA hazardous wastelandfill that meets the requirements of RCRASubtitle C. The design features of a RCRAhazardous waste landfill are defined in 40 CFR 264Subpart N. The major requirements of such landfillsinclude an impervious cap; a double liner; a leachatedetection, collection, and removal system; run-onand runoff control systems; and wind dispersalcontrols.


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In the absence of other regulations, solid wastelandfills will be regulated under RCRA Subtitle D.In most cases, however, state regulations governthe design, construction, operation, and closure ofsolid waste landfills. Currently, in many states, therequirements for new solid waste landfills areapproaching the complexity and restrictiveness ofrequirements for disposal of hazardous waste.

CERCLA Section 121(d)(3) and the CERCLAoffsite policy contain another set of requirementsthat will impact the offsite disposal of CERCLAwastes. EPA’s current offsite policy (OSWERDirective 9834.11, November 13, 1987ff) describesprocedures that must be observed when aCERCLA response action involves offsitemanagement of CERCLA wastes. The generalrequirements of the offsite policy are to be codifiedand expanded in a proposed rule, which willsupersede the current policy when finalized (see 53FR 48218 (November 29, 1988)). Generally, thispolicy requires that an offsite facility accepting thewaste have no relevant violations or otherenvironmental conditions that pose a significantthreat to public health, welfare, or the environment,or otherwise affect the satisfactory operation of thefacility. The purpose of this policy is to direct thesewastes only to facilities determined to beenvironmentally sound and thus avoid havingCERCLA waste contribute to present or futureenvironmental problems. A Regional OffsiteCoordinator has information on the acceptability ofcommercial facilities in the region to receiveCERCLA wastes.

Some implementation and O&M considerationsconcerning offsite disposal of contaminated soils ina RCRA or hazardous waste landfill include:

• Landfilling may be the best or only disposalmethod for certain solid hazardous wastes.

• Based on LDRs, treatment of soils may berequired prior to disposal.

• In addition to the LDRs, offsite disposalmust comply with the CERCLA offsitepolicy.

• High volume wastes may be disposed ofmore economically by landfilling than bytreatment, although landfilling does notreduce toxicity, mobility, or volume ofwastes.

• Waste handling and landfilling technology iswell developed. However, offsite disposalin a landfill cannot be consideredpermanent remediation of the contaminatedmateria l, and future risk and liability areassociated with landfilling of wastes.

There are no specific design considerationsassociated with offsite disposal; however,associated technologies such as excavation andsoils treatment may be employed prior to offsitedisposal.

In order to evaluate the offsite disposal options, thefollowing data should be gathered:

• Characteristics of waste to determinesuitability for offsite disposal (for example,RCRA characteristic tests, moisturecontent, hazardous waste parameters). Thepotential landfill(s) that may be used foroffsite disposal should be contacted todetermine what analysis they require.These tests should be included in theanalysis of hot spots.

• Volume of waste to be disposed offsite.

4.2.4 Hot Spots Treatment

Based on review of the remedial actions that arebeing conducted at municipal landfill sites on theNPL, it was found that the most often selected soilstreatment technology is onsite thermal treatment(incineration). Offsite incineration is rarely chosenas an acceptable alternative because of the currentlack of available capacity. Although in-situtreatment is likewise rarely used, this type ofresponse action, particularly in-situ stabilization andin-situ vapor extraction, may warrant someconsideration if the type of soil contamination istreatable by this technology. Other technologies fortreatment of hot spots are, at the present time,rarely selected. This is probably because of theheterogeneous nature of landfill wastes and the


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corresponding complexity associated withimplementing in situ technologies at landfill sites. Aswith excavation, soil treatment is considered afeasible alternative only for hot spots and, whenpracticable, for contents of small to moderatelandfills (e.g., less than 100,000 cubic yards).

4.2.4.1 Thermal Treatment (Onsite)

Thermal treatment is an appropriate method for thedestruction or treatment of combustible organics insoil. Onsite thermal treatment can be conducted ina field-erected facility or mobile unit. Lowtemperature thermal volatilization can also be usedto remove VOCs (or semivolatiles if operated athigh enough temperatures) in a soil drying unit.However, this technology is rarely effective byitself because of the mixed nature of landfill wastematerial that incudes inorganics and nonvolatilefraction of organics.

Thermal treatment exposes waste material to a hightemperature for a specific period of time. Whenheated in the presence of sufficient oxygen forcombustion (incineration), the waste is chemicallytransformed into innocuous substances such ascarbon dioxide and water. This process alsoproduces ash and a certain amount of oxides andacid gases, depending on the composition of thewaste and the process conditions under which it isoxidized. When heated in the absence of oxygen(pyrolysis), the waste decomposes, producing aresidue and a variety of vapor-phase compoundsthat can then be incinerated.

Analysis and characterization of the waste usuallydetermine whether it can be treated by incineration.The analysis also provides the physical propertydata used in the design of process equipment.

Incineration technologies include rotary kiln,fluidized bed, multiple hearth, radiant heat, moltensalt, liquid injection, and molten glass. Pyrolysistechnologies include conventional pyrolytic reactors,rotary hearth pyrolyzer, ultra-high temperaturereactors, and starved-air combustion. The mostcommonly used system has been rotary kilnincineration. It is usually desirable not to specify inthe feasibility study which incineration processoption will be used.

Rather a representative option, such as rotary kiln,can be presented as an example with the actualprocess option decision being made during design orby the contractor based on performancespecifications. It should be noted that the use ofperformance specifications allows for a variety ofboth innovative and established incinerationtechnologies to be considered.

Some implementation and O&M considerationsconcerning the use of thermal treatment forcontaminated hot spot material include thefollowing:

• Space requirements typically are modestbut should be considered.

• Typically, efficiency of destruction is high,emissions can be effectively controlled, anddestruction/treatment is immediate.

• Waste heat recovery may be possible andshould he considered.

• The weight and volume of combustiblewaste may be reduced by more than 90percent through thermal treatment. In somecases, incineration of solid waste (e.g.,soils) may result in little or no reduction involume; however, the solid feed will bedecontaminated.

• Residues may be delistable and disposed ofonsite (although exceedance of the TCLPcharacteristics for metals may requiresolidification prior to onsite disposal).

• Capital and operating costs are typicallyhigh and should be considered.

• Ash disposal may have to be at a RCRAlandfill if it is classified as a hazardouswaste.

• Supplemental fuel is required for startupand may be necessary to maintaincombustion.

• Significant material handling, prepro-cessing, and post-processing may be


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required (for example, for rocks, drums).

• Products of incomplete combustion (PICs)may be generated that are difficult toassess or control.

Data needed for evaluation of thermal treatmenttechnologies and for design purposes include thefollowing:

• Waste characterization data (For wasteswith high concentrations of inorganics,thermal treatment may not be the bestalternative, or other treatment technologiesmay be needed inconjunction withincineration. Also, physical characteristicssuch as large percentage of rocks andboulders may indicate that wastesegregation or pretreatment is required.)

• Heat content of waste (A BTU analysisshould be done to evaluate the need forauxiliary fuel.)

• Pilot testing during either the feasibilitystudy or the predesign phase (Such testingis often required to evaluate the treatabilityof the contaminated soils by thermalmeans.)

4.2.4.2 Stabilization

Stabilization, which is used for treatment of viscousfluids, solids, and contaminated soil, is a feasibleoption for hot spots. To date, stabilization (orsolidification) has rarely been used at municipallandfill sites. However, it appears to be potentiallyfeasible for soils contaminated by inorganics.Stabilization has also been used for treatment oflow-level-radiation-contaminated soils and for soilscontaminated by low concentrations of organics,whereby leaching of organics is reduced but noteliminated.

Stabilization using an onsite batch process consistsof excavation of wastes, onsite mixing withreagents in a batch plant (for example, a cementkiln) and finally, replacement in the landfill area.Use of a batch process will trigger LDRs; treatedwaste will either have to be disposed of in an offsiteRCRA landfill or may be delisted and disposed of

onsite or in an offsite solid waste landfill. In situstabilization refers to processes where stabilizingreagents (pozzalanic material) are added in place toimprove physical characteristics of waste byrendering wastes nonhazardous and nonleachable.Reagents are mixed with the contaminated wasteusing standard earth-moving equipment such asbackhoes, drag lines, bucket loaders, or bylarge-diameter augers. In situ stabilization offers theadvantage that soils can be treated in place.However, greater quality control, such as assuranceof complete mixing of regents, can be achievedusing a batch plant.

Pretreatment such as screening, segregation, andremoval of larger objects such as drums and debrismay be necessary. In situ stabilization is typicallyaccomplished in relatively shallow lifts, commonlyabout 2 feet deep, since large quantities of materialsare moved as a mass to accomplish mixing. Depthof contamination is also generally limited toapproximately 12 feet, although this technology canpotentially be used for deeper contamination byprogressively removing solidified wastes whileincreasing working depth. For deeper sites,excavation and addition of reagents using a batchplant may be appropriate.

The ratio and composition of reagents varydepending on the waste. A wide range ofcommon pozzolanic stabilizing reagents canbe selected, depending on what is locallyavailable, and reagents can be proportionedon the basis of untreated waste characteristics. Atypical formulation of stabilizing agents might be30 percent fly ash, 30 percent kiln dust, 20 percentportland cement, and 20 percent hydrated lime.Most inorganic hazardous sludges can be mixeddirectly with pozzolanic materials to form ahardened soil-like material. Extraneous materialssuch as asbestos, sulfides, and solid plastics mayincrease the strength of the treated material.Impurities such as organic materials, silt, clay,lignite, fine dust, sulfates, or soluble metal salts mayretard or inhibit setting and curing, mayreduce strength, or may cause swelling andsplitting of the solidified mass. Typically,wastes containing high levels of organic (e.g., 10to 20 percent) constituents require someform of pretreatment before solidificationwith pozzolanic materials. Treatability


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studies must be performed to determine if thecontaminated waste/soil is amenable to stabilization.

Because of the nature of stabilization, the finalvolume of treated waste typically is 10 to 30percent greater than the original volume of waste.However, volume increases of 50 to 100 percentare possible, depending on waste and sitecharacteristics.

Some implementation and O&M considerationsconcerning stabilization include the following:

• A wide variety of inexpensive reagents isavailable.

• The technology is applicable to manydifferent waste materials.

• Waste remains onsite (this may or may notbe an advantage, depending on site-specificcircumstances).

• Use of a batch process will trigger LDRs.

• There may be a significant increase involume that should be considered.

• Difficulty may arise in verifying sufficientmixing and completion of the process.

• Stabilization may not be applicable towastes containing moderate to highconcentrations of organics.

• It may be difficult to control odors, VOCs,or dust during processing.

• Wastes containing drums, constructiondebris, etc., may require somepretreatment.

• Long-term monitoring will be necessary toverify whether contaminants are leachingto the groundwater.

• Evaluating the long term effectiveness ofstabilization should be included in the5-year review.

Data that should be gathered for design andimplementation of stabilization include:

• Waste characterization (Inorganic andorganic hazardous constituents, and ameasure of the total organics present suchas total organic carbon [TOC]).Treatability studies should also beperformed during the FS to evaluate if thewaste is amenable to stabilization,particularly when organics are present.Treatability tests will need to be conductedduring design to optimize the formulation ofstabilization agents.

• Depth of waste to be stabilized (Depthshould be less than 12 feet for in situstabilization.)

• Total bulk unit weight of material (Soils willtypically be between 80 to 110 lbs/ft3;liquids and sludges typically range between63 to 80 lbs/ft3.)

4.2.5 Innovative Treatment Technologies

4.2.5.1 Description of Technologies

The focus of this document has been on traditional,previously used, and proven remedial technologies.This section is intended to address some innovativetreatment technologies that may be appropriate forremedial actions at municipal landfill sites. It isimportant that the evaluation of alternatives formunicipal landfill sites not be limited to conventionaltechnologies, particularly in situations where moreeffective or less costly treatment can be achievedby using innovative remedial technologies.

The following two technologies are presented asinnovative technologies that may be viable for hotspots at municipal landfill sites:

• Vapor extraction • In situ bioremediation

Other innovative technologies may also be viableand should be considered if they are appropriate tosite characteristics.


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Soil Vapor Extraction. Soil vapor extraction(SVE) is an in situ process used to remove VOCsfrom soil. This technology may be suitable fortreating hot spots contaminated with VOCs;removal of VOCs can significantly reduce themobility of the other contaminants present, such asinorganics or semivolatile organics. SVE consists ofa network of wells with perforated well screens.These wells are packed with gravel and sealed atthe top with bentonite to prevent short circuiting.The extraction wells are connected to the suctionside of a vacuum extraction unit through a surfacecollection manifold. The vacuum extraction unitinduces a flow of air through the subsurface into theextraction wells. The vacuum not only drawsvapors from the unsaturated zone, but it alsodecreases the pressure in soil voids, thereby causingthe release of additional volatile organic compounds(VOCs). The extracted gas flows through thesurface collection manifold and is either vented tothe atmosphere, connected to a vapor-phase carbonadsorption system, or flared, depending on thenature and extent of VOC contamination. AlthoughSVE is considered to be an innovative technology,many full-scale applications have already beeninstalled and are currently operating or have alreadyachieved performance objectives.

Standard procedures that exist for installing landfillgas recovery wells in municipal landfills should beapplied to the installation of SVE wells. Thepresence of landfill gas in municipal landfillsrequires that special health and safety precautionsbe taken. The presence of landfill gas may alsorequire modified VOC control systems. SVE can be“shortcircuited” by debris and noncontinuous lifts ofmaterial. More extraction wells installed closertogether are necessary to ensure sufficienttreatment. One or more wells in each lift may benecessary.

SVE treatment may be particularly cost-effectivefor municipal landfills that will require landfill gascontrol. Once SVE treatment is completed, thewells can be used to collect or vent landfill gas (seeSection 4.4).

In Situ Bioremediation. In situ biodegradation isthe process of enhancing microbial action toremediate subsurface contaminants that are

adsorbed to soil particles or dissolved in the waterphase. This technology is designed to biodegradechlorinated and non-chlorinated organiccontaminants by employing aerobic bacteria thatuse the contaminants as their carbon source. Thistechnology could be applied to remediatecontaminated soil and groundwater withoutexcavating overlying soils. The technology usesspecial strains of cultured bacteria and naturallyoccurring microorganisms to achievebiodegradation. The end result is carbon dioxide,water, and bacterial biomass.

The most common in situ biodegradation methodcouples the stimulation of the activity of nativemicroorganisms through oxygen and inorganicnutrient addition with the more conventional“groundwater pump and treat” approach. Thisapproach is generally the most demonstrated andmost appropriate application or in situbiodegradation.

Conventional pump and treat cleanup is a passiveapproach that largely relies on the partitioning ofadsorbed contaminants into the water phase. Thispartitioning will be the rate limiting step in theremoval process, potentially requiring an extendedperiod of time to completely remove the adsorbedcontaminant from the soil. In situ biodegradation(i.e., by adding nutrients to groundwater) providesa more direct attack on the adsorbed contaminantphase. This direct attack may significantly reducethe amount of time required for the remediation ofthe adsorbed contaminants. Stimulating subsurfacemicrobial activity can also increase the rate atwhich contaminants are flushed from thesubsurface in a pump and treat system.

4.2.6 References

Some of the more common references on remedialtechnologies for soils/landfill contents are listedbelow.

Containment:

Ghassemi, M. Assessment of Technology forConstructing and Installing Cover and BottomLiner Systems for Hazardous Waste Facilities:Vol. I. Ghassemi EPA Contract No. 68-02-


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3174. U.S. Environmental Protection Agency. May1983.

Kmet, P., K.J. Quinn, and C. Slavik. Analysis ofDesign Parameters Affecting the CollectionEfficiency of Clay Lined Landfills. University ofWisconsin. September 1981.

Lutton, R.J. et al. Design and Construction ofCovers for Solid Waste Landfill. 600-2-79-165.U.S. Environmental Protection Agency. August1979.

Lutton, R.J. Evaluating Cover Systems for Solidand Hazardous Waste . SW867. U.S.Environmental Protection Agency. 1982.

Morrison, W.R. and L.R. Simmons. Chemical andVegetative Stabilization of Soil: Laboratory andField Investigations of New Materials andMethods for Soil Stabilization and ErosionControl. Bureau of Reclamation Report No. 7613.U.S. Bureau of Reclamation. 1977.

U.S. Environmental Protection Agency. RCRAGuidance Document Landfill Design, LinerSystems and Final Cover. (Draft). July 1982.

U.S. Environmental Protection Agency. Lining ofWaste Impoundment and Disposal Facilities.SW870. 1983.

U.S. Environmental Protection Agency. Handbookof Remedial Action of Waste Disposal Sites(Revised). EPA/625/6-85/006. October 1985.

U.S. Environmental Protection Agency. ACompendium of Technologies Used in theT r e a t m e n t o f H a z a r d o u s Wastes .EPA/625/8-87/014. September 1987.

U.S. Environmental Protection Agency. FinalCovers on Hazardous Waste Landfills andSurface Impoundments. EPA/530-SW-89-047.July 1989.

U.S. Environmental Protection Agency. Covers forUncontrolled Hazardous Waste Sites.EPA/540/2085-002.

U.S. Environmental Protection Agency.

Procedures for Modeling Flow Through ClayLiners to Determine Required Liner Thickness.EPA/530-SW-84-001.

U.S Environmental Protection Agency. TechnicalGuidance Document: Final Covers onHazardous Waste Landfills and SurfaceImpoundments, EPA/530-SW-89-047. July 1989.

Warner, R.C. et al. Demonstration andEvaluation of the Hydrologic Effectiveness of aThree Layer Landfill Surface Cover UnderStable and Subsidence Conditions. Phase I, FinalProject Report. U.S. Environmental ProtectionAgency.

Removal/Disposal:

U.S. Army. Dewatering and GroundwaterControl for Deep Excavations, Technical ManualNo. 5-818-5. Prepared by the Army EngineersWaterways Experiment Station. 1971.


U.S. Environmental Protection Agency.Technology Briefs, Data Requirements forSelecting Remedial Action Technology .EPA/600/2-87/001. January 1987.

Soil Treatment:


U.S. Environmental Protection Agency. Systems toAccelerate In-Situ Stabilization of WasteDeposits. EPA/540/2-86/002. September 1986.

U.S. Environmental Protection Agency.Technology Briefs, Data Requirements forSelecting Remedial Action Technology.EPA/600/2-87/001. January 1987.

Innovative Remedial Technologies:

Michaels, P.A., and M.K. Stinson. TechnologyEvaluation Report, Vacuum Extraction System.


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Groveland, Massachusetts. Risk ReductionEngineering Lab., ORD.EA68-03-3255. 1989.

U.S. Environmental Protection Agency. Handbookof Remedial Action at Waste Disposal Sites(Revised). EPA/625/6-85/006. October 1985.

U.S. Environmental Protection Agency.Technology Briefs; Data Requirements forSelecting Remedial Action Technology.EPA/600/2-87/001. January 1987.

U.S. Environmental Protection Agency.Technology Screening Guide for Treatment ofCERCLA Soils and Sludges. EPA/540/2-88/004.September 1988.

U.S. Environmental Protection Agency. Terra VacIn Situ Vacuum Extraction System, ApplicationsAnalysis Report. EPA/540/A5-89/003. July 1989.

U.S. Environmental Protection Agency. TheSuperfund Innovative Technology EvaluationP r o g r a m : T e c h n o l o g y P r o f i l e s .EPA/540/5-89/013. November 1989.

U.S. Environmental Protection Agency. Handbookon In Situ Treatment of HazardousWaste-Contaminated Soils. EPA/540/2-90/002.January 1990.

U.S. Environmental Protection Agency.International Waste Technologies/Geo Con InSitu Stabilization/Solidification, ApplicationsAnalysis Report. EPA/540/A5-89/004, August1990.

U.S. Environmental Protection Agency.Experience in Incineration Applicable toSupefund Site Remediation. EPA/625/9-88/008.

U.S. Environmental Protection Agency. HighTemperature Treatment for CERCLA Waste:Evaluation of Onsite and Offsite Systems .EPA/540/4-89/006.

U.S. Environmental Protection Agency.Stabilization/Solidification of CERCLA andRCRA Wastes. EPA/625/6-89/022.

U.S. Environmental Protection Agency. State ofTechnology Review: Soil Vapor ExtractionSystems. EPA/600/2-89/024.

4.3 Leachate

4.3.1 Collection of Leachate

Leachate from landfills is a product of naturalbiodegradation, infiltration, and groundwatermigrating through the waste. Landfill leachate istypically high in biochemical oxygen demand(BOD), chemical oxygen demand (COD), andheavy metals. The function of a leachate collectionsystem is to minimize or eliminate the migration ofleachate away from the solid waste unit. Thissystem is typically used to control seepage along thesideslopes of a landfill and to prevent discharges tosurface and groundwater systems. Leachatecollection systems commonly used are subsurfacedrains and vertical extraction wells.

4.3.1.1 Subsurface Drains

Subsurface drains consist of underground,gravel-filled trenches generally equipped with tile orperforated pipe for greater hydraulic efficiency.They are used to intercept and channel leachate toa sump, wet well, or appropriate surface dischargebefore it can infiltrate to the main aquifer system.Drains, usually installed at the edge of the waste fill,can also be used to collect contaminatedgroundwater and transport it to a central area fortreatment or proper disposal. Typically, subsurfacedrains are installed at the perimeter of the landfill,although in landfills where the thickness of fill is lessthan approximately 15 feet, it may be appropriate toconsider installation within the landfill. Depth ofwaste as well as hazards associated withexcavating landfill material usually preventsinstallation of drains within the landfill.

4.3.1.2 Vertical Extraction Wells

Vertical extraction wells are wells drilled in thewaste and screened in a highly permeable waterbearing zone. This zone may be perched above thesurrounding water table or may be in thegroundwater. The intent is to collect highly


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contaminated leachate or leachate/groundwatermix. The wells, which typically run to the base ofthe landfill, are fitted with a pump to extractleachate and create a negative pressure zone topromote leachate flow towards the wells. It shouldbe noted that without the proper precautions,placing wells into the landfill contents may createhealth and safety risks. Perimeter wells may also beinstalled at the landfill boundary as a source controlmeasure to control offsite migration of leachate andcontaminated groundwater. Maintenance of thewells is essential because the permeable layer isprone to fouling due to biological growth orprecipitation of metal hydroxides.

Some implementation and O&M considerationsconcerning leachate collection include the following:

• A properly designed leachate collectionsystem should provide a reduction in thepotential for migration of leachate tosurface water and groundwater.

• Distribution and discontinuities of liquidswithin the landfill will affect the placementand number of wells required.

• Hydraulic head will vary throughout thelandfill.

• Extraction systems will require ongoingmaintenance to maintain effectiveness.

• Drilling conditions must be considered.

• Creating a low-pressure zone may attractwater in the landfill.

• Leachate collection is typically cost-effective compared to recovering dispersedcontaminants (that is, extraction andtreatment of offsite contaminatedgroundwater plume).

• A leachate collection system may result inan increase in landfill settlement as a resultof leachate extraction.

• An effective collection system generallywill require a thorough characterization

of the hydrogeology of the site beforedesign or installation of the system.

• Consideration should be given to possiblehealth and safety risks, difficulty in drillingand installation conditions in landfillmaterials, and resultant high costs (drillingwithin the landfill may require at leastLevel B health and safety protection).

The primary data needed for designing a leachatecollection system include:

• Topographic characteristics of the site (forexample, slopes, drainage divides)

• Site soil characteristics (for example,permeability, grain size distribution)

• Climatological characteristics (for example,precipitation, temperature)

• Hydrogeologic characteristics (forexample, depth to groundwater,groundwater flow direction and velocity)

• Waste characteristics (for example,composition, moisture content, age)

4.3.2 Treatment of Leachate

Either onsite or offsite treatment of leachate maybe feasible options for municipal landfill sites.Leachate from municipal landfill sites may havehigh concentrations of organic matter (measured interms of BOD and COD), and high concentrationsof inorganics. Leachate quality varies from site tosite, and will also vary over time. For example,BOD concentrations may decrease over time.Once the constituents and associatedconcentrations are known for the leachate,appropriate treatment technologies can be selected.

Typical concentration ranges for somecontaminants that leach from municipal landfills arelisted in Table 3-2 of this document. The largeranges may be due in part to analysis of leachatethat has been diluted by groundwater. Additionalinformation on leachate composition andcontaminant concentrations in leachate can befound in Characterization of MWC Ashes and


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Leachates from MSW Landfills, Monofills andCo-Disposal Sites (EPA, 1987f).

Leachate generally is treated by conventionalmeans such as biological treatment, physicaltreatment, or chemical treatment. The chemicalcharacteristics of the leachate must be determinedin order to design an onsite treatment system. Thischemical analysis includes:

• Quantifying the constituents in theleachate (organics and inorganics),especially the compounds to be removed

• Determining the variability of leachatecharacteristics

• Measuring BOD, COD, and TOC (grossindicators of organic loading for biologicaltreatment and granular activated carbon[GAC])

• Measuring other conventional parametersfor leachate such as total dissolved solids(TDS), chlorine, alkalinity, nitrate, nitrite,ammonia, total phosphorous, and sulfide

• Measuring pH (effects the efficiency ofbiological treatment and reagentrequirements of metals precipitation)

• Determining influent flow to the treatmentsystems (and anticipated variability in flowsuch as from seasonal variation inleachate production)

• Measuring total suspended solids (TSS) inthe leachate (high solids content [forexample, >50 ppm] may requirepretreatment before carbon adsorption)

• Measuring oil and grease in the leachate(high concentrations [for example, >10ppm], may require pretreatment)

• Conducting treatability during predesign,as required, to optimize the treatmentsystem

4.3.2.1 Onsite Treatment

The degree of treatment depends to a great extenton the strength of the leachate and whether theeffluent is to be discharged directly to surface wateror to a publicly owned treatment works (POTW).The most common technologies used at municipallandfill sites to treat leachate include biologicaltreatment for removal of biodegradable organics,physical treatment such air stripping and carbonadsorption for VOC removal, and chemicaltreatment, such as metals precipitation for removalof inorganics. Treated leachate could be dischargedonsite depending on the extent of treatment. Onsitedischarge can be done by groundwater aquiferreinjection or by discharge to surface water.Groundwater aquifer reinjection depends on stategroundwater standards in the area where the site islocated. Discharge to surface water will have tocomply to NPDES Permit requirements.

Chemical Treatment. In chemical treatment,hazardous constituents are altered by chemicalreactions. During the process, hazardouscompounds may be destroyed or altered; theresultant products may still be hazardous buttransformed to a more convenient form for furtherprocessing. The most common chemical treatmentfor landfill leachate is precipitation of heavy metals.Precipitation will remove soluble heavy metals fromleachate by forming insoluble metal hydroxides,sulfides, or carbonates. Heavy metals typicallyremoved by precipitation include arsenic, cadmium,chromium, copper, lead, mercury, nickel, and zinc.Metals are often removed to either meet NPDESpermit limits or as pretreatment to reduce metalstoxicity for biological treatment. Chemicalprecipitation involves alteration of the ionicequilibrium to convert soluble metal ions to insolubleprecipitates. These precipitates are then removedby solids separation processes such assedimentation and filtration.

Precipitation reactions for leachate treatmentpurposes are usually induced by one or more of thefollowing steps:


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• Add a substance that reacts directly withthe compound in solution to form a lesssoluble compound.

• Add a substance that shifts the solubilityequilibrium to a point that no longer favorsthe continued solubility of the compound.For instance, pH affects the equilibriumconcentration of ionic species. This isparticularly true when the respective solidphase is a hydroxide or carbonatecompound.

• Change the temperature of a saturated ornearly saturated solution to decreasesolubility.

Most precipitation reactions are carried out byadding appropriate chemicals and mixing. Commonadditives include time, soda ash, and caustic. Themain liquid stream's pH may need to be adjustedafter removal of the solid precipitates.

Biological Treatment. Biological means are usedin treating leachate contaminated primarily bybiodegradable organic compounds. Biologicaltreatment is especially effective in treating landfillleachate that typically has high levels of BOD andCOD (e.g., 0-750,000 mg/1).

In biological treatment, wastewater is contacted bya culture of microorganisms either suspended in thewastewater or attached to a solid medium. Theorganic compounds in the wastewater aremetabolized by the organisms as a food and energysource. Organics are thus removed from solutionand biomass and metabolic waste gases such ascarbon dioxide and methane are produced.Biological treatment systems are configured asfixed growth, suspended growth, or a combinationof both. They can be designed to treat hundreds ofmillions of gallons per day (MGD) or as little as 1gallon per minute (0.0014 MGD).

Biological treatment processes can be classified asaerobic or anaerobic. Aerobic treatment systemsrequire oxygen, either in air or in pure form, to meetthe metabolic needs of the micro-organisms.Aerobic treatment systems are the most frequentlyused form of biological treatment. These systems

consist of a reactor, where the waste stream isbrought in contact with a culture of organisms, andusually a clarifier or other solids-separation devicewhere organisms suspended in solution are removedby sedimentation.

Anaerobic treatment systems are used most oftenfor treating high-strength wastes. These systemsare often followed by an aerobic treatment systemfor additional organics removal. Compared toaerobic systems, anaerobic treatment systemsproduce less biomass per pound of BOD removed.In addition, anaerobic treatment produces methaneof sufficiently high concentration to be used in somecases for energy recovery. Anaerobic digesters arealso frequently used in the treatment of sludgeproduced in aerobic treatment. In this process, thesludge is reduced in volume and methane gas isproduced as a by-product.

Physical Treatment. Two types of physicaltreatment technologies most commonly used to treatleachate are air stripping and granular activatedcarbon (GAC) for the removal of organics. Otherconventional physical treatment technologies suchas sedimentation and filtration may also have to beincorporated as part of the overall treatmentsystem.

Activated carbon is usually applied afterconventional treatment as a polishing operation forremoval of trace concentrations of residual organicsand/or heavy metals. It is also used for thereduction of COD and BOD, for the removal oftoxic or refractory organics, and for the removaland recovery of certain organics and inorganicsfrom aqueous waste. Applications involving organicsolutes are most effective when the solutes have ahigh molecular weight, low water solubility, lowpolarity, and a low degree of ionization. Manyorganic compounds such as phenolics, aromatics,and chlorinated hydrocarbons are readily adsorbedon the surface of activated carbon. In addition,certain heavy metals such as cadmium, chromium,copper, nickel, lead, and zinc can be removed fromwater with carbon, although this technology is notwidely used for metals removal.

Most organic and some inorganic solutes areabsorbed as the leachate stream is passed


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through the carbon, usually in packed beds. Whenthe carbon reaches its maximum capacity foradsorption, or when effluent concentrations areunacceptable, the spent carbon is replaced by freshcarbon. The carbon may be regenerated offsitewhereby the adsorbed contaminants areincinerated, or the carbon may be disposed of in aRCRA landfill if regeneration is not cost-effective.

Contacting methods for granular carbon includeadsorbers in parallel, adsorbers in series,moving-bed, and upflow-expanded beds. Carbonloadings can approach 1 pound of COD removalper pound of carbon. The concentration of COD inthe influent can typically be as high as 1 to 5percent. Suspended solids in the influent shouldgenerally be less than 50 ppm to minimizebackwash requirements. Actual carbon usage ratesare determined during pilot testing.

Air stripping is used in municipal landfill applicationsfor the removal of VOCs from leachate orgroundwater. When leachate containing a volatilecompound is brought to equilibrium conditions withair, some portion of the volatile compound transfersfrom the water to the air. The resultingconcentrations of the volatile compound in the airand in the water are a function of the beginningconcentration in the water, the temperature, thepressure, and the degree of volatility of thecompound. The volatility of the compound--that is,its tendency to leave the water and enter the air--isexpressed by Henry's law constant for theparticular compound. The Henry's law constant isthe ratio of the concentration of the compound inthe air to its concentration in water at equilibriumconditions.

Leachate contaminated with a volatile compound isfed into the top of a tower while a large air streamis forced into the bottom. The tower is usually filledwith a packing medium that provides a largesurface area for contact between the air andleachate. The air exits the top of the tower with thevolatile compound. The leachate is collected at thebottom of the tower and is either pumped to anotherprocess area for further treatment or discharged. Itshould be noted that leachate may foul the packingmedium and reduce the effectiveness of air

stripping.

If sufficiently low concentrations are involved, theair can be discharged to the atmosphere. Otherwise,air pollution control devices such as vapor-phasecarbon may be needed. State air pollutionregulations must be followed for emission controls.

Computerized mathematical models are available toestimate the effectiveness of air stripping forremoving many organic compounds. However,critical operating parameters should be determinedexperimentally through pilot studies.

4.3.2.2 Offsite Treatment

Direct discharge to a POTW may be appropriatefor leachate streams containing concentrations ofcontaminants that are amenable to treatmentprovided by the POTW. More often, pretreatmentmay be required before discharge to the POTW.Major considerations include the constituents of theleachate and their concentrations, the type oftreatment used by the POTW, the remainingtreatment capacity of the POTW, the volume ofleachate to be disposed of, and the expectedduration of the discharge. A high rate of flow for anextended time may require a capital expenditure toincrease the capacity of the treatment works. Earlycontact with the POTW during the feasibility studyprocess is important to determine the acceptabilityof the leachate for treatment at the POTW.

Treatment to reduce the concentrations oforganics and metals can be expectedat most POTWs. However, the NPDESpermit for the POTW may have metalslimitations that will preclude the treatmentof leachate. The removal efficiency dependson the type and concentration ofcontaminants. Removal of organics andmetals will be primarily from stripping inaeration basins, adsorption onto biological floc,and biological degradation. Fate of PriorityPollutants in Publicly Owned TreatmentWorks (U.S. EPA, 1982c) is a good sourcefor information on treatability and on theapplicability of different treatments for a particularwaste stream. The need for treatability testing


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or pretreatment of the waste stream must bedetermined on the basis of the probable effect ofthe contaminants on the POTW.

Treatment processes typically employed at POTWsinclude:

• Anaerobic processes–Including rotatingbiological contactors, oxidation ditches,activated sludge reactors, and trickingfilters

• Aerobic processes–Including anaerobiccontact reactors, anaerobic filters,fluidized bed systems, and various fixed-film systems

• Physical/chemical processes–Includingdissolved-gas flotation, chemicalcoagulation, sedimentation, and filtration

Special considerations for discharge to a POTWinclude the proximity of the nearest POTW sanitarysewer sufficient to handle the flow, pretreatmentrequirements, and the potential health risk toPOTW employees of treating wastes fromCERCLA sites. Construction of gravity main orforce mains to transport the discharge to thePOTW collection system may be cost effectivecompared to onsite treatment. Typically it is costeffective to transport only low flow rates (forexample, less than 2 gpm) via trucks to the POTW.

If the leachate is to be trucked offsite for treatment,and it is classified as a RCRA hazardous waste, aRCRA Part B permit would be required by thePOTW to accept the leachate. In this situation,another offsite option would be to treat the leachateat a RCRA treatment, storage, and disposal facility(TSDF). There are several RCRA TSDF in variousparts of the country that treat leachate. If theleachate is discharged to the sewer system (that is,piped to the POTW) the POTW is exempt fromRCRA as outlined in 40 CFR 261.4(a)(1)(ii).

A discharge to a POTW is generally considered onoffsite activity, even if CERCLA waste isdischarged to a sewer located onsite. Therefore,the offsite policy and proposed regulations wouldgcneraly apply to a discharge of CERCLA waste

to a POTW (see Section 4.2.3.3).

Some implementation and O&M considerationsconcerning offsite treatment include the following:

• The possible elimination of potentiallystrict limits for discharging to surfacewater or groundwater

• The acceptability at sites with sensitivepublic relations issues

• The limited capacity of a POTW to handlethe leachate volume and contaminantloading

• The possible tendency of the POTWpermitting authority to set stringentdischarge standards because there is nocategorical standard for CERCLAoperations and because of public fear ormistrust of “hazardous waste”(Frequently, discussions on theacceptability of the discharge anddischarge standards will extend well intothe predesign and design phases ofSuperfund sites.)

• The liability of a discharger if thedischarge causes the POTW to violate itsNPDES permit, or if sludge from thePOTW fails toxicity criteria or otherstandards (Some treatability testing at thePOTW may be required to determinewhether pass-through of leachatecontaminants is likely.

• Problems at sites with leachate of variablequality

• User fees usually imposed by POTWsreceiving discharge

• The partial removal of many organics byadsorption on the biomass (Landapplication of the sludge by the POTWmay reintroduce contaminants to theenvironment and should be evaluated.)

• Need to contact the POTW to determineif overflows or bypasses occur


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during wet weather in the sewer to beused (If so, then precautions such astemporary storage of leachate during wetweather may be necessary.)

• Classification as a RCRA waste ofleachate that is trucked offsite (RCRAwaste will have to be treated at a RCRATSDF instead of at a POTW.)

Data on leachate characteristics, which mayinclude parameters such as COD, BOD, pH, TSS,TOC, TDS, as well as hazardous constituents suchas inorganics (metals, cyanide), volatile organics,and semivolatile organics will be required by thePOTW to assess whether it can accept the wastestream. Treatability testing will be necessary toevaluate the effects of the leachate on the POTWsystem as well as on removal capabilities.

4.3.3 References

Additional references on remedial technologies forleachate are listed below.

Collection:


U.S. Environmental Protection Agency. Lining ofWaste Impoundment and Disposal Facilities.SW870. 1983.


U.S. Environmental Protection Agency. LeachatePlume Management. EPA/540/2-85/004.November 1985.


U.S. Environmental Protection Agency. Guidanceon Remedial Actions for ContaminatedGroundwater at Superfund Sites. EPA/540/6-88/003. December 1988.

Treatment:

Cheremisinoff, P. N., and Ellerbush, F. CarbonAdsorption Handbook . Ann Arbor Science, AnnArbor, MI. 1980.

Clark, Viessman, and Hammer. Water Supply andPollution Control. IEP-Dun-Donnell. New York.1977.

Metcalf & Eddy, Inc., revised by Tchobanoglous.Wastewater Engineering: Treatment, Disposal,Reuse. 2nd Ed. McGraw-Hill. New York, NewYork. 1979.

Treybal, R. Mass Transfer Operations. 3rd Ed.McGraw-Hill. 1983.

U.S. Environmental Protection Agency. Fate ofPriority Pollutants in Publicly Owned TreatmentWorks. EPA/440/1-82/303. 1982.

U.S. Environmental Protection Agency. PermitGuidance Manual on Hazardous Waste LandTreatment Demonstrations, Draft. EPA 530-SW-84-015. December 1984.


U.S. Environmental Protection Agency. Guide forIdentifying Cleanup Alternatives at HazardousWaste Sites and Spills. EPA/600/3-83/063.December 1985.


U.S. Environmental Protection Agency.Characterization of MWC Ashes and Leachatesfrom MSW Landfills and Co-Disposal Sites.EPA/530/SW-87/028A. October 1987.



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U.S. Environmental Protection Agency. CERCLASite Discharges to POTWs. EPA/540/6-90/005.August 1990.

4.4 Landfill Gas

4.4.1 Collection of Landfill Gas

Landfill gas (LFG) is produced naturally whenorganic material from a landfill decomposes. LFGcollection should be considered in the followingsituations:

• When homes and buildings are (or areplanned to be) adjacent or close to thelandfill

• When wastes have a high organic content

• When future use of the site may involveallowing access to the public (forexample, as a park)

• When emissions pose an unacceptablehealth risk

• When the landfill produces excessiveodors

• When gas pressure building under the capcan damage it and/or curb vegetativegrowth on the cap

• When state ARARs require treatment ofthe LFG

A proper landfill cover decreases odors and verticalmigration of gas. However, it increases lateral gasmigration and with it the potential of entrappingexplosive methane gas in nearby structures. Thelateral movement of LFG can be intercepted byeither permeable or impermeable systems.Permeable interception systems capture gas that ismoving laterally and provide conduits for the gas toescape to the surface. These systems typicallyconsist of horizontal trenches and/or pipes andvertical wells. Impermeable interception systemsblock the flow of the gas and also provide conduitsto the surface. Typical components of impermeablesystems are barriers made of clays and synthetic

liners.

Most often they are used in conjunction withtrenches.

Design considerations for LFG collection include:

• Volume and type of wastes present

• Depth of fill

• Subsurface geology of the site

• Field measurements

- Waste constituents- LFG concentrations- Moisture content of waste- Preferential flow paths- Soil permeabilities

LFG collection systems are divided into two maingroups: passive systems and active systems.

4.4.1.1 Passive Systems

Passive LFG control systems alter subsurface gasflow paths without using mechanical components.Generally, they direct subsurface flow to points ofcontrolled release through the use ofhigh-permeability systems. Flow paths to outsideareas are blocked through the use of low-permeability barriers. High-permeability systemsusually consist of trenches or wells excavated at theboundary of the landfill and backfilled withpermeable material (for example, gravel, crushedstone, etc.) to create a preferential gas flow path.Low-permeability barriers typically consist ofclay-lined or synthetic-lined (HDPE, PVC, Hypalon,etc.) trenches or walls. Passive systems are notused to recover landfill gas, instead their only use isto control the release of landfill gas to theatmosphere. Typical passive systems are pipe ventsand trench vents.

Pipe Vents. Pipe vents are used for venting LFGat points where it is collecting and building uppressure. They are often used with flares that burnthe gas at the point of release. Pipe vents typicallyare simple, inexpensive, and effective at reducinglocalized LFG pressure.


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However, some considerations concerning pipevents include the following:

• They potentially will have a small zone ofinfluence (less than 5 feet in compactedrefuse).

• They may result in increased odorproblems (due to LFG release to theatmosphere).

• There may be a potential danger ofexplosion at the point of release, whichshould be considered and evaluated.

Trench Vents . Trench vents usually consist ofgravel trenches surrounding the waste site. Theyform a path of least resistance through which gasesmigrate upward to the atmosphere. A barriersystem can be added to the outside of the trench toincrease its effectiveness in controlling LFG.

Trench vents typically are more effective than pipevents for containment and control. They requirelittle maintenance, and they are relativelyinexpensive. If there are houses nearby, trenchvents, possibly in conjunction with pipe vents,should be considered to minimize the potential forlateral migration of LFG. Gas migrating laterallyinto basements can create toxic or explosiveconditions. Some considerations concerning trenchvents include the following:

• Runoff can infiltrate and clog open vents.

• Gases may migrate under the trench if itis not constructed to a sufficient depth orkeyed into an impervious layer.

• There is potential for failure of the barriersystem below a 15- to 20-foot depth.

• Odor problems are possible.

The most important data needed for designing apassive gas control system are:

• Topographic characteristics of the site (forexample, contour elevation map)

• Soil characteristics (for example,permeability, grain-size distribution, soilcontent)

• Geologic characteristics (for example,type of subsurface strata, pH,temperature, depth of bedrock)

• Climatologic characteristics (for example,precipitation, temperature)

• Hydrogeologic characteristics (forexample, depth to groundwater inside andoutside the landfill)

• Waste characteristics (for example,composition, biodegradables and organicscontent, moisture content)

4.4.1.2 Active Systems

Active systems to control LFG restrict subsurfacemigration of gases. The systems use mechanicalmeans to alter pressure gradients and redirectsubsurface gas flow. Major system componentsgenerally include gas extraction wells, gas collectionheaders, vacuum blowers or compressors, and gastreatment or use systems. Active systems aretypically used in landfills where severe odorproblems exist, they are also used to prevent LFGfrom migrating to and endangering nearbystructures. LFG recovery and sale or use as asource of energy are only possible with activesystems.

Gas extraction wells are drilled to the seasonal lowgroundwater level or to the base of the landfill.Typically, a perforated pipe is set in the well withpermeable material surrounding the pipe. At the topof the well, the pipe is nonperforated and thesurrounding area is sealed with concrete or clay. Agas collection header is connected to the top of thepipe and to several other extraction wells spaced atregular intervals. Vacuum blowers or compressors,connected to the headers, are used to create anegative pressure area, which causes gases to bedrawn up from the extraction wells. Thengases are treated and either released to


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the atmosphere or recovered and used to generateenergy.

The most common active system is an onsiteextraction well system. It consists of a series ofextraction wells in the landfill, typically 100 to 300feet apart. The applied extraction vacuumwithdraws LFG in both the horizontal and verticaldirections. Vacuum blowers extract the LFG fromthe wells, and push the collected LFG through afree vent or waste-gas burner. Enclosed flareshave proven effective in destroying the combustiblecomponents of the LFG and thereby eliminatingodor problems.

Some implementation and O&M considerationsconcerning active gas control systems include thefollowing:

• Active gas control systems can provideeffective LFG control with an area ofinfluence larger than that of passivesystems (depending on the design).

• Odors and reactive organic gas emissionsare reduced as compared to passivesystems.

• There is potential for use of LFG.

• The expense is greater compared topassive systems because of thecomplicated design and mechanicalequipment required.

• Regular O&M is required for optimalresults (depends on the design and volumegenerated). For example, collectionsystems may become clogged withbiological growth or sediments.

• Condensate handling is required (possiblyclassified as a RCRA hazardous waste).

• Modifications after startup may benecessary because of the variability ofsolid waste and soils placed at the site(affects gas production).

• Landfill settlement may cause collectionpiping to bend.

The typical data needed for designing an activesystem include:

• Topographic characteristics of the site (forexample, contour elevations map)

• Soil characteristics (for example,permeability, moisture content, grain sizedistribution)

• Geologic characteristics (for example,type of subsurface strata, pH,temperature, depth of bedrock)

• Hydrogeologic characteristics (forexample, depth to groundwater)

• Waste characteristics (for example,composition, moisture content, percentcompaction)

• Depth, volume, and approximatesettlement rate of wastes

4.4.2 Treatment of Landfill Gas

4.4.2.1 Thermal Treatment (Enclosed GroundFlares)

When treatment of LFG is necessary, the mostcommon technology used at CERCLA municipallandfill sites is thermal treatment using enclosedground flares. Treatment of landfill gas may benecessary in situations where homes or buildingsare close to the landfill, when final use of the siteincludes allowing public access, when the landfillproduces excessive odors, or when state or federalair standards are violated. Flares are awell-established technology and are being used atmany landfills worldwide.

Enclosed ground flare systems consist of arefractory-lined flame enclosure (or stack) with aburner assembly at its base. A pilot light is installednear the waste-gas burner head. Combustion airdampers are installed at the base of the flare tocontrol excess air. In the operation of an enclosedground flare system, landfill gas is mixed with asupplemental fuel, if required to support combustion,and fed through a vertical, open-ended pipe. Pilotburners (usually at least three) next to the end ofthe pipe ignite the waste.


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Enclosed ground flares are used extensively foroperations involving landfill gas disposal. (They canalso be used to burn gases collected from a soilvapor extraction operation.) Earlier operations withlandfill gas flaring have consistently used elevatedopen flares. Open flares are still very common atnon-CERCLA municipal landfill sites. However, theenclosed flare is increasingly popular and is, insome instances, being considered the BestAvailable Control Technology (BACT) for newinstallations. This emerging technology is a result ofthe perceived improvement in combustionefficiency and in control of enclosed flares overopen flares. Particularly at CERCLA sites, thepresence of a visible flame on open flares maycause public concern or may be considered anuisance. Use of open flares is still common inemergencies or for when the quality and quantity ofgas fluctuates widely.

The most important limitation for flare operation isthe quality of the gas. If the LFG is less than 20percent methane, then auxiliary fuel is necessary.Auxiliary fuel is desirable if methane concentrationranges from 20 to 30 percent. If high operatingtemperatures are desired, additional fuel may berequired in any case. Auxiliary fuel will rapidlydrive the operational costs up, especially ifinexpensive fuel is not available nearby.

Regulatory guidance for flare operation is limited,so operating conditions are usually guided byengineering judgment. The assumed minimum limitsfor operations are 1,400EF and 1 second ofresidence time. Data for evaluating destructionefficiency are somewhat limited. The indicationsare that destruction efficiencies should be greaterthan 90 percent for most trace air-toxic compounds,with many flares probably realizing greater than 99percent destruction efficiencies.

Caution should be used when predicting treatmentperformance. Destruction efficiency can be highlyvariable, and predicting performance for a specificsite may require pilot testing. Most organiccompounds should be destroyed effectively withadequate temperature and residence time;however, test data are limited. In many cases,demonstrating high destruction efficiency is difficultbecause detection levels cannot be measured

precisely using current sampling and analyticalprotocols. In most cases, enclosed flaresconsistently achieve greater than 98 percent inoverall combustion efficiency. Operations usuallycan achieve smokeless combustion with no visibleflame outside the stack. Enclosed ground flares canbe built for virtually any flow of LFG from a landfillsite. However, 5,000 standard cubic feet per minuteof LFG per flare is a practical upper limit, and lowerflows may be more appropriate to allow foroperational flexibility and to reduce potentialequipment problems.

The EPA Office of Air Quality, Planning, andStandards is developing new source emissionguidelines and performance standards for collectionand treatment of landfill gas. The air emissionstandards will apply to new municipal solid wastelandfills as well as to those facilities that haveaccepted waste since November 8, 1987, or thathave capacity available for future use. Theproposed rule would require an active landfill gascollection and control system for solid wastelandfills where emissions exceed 100 megagramsper year of nonmethane organic compounds(NMOC). Control (i.e., treatment) would beachieved using flares. Since the proposed rule iscurrently under development, some changes may bemade. Also, judgment should be used in determiningwhether these guidelines and standards are relevantand appropriate to a specific CERCLA municipallandfill site. These standards and guidelines weredeveloped for municipal solid waste landfill sites asopposed to CERCLA sites where there is typicallyco-disposal of both municipal solid waste andhazardous waste.

Some implementation and O&M considerationsconcerning enclosed ground flares include thefollowing:

• Enclosed ground flares should eliminateodors and air emissions.

• Generally, enclosed ground flares are easyto implement and can be used forshort-term as well as long-termapplications.

• There is no possibility for heat recovery.


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• There is a potential need for steam tocontrol emissions.

• There are high noise levels.

• Costs of supplemental fuel and itsavailability must be considered.

The data needed for screening and predesign of aflaring system include:

• The quantity (standard cubic feet perminute) of LFG to be treated

• The heat content of waste (Btu/cubicfoot)

• Waste constituents, including methanecontent

Bench or pilot testing is often required to determinedestruction and removal efficiencies.

4.4.3 References

Additional references on remedial technologies forLFG are listed below:

Argonne National Laboratory. An AnnotatedBibliography: Environmental Impacts ofSanitary Landfills and Associated Gas RecoverySystems. ANL/CNSV-27. February 1982.

Emcon Associates-Ann Arbor Science. MethaneGeneration and Recovery from Landfills. 1980.

Lutton, R.J. et al. Design and Construction ofCovers for Solid Waste Landfills. 600-2-79-165.U.S. Environmental Protection Agency. August1979.

Noyes Data Corporation. Landfill MethaneRecovery. Energy Technology Review #80. 1983.

Seebold, James A. Practical Flare Design.Chemical Engineering. December 1984.


4.5 Groundwater

4.5.1 Collection, Treatment, and Disposal

Collection and treatment of groundwater is acommon component of the overall remediation ofmunicipal landfill sites. Typically, groundwater isextracted at the perimeter of the landfill to manageoffsite migration of leachate and is extracteddowngradient to capture the contaminatedgroundwater plume. The two types of groundwatercollection systems used most often are extractionwells and subsurface drains.

Subsurface drains (which are also often used forleachate collection) consist of underground,gravel-filled trenches generally equipped with tile orperforated pipe for greater hydraulic efficiency. Thedrains can be used to collect contaminatedgroundwater and transport it to a central area fortreatment or proper disposal. Drains are typicallyused in geological units of low permeability.

Extraction wells are used more frequently thensubsurface drains. Well diameter, flow rate, andspacing are determined based on the desiredgroundwater capture zone and the hydrogeologiccharacteristics of the aquifer.

Contaminated groundwater is usually treated anddisposed of along with leachate (see Section 4.3.2).The chemical parameters that are typically elevatedin samples of contaminated groundwater frommunicipal landfill sites include BOD, COD, VOC,TDS, chloride, nitrite, nitrite, ammonia, totalphosphorous, sulfides, and metals. As with leachate,treatment of contaminated groundwater (orpretreatment in cases where discharge is to aPOTW) may involve conventional treatmentsystems such as biological treatment (organicremoval), metals precipitation, and air stripping orGAC for VOC removal (polishing).

4.5.2 Containment

4.5.2.1 Vertical Barriers (Slurry Walls)

Vertical barriers may be a viable technology forgroundwater containment at municipal landfill sites.Their use warrants some consideration


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since they may improve the overall effectiveness ofa containment system. Extraction wells are oftenused with slurry walls to increase the effectivenessof the slurry wall by creating an inwardgroundwater gradient. In some cases, groundwaterextraction wells alone may provide adequatecontainment of contaminated groundwater.

An upgradient barrier may be used to reduce theamount of groundwater contacting a contaminatedarea whereas a downgradient barrier may be usedto restrict the migration of contaminatedgroundwater away from a contaminated area.These barriers acting alone are probably notsuitable for most landfill sites because of theirlimited effects on movement of groundwater. It isdifficult to completely intercept groundwater usingjust slurry walls, therefore, they are usuallyimplemented with other containment technologiessuch as a groundwater extraction system andlandfill cap.

An ideal barrier will completely encircle the landfillarea, will be keyed into a lower acquitard(impervious layer), and will include a lowpermeability cap and a groundwater collectionsystem to maintain an inward hydraulic gradientacross the barrier. Such a barrier is generally muchmore effective in controlling movement ofgroundwater and pollutants than an upgradient ordowngradient barrier or a partially-penetratingbarrier (that is, one that is not keyed in to animpervious layer).

The most common type of vertical barrier used atlandfill sites, (as well as other hazardous wastesites) is a soil-bentonite slurry wall. Soil-bentoniteslurry walls are used as vertical barriers to reducethe horizontal permeability of soil. These walls canbe excavated a limited distance into rock material(i.e., keyed into bedrock) but are not generallyinstalled in rock.

Typically, the wall is constructed using a backhoeor specialty clamshell, which is used to excavate atrench 2.5 to 4 feet wide in one pass. The trench iskept open by the use of a bentonite slurry. Inaddition, this bentonite slurry creates a filter cakeon the sides of the trench as the slurry flowslaterally into the soil. This filter cake consists of alayer of bentonite with low permeability.

Trenches are generally less than 200 feet deep.Trenches up to 50 feet deep are usually excavatedusing special backhoes; deeper trenches areexcavated with clanishells or other equipment.

The soil excavated from the trench is usually usedas backfill material to mix with the bentonite slurry.Where sufficiefft fines are not present (10 to 30percent by weight that can pass through a No. 200sieve), additional fines from adjacent borrow areasand/or bentonite may be added to decrease thepermeability. The backfill mixing is generally doneadjacent to the trench and requires an area at leastas wide as the depth of the trench. The backfillmaterial is then placed into the trench using abulldozer.

The permeability of the composite trench willgenerally be in the order of 1 x 10-7 to 1 X 10-6

cm/sec, depending on the type of backfill materialused. The. backfill permeability is sometimesaffected by the migrating contaminants, andcompatibility testing should be performed todetermine this effect. For example, if there ismigration of nonaqueous-phase solvent from thelandfill, the bentonite slurry may not be an effectivebarrier. Other design considerations include thepiping of the bentonite fines into the trench underpressure in situations where there is largedifferential in water pressure on the barrier.

Some implementation and O&M considerationsconcerning slurry walls include the following:

• Slurry walls can improve the overalleffectiveness of a containment system byusing the walls in conjunction withextraction wells and a landfill cap.

• A slurry wall is generally a relatively lowcost, proven technology.

• The necessary construction equipment iswidely available.

• The use of slurry walls is generally limitedto relatively flat and unconfined sites.


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• For a slurry wall to be effective, thegeologic characteristics of the site shouldallow it to be keyed into bedrock or intoan aquitard.

• There may be problems with constructionif the landfill site is located within awetland area.

• There may be construction difficulties forslurry walls deeper than 50 feet.

• The production of large quantities ofexcess slurry (for deep trenches) thatmay have to be disposed of as ahazardous waste should be considered.

• A distance of 50 to 75 feet of open areaadjacent to the trench is required formixing bentonite with backfill materials.

The primary data needed for designing a slurry wallinclude:

• Existing topography and boundary of theproposed slurry wall. (The construction ofa slurry wall requires relatively flattopography and sufficient area to mix thebentonite slurry and operate excavationequipment.)

• Geologic data such as soils type, soilchemistry, and types of subsurfaceformations

• Depth to acquitard and groundwater aswell as rate and direction of flow

• Chemical characterization of leachate,groundwater, and landfill wastes(Compatibility testing with slurry wallmaterial may also be required.)

4.5.3 References

Additional references on groundwater remediationare listed below.

Collection, Treatment, and Disposal

Clark, Viessman, and Hammer. Water Supply and

Pollution Control. IEP-Dun-DonneIl. New York.1977.

Freeze et al. Groundwater. Prentice-Hall, Inc.Englewood Cliffs, New Jersey. 1979.

Keely. Optimizing Pumping Strategies forContaminant Studies and Remedial Actions.Groundwater Monitoring Review. 1984. p. 63-14.

Keely and Tsang. Velocity Plots and CaptureZones of Pumping Centers for GroundwaterInvestigations: Groundwater, Vol. 21, No. 6. 1983.p. 701-14.

Metcalf & Eddy, Inc., revised by Tchobanoglous.Wastewater Engineering: Treatment, Disposal,Reuse. 2nd Ed. McGraw-Hill. New York, NewYork. 1979.

Treybal, R. Mass Transfer Operations. 3rd Ed.McGraw-Hill. 1983.

U.S. Environmental Protection Agency. Handbookof Remedial Action of Waste Disposal Sites.(Revised) EPA/625/6-85/006. October 1985.

U.S. Environmental Protection Agency. RCRA,Groundwater Monitoring Technical EnforcementGuidance Document. OSWER-9950.1. September1986.



U.S. Environmental Protection Agency. Evaluationof Groundwater Extraction Remedies, Volume I,Summary Report. EPA/540/2-89/054. September1989.

U.S. Environmental Protection Agency.Performance Evaluations of Pump and TreatRemediations: Groundwater Issue Paper.EPA/540/4-89/005. 1989.


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U.S. Environmental Protection Agency. Basics ofPump and Treat Groundwater RemediationTechnologies. EPA/600/8-90/003, March 1990.

U.S. Environmental Protection Agency. CERCLASite Discharges to POTWs . EPA/540/6-90/005.August 1990.

Xanthakos, P. Slurry Walls, New York.McGraw-Hill. 1979.

4.6 Wetlands

Many municipal landfill sites may have been builton or adjacent to natural wetlands and remedialactivities may affect the wetland habitat. Thissection briefly reviews the possible consequencesto wetlands of a nearby municipal landfill at anNPL site, and provides a rationale for mitigatingunavoidable damage. Two topics are discussed:removing or managing contaminated wetland soil,and mitigating the effects on wetlands of siteremediation. When evaluating damage toenvironmentally sensitive areas, considerationshould also be given to potential natural resourcedamage claims.

4.6.1 Removal or Management of WetlandsSediments

Wetlands adjacent to municipal landfills may becontaminated by inflows of leachate throughsurface water and groundwater pathways includingsprings and seeps. Anaerobic sediments in thewetlands may concentrate and sequester heavymetals or complex organics present in the leachate.These compounds may reach levels that arehazardous to humans or to the biologicalcomponents (flora and fauna) of the wetland.Under these conditions, remediation of the wetlandareas may be required. Wetlands sediments can bephysically removed through dredging and thendisposed of with other hazardous solids.

Because of the potential for dredging to harmindigenous wetland biota, it should be consideredonly as a last resort after a careful environmentalrisk assessment of the site demonstrates that asignificant risk actually exists. If the potential for

risk is marginal and is outweighed by the potentialfor environmental harm from sediment removal,then sediment pollutants can be stabilized andreduced over time by liming, bioremediation, orother technologies. Adding lime to a wetlands areawould be done to neutralize acidic groundwater orleachate that had migrated into the wetland. In situstabilization could potentially be used to immobilizecontaminated sediments, although this may harmwetland biota. In situ bioremediation couldpotentially be implemented to reduce concentrationof organic contamination over time. Moreinformation on these and other technologies can befound in the document titled Handbook ofRemedial Action at Waste Disposal Sites (U.S.EPA, 1985a). This onsite management ofcontaminated sediments may require monitoring toverify the rate of contaminant reduction.

4.6.2 Mitigating Wetlands Losses

When existing natural wetlands must be disturbedthrough the removal of contaminated sediments toprotect human health and the environment,alternative approaches may be used to compensatefor the functional loss of wetlands. To this end,disturbance to wetlands will be minimized if theaffected area is as small as possible. The effects ofdredging may be mitigated by timing dredgingactivities to avoid critical biota lifestages (forexample, dredging can be conducted when plantpopulations are dormant and migratory wildlife arenot present). Silt screens, hay bales, and otherconstruction techniques should be used to minimizethe potential for migration of contaminatedsediments during dredging activities. In addition,compensation for wetland loss may be achieved byrestoring damaged wetlands or creating newwetlands. Restoration may include enhancing waterflows to or natural hydrology of existing drainedwetlands. Restoration provides faster and morevaluable habitat enhancement than does creation ofnew wetlands. However, creation of new wetlandsmay be necessary when restoration is not possible.

Creating wetlands can also mitigate thewetlands damage associated with someremedial activities at municipal landfill sites. To thegreatest extent practical, new wetlands shouldprovide functional values greater than or equal


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to the values lost from the effected wetland. Thesevalues can be assessed using the Corps ofEngineers Wetlands Evaluation Technique.Additional information can be found in thedocument titled Wetland Evaluation Technique(WET), Volume II: Methodology, Corps ofEngineers (U.S. Army Corps of Engineers, 1987).When practical, created wetlands should be of thesame general habitat type as the areas that wereaffected and should be located in the samewatershed. Since larger, contiguous wetland areasgenerally provide better habitat and associatedenvironmental values than smaller, isolatedwetlands, new wetlands should be constructed aspart of larger wetlands/aquatic systems. A larger,new wetland area may be created to offset the lossof a number of smaller, isolated wetlands affectedby municipal landfill remediation.

4.6.3 References

Additional information on evaluation and mitigationof wetlands can be found in the followingdocuments:

Adamus, P.E., et al. Wetland EvaluationTechnique (WET): Volume II--Methodology. U.S.Army Corps of Engineers. 1987.

Hammer, D.A. Constructed Wetlands forWastewater Treatment. Lewis Publishers, Chelsea,Michigan. 1989.

U.S. Army Corps of Engineers. WetlandEvaluation Technique (WET). U.S. ArmyEngineer Waterways Experiment Station. WetlandsResearch Program. 1987.

U.S. Environmental Protection Agency.Constructed Wetlands and Aquatic PlantSystems for Municipal Wastewater Treatment.(Design Manual) EPA/625/1-88/022. 1988.

U.S. Fish and Wildlife Service, et al. FederalManual for Identifying and DelineatingJurisdictional Wetlands. An InteragencyCooperative Publication. 1989.

4.7 Surface Water and Sediments

4.7.1 Treatment of Surface Water

Generally, surface waters such as large ponds,rivers, or streams are not treated at municipallandfill sites. However, in situations where smallonsite ponds or lagoons exist, it may be viable totreat and dispose of contaminated surface water.Management of surface waters in these instanceswill likely be done in conjunction with contaminatedgroundwater and leachate. Contaminated surfacewater will likely be more dilute than leachate orgroundwater and may require only minor polishing.Although, this may not be true for onsite lagoons insituations where disposal of liquid wastes may haveoccurred. Typically, removal of VOCs andsemivolatile compounds from surface water may beachieved using air stripping and/or GAC. Moreconcentrated waste streams may also requireneutralization, metals precipitation, and biologicaltreatment for removal of COD and BOD. In situstabilization is also commonly used for lagoonclosures for wastes containing primarily inorganiccontaminants and 10 to 20 percent of organicconstituents. Additional discussion regarding viabletreatment technologies can be found in Section4.3.2. Since treatment of surface waters will likelybe for a short duration compared to groundwater orleachate treatment, routing surface water to thegroundwater treatment system may be feasible, orit may make sense to use portable (skid mounted)treatment units if additional capacity is needed.

4.7.2 Removal and Management of Sediments

In some cases, it may be necessary to removecontaminated sediments from adjacent surfacewaters. Because of the potential for dredging toharm indigenous biota, dredging should beconsidered only after a careful riskassessment demonstrates that a significantrisk actually exists from contaminated sediments.When evaluating the risks posed by contaminatedsediments, consideration should also be givento the potential for environmental harm from


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sediment removal. However, with this in mind, arisk assessment for a particular site may result inthe conclusion that removal of contaminatedsediments is necessary to mitigate unacceptablerisks to human health or the environment.

When excavating sediments below the watersurface (dredging) the type of equipment dependson considerations such as the need to controlsecondary migration, the depth of the contaminatedsediment, the consistency of the contaminatedsediment, the size of the area to be excavated, andthe depth of excavation. For small deposits, thesediment may be reached from shore using abackhoe or clamshell. For large deposits, equipmentsuch as a floating clamshell, backhoe, or acutterhead hydraulic dredge should be considered.The most feasible and common alternative formanaging excavated sediments is to consolidatethem with other landfill material under the landfillcap, although sediments may need to be filteredprior to consolidation to remove excess water. Seethe discussion on ARARs (Section 5.2) formunicipal landfill sites regarding the viability ofconsolidation of sediments managed as a hazardouswaste. Excavation of contaminated material willinclude semi-solids and sediments.

Semi-solids are composed of saturated earth orother materials that have the consistency of wetconcrete. These materials may flow when disturbedand are too soft for excavation with ordinaryearth-moving equipment such as bulldozers orfront-end loaders. Tracked equipment may be usedworking from firm ground or barge mountedequipment can be used. Accurate control of thedepth of excavation of semi-solids is difficult withdraglines and crane-suspended clam shells. Moreaccuracy can be obtained by using a toothlessbucket as found on a "Gradall" (used for cleaningditches and slopes) or as adapted to a conventionalbackhoe. Cutterhead dredges can also be operatedwith reasonable accuracy.

Sediments are fluid-like deposits that do not holdtheir shape and must be excavated as a slurry. Thisrequires handling large volumes of water(frequently 80 to 90 percent). Excavationequipment may be either floating or operated fromshore. Equipment used for removing sediments may

include hydraulic dredges (with or withoutcutterhead), barge-mounted pumps, vacuum trucks,or a pneumatic dredge. In pneumatic dredging,compressed air is injected into a Venturi pipe, andair, water, and sediment is lifted and discharged atthe surface.

Secondary migration is often a problem withsediment removal below water and thus mayrequire dewatering of the excavation area, usingsediment control barriers to minimize migration ofsediments, or conducting a final sweep of the areato remove any redeposited sediment. Dewatering asubmerged site is often advantageous because itminimizes the contaminated liquid that is carriedwith the solids. Post-removal verification samplingcan also be difficult without dewatering. Temporarydewatering is done by driving sheet metal piling orshoring into the ground around the excavation areaand continuously pumping (that is baling) water outof the area until excavation is complete.

4.7.3 References

Additional references on remedial technologies forsurface water and sediments are listed below:

U.S. Environmental Protection Agency. Handbookof Remedial Action at Waste Disposal Sites(Revised). EPA/625/6-85/006. October 1985.

U.S. Environmental Protection Agency. TheSuperfund Innovative Technology EvaluationProgram: Technology Profiles. EPA/540/5-89/033. November 1989.

U.S. Environmental Protection Agency. Systems toAccelerate In Situ Stabilization of WasteDeposits. EPA/540/2-86/002. September 1986.

U.S. Steel. Steel Sheet Piling Handbook . 1976.


This section provides a description oftechnologies most practicable for remediationof CERCLA municipal landfill sites. This list oftechnologies is based on the NCP expectations anda review of remedial actions selected in


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RODs for CERCLA municipal landfill sites throughFY 1989.

In Section 5, these technologies are analyzedagainst each of the nine criteria used to evaluate

alternatives at Superfund sites. The objective is toillustrate how each technology might affect thealternative evaluation process.


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Section 5EVALUATION CRITERIA

Once remedial action alternatives are sufficientlydefined, each alternative is assessed against nineevaluation criteria. During the detailed analysis ofalternatives, these criteria are considered individualand are equally weighted for importance. For thepurpose of this section, the evaluation criteria havebeen divided into three groups based on the functionof the criteria during remedy selection. The threegroups include the threshold criteria, the balancingcriteria, and the modifying criteria.

The threshold criteria relate to statutoryrequirements that each alternative must satisfy inorder to be eligible for selection. These are:

• Overall protection of human health andthe environment--The assessment againstthis criterion describes how thealternative, as a whole, achieves andmaintains protection of human health andthe environment.

• Compliance with applicable or relevantand appropriate requirements (ARARs),unless a waiver is obtained--Under thiscriterion, an alternative is assessed interms of its compliance with ARARs, or ifa waiver is required, how it is justified.

The balancing criteria are the technical criteriathat are considered during the detailed analysis. Thetechnologies identified as being most practicable forremediation of CERCLA municipal landfill siteshave, therefore, been evaluated in light of thefollowing feasibility study balancing criteria:

• Long-term effectiveness andpermanence--Under this criterion, analternative is assessed in terms of its long-term effectiveness in maintainingprotection of human health and theenvironment after response objectiveshave been met. The magnitude of residualrisk and adequacy and reliability ofcontrols are taken into consideration.

• Reduction of toxicity, mobility, or volume(TMV) through treatment–Under thiscriterion, an alternative is assessed interms of the anticipated performance ofthe specific treatment technologies itemploys. Factors such as the volume ofmaterials destroyed or treated, the degreeof expected reductions, the degree towhich treatment is irreversible, and thetype and quantity of remaining residualsare taken into consideration.

• short-term effectiveness--Under thiscriterion, an alternative is assessed interms of its effectiveness in protectinghuman health and the environment duringthe construction and implementation of aremedy before response objectives havebeen met. The time until the responseobjectives have been met is also factoredinto this criterion.

• Implementability--Under this criterion, analternative is assessed in terms of itstechnical and administrative feasibility andthe availability of required goods andservices. Also considered is the reliabilityof the technology, the ability to monitor theeffectiveness of the remedy, and the easeof undertaking additional remedial actions,if necessary.

• Cost--Under this criterion, an alternative isassessed in terms of its present worthcapital and operation and maintenance(O&M) costs.

Each of the five balancing criteria represents asignificant element of the evaluation process.However, in the case of certain technologiesfrequently used at municipal landfills, evaluationunder some of the five criteria may require lessanalysis. For example, a clay cap does notreduce TMV through treatment, so the evaluationof a clay cap under this criterion does notrequire any effort, regardless of the site. Eventhough these criteria do not require additional


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analysis to evaluate, the basic conclusion will still beimportant during the alternative evaluation. It shouldbe noted that all alternatives may not need to beevaluated with respect to all of a criterion’ssubcriteria. The key is to identify the subcriteria bywhich the alternatives vary significantly and tofocus the evaluation on those factors.

Table 5-1 identifies technologies frequently used atmunicipal landfill sites and summarizes how thetechnology may affect the alternative evaluationcriteria. The objective of the table is to presentbasic conclusions that can be made for eachtechnology in light of each of the balancing criteria,and to identify for each technology the level ofeffort required under each criterion. The effort foranalysis (i.e., level of analysis) is deemed low,moderate, or significant, depending on thetechnology being considered for inclusion in aparticular alternative. For example, usingincineration as part of an alternative may requiresignificant analysis of potential risks to humanhealth and the environment due to air emissionsfrom the incinerator. The two threshold criteria(overall protectiveness of human health and theenvironment, and compliance with ARARs) havenot been included in Table 5-1 because thesecriteria are evaluated only once the technologieshave been assembled into complete alternatives.

The modifying criteria are formally assessed afterthe public comment period. However, state orcommunity views are considered during thefeasibility study to the extent they are known. Themodifying criteria are as follows:

• State/support agency acceptance• Community acceptance

Communication with the state/support agency andcommunity is initiated during scoping and continuesthroughout the RI/FS. Once the preferredalternative has been identified in the proposed plan,and the proposed plan has been issued for publiccomment, these criteria are evaluated. Based on thecomments received during the formal commentperiod, the lead agency may modify aspects of the

preferred alternative or decide that anotheralternative is more appropriate. More informationabout all of the criteria, including a comprehensivelist of subcriteria, can be found in Chapter 6 ofGuidance for Conducting RemedialInvestigations and Feasibility Studies UnderCERCLA (U.S. EPA, 1988d). Below, a summary isprovided regarding all criteria as they affectmunicipal landfill sites.

5.1 Overall Protection ofHuman Health and

the Environment

When evaluating alternatives in terms of overallprotection of human health and the environment,consideration should be given to the manner inwhich site risks identified in the conceptual sitemodel are eliminated, reduced, or controlled throughtreatment, engineering controls (for example,containment), or institutional controls. Potentialthreats to human health and the environmentresulting from municipal landfills may include:

• Leachate generation and groundwatercontamination

• Soil contamination (including hot spots)

• The landfill contents themselves

• Landfill gas

• Wetlands contamination

• Contamination of surface waters andsediments

The overall assessment of protection of humanhealth and the environment is based on evaluatinghow each of these potential threats has beenaddressed in terms of a composite of factorsassessed under other evaluation criteria, especiallylong-term effectiveness and permanence,short-term effectiveness, and compliance withARARs.


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Table 5-1EVALUATION OF TECHNOLOGIES FREQUENTLY USED AT

MUNICIPAL LANDFILLSPage 1 of 3

TechnologyEvaluation in Terms of Long-Term Effectiveness

and PermanenceEvaluation in Terms of Reduction

of TMV Through TreatmentEvaluation in Terms of Short-Term

EffectivenessEvaluation in Terms of

ImplementabilityEvaluation in Terms of Cost

DeedRestrictions

Relies on access development restrictions tomanage residual risk. Difficulty in enforcementresults in low reliability of controls. Because ofvirtually no long-term effectiveness, almost noeffort to evaluate.

Not a treatment technology. No effortto evaluate.

No health or environment impacts duringimplementation. This criteria is not very importantfor this technology and will not vary from site tosite. Almost no effort to evaluate.

Ability to implement depends on localordinances. May be difficult if legalrequirements are not in place, especially offsite.Owner approval needed for deed restrictions.Important criteria since the ability to implementwill vary from site to site. Need to contact stateor local authorities. Significant effort toevaluate.

Low.Significanteffort (difficult)to cost but is aminor cost.

Fencing Relies on limiting access to manage residual riskfrom direct contact. Reliability of controls isuncertain. Fencing limits access to the sitealthough trespassing is possible. Because ofvirtually no long-term effectiveness, almost noeffort to evaluate.


With the exception of physical hazards associatedwith routine construction activities, minimalhealth or environmental impacts duringimplementation. Almost no effort to evaluate.

Easy to implement. Equipment readilyavailable. Almost no effort to evaluate.

Low. Littleeffort to cost.

Grading/Revegetation

Minimal reduction of residual risk, may reduce riskfrom direct contact and reduce leachate formationby controlling runoff. May lessen risk from directcontact. Continued maintenance required to achievelong-term reliability. Because of virtually no long-term effectiveness, almost no effort to evaluate.


Inhalation and direct contact risk if waste isdisturbed. Proper health and safety protection maymitigate risk. If risk is quantified, moderate effortto evaluate.

Easy to implement. Almost no effort to evaluate. Low. Littleeffort to cost.

Soil Cover Reduction of residual risk from direct contact. Withproper maintenance is reliable in longer term. Mayuse HELP model to evaluate leachate reduction.Significant effort to evaluate.


Inhalation and direct contact risk if waste isdisturbed. Community impact through increaseddust and noise from construction and truck traffic ifsoil is from offsite. Need to determine amount oftruck traffic and risk from vehicular andconstruction accidents. Moderate effort to evaluate.

Easy to implement. Determine presence of soilnearby. Moderate effort to evaluate.

Low. Moderateeffort to cost.

Single-BarrierCap

Reduction of residual risk from direct contact.Lessens future leachate formation and subsequentgroundwater contamination by reducing potentialfor infiltration by 70-90 percent. Requires long-term maintenance. May use HELP model and riskassessment to help evaluate. Significant effort toevaluate.


Inhalation and direct contact risk to workers ifwaste is disturbed. Community impact throughincreased dust and noise from construction andtruck traffic if clay source if offsite. Need todetermine amount of truck traffic and risk fromvehicular and construction accidents. Moderateeffort to evaluate.

For a clay cap, relatively easy to implement.Need local source of clay, which may bedifficult to find in certain regions. Syntheticliner requires specialty contractors to assureproper installation. Moderate effort to evaluate.

Medium iflandfill is large.Moderate effortto cost.

Composite-Barrier Cap

Reduction of residual risk from direct contact.Minimizes future leachate formation andgroundwater contamination by virtuallyeliminating infiltration (99 percent reduction).Will last for 20 to 30 years before replacement isneeded if properly designed and maintained.Greater reliability than single barrier cap because ofredundancy of barriers, although reliability withlarge differential settlements may be poor. May useHELP model or risk assessment. Significant effortto evaluate.


Inhalation and direct contact risk to workers ifwaste is disturbed. Community impact throughincreased truck traffic if clay/soil source is offsite.Need to determine amount of truck traffic and riskfrom vehicular and construction accidents.Moderate effort to evaluate.

Synthetic liner requires specialty contractors toassure proper installation. Need a source of clay,which may be difficult to obtain in someregions. Determine presence of clay nearby.Moderate effort to evaluate.

Medium-High,depending onsize of landfill.Moderate effortto cost.


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Excavation:Consolidation

Long-term effectiveness same as cap afterconsolidation. May use a risk assessment. May needsignificant effort to evaluate.


Disturbance of waste is a risk to workers. Properhealth and safety requirements may mitigate risk.Community impacts through volatilization ofwaste, dust, and increased truck traffic if cap sourceis offsite. Significant effort to evaluate to determinevolatilization risk, amount of truck traffic, and riskfrom vehicular and construction accident.

Same as cap chosen; if dewatering of excavationvolume is large, may complicateimplementation. Sampling needed to determineextent of hot spot. Significant effort to evaluatedepending on extent of RI data.

Medium-High,depending onarea beingconsidered.Moderate effortto cost.

Excavation ofHot Spots:Offsite Disposalat Landfill

Effectiveness dependent on the type of offsitefacility and whether or not there was a significantreduction in risk due to excavating the hot spotarea. Significant effort to evaluate if use riskassessment.


Disturbance of waste is risk to workers.Community impacts through volatilization,transport of hazardous material throughcommunity, and increased truck traffic. Significanteffort to evaluate to determine volatility risk,release of hazardous waste risk, extent of trucktraffic, and risk from vehicular and constructionaccidents.

Same as cap plus possible added difficulty ofexcavating waste in water. Sampling needed todetermine extent of hot spots. Need to findhazardous waste landfill with capacity.Significant effort to evaluate.

Medium-High.Moderate effortto cost.

Excavation ofHot Spots:OnsiteIncineration

Less residual waste onsite to manage. Thereduction in risk will depend on how much of theoverall risk posed by the site has been reduced byexcavating the hot spot area. Incineration veryeffective in long-term for hot spot waste.Significant effort to evaluate if risk assessment isconducted.

Treatment to reduce toxicity,mobility, and volume. Thesignificance of TMV reduction willdepend on the magnitude of the threatthe hot spot area posed. Moderateeffort to evaluate.

Possible impacts from disturbance of waste andimproper air emissions. No hazardous waste takenthrough community. Significant effort to evaluateby determining risk from air emissions.

Metals present may still fail TCLP characteristictest. It may be difficult to control air emissionsand sufficient space must be available on site.Significant effort to evaluate.

High.Significanteffort to cost.

Stabilization Improved long-term effectiveness over cap alone ifused with cap. If used for outlying hot spotswithout cap will result in some reduction in riskbut will not be as effective as excavation byreducing mobility and consolidation under a cap.May not be effective in immobilizing organiccontaminants. All waste remains. Need todetermine permanence and long-term risk. May besignificant effort to evaluate.

Reduction in mobility ofcontaminants. No reduction intoxicity. Potential increase of wastevolume of 10-50 percent.Stabilization may be reversible overtime. Significant effort to evaluate.

Significant health and environmental impactspossible because waste is completely mixed.Impacts from odor, dust, and volatiles. Moderateeffort to evaluate.

Materials readily available. May be difficult toachieve sufficient mixing in situ to stabilizewaste. Need treatability studies to determinefeasibility. Significant effort to evaluate.

Medium-High.Significanteffort to cost.

SubsurfaceDrains (leachate& G.W.)

Some risk from groundwater remains for a longtime until groundwater remediation is complete. Ifdesigned as such, may control further migration.Capture zone analysis may be required. Significanteffort to evaluate.

Not a treatment technology. Evaluatewith treatment.

No significant impacts during implementation.Drains are usually not installed in landfill. Longtime needed to achieve cleanup goals. Significanteffort required to determine time until cleanupgoals are met.

Easy to implement if subsurface is consistentwith well known. Wells not reliable in fracturedbedrock. Significant effort to evaluate.

Low-Medium.Significanteffort to cost.

GroundwaterExtraction Wells(leachate &G.W.)

Some risk from groundwater remains for a longtime until groundwater remediation is complete.May effectively control further migration ofcontaminated groundwater migration. Capture zoneanalysis may be required. Significant effort toevaluate.

Not a treatment technology. Evaluatewith treatment.

Installation of wells in landfill material may resultin impacts to the community and workers frompotential VOC emissions. Also, drilling createspotential explosion hazards. Significant effortrequired to determine time until cleanup goals aremet.

Easy to implement if subsurface is consistentand well-defined. Wells not reliable in fracturedbedrock. Significant effort to evaluate.



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Onsite WaterTreatment andDischarge(leachate andG.W.)

Conventional technologies used to treat leachate andGW (metals precip, air stripping, GAC, biotreatment) are proven and reliable as long as O&M iscontinued and proper disposal assumed. Significanteffort to determine influent and effluentconcentrations and reliability.

Treatment provides a reduction intoxicity and/or volume depending onthe process option selected. Theremay be residuals left in the form ofsludge or carbon. Treatment is notnecessarily irreversible. Significanteffort to evaluate.

If air striping is used without gaseous control, maybe some impacts. Ultimate disposal of water andresiduals may have an impact. Time untilenvironmental clean up goals are met depends onextraction. Collection system may have to beoperated permanently because there are continuedloadings from the landfill. Very difficult toreliability predict when groundwater goals can bemet at landfill perimeter. Significant effort toevaluate.

Usually easy to implement and equipment isavailable. Treatment of leachate and GWgenerally uses conventional, proventechnologies. Unusual processes may be moredifficult. Discharge requires either NPDESpermit or meeting substantive requirements ofthe permit.

Low-Medium.Moderate effortto cost.

Treatment ofPOTW

May not be reliable as onsite treatment since thePOTWs typically do not remove all hazardousconstituents. Contaminants may accumulate insludges, and proper disposal may not be assured.Potentially less reliable in rural areas with smallsystems. Difficult to determine reliability.Significant effort to evaluate.

Toxicity and/or volume may bereduced by POTW. However,residuals remain. Significant effort toevaluate.

Transport of water via pipe has potential fornegative impacts on the environment via spills, piprupture, leaks resulting in infiltration. POTWbypasses through overflows, exposure to POTWworkers. Significant effort to evaluate to determineenvironmental impacts.

Often, POTWs refuse to accept water, even ifpretreated. Reliability is plant specific. POTWwould need additional monitoring to evaluateeffectiveness. Significant effort to determinefeasibility and find capacity.

Low.Significanteffort to cost.Depends oninformationsupplied byPOTW.

Slurry Walls Difficult to maintain and therefore may not providelong-term reliability Moderate effort to evaluatebecause of difficult to quantify, may be qualitativeevaluation.


If waste is disturbed, may be limited risk toworkers or community. Almost no effort toevaluate.

Technical implementability depends on sitegeologic conditions. Difficult to monitorreliability. Significant effort to evaluate.

Medium-High.Significanteffort to cost.

LFG PassiveVents

Not as effective as an active system in controllingoffsite migration in the long-term. Primarily protectscap from a buildup of gas and collects gas local tothe passive well or trench. Moderate effort toevaluate.


Protects cap in short-term. May impact theenvironment and community through gas release.Modeling may be required. Significant effort toevaluate.

Can be installed as part of new cap or in existingcap. Moderate effort to evaluate.

Low. Moderateeffort to cost.

Active GasCollection

Collects gas either through landfill or thoughsubsurface adjacent to landfill. Is effective for long-term collection of gas. With proper disposal,removes most risk from the landfill gas. Modelingmay be needed to determine effectiveness.Significant effort to evaluate.

Not a treatment technology. Evaluatewith treatment technology.

May be an impact to workers drilling throughlandfill. Moderate effort to evaluate if waste isdisturbed.

Fairly easy to implement as part of new cap orexisting cap. Able to monitor effectiveness.Moderate effort to evaluate.


LFG ThermalTreatment(Flares)

Effective means of managing collected LFG.Treatment levels may vary over time, requiring long-term monitoring. Significant effort to determinereliability and treatment levels.

Reduces toxicity and volumeconsiderable. Treatment isirreversible. Moderate effort toevaluate although not difficultbecause of irreversibility.

No significant impact during installation. Evenwith proper operation, may be slight risk to thecommunity depending on the constituents in thegas. Significant effort to evaluate if modeling isconducted.

Easy to implement. May be difficult to monitoreffectiveness because of low detection limitsneeded. Significant effort to evaluate.

Medium.Significanteffort to cost.

Removal,OnsiteConsolidationof Sediments

Long-term effectiveness affected by cap type usedafter consolidation. Effectiveness also depends onmagnitude of risk reduced through excavation ofsediments. Significant effort to evaluate.


Disturbance of sediments may further contaminatethe surface water. Dredging may have impact onwetlands or surface water biota. Sediments are oftenleft in place to protect aquatic life. Significanteffort to evaluate if risk is determined.

Technical difficult to implement due to thepossibility of dispersing contamination duringdredging. Approval for dewatering/rerouting ofstream before excavation may be difficultbecause of environmental impacts. Samplingduring removal needed. Feasibility requiressignificant effort to evaluate.


CompensatoryWetlands

No management of residuals. Only a replacement ofdamaged wetlands. Effectiveness is not an issue.Almost no effort to evaluate.

Not a treatment technology and noresiduals remain. No effort toevaluate.

The construction of weltand in a clean area willhave positive environmental impacts. No impact tocommunity or workers if area is clean. Almost noeffort to evaluate.

Complex to implement successfully. Manyecological factors need to be taken into account.Significant effort to determine implementability.

Medium-High.Significanteffort to cost, ifpossible.


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5.2 Compliance With ARARS

Onsite remedial actions at CERCLA municipallandfill sites must comply with all ARARs of otherenvironmental statutes, unless a waiver can bejustified. These statutes include those established byU.S. EPA and other federal agencies and thoseestablished by the state in which the releaseoccurred, if the state’s standards are promulgated,more stringent than the federal standards, and areidentified in a timely manner.

By way of defining “applicable” and “relevant andappropriate”: applicable requirements are federalor state requirements that “specifically address ahazardous substance, pollutant, contaminant,remedial action, location, or other contaminant,remedial action, location, or other circumstancefound at a CERCLA site” (NCP Sec. 300.5).Relevant and appropriate requirements arefederal or state laws that, while not applicable to ahazardous substance, pollutant, contaminant,remedial action, or other circumstance at aCERCLA site, “address problem or situationssufficiently similar to those encountered at theCERCLA site that their use is well suited to theparticular site.” (NCP Sec. 300.5).

Another factor in determining which requirementsmust be compiled with is whether the requirementis substantive or administrative. Onsite CERCLAresponse actions must comply with substantiverequirement of other environmental laws but notwith administrative requirements. Substantiverequirements include cleanup standards or levels ofcontrol; in general, administrative requirementsprescribe methods and procedures such as fees,permitting, inspection, and reporting requirements.

In addition to the legally binding requirementsestablished as ARARs, many federal and stateprograms have developed criteria, advisories,guidelines, or proposed standards “to beconsidered” (TBC). This TBC material mayprovide useful information or recommendprocedures if (1) no ARAR addresses a particularsituation, or (2) if existing ARARs do not provideprotection. In such situations, TBC criteria orguidelines should be used to set remedial actionlevels. Their use should be explained and justified inthe administrative record for the site.

A more detailed discussion of the general issuesassociated with ARARs and TBCs can be found inthe following documents: the preamble to the NCP,55 FR 8741-8766 of March 8, 1990; and CERCLACompliance with Other Laws Manual (U.S. EPA,1988b).

ARARs are divided into three types:

• Chemical-specific ARARs• Location-specific ARARs• Action-specific ARARs

Tables 5-2 and 5-3 list the federal location andaction-specific ARARs that typically are pertinentto CERCLA municipal landfill sites. ARARspertinent to air striping, incineration, and directdischarge to POTWs are also included becausethese technologies are frequently used at municipallandfill sites. Chemical-specific ARARs have beenidentified for an example site and are listed inSection 4.1 of Appendix A. A discussion of stateARARs follows the information regarding federalARARs.

5.2.1 Federal ARARs

5.2.1.1 Chemical-Specific ARARs

Chemical-specific requirements are usuallytechnology- or risk-based numerical limitations ormethodologies that, when applied to site-specificconditions, result in the establishment of acceptableconcentrations of a chemical that may be found inor discharged to the ambient environment.Information regarding the use of chemical-specificARARs in risk assessments can be found in thedocuments Risk Assessment Guidance forSuperfund, Volume II--Human HealthEvaluation Manual (Part A), Interim Final (U.S.EPA, 1989j), and Risk Assessment Guidance forSuperfund, Volume II--EnvironmentalEvaluation Manual, Interim Final (U.S. EPA,1989c). Examples of chemical-specific ARARs andTBCs are listed for the example site and can befound in Appendix A of this report. The following isa discussion of the chemical-specific ARARs thattypically are pertinent to landfill site.


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Table 5-2POTENTIAL FEDERAL LOCATION-SPECIFIC ARARs AT MUNICIPAL LANDFILL SITES

Page 1 of 2

Location Requirement Prerequisite(s) Citation Comments

1. Within 61 meters (200 feet)of a fault displaced inHolocene time

New treatment, storage, or disposal ofhazardous waste prohibited.

RCRA hazardous waste; PCBtreatment, storage, or disposal.

40 CFR 264.18(a) Counties considered seismically active listed in40 CFR 264 Appendix VI.

2. Within 100-year floodplain Facility must be designed, constructed,operated, and maintained to avoid washout.

RCRA hazardous waste; PCBtreatment, storage or disposal.

40 CFR 264.18(b)40 CFR 761.75

Applicable if part of the landfill is in the 100-yearfloodplain.

3. Within floodplain Action to avoid adverse effects, minimizepotential harm, restore and preserve naturaland beneficial values of the floodplain.

Action that will occur in afloodplain, i.e., lowlands, andrelatively flat areas adjoining inlandand coastal waters and other flood-prone areas.

Executive Order11988, Protectionof Floodplains,(40 CFR 6,Appendix A)

Applicable if part of the landfill is in the 100-yearfloodplain.

4. Within salt dome formation,underground mine, or cave

Placement of noncontainerized or bulk liquidhazardous waste prohibited.

RCRA hazardous waste; placement. 40 CFR 264.18(c) Need to verify that the site does not contain anysalt dome formations, underground mines, orcaves used for waste disposal.

5. Critical habitat upon whichendangered species orthreatened species depends

Action to conserve endangered species orthreatened species, including consultationwith the Department of the Interior.

Determination of endangered speciesor threatened species.

EndangeredSpecies Act of1973 (16 USC1531 et seq.); 50CFR Part 200, 50CFR Part 402

Need to identify whether any endangered speciesare known to exist on the site. May apply in ruralareas.

6. Wetland Action to minimize the destruction, loss, ordegradation of wetlands.

Wetland as defined by ExecutiveOrder 11990 Section 7.

Executive Order11990, Protectionof Wetlands, (40CFR 6, AppendixA)

Applicable if wetlands are present next to or onthe site.

Action to prohibit discharge of dredged orfill material into wetland without permit.

Clean Water ActSection 404; 40CFR Parts 230,231

7. Wilderness area Area must be administered in such a manneras will leave it unimpaired as wilderness andto preserve its wilderness character.

Federally owned area designated aswilderness area.

Wilderness Act(16 USC 1131 eqseq.); 50 CFR35.1 eq seq.

Need to verify that the site is not within a FederalWilderness Area.

8. Wildlife refuge Only actions allowed under the provisions of16 USC Section 668 dd(c) may beundertaken in areas that are part of theNational Wildlife Refuge System.

Area designated as part of NationalWildlife Refuge System.

16 USC 668 dd etseq.; 50 CFR Part27

Need to verify that the site is not within aNational Wildlife Refuge.


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Table 5-2POTENTIAL FEDERAL LOCATION-SPECIFIC ARARs AT MUNICIPAL LANDFILL SITES

Page 2 of 2

Location Requirement Prerequisite(s) Citation Comments

9. Area affecting stream or river Action to protect fish or wildlife. Diversion, channeling, or otheractivity that modifies a stream orriver and affects fish or wildlife.

Fish and WildlifeCoordination Act (16 USC 661 etseq.); 40 CFR6.302

The Fish and Wildlife Coordination Act requiresconsultation with the Department of Fish andWildlife prior to any action that would alter abody of water of the United States.

10. Within area affecting national wild,scenic, or recreational river

Avoid taking or assisting in actionthat will have direct adverse effecton scenic river.

Activities that affect or may affectany of the rivers specified in Section1276(a).

Scenic Rivers Act(16 USC 1271 etseq. Section 7(a);40 CFR 6.302(e)

Need to verify that national wild or scenic riversare not located on the site and will not beaffected by site remediation.

11. Within coastal zone Conduct activities in mannerconsistent with approved statemanagement programs.

Activities affecting the coastal zoneincluding lands thereunder andadjacent shorelands.

Coastal ZoneManagement Act(16 USC Section1451 et seq).

Applicable if the site has direct access to coastalareas.

12. Oceans or waters of the UnitedStates

Action to dispose of dredge and fillmaterial into ocean waters isprohibited without a permit.

Oceans and waters of the UnitedStates.

Clean Water ActSection 404, 40CFR 125 SubpartM; MarineProtectionResources andSanctuary ActSection 103

Applicable if disposal of dredge and fill materialin ocean waters is planned.

13. Within area where action may causeirreparable harm, loss, ordestruction of significant artifacts

Action to recover and preserveartifacts.

Alteration of terrain that threatenssignificant scientific, prehistorical,historical, or archaeological data.

NationalArchaeologicaland HistoricalPreservation Act(16 USC Section469); 36 CFR Part65

Should scientific, prehistorical, or historicalartifacts be found at the site, this will becomeapplicable.

14. Historic project owned orcontrolled by federal agency

Action to preserve historicproperties; planning of action tominimize harm to National HistoricLandmarks.

Property included in or eligible forthe National Register of HistoricPlaces.

National HistoricPreservation ActSection 106 (16USC 470 et seq.)36 CFR Part 800

Need to identify whether the site is included inthe national Register of Historic Places.


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Table 5-3POTENTIAL FEDERAL ACTION-SPECIFIC ARARs FOR MUNICIPAL LANDFILL SITES

Page 1 of 13

Actions Requirements Prerequisites Citation Comments

Air Stripping Design system to provide odor-free operation. CAA Section 101a Odor regulations are intended to limit nuisance conditions from air pollutionemissions.

File an Air Pollution Emission Notice (APEN)with the State to include estimation of emissionrates for each pollutant expected.

40 CFR 52a State will have particular interest in emissions for compounds on their hazardous,toxic, or odorous list. Preliminary meeting with state prior to filing APEN isrecommended in the regulation. Meeting would identify additional issues ofconcern to the State.

Include with filed APEN the following:

• Modeled impact analysis of source emissions.

• Provide a Best Available Control Technology(BACT) review for the source operation.

This additional work and information is normallyapplicable to sources meeting the “major” criteriaand/or to sources proposed for nonattainment areas.

40 CFR 52a State may identify further requirements for permit issuance after first review. Theseprovisions follow the federal Prevention of Significant Deterioration(PSD)framework with some modifications. Additional requirements could includeambient monitoring and emission control equipment design revisions to matchLowest Achievable Emission Requirements (LAER).

While a permit is not required for an onsite CERCLA action, the substantiverequirements identified during the permitting process are applicable.

Predict total emissions of volatile organiccompounds (VOCs) to demonstrate emissions donot exceed 450 lb/hr, 3,000 lb/day, 10 gal/day, orallowable emission levels from similar sourcesusing Reasonable Available Control Technology(RACT).

Source operation must be in an ozonenonattainment area.

40 CFR 52a The control technology review for this regulation (RACT) could coincide with theBACT review suggested under the PSD program.

Verify through emission estimates and dispersionmodeling that hydrogen sulfide emissions do notcreate an ambient concentration greater than orequal to 0.10 ppm.

40 CFR 61b

Verify that emissions of mercury, vinyl chloride,and benzene do not exceed levels expected fromsources in compliance with hazardous air pollutionregulations.

40 CFR 61a Regulation 8 indicates any source emitting the regulated compounds is subject tothis regulation. However, some of the specific regulations further restrict the scopeof applicability.

Capping Placement of a cap over hazardous waste (e.g.,closing a landfill, or closing a surfaceimpoundment or waste pile as a landfill, or similaraction) requires a cover designed and constructedto:

• Provide long-term minimization of infiltrationof liquids through the capped area.

• Function with minimum maintenance.

• Function with minimum maintenance.

• Promote drainage and minimize erosion orabrasion of the cover.

• Accommodate settling and subsidence so thatthe cover’s integrity is maintained.

• Have a permeability less than or equal to thepermeability of any bottom liner system ornatural subsoils present.

RCRA waste in landfill.

Significant management (treatment, storage, ordisposal) of hazardous waste will makerequirements applicable; capping withoutdisturbance will not make requirements applicable,but technical requirements may be relevant andappropriate.

40 CFR 264.228(a) (Surface Impoundments)40 CFR 264.258(b) (Waste Piles)40 CFR 264.310(a)(Landfills)

RCRA capping requirements could be relevant and appropriate to cappinghazardous wastes in place. RCRA is generally considered relevant if it can beverified, through review of records, interviews, or other means, that the landfillaccepted RCRA wastes after November 19, 1980. The appropriateness of RCRArequirements is based also on each requirement’s technical merit in a givensituation.

If a groundwater containment problem exists, a RCRA cap would serve to isolateand contain landfill solids and contaminated soils and limit infiltration ofprecipitation. EPA guidance on RCRA caps for new RCRA landfill cells includesmultibarrier caps of clay and liners.

Excavation and reconsolidation of the wastes onsite, in a location outside of thecurrent area of contamination, would make these requirements, as well as thelandfill construction and operation requirements applicable for wastes that can bedesignated as hazardous. If the wastes are excavated and reconsolidated in theircurrent location, the capping requirements are applicable. The major determiningfactors are the location of the final disposal, and the classification of the wastematerials.


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Estimate free liquids, stabilize wastes before capping(surface impoundments)

40 CFR 264.228(a)

Restrict post-closure use of property as necessary toprevent damage to the cover.

40 CFR 264.117(c)

Prevent run-on and run-off from damaging cover. 40 CFR 264.228(b)49 CFR 264.310(b)

Protect and maintain surveyed benchmarks used tolocate waste cells (landfills, waste piles).

40 CFR 264.310(b)

Disposal or decontamination of equipment,structures, and soils.

40 CFR 264.111

Closure with Wastein Place (Capping)

Eliminate free liquids by removal or solidication. 40 CFR 264.228(a)(2) See discussion under Capping.

Stabilization of remaining waste and waste residuesto support cover.

40 CFR 264.228(a)(2)and

40 CFR 264.258(b)

Installation of final cover to provide long-termminimization of infiltration.

40 CFR 264.310

Post-closure care and groundwater monitoring. 40 CFR 264.310

Clean Closure(Removal)

General performance standard requires minimizationof need for further maintenance and control;minimization or elimination of post-closure escape ofhazardous waste, hazardous constituents, leachate,contaminated runoff, or hazardous wastedecomposition products.

Disturbance of RCRA hazardous waste (listed orcharacteristic) and movement outside the unit orarea of contamination.

May apply to surface impoundment or tocontaminated soil, including soil from dredgingor soil disturbed in the course of drilling orexcavation and returned to land.

40 CFR 264.111 Clean closure removal of contaminated materials does not appear to befeasible for most municipal landfill sites because of the large volume ofwastes. However, clean closure removal may be considered for portions of thesite, such as hot spot areas. The RCRA clean closure requirements would beconsidered relevant and appropriate to contaminated wastes which are nothazardous, but which are similar to hazardous wastes.

Disposal of decontamination of equipment,structures, and soils.

40 CFR 264.111 and 268 The RCRA Land Disposal Restrictions require treatment of RCRA wastes tospecified levels or by specified technologies. The RCRA requirements wouldbe considered relevant and appropriate to wastes that are not RCRAhazardous wastes, but which are similar (same constituents) as RCRA wastes.

RCRA Land Disposal Restrictions require treatment of RCRA wastes tospecified levels or by specified technologies before land disposal. If treatment to the specified level or by the specifiedtechnology is not achievable or appropriate, a variance must be obtained fromthe EPA. If the wastes are determined to be RCRA wastes, these requirementswould be applicable.


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Page 3 of 13


Clean Closure(Removal)(cont’d.)

Removal or decontamination of all waste residues,contaminated containment system components (e.g.,liners, dikes), contaminated subsoils, and structuresand equipment contaminated with waste and leachate,and management of them as hazardous waste.

Meet health-based levels at unit.

Not applicable to undisturbed material.

Disposal of RCRA hazardous waste (listed orcharacteristic) after disturbance and movementoutside the unit or area of contamination.

40 CFR 264.228(a)1) and

40 CFR 264.258

In the event that the wastes being removed are determined to be hazardouswastes, the requirements of this section would be applicable.

Consolidation Area from which materials are removed should beremediated.

Disposal by disturbance of hazardous waste(listed or characteristic) and moving it outsideunit or boundary of contaminated area.

See Closure If nonhazardous wastes are excavated and moved outside the current area ofcontamination, these requirements will become relevant and appropriate.These regulations are intended to insure that when wastes are consolidated ata central location, the satellite areas (former locations of the wastes) areremediated.

If the wastes which are excavated for consolidation are determined to behazardous wastes, this regulation will be applicable.

Consolidation in storage piles/storage tanks willtrigger storage requirements.

See Container Storage, Tank Storage,Waste Piles in this table.

RCRA requirements for storage in containers, tanks, or piles will be relevantand appropriate for nonhazardous wastes which are similar to RCRAhazardous wastes, or for hazardous wastes disposed prior to November 1980,which are excavated from the site and stored prior to consolidation and/ordisposal.

If excavated materials can be classified as hazardous wastes, the requirementwill be applicable.

Placement on or in land outside unit boundary or areaof contamination will trigger land disposalrequirements and restrictions.

After November 8, 1988. 40 CFR 286 (Subpart D) Certain listed hazardous wastes are not eligible for disposal in landfills orother land-based facilities unless treated to RCRA specified criteria. Therequirement may be relevant and appropriate to some nonhazardous wastes atmunicipal landfill sites which are contaminated with hazardous constituentsat levels similar to those in listed wastes, and are excavated forreconsolidation and disposal outside the current area of contamination.

If any of the wastes are determined to meet the definitions of the restrictedhazardous wastes, the requirements will be applicable.

Develop fugitive and odor emission control plan forthis action if existing site plan in inadequate.

CAA Section 101a and 40 CFR 52a Odor regulations are intended to limit nuisance conditions from air pollutionemissions. Fugitive emission controls are one feature of the stateimplementation plan used to achieve/maintain the ambient air qualitystandards for particulate matter.

File an Air Pollution Emission Notice (APEN) withstate to include estimation of emission rates for eachpollutant expected.

40 CFR 52a See discussion under Air Stripping.

Include with the filed APEN the following:

• Modeled impact analysis of source e missions

• A Best Available Control Technology (BACT)review for the source operation

This additional work and information is normallyapplicable to sources meeting the “major” criteriaand/or to sources proposed for nonattainmentareas.



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Page 4 of 13


Consolidation(cont’d.)

Predict total emissions of volatile compounds (VOCs)to demonstrate emissions do not exceed 450 lb/hr,3,000 lb/day, 10 gal/day, or allowable emission levelsfrom similar sources using Reasonably AvailableControl Technology (RACT).



Verify through emission estimates and dispersionmodeling that hydrogen sulfide emissions do notcreate an ambient concentration greater than or equal to0.10 ppm.


Verify that emissions of mercury, vinyl chloride, andbenzene do not exceed levels expected from sources incompliance with hazardous air pollution regulations.


Containment(Construction ofNew SurfaceImpoundmentOnsite) (SeeClosure and Wastein Place and CleanClosure)

Use two liners below the waste, a top liner thatprevents waste migration into the liner, and a bottomliner that prevents waste migration through the linerthroughout the post-closure period.

RCRA hazardous waste (listed or characteristic)currently being placed in a surface impoundment.

Soil/debris being managed as RCRA hazardouswaste.

40 CFR 264.220 If a new, onsite surface impoundment is constructed to hold influent and/oreffluent from a treatment process, or to hold groundwater, surface water orleachate that is not a hazardous waste, these requirements are relevant andappropriate to construction, operation, and maintenance of the impoundment.

Dike Stabilization Design and operate facility to prevent overtopping dueto overfilling; wind and wave action; rainfall; run-on;malfunctions of level controllers, alarms, or otherequipment; and human error.

Existing surface impoundment containinghazardous waste or creation of new surfaceimpoundments.

40 CFR 264.221 These requirements would be relevant and appropriate to the constructionand operation of a new surface impoundment or the operation andmaintenance of an existing surface impoundment onsite to containgroundwater, surface water, leachate, or the influent or effluent of a treatmentsystem that is not a hazardous waste.

Direct Dischargeof TreatmentSystem Effluent

Applicable federal water quality criteria for theprotection of aquatic life must be complied with whenenvironmental factors are being considered.

Surface discharge of treated effluent. 50 FR 30784(July 29, 1985)

Applicable federally approved state water qualitystandards must be complied with. These standards maybe in addition to or more stringent than other federalstandards under the CWA.

Surface discharge of treated effluent. 40 CFR 122.44 and state regulationsapproved under 40 CFR 131

If state regulations are more stringent than federal water quality standards,the state standards will be applicable to direct discharge. The state hasauthority under 40 CFR 131 to implement direct discharge requirementswithin the state, and should be contacted on a case-by-case basis when directdischarges are contemplated.

The discharge must be consistent with the requirementof a Water Quality Management plan approved by EPAunder Section 208(b) of the Clean Water Act.

CWA Section 208(b) Discharge must comply with substantive but not administrativerequirements of the management plan.

Use of best available technology (BAT) economicallyachievable is required to control toxic andnonconventional pollutants. Use of best conventionalpollutant control technology (BCT) is required tocontrol conventional pollutants. Technology-basedlimitations may be determined on a case-by-case basis.

Surface discharge of treated effluent. 40 CFR 122.44(a) If treated effluent is discharged to surface waters, these treatmentrequirements will be applicable. Permitting and reporting requirements willbe applicable only if the effluent is discharged at an offsite location. Thepermitting authority should be contacted on a case-by-case basis todetermine effluent standards.

The discharge must conform to applicable waterquality requirements when the discharge affects a stateother than the certifying state.

Surface water discharge affecting waters outsidecertifying state.

40 CFR 122.44(d)(4) No discharge is expected to affect surface water outside certifying state.


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Page 5 of 13


Direct Dischargeof TreatmentSystem Effluent(cont’d.)

Discharge limitations must be established for all toxicpollutants that are or may be discharged at levelsgreater than those that can be achieved by technology-based standards.

Surface discharge of treated effluent. 40 CFR 122.44(e) Exact limitations are based on review of the proposed treatment system andreceiving water characteristics, and are usually determined on a case-by-casebasis. The permitting authority should be contacted to determine effluentlimitations.

Discharger must be monitored to assure compliance.Discharge will monitor:

• The mass of each pollutant discharged.

• The volume of effluent discharged.

• Frequency of discharge and other measurements asappropriate.

Surface discharge of treated effluent. 40 CFR 122.43(i) These requirements are generally incorporated into permits, which are notrequired for onsite discharges. The substantive requirements are applicable,however, in that verifiable evidence must be offered that the dischargestandards are being met. The permitting authority should be contacted todetermine monitoring and operational requirements.

Approved test methods for waste constituents to bemonitored must be followed. Detailed requirements foranalytical procedures and quality controls areprovided.

Permit application information must be submitted,including a description of activities, listing ofenvironmental permits, etc.

40 CFR 122.21

Monitor and report results as required by permit (atleast annually).

40 CFR 122.44(i)

Comply with additional permit conditions such as:

• Duty to mitigate any adverse effects of any

discharge.

• Proper operation and maintenance of treatmentsystems.

40 CFR 122.41(i)

Develop and implement a Best Management Practices(BMP) program and incorporate in the NPDES permitto prevent the release of toxic constituents to surfacewaters.

The BMP program must:

• Establish specific procedures for the control of toxicand hazardous pollutant spills.

• Include a prediction of direction, rate of flow, andtotal quantity of toxic pollutants where experienceindicates a reasonable potential for equipmentfailure.

• Assure proper management of solid and hazardouswaste in accordance with regulations promulgatedunder RCRA.

Surface water discharge. 40 CFR 125.100

40 CFR 125.104

These issues are determined on a case-by-case basis by the NPDES permittingauthority for any proposed surface discharge of treated wastewater. Althougha CERCLA site remediation is not required to obtain an NPDES permit foronsite discharges to surface waters, the substantive requirements of theNPDES permit program must be met by the remediation action if possible.The permitting authority should be consulted on a case-by-case basis todetermine BMP requirements.


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Page 6 of 13


Direct Dischargeof TreatmentSystem Effluent(cont’d.)

Sample preservation procedures, container materials,and maximum allowable holding times are prescribed.

Surface water discharge 40 CFR 136.1-136.4 These requirements are generally incorporated into permits, which are notrequired of onsite discharges. The substantive requirements are applicable,however, in that verifiable evidence must be offered that standards are beingmet. The permitting authority should be consulted on a case-by-case basis todetermine analytical requirements.

Discharge toPOTW d

Pollutants that pass through the POTW withouttreatment, interfere with POTW operation, orcontaminate POTW sludge are prohibited.

40 CFR 403.5 If any liquid is discharged to a POTW, these requirements are applicable. Inaccordance with guidance, a discharge permit will be required even for anonsite discharge, since permitting is the only substantive control mechanismavailable to a POTW.

Specific prohibitions preclude the discharge ofpollutants to POTWs that:

• Create a fire or explosion hazard in the POTW.

• Are corrosive (pH<5.0).

• Obstruct flow resulting in interference.

• Are discharged at a flow rate and/or concentrationthat will result in interference.

• Increase the temperature of wastewater entering thetreatment plant that would result in interference; butin no case raise the POTW influent temperatureabove 104EF (40EC).

Categorical standards have not been promulgated for CERCLA sites, sodischarge standards must be determined on a case-by-case basis, dependingon the characteristics of the waste stream and the receiving POTW. Somemunicipalities have published standards for non-categorical, non-domesticdischarges. Changes in the composition of the waste stream due topretreatment process changes or the addition of new waste streams willrequire renegotiation of the permit conditions.

Discharge must comply with local POTW pretreatmentprogram, including POTW-specific pollutants, spillprevention program requirements, and reporting andmonitoring requirements.

40 CFR 403.5 and local POTWregulations

RCRA permit by rule requirements must be compliedwith for discharges of RCRA hazardous wastes toPOTWs by truck, rail, or dedicated pipe.

40 CFR 264.71and

40 CFR 264.72


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Discharge ofDredge and FillMaterial toNavigable Waters

The five conditions that must be satisfied beforedredge and fill is an allowable alternative are:

• There must be no practicable alternative.

• Discharge of dredged or fill material must not causea violation of state water quality standards, violateany applicable toxic effluent standards, jeopardizean endangered species, or injure a marine sanctuary.

• No discharge shall be permitted that will cause orcontribute to significant degradation of the water.

• Appropriate steps to minimize adverse effects mustbe taken.

• Determine long- and short-term effects on physical,chemical, and biological components of the aquaticecosystem.

40 CFR 230.1033 CFR 320-330

This action is not envisioned as part of the site remediation.

Dredging Removal of all contaminated sediment. Disposal by disturbance of hazardous waste andmoving it outside the unit or area ofcontamination.

See discussions under Clean Closure,Consolidation, Capping

Excavation Area from which materials are excavated may requirecleanup to levels established by closure requirements.

Disposal by disturbance of hazardous waste andmoving it outside the unit or area ofcontamination.

40 CFR 264 Disposal and ClosureRequirements

If contaminated materials that are not hazardous wastes are excavated fromthe site during remediation, the RCRA requirements for disposal and siteclosure (of the excavated area) may become relevant and appropriate. Seediscussions under Capping, Clean Closure, Closure with Waste In-Place, etc.

If the excavated materials can be classified as hazardous wastes, the disposaland closure requirements would be applicable.

Movement of excavated materials to a previouslyuncontaminated, onsite location, and placement in oron land may trigger land disposal restrictions.

Materials containing RCRA hazardous wastessubject to land disposal restrictions.

40 CFR 268 (Subpart D) The land disposal restrictions restrict disposal of certain hazardous wastes.Some municipal landfill wastes may be derived from or may be sufficientlysimilar to restricted wastes to make the land disposal restrictions relevantand appropriate.

For wastes that can be classified as restricted hazardous wastes, land disposalis prohibited unless they are treated to defined standards. Chemicalcharacterization f the wastes will be necessary to determine the applicabilityor relevance of this requirement.

All listed and characteristic hazardous wastes or soilsand debris contaminated by a RCRA hazardous wasteand removed from a CERCLA site may not be landdisposed until treated as required by Land Ban. Ifalternative treatment technologies can achievetreatment similar to that required by Land Ban, and ifthis achievement can be documented, then a variancemay not be required.

Waste disposed was RCRA waste. 40 CFR 268 If soil is a characteristic waste, and if waste disposed prior to November 1980is now designated as a RCRA waste, then soils/sediment and leachatecontamination from those wastes must be managed as a RCRA waste.


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Excavation(cont’d.)

Develop fugitive and odor emission control pan forthis action if existing site plan is inadequate.

CCA Section 101a and 40 CFR 52a See discussions under Consolidation.


40 CFR 52a See discussions under Consolidation.



• A Best Available Control Technology (BACT)review for the source operation.



Predict total emissions of volatile organic compounds(VOCs) to demonstrate emissions do not exceed 450lb/hr, 3,000 lb/day, 10 gal/day, or allowable emissionlevels from similar sources using ReasonablyAvailable Control Technology (RACT).







Gas Collection Proposed standards for control of emissions of volatileorganics (CAA requirements to be provided).

Proposed standard; not yet ARAR. 52 FR 3748(February 5, 1987)

This is a proposed rule. If the requirement is finalized in its proposed form, itmay be applicable or relevant and appropriate to some of the remedial actionsat municipal landfill sites. The proposed standard would impose restrictionson RCRA treatment, storage, and disposal facilities that would limit theallowable emissions of volatile organics from these facilities. If thisrequirement is finalized, it will be closely examined with respect to remedialalternatives at municipal landfill sites.

Design system to provide odor-free operation. CAA Section 101a

and 40 CFR 52a

See discussion under Consolidation.









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Gas Collection(cont’d.)

Predict total emissions of volatile organic compounds(VOCs) to demonstrate emissions do not exceed 450lb/hr, 3,000 lb/day, 10 gal/day, or allowable emissionlevels from similar sources using ReasonablyAvailable Control Technologies (RACT)


40 CFR 52a See discussion under Consolidation.


40 CFR 61a



GroundwaterDiversion

Excavation of soil for construction of slurry wall maytrigger cleanup or land disposal restrictions.


See Consolidation, Excavation inthis table.

If waste materials or contaminated soil that are not hazardous wastes areexcavated or otherwise disturbed during the construction of a groundwaterdiversion structure, the requirements of this section would be relevant andappropriate.

If the excavated wastes or contaminated soil can be classified as hazardouswastes, these requirements would be applicable.

Incineration(Onsite)

Analyze the waste feed.

Dispose of all hazardous waste and residues, includingash, scrubber water, and scrubber sludge.

RCRA hazardous waste. 40 CFR 264.341

40 CFR 264.351

If incineration is selected as one of the remedial alternatives for siteremediation, these requirements would be relevant and appropriate to thedisposal by incineration of potentially nonhazardous site wastes. The wasteswould have to be analyzed prior to incineration to insure that the wastescannot be classified as hazardous wastes.

No further requirements apply to incinerators that onlyburn wastes listed as hazardous solely by virtue of thecharacteristic of ignitability, corrosivity, or both; orthe characteristic of reactivity if the wastes will not beburned when other hazardous wastes are present in thecombustion zone; and if the waste analysis shows thatthe wastes contain none of the hazardous constituentslisted in Appendix VIII which might reasonably beexpected to be present.

40 CFR 264.340 If wastes to be incinerated can be classified as hazardous wastes, therequirements of 40 CFR 264.341, 351, and 340 would be applicable.

Performance standards for incinerators:

• Achieve a destruction and removal efficiency of99.99 percent for each principal organic hazardousconstituent in the waste feed and 99.9999 percent forPCBs and drums.

40 CFR 264.343

• Particulate emissions must be less than 180 mg/dscf(.08 grains/dscf) corrected to 7% O 2.

40 CFR 264.342

• Reduce hydrogen chloride emissions to 1.8 kg/hr or

1 percent of the HCL in the stack gases beforeentering any pollution control devices.


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Incineration(Onsite) (cont’d.)

Monitoring of various parameters during operation ofthe incinerator is required. These parameters include:

• Combustion temperature.• Waste feed rate.• An indicator of combustion gas velocity.• Carbon monoxide.

40 CFR 264.343

Land Treatment Ensure that hazardous constituents are degraded,transformed, or immobilized within the treatment zone.

RCRA hazardous waste. 40 CFR 264.271 See discussions under Consolidation.

Maximum depth of treatment zone must be no morethan 1.5 meters (5 feet) from the initial soil surface, andmore than 1 meter (3 feet) above the seasonal highwatertable.

40 CFR 264.271

Demonstrate that hazardous constituents for each wastecan be complete degraded, transformed, or immobilizedin the treatment zone.

40 CFR 264.272

Minimize run-off of hazardous constituents. 40 CFR 264.273

Maintain run-on/run-off control and managementsystem.

40 CFR 264.273

Special application conditions if food-chain crops aregrown in or on treatment zone.

40 CFR 264.276

Unsaturated zone monitoring. 40 CFR 264.278

Special requirements for ignitable or reactive waste. 40 CFR 264.281

Special requirements for incompatible wastes. 40 CFR 264.282

Special requirements for RCRA hazardous wastes. RCRA waste No’s. F020, F021, F022, F023, F026,F027.

40 CFR 264.283

Design system to operate odor free. CAA Section 101a and40 CFR 52a









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Land Treatment(cont’d.)

Predict total emissions of volatile organic compounds(VOCs) to demonstrate emissions do not exceed 450lb/hr, 3,000 lb/day, 10 gal/day, or allowable emissionlevels from similar sources using ReasonablyAvailable Control Technology (RACT).






40 CFR 61a See discussion under Consolidation.

Operation andMaintenance(O&M)

Post-closure care to ensure that site is maintained andmonitored.

40 CFR 264.118 (RCRA, Subpart G) Post-closure requirements for operation and maintenance of municipallandfill sites are relevant and appropriate to new disposal units withnonhazardous waste, or existing units capped in-place.

In cases where municipal landfill site wastes are determined to be hazardouswastes, and new disposal units are created, the post-closure requirements willbe applicable.

Removal General performance standard requires minimization ofneed for further maintenance and control; minimizationor elimination of post-closure escape of hazardouswaste, hazardous constituents, leachate, contaminatedrunoff, or hazardous waste decomposition products.

Disturbance of RCRA hazardous waste (listed orcharacteristic) and movement outside the unit orarea of contamination.

May apply to surface impoundment or tocontaminated soil, including soil from dredgingor soil disturbed in the course of drilling orexcavation and returned to land.

40 CFR 264.111 Clean closure removal of contaminated materials does not appear to befeasible for municipal landfill sites in general due to the lack of suitableoffsite treatment or disposal facilities to accept the large volume of wastestypically found at municipal landfill sites and the impossibility of meetingthe requirement at a site with contaminated groundwater. However, cleanclosure removal may be considered for portions (hot spots) of municipallandfill sites. The RCRA clean closure requirements would be consideredrelevant and appropriate to contaminated wastes which are not hazardous, butwhich are similar to hazardous wastes.

Disposal or decontamination of equipment, structures,and soils.

40 CFR 264.111

Removal or decontamination of all waste residues,contaminated containment system components (e.g. ,liners, dikes), contaminated subsoils, and structuresand equipment contaminated with waste and leachate,and management of them as hazardous waste.

Not applicable to undisturbed material.

Disposal of RCRA hazardous waste (listed orcharacteristic) after disturbance and movementoutside the unit or area of contamination.

40 CFR 264.228(a)(1)and

40 CFR 254.258

In the event that the wastes being removed are determined to be hazardouswastes, the requirements of this section would be applicable.

Meet health-based levels at unit. 40 CFR 244.111

RCRA hazardous wastes are subject to land disposalrestrictions. Land disposal restrictions set performancerequirements on treatment of the wastes before landdisposal. The effective data for final group of RCRAwastes is May 8, 1990. Extensions to the effectivedates have been granted for specific RCRA wastes thatare contained in soil and/or debris.

Management of listed hazardous waste. 40 CFR 268 If the wastes found at the municipal landfill site are found to be RCRAwastes, the Land Disposal Restrictions will be applicable.

If the wastes are not RCRA wastes but contain the same or similarconstituents to those in RCRA wastes, then the Land Disposal Restrictionsmay be relevant and appropriate.


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Slurry Wall Excavation of soil for construction of slurry wall maytrigger cleanup or land disposal restrictions.


See Consolidation, Excavation inthis table.

See discussions under Consolidation and Excavation.

Surface WaterControl

Prevent run-on, and control and collect runoff from a24-hour, 25-year storm (waste piles, land treatmentfacilities, landfills)

Land-based treatment, storage, or disposal units. 40 CFR 264.251(c)(d)

40 CFR 264.273(c)(d)

40 CFR 264.301(c)(d)

The requirements for control of run-on and run-off will be relevant andappropriate to all remediation alternatives that manage nonhazardous wasteand include onsite land-based treatment, storage, or disposal.

The requirements will be applicable to any remediation measures that includeland-based treatment, storage, or disposal of hazardous wastes.

Prevent over-topping of surface impoundment. 40 CFR 264.221(c) This requirement will be relevant and appropriate to the construction andoperation of an onsite surface impoundment, or to operation of an existingonsite surface impoundment managing nonhazardous wastes.

These requirements would be applicable to the construction or operation of asurface impoundment for the storage or treatment of hazardous waste.

Treatment Standards for miscellaneous units (long-termretrievable storage, thermal treatment other thanincinerators, open burning, open detonation, chemical,physical, and biological treatment units using otherthan tanks, surface impoundments, or land treatmentunits) require new miscellaneous units to satisfyenvironmental performance standards by protection ofgroundwater, surface water, and air quality, and bylimiting surface ans subsurface migration.

Use of other units for treatment of hazardouswastes. These units do not meeting thedefinitions for units regulated elsewhere underRCRA.

40 CFR 264 (Subpart X)

The requirement will be relevant and appropriate to the construction,operation, maintenance, and closure of any miscellaneous treatment unit (atreatment unit that is not elsewhere regulated) constructed on municipallandfill site for treatment and/or disposal of nonhazardous wastes.

These requirements would be applicable to the construction and operation ofa miscellaneous treatment unit for the treatment and/or disposal of hazardouswastes.

Treatment of wastes subject to ban on land disposalmust attain levels achievable by test demonstratedavailable treatment technologies (BDAT) for eachhazardous constituent in each listed waste.

Effective data for CERCLA actions is November8, 1988, for F001-F005 hazardous wastes, dioxinwastes, and certain “California List” wastes. Otherrestricted wastes have different effective dates aspromulgated in 40 CFR 268.

40 CFR 268(Subpart D)

These regulations are applicable to the disposal of any municipal landfill sitewaste that can be defined as restricted wastes.

These requirements are relevant and appropriate to the treatment prior to landdisposal of any wastes that contain components of restricted wastes inconcentrations that make the site wastes sufficiently similar to the regulatedwastes. The requirements specify levels of treatment that must be attainedprior to land disposal.

Prepare fugitive and odor emission control plan for thisaction

CAA Section 101a and40 CFR 52a

See discussions under Consolidation.









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Page 13 of 13


Treatment (cont’d.) Predict total emissions of volatile organic compounds(VOCs) to demonstrate emissions do not exceed 450lb/hr, 3,000 lb/day, 10 gal/day, or allowable emissionlevels from similar sources using ReasonablyAvailable Control Technology (RACT).



Verify through emission estimates and dispersionmodeling that hydrogen sulfide emissions does notcreate an ambient concentration greater than or equal to0.10 ppm.




UndergroundInjection ofWastes andTreatedGroundwater

UIC program prohibits: 40 CFR 144.12

• Injection activities that allow movement of

contaminants into underground sources of drinkingwater (USDW) and results in violations of MCLs oradversely affect health.

• Construction of new Class IV wells, and operationand maintenance of existing wells.

40 CFR 144.13

Wells used to inject contaminated groundwater thathas been treated and is being reinjected into the sameformation from which it was withdrawn are notprohibited if activity is part of CERCLA or RCRAactions.

40 CFR 144.14

All hazardous waste injection wells must also complywith the RCRA requirements.

40 CFR 144.16

Waste Pile Use liner and leachate collection and removal system. RCRA hazardous waste, non-containerizedaccumulation of solid, nonflammable hazardouswaste that is used for treatment or storage.

40 CFR 264.251

Notes:a All of the Clean Air Act ARARs that have been established by the federal government may be covered by matching state regulations. The state may have the authority to manage these programs through the approval of its implementation plans (40 CFR 52

Subpart G).b Action alternatives from ROD keyword index.c Bulk storage requires the preparation and implementation of a spill prevention, control, countermeasures (SPCC) plan (see 40 CFR 761.65(c)(7)(ii) for specification of container sizes that are considered “bulk” storage containers). d These regulations apply regardless of whether the remedial action discharges into the sewer or trucks the waste to an inlet to the sewage conveyance system located “upstream” of the POTW. e An approved incinerator (under Section 761.70) can be used to destroy any concentration pf PCBs; a high-efficiency boiler approved under Section 761.60(a)(2)(iii) can be used for mineral oil dielectric fluid from PCB-contaminated electrical equipment

containing PCBs in concentrations greater than or equal to 50 ppm but less than 500 ppm; and a RCRA-approved incinerator (under RCRA paragraph 3005(a)) can be used for PCBs that and not subject to the incinerator requirements of TSCA.


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Maximum Contaminant Levels (MCLs).MCLS are enforceable drinking water standardsestablished by U.S. EPA under the Safe DrinkingWater Act. MCLs establish the maximum level ofa contaminant that is allowed in water delivered toany user of a public water system. An MCL for aspecific contaminant is required by law to be set asclose as feasible to the maximum contaminant levelgoal (MCLG) (see Section 5.2.2.1) for the samecontaminant, taking into consideration the besttechnology, treatment techniques, and other factors(including costs).

MCLS, as the enforceable requirements of theSDWA, are potential ARARs pursuant toCERCLA Section 121(d)(2)(A)(i). The NCPfurther states that MCLs generally have the statusof ARARs for groundwater when the MCLGs arenot an ARAR and the MCLs are relevant andappropriate under the circumstances of the release.A discussion of this issue can be found on page8753 of the preamble to the March 8, 1990, finalNCP. Typically, MCLs are considered relevant andappropriate to groundwater Class I and II aquifers.Compliance with an ARAR generally would bemeasured at the landfill boundary (not at theproperty boundary).

In some cases, a waiver of the MCLs may need tobe obtained. As an example, a landfill with wastebelow the water table may continue to exceedMCLs in groundwater far into the future because ofcontinued leaching of waste. In such cases,groundwater collection and treatment may notachieve MCLs at the landfill boundary, and awaiver for technical impracticality would need to beobtained. A technical impracticality waiver fortermination of a groundwater/leachate collectionand treatment system is usually available at someextended time in the future for municipal landfillsites in the vent that MCLs are not achievable[SARA 121(d)(4)(C)].

Maximum Contaminant Level Goals(MCLGs). MCLGs are non-enforceable goals fordrinking water set by U.S. EPA under the SafeDrinking Water Act. MCLGs represent acontaminant level presenting “no known oranticipated adverse effects on the health of

persons; and allowing for an additional adequatemargin of safety beyond that level. MCLGs arelisted in 40 CFR 141.50.

Based on the NCP, 40 CFR 300.430(e)(2)(i)(B),MCLGs above zero should be attained by remedialactions for ground or surface water that is a currentor potential source of drinking water where theMCLGs are determined to be relevant andappropriate under the circumstances of the release.When the MCLG for a contaminant has been set atzero, the MCL promulgated for that contaminantshould be attained for current or potential sourcesof drinking water, where the MCL is relevant andappropriate. In cases where ARARs (for example,MCLs, MCLGs) are not available for a particularcontaminant, or in cases where ARARs are notsufficiently protective (e.g., because of multiplecontaminants), remediation goals should be basedon a risk assessment where acceptable exposurelevels generally are concentrations that represent anexcess upper bound lifetime cancer risk to anindividual of between 10-4 and 10-6.

Secondary Maximum Contaminant Levels.Secondary MCLs are non-enforceable goals fordrinking water established by EPA under the SafeDrinking Water Act. Secondary MCLs pertain tocontaminants that, if present in excessive quantities,may discourage the utilization of a public watersupply because they affect qualities such as taste,color, odor, and corrosivity. Secondary MCLs areTBCs and are listed in 40 CFR 143. In many cases,exceedance of secondary MCLs is the firstindication of a more serious problem with a drinkingwater source.

Federal Water Quality Criteria (FWQC).FWQCs are non-enforceable guidelines developedby EPA under the Clean Water Act. However, theyare potential ARARs because SARA and the NCPstate that FWQC shall be attained “where relevantand appropriate under the circumstances of therelease” (CERCLA Section 121(d)(2)(B); 40 CFR300.430(e)(2)(i)(E)). Two types of criteriahave been set by EPA, one for the protection ofhuman health and another for the protection ofaquatic life. FWQCs set quantitative levels of


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pollutants in water, the levels such that waterquality is adequate for a specified use. These levelsare based solely on data and scientific judgmentsregarding the relationship between concentrationsof a pollutant and resulting effects on environmentaland human health. FWQCs do not reflectconsideration of economic or technologicalfeasibility. FWQCs are used by the states to settheir own water quality standards for surfacewater. They are also typically used by state andfederal agencies in setting National PollutionDischarge Elimination System (NPDES) dischargepermit levels.

Whether a water quality criterion is relevant andappropriate depends on the designated or potentialwater uses, the environmental media affected, thepurpose for which such criteria were developed,and the latest available scientific informationavailable (see CERCLA Section 121(d)(2)(B)(i)).Although a state may develop its own useclassification scheme, designated uses generallyinclude recreation, protection, and propagation offish and aquatic life; agricultural and industrial uses;public water supply; and navigation.

For water designated as a public water supply,MCL/MCLGs would generally be relevant andappropriate; the criteria that reflect fishconsumption may also be relevant and appropriateif fishing is included in the state’s designated use. Ifthe state has designated a water body forrecreation, a water quality criteria reflecting fishconsumption alone may be relevant and appropriateif fishing is included in the recreational usedesignation. Generally, water quality criteria are notrelevant and appropriate for other uses, such asindustrial or agricultural, since exposure reflected inthe water quality criteria are not likely to occur. Thetwo types of FWQC are discussed below:

• FWQCs for Human Health Protection:One goal of the FWQC is to protecthumans from hazards associated with tworoutes of exposure, including exposurefrom drinking the water and exposure fromconsuming aquatic organisms, primarilyfish. There are nonbinding guidelinesprovided that address exposure from bothroutes, and from fish consumption alone.The criteria identify concentrations

equating to specified levels of cancer risk(10- 5, 10-6, and 10-7) for carcinogens orthreshold-level concentrations fornoncarcinogens that represent the waterconcentrations at which there would be nochronic adverse health effects. There arealso criteria for chemicals with organolepticproperties (that is, affecting taste or odorbut not health). These criteria are based onconcentrations at which there would be notaste or odor problems. The FWQC valuesfor human health protection can be found inthe Federal Register, Vol. 45 (No. 231), FRpg. 79318, November 29, 1980--WaterQuality Criteria.

• FWQCs for Aquatic Life Protection: TheFWQC criteria for the protection of aquaticlife present two sets of values, one basedon the protection of aquatic life from acuteexposure and the other from chronicexposures. When data are not sufficient toset a criterion, the lowest reported acute orchronic-effects level published in theliterature is used. A summary of waterquality criteria may be found in QualityCriteria for Water (U.S. EPA, 1986aa),which is commonly referred to as the “GoldBook.”

Office Of Drinking Water Health Advisories.The health advisories are non-enforceableguidelines (TBCs) that present the EPA Office ofWater’s most recent determination regarding theconcentration level of drinking water contaminantsbelow which adverse effects would not beanticipated to occur. This level includes a margin ofsafety to protect sensitive members of thepopulation and is subject to change as new healthinformation becomes available. Levels are specifiedfor 1-day, 10-day, longer term (e.g., 10 percent ofone’s lifetime, 7 years), and lifetime exposureperiods.

5.2.1.2 Location-Specific ARARs

Location-specific ARARs are the restrictionsplaced on the concentration of hazardoussubstances or the conduct of activities solelybecause they occur in special locations. These


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requirements relate to the geographical or physicalposition of municipal landfill sites rather than to thenature of the contaminants or the proposed remedialactions. These requirements may limit the type ofremedial action that can be implemented and mayimpose additional constraints on the cleanup action.The restrictions caused by flood plains and wetlandsare among the most common location-specificpotential ARARs for municipal landfill sites. Federallocation-specific ARARs for municipal landfill sitesare presented in Table 5-2, at the end of thissection. The following is a discussion of thelocation-specific ARARs that typically are mostpertinent to landfill sites.

Wetlands . Remediation of municipal landfill siteslocated next to wetland areas will have to beimplemented in a manner which minimizes thedestruction, loss or degradation of wetlands (40CFR 6.302(a)). Additionally, the Clean Water ActSection 404 prohibits discharge of dredged or fillmaterial into a wetland area. Situations wherewetlands are filled or have been irreparably harmedmay require the creation of new wetlands.Information on the Corps of Engineers methodologyfor identifying and evaluating wetland areas can befound in the document Wetland EvaluationTechnique (WET) (U.S. Army Corps of Engineers,1987).

Floodplains . Remediation of landfill sites locatedwithin floodplains (for example, lowlands, andrelatively flat areas adjoining inland and coastalwaters) will have to be carried out to the extentpossible, to avoid adverse effects, and to preservenatural and beneficial values of the floodplain (40CFR 6.302(b)). For example, remedial actionsshould not be designed and constructed in a mannerthat destroys the usefulness of a floodplain, therebypotentially causing adjacent areas to becomeflooded.

5.2.1.3 Action-Specific ARARs

Action-specific ARARs are usually technology-or activity-based requirements or limitations onactions taken with respect to hazardous sub-stances. These requirements typically define

acceptable treatment, storage, and disposalprocedures for hazardous substances during theimplementation of the response action. Therequirements generally set performance or designstandards for specific activities related to managinghazardous wastes at municipal landfill sites.Action-specific ARARs for municipal landfill sitesare shown in Table 5-3, located at the end of thissection. The following is a discussion of theaction-specific ARARs that typically are mostpertinent to landfill sites.

RCRA Closure Requirements . A determinationmust be made on which RCRA closurerequirements are applicable or relevant andappropriate for the specific site of concern. RCRASubtitle D requirements are generally applicableunless a determination is made that Subtitle C isapplicable or relevant and appropriate. RCRASubtitle C would be applicable if the waste is alisted or characteristic waste under RCRA, and (1)if the waste was disposed of after November 19,1980 (effective date of RCRA) or (2) the responseaction constitutes current treatment, storage, ordisposal as certified by RCRA. The decision aboutwhether a RCRA requirement is relevant andappropriate is based on consideration of a variety offactors, including the nature of the waste and itshazardous properties, and the nature of therequirement itself. State closure requirements thatare an ARAR and that are more stringent than thefederal requirements must be attained (or waived).Listed hazardous wastes are found in 40 CFR Part261, Subpart D. Characteristic hazardous wastesunder RCRA are described in 40 CFR Part 261,Subpart C.

Because containment of landfill wastes is acommon element of most remedial actions atmunicipal landfill sites, the most significant closurerequirements will likely be the RCRA requirementsconcerning landfill covers. RCRA Subtitle C closurerequirements specify that a landfill cover for apermitted facility have a permeability less than orequal to the permeability of any bottom liner systemor natural subsoils present (40 CFR 264.310).Additional information on landfill covers can befound in Section 4 of this document.


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Land Disposal Restrictions . Offsite disposal ofcontaminated soils from hot spots may be a viablecomponent of a remedial action alternative for amunicipal landfill site. In situations where thematerial is regulated as hazardous under RCRASubpart C, land disposal of contaminated soilsoffsite will be based largely on the RCRA LandDisposal Restrictions (LDRs). The LDRs may beapplicable to the contaminated soils if it isdetermined that the soils have been contaminatedby a restricted, listed RCRA waste or if thecontaminated soils are a RCRA characteristicwaste. The LDRs may require that a specificconcentration level be achieved or that a specifiedtechnology be used for treatment prior to landdisposal in a RCRA facility. Treatment of hot spotsand subsequent disposal may also trigger LDRs.

If soils contain RCRA waste, offsite land disposalmust be at a permitted RCRA hazardous wastelandfill that meets the requirements of RCRASubtitle C, that is in compliance with CERCLASection 121(d)(3) and the Superfund offsite policy.The design features of a RCRA hazardous wastelandfill are defined in 40 CFR 254 Subpart N. If thesoils are not a RCRA waste or if they are delisted,offsite disposal may be at a solid waste landfill thatis in compliance with the offsite policy andCERCLA Sec. 121(d)(3). In the absence of otherregulations, solid waste landfills are regulated underRCRA Subtitle D. However, in most cases, stateregulations govern the design, construction,operation, and closure of solid waste landfills.

Air Emission Treatment Requirements .Several alternatives for remediation of landfill sitesmay include technologies that result in a dischargeof contaminants to the air. Table 5-3 presents asummary of the federal requirements concerning airemissions for technologies commonly implementedat municipal landfill sites. The need for air emissiontreatment should be evaluated based on federal andstate requirements and an evaluation of humanhealth risks. Technologies that typically result in airemissions include air stripping, collection andtreatment of landfill gas, excavation andconsolidation of contaminated soils, and incineration.

The EPA Office of Air Quality, Planning, andStandards is currently developing new sourceemission guidelines and performance standards forcollection and treatment of landfill gas. Theproposed rule (a TBC) would require an activelandfill gas collection and control system for solidwaste landfills with emissions exceeding 100megagrams per year of nonmethane organiccompounds. Treatment of landfill gas (e.g., byenclosed ground flares) would be required todemonstrate a destruction removal efficiency of 98percent or emissions less than or equal to 20 ppm(volume dried) of nonmethane organic compounds.Since these emission guidelines and standards arecurrently under development, some changes may bemade.

The proposed air emission standards will apply tonew municipal solid waste landfills as well as tothose facilities that have accepted waste sinceNovember 8, 1987, or that have capacity availablefor future use. For CERCLA municipal landfillremediations, these requirements would be potentialARARs for all records of decision (RODs) signedafter the rule’s promulgation date. The standards inthis rule, once promulgated, will be applicable forthose municipal landfill sites on the NPL thataccepted waste on or after November 8, 1987, orthat are operating and have capacity for future use.In cases where these standards are not applicable,such as landfill sites that accepted waste prior toNovember 8, 1987, they may still be determined tobe relevant and appropriate. The determination ofrelevance and appropriateness is made on asite-specific basis pursuant to NCP Section300.400(g) (55 Federal Register 8841, March 8,1990). Judgment should be used in applying theseguidelines and standards since they will apply tomunicipal solid waste landfills as opposed toCERCLA sites where there is typically co-disposalof both municipal solid waste and hazardous waste.

5.2.2 State ARARs

In general, in order for a state requirement to beconsidered an ARAR, it must:

• Be promulgated (be legally enforceable andof general applicability)


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• Be identified to EPA in a timely manner

• Not result in an in-state ban on landdisposal of hazardous waste

• Be more stringent than federalrequirements

Even if the state standard meets these conditions, itmay be waived if it is found not to have beenapplied uniformly and consistently throughout thestate.

Because many states may be revising theirstandards in any given year, more stringent statestandards for municipal landfill sites need to beidentified on a case-by-case basis. The aspects ofstate requirements that are likely to be morestringent are described below.

5.2.2.1 Chemical-Specific ARARs

State Drinking Water Acts. Many statesadminister drinking water acts that containchemical-specific standards and criteria that areoften ARARs for groundwater remediation. Areview of state standards should be conducted tosee if any standards or criteria (such as drinkingwater action levels) exist that are more stringentthan federal standards (for example, MCLs andMCLGs). For cases where a more stringent statestandard exists for a particular compound, the statestandard should be used, where relevant andappropriate under the circumstances of the release(most drinking water standards are not legally“applicable” to groundwater). In addition, statesoften have health advisories that are more stringentthan federal criteria. These TBCs may beconsidered as well.

Clean Water Act. Many states administer thefederal Clean Water Act and its importantcomponent, the NPDES program, which containsstandards and criteria for discharge of treatedwaters to nearby surface waters (see Section5.2.2.3).

5.2.2.2 Location-Specific ARARs

Wetlands . State requirements for designation of

wetlands should be reviewed to determine if theyare more stringent than the Corps of Engineers’methodology. Stringent state methodologies foridentifying wetlands can expand the extent ofwetlands requiring mitigation. In cases wherewetlands have been contaminated or destroyed,mitigation measures may need to be included in theremedial action. State requirements can differsignificantly from federal regulations.

Floodplains . State ARARs often prohibit the sitingof landfills in floodplains, which in turn may restrictonsite disposal options.

5.2.2.3 Action-Specific ARARs

NPDES Program. Pretreatment requirements fordischarge directly to a publicly owned treatmentworks (POTW) under the NPDES program may bedictated by a local or regional government agency.A careful review of a state’s NPDES requirementsand of the potential pretreatment requirements thatwould be imposed by the POTW is thereforenecessary. Frequently, discussions on theacceptability of a discharge to a POTW will extendwell into the predesign and design phases atSuperfund sites. There is also a tendency forPOTW permitting authorities to set stringentdischarge standards because there is no categoricalstandard for CERCLA operations and because ofpublic fear or mistrust of “hazardous waste.”

Direct discharge of treated effluent offsite to asurface water body would also require an NPDESdischarge permit. In many cases EPA hasdelegated implementation of this program to thestates. Therefore, as with discharge to a POTW, areview of a state’s NPDES requirements should beconducted if direct discharge offsite to a surfacewater is being considered.

Closure Requirements . State requirements forcover of hazardous and solid waste landfills shouldbe reviewed to determine whether more stringentdesign criteria exist for the construction, operation,and closure of landfills. The state may also haveerosion and sedimentation control regulations. Localrequirements (e.g., erosion control regulations) andclosure requirements such as minimum standardsfor cover designs may be important TBC material


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although they are generally not ARARs (unlessthey represent the state standards).

Air Emission Treatment Requirements . Aswith the water programs, many states administerthe Clean Air Act (CAA). State air emissionstandards should be reviewed for technologies suchas incineration or air stripping to see if requirementsmore stringent than federal CAA requirementsexist. Landfill gas emissions may also be regulatedUnder state air regulations.

5.3 Long-Term Effectiveness andPermanence

Some aspects of long-term effectiveness includethe ability of a cap to maintain its integrity, theability of groundwater extraction to meet cleanuplevels, and the long-term maintainability of leachateor gas treatment systems. Long-term effectivenessalso includes an evaluation of the magnitude ofresidual risk. Because the technologies generallyconsidered practicable for municipal landfill siteswill not completely eliminate the hazardoussubstances at a landfill, long-term management ofwaste is a critical issue. Complete evaluation underthis criterion should require determining the riskposed by the remaining waste. One of the moretime-consuming tasks associated with the evaluationunder this criterion may be the need to estimateinfiltration through an existing or new landfill cap.Groundwater and air modeling also may be needed.EPA’s computer model HELP (hydrologicevaluation of landfill performance), which isdiscussed in Section 4.2 (Landfill Contents), may beuseful in evaluating this criteria.

5.4 Reduction of TMV ThroughTreatment

Generally, reduction of TMV at municipal landfillsites occurs through treatment of hot spots.However, TMV can also be reduced throughtreatment of groundwater, leachate, or landfill gas.When treatment is used, a number of factors mustbe considered. Naturally, the treatment process

used and the materials treated must be evaluated.This evaluation can be particularly significant forinnovative technologies or conventional technologiesbeing applied to a waste that has unusualcharacteristics. The volume of material destroyedor treated must be evaluated, as well as the degreeof expected reductions. Also, the degree to whichtreatment is irreversible must be considered,particularly for technologies like stabilization.Technologies such as capping and fencing thatprovide no treatment do not require evaluationunder this criterion.

5.5 Short-Term Effectiveness

A significant issue of short-term effectiveness is theeffect on the community of truck traffic as largequantities of cap material are hauled onto the site.Both noise and potential increases in vehicularaccidents must be considered (construction of atypical 40-acre multilayer cap requires about 32,500truckloads of capping material). Other issues suchas potential VOC emissions during excavation ofhot spots and during construction and operation ofonsite treatment systems are associated withworker and community protection during remedialactivities. Also included under this criterion are theenvironmental impacts resulting from the remedialaction. To evaluate this criterion, the time requiredto achieve the response objectives must bedetermined, including an estimate of time to achieveremediation of leachate and groundwater.

5.6 Implementability

Administrative implementability is the relativedifficulty of coordinating and obtaining approvalsfrom other agencies to perform certain activities.The difficulty of meeting this subcriterion will varyfrom site to site, and depends primarily on thelocation of the site and what other agencies areinvolved. There may be significant administrativeimplementability issues associated with offsite deedrestrictions and alternative water supplies. Theenforceability of deed restrictions tends to varygreatly, depending on local laws and ordinances.Likewise, the administrative implementability of


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treating leachate or groundwater at a POTWdepends on how receptive local treatment plantofficials are to accepting contaminated water fromthe site. It is not uncommon for discussions withPOTWs to extend well into the remedial designphase.

The technical implementability of a technology,including the ability to construct and/or operate thetechnology, and the reliability of the technology,largely depends on the treatability of thecontaminated material. For example, technicaldifficulties are likely when using incineration forwastes that are high in metals, or when using in situstabilization for wastes containing moderate to highlevels of organics. The technical implementability ofsome technologies would also depend on availabilityof sufficient space for the materials-handling and/orequipment. Also, the ability to monitor theeffectiveness of a remedy is a consideration,particularly for a technology like in situ stabilization.The ease of undertaking additional remedial actions,if necessary, must also be considered. Thetreatment technologies that have been identified asbeing most practicable for municipal landfill sitesare proven conventional technologies (a fewinnovative technologies have also been discussed).

The availability of goods and services will also varyfrom site to site and will depend primarily on a site’slocation and accessibility. As an example, theimplementability of bringing in truckloads of fillmaterial will depend on the source of the materialand the accessibility to the site.

5.7 Cost

In Table 5-1, an indication is given of whether eachtechnology will have a low, medium, or high impacton total cost if included as part of an alternative.Costs can be difficult to estimate for groundwaterextraction and treatment and for hot spotexcavation and/or treatment because the volume of

contaminated groundwater and hot spots is difficultto estimate accurately during the RI/FS. FS costestimates should provide an accuracy of +50percent to -30 percent using data available from theRI.

5.8 State Acceptance

Under this criterion, an alternative is evaluated interms of the technical and administrative issues andconcerns the state (or support agency) may have.This is a criterion that is addressed in the record ofdecision (ROD) once formal comments arereceived on the RI/FS report (to the extent they areknown, state concerns are considered earlier in theprocess as well). Frequently, state acceptance isclosely related to compliance with state ARARs.

5.9 Community Acceptance

Under this criterion, an alternative is evaluated interms of the issues and concerns the public mayhave. As with state acceptance, this is a criterionthat is addressed in the ROD once the commentshave been formally received on the RI/FS report(also, to the extent they are known, communityconcerns are considered early in the process aswell).


This section presents each of the evaluation criteriaand illustrates how each of the technologiesidentified in Section 4 may affect each of thealternative evaluation criteria. In the followingsection, alternatives typically developed for amunicipal landfill site are presented. The sectiondescribes how the technologies discussed in thissection (Table 5-1) might be combined and thenevaluated as alternatives using the nine criteria.


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Section 6DEVELOPMENT AND EVALUATION OF ALTERNATIVES

FOR THE EXAMPLE SITE

Based on the review of practicable technologies formunicipal landfill sites (see Section 4) and the actualcharacteristics of the example site (see AppendixA), a range of typical alternatives has beendeveloped. The purpose is to illustrate howtechnologies might be combined to form alternativestypically developed for landfill sites. Somecomponents of these alternatives may not beapplicable to other sites, depending on their specificcharacteristics. Table 6-1 presents an evaluation ofeach alternative with respect to the thresholdcriteria, overall protection of human health and theenvironment, and compliance with ARARs and thefive balancing criteria described in Section 5. Themodifying criteria, state acceptance, and communityacceptance are not included in Table 6-1 since theyare not formally evaluated during the FS. These twocriteria are addressed in the Record of Decision(ROD) and are used as a basis for modifying analternative due to formal comments from the stateor community on the FS report and proposed plan.Addressing state and community concerns isincorporated throughout the RI/FS process; formaluse of the modifying criteria once the proposed planhas been issued is not the first time these concernsare addressed.

The example site, considered a co-disposal facilitywith a known hot spot, is described in AppendixA--Site Characterization Strategy for an ExampleSite. To summarize, the site is approximately 60acres in size (20 acres of which is a landfill) and isin a rural area. In addition to municipal trash, thelandfill accepted chemical wastes such as solvents,paint, paint thinners and lacquers, and industrialplating sludges. Available records show noindication of segregation of wastes. Industrial,commercial, and municipal wastes are generallymixed throughout the landfill, except for liquidindustrial solvent wastes. Disposal of this wastewas generally restricted to the southern portion of

the landfill. Exposed areas in the southern half ofthe landfill have been temporarily covered with apartial cap consisting of 2 feet of compacted clay.The remainder of the landfill has a temporary soilcover, although there are some areas of exposedwastes.

The unconsolidated deposits underlying the site areapproximately 135 feet thick and consist primarilyof sand and gravel of glaciofluvial and alluvialorigin. Bedrock in the vicinity of the site,encountered at an approximate depth of 135 feet,consists of undifferentiated Cambrian sandstone upto 1,200 feet thick. These sandstones are fine tocoarse grained and contain a small amount of shale.

Some of the contaminants of concern aretrichloroethene (TCE) and vinyl chloride (VC) inthe soil and groundwater; lead, arsenic, and totalchromium in the soil; and methane gas.

The areas of concern for the example site include:

• Landfill contents under the existing soilcover

• The hot spot outside the existing soil cover

• High-strength (onsite) groundwater(leachate)

• Low-strength (offsite) groundwater

• Surface water sediments (from a nearbyunnamed tributary)

• Landfill gas

The ARARs for the Example Site are discussedbelow:


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Table 6-1RECOMMENDED ALTERNATIVES: SUMMARY OF DETAILED ANALYSIS

EXAMPLE SITE

Page 1 of 6

Alternative 1 Alternative 2 Alternative 3 Alternative 4

No Action

Single-Barrier CapConsolidation of Hot Spot

High-Strength Groundwater (Leachate)Collection and Onsite Treatment

Low-Strength Groundwater Extraction andOnsite Treatment

Discharge to Unnamed TributaryConsolidation of Surface Water Sediments

Institutional ControlsFive-Year Review

Composite-Barrier CapConsolidation of Hot Spot





Single-Barrier CapTreatment of Hot Spot (onsite)

High-Strength Groundwater (Leachate) Collection and Onsite Treatment

Low-Strength Groundwater Extraction and OnsiteTreatment

Discharge to Unnamed TributaryConsolidated of Surface Water Sediments


Evaluation Criteria

Overall Protection of HumanHealth and the Environment

No action taken. Notconsidered to be protectiveof human health and theenvironment

Construction of a cap reduces the risk ofexposure to the landfill contents, and reducesleaching of contaminants to the groundwater.Institutional controls and monitoring ofgroundwater quality will be required duringaquifer restoration to protect public health andthe environment.

A composite-barrier cap will be more reliablethan a single-barrier cap in terms of preventingdirect contact with landfill contents andreducing infiltration. Institutional controls willstill be required during the period of aquiferrestoration for protection of public health andthe environment.

Treatment of hot spots provides additional protection tohuman health and the environment by reducing the volumeof contamination at the site. As with Alternative 2 andAlternative 3, institutional controls will still be requiredduring the period of aquifer restoration to prevent the useof contaminated groundwater.

Compliance with ARARs No action taken. Notconsidered to be incompliance with ARARs.

Expected to be in compliance with ARARs. Expected to be in compliance with ARARs. Expected to be in compliance with ARARs.

Long-Term Effectiveness

• Magnitude of ResidualRisk

Existing infiltrationthrough cap will continue.Infiltration allows leachingof contaminants togroundwater. Risks fromdirect contact will alsoremain.

Reduction of residual risk from direct contact.Lessens future potential for groundwatercontamination by reducing infiltration. Thegroundwater is collected and treated; however,the source of contamination remains,presenting a possible future risk thatcontamination will breach the containmentsystem.

Potential for infiltration is reduced over single-barrier cap protection. The groundwater iscollected and treated; however, the source ofcontamination remains, presenting a possiblefuture risk that contamination will breach thecontainment system.

Less residual waste onsite to manage since hot spots willbe excavated and incinerated and the groundwater will becollected and treated. Excavation may reduce long-termrisk. The groundwater is collected and treated; however, aportion of the source of contamination remains, presentingpossible future risk that contamination will breach thecontainment system.

• Adequacy andReliability of Controls

Continued erosion ofexisting cap likely to occur.Wastes could eventually beexposed with potential forexposure onsite or transportof contaminants in runoff towetlands.

Improved reliability over no action. Requireslong-term maintenance to maintain theintegrity of the cap.

Increased reliability over the single-barrier cap.Synthetic liner provides an additional barrierfor reducing infiltration and leachate generationresulting from infiltration. Potential for ruptureof synthetic liner from differential settling.Requires long-term maintenance to maintain theintegrity of the cap.

Provides the greatest long-term effectiveness andpermanence since hot spots will be treated. Continuedmaintenance will be required to maintain the integrity ofthe cap.


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EXAMPLE SITE

Page 2 of 6


No Action
















Evaluation Criteria

Reduction of Toxicity,Mobility, and Volume

! Treatment Process Usedand Materials Treated

A treatment technology isnot included as part of thisalternative.

Conventional treatment of groundwaterincluding metals precipitation, biologicaltreatment (activated sludge), GAC.

Conventional treatment of groundwaterincluding metals precipitation, biologicaltreatment (activated sludge), GAC.

Hot spots to be treated onsite via incinerator. Same asAlternative 2 and 3 for groundwater treatment.

! Amount of HazardousMaterials Destroyed orTreated


High-strength groundwater (leachate) collectedfrom perimeter wells will be treated, primarilyto prevent offsite migration of contaminatedgroundwater. Offsite groundwater will becollected and treated. The rate of hazardousmaterials destroyed will depend on theextraction rate (that is, whether a high or lowflow rate is selected).

High-strength groundwater (leachate) and lowstrength groundwater (offsite) will be collectedand treated. The amount of hazardous materialsdestroyed will depend on the extraction rate(that is, whether a high or low flow rate isselected).

Reduction in the hazardous organic constituents would beachieved by incineration of hot spots. Same as Alternative2 and 3 for groundwater.

! Expected Reductions inToxicity, Mobility, andVolume


Toxicity or volume of contaminatedgroundwater may be reduced by treatmentsystem.

Toxicity or volume of high strengthgroundwater may be reduced by treatmentsystem.

TMV would be reduced through the treatment of hot spotareas. Same as Alternative 2 and 3 for groundwater.

! Irreversibility of theTreatment


Groundwater treatment process may not beirreversible.

Groundwater treatment process may not beirreversible.

Incineration is permanent. Same as Alternative 2 and 3 forgroundwater.

! Type and Quantity ofTreatment Residual


Sludge from metals precipitation process mayneed to be disposed of at a RCRA landfill.

Sludge from metals precipitation process mayneed to be disposed of at a RCRA landfill.

Ash from incinerator will be placed under cap. Same asAlternative 2 and 3 for groundwater residuals.


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EXAMPLE SITE

Page 3 of 6


No Action
















Evaluation Criteria

Short-Term Effectiveness

! Protection ofCommunity duringRemedial Action

Not action taken. Possible impacts from consolidation activities.Community impact through increased dust andnoise from construction and truck traffic. Trucktraffic introduces risk from vehicular accidents.

Possible impacts from consolidation activities.Community impact through increased dust andnoise from construction and truck traffic. Trucktraffic introduces risk from vehicular accidents.

Possible impacts from disturbance of waste and improperair emissions. Adverse impacts to air quality frommalfunctions of incinerator and poor destruction efficiencycould also be expected. Community impact throughincreased dust and noise from construction and trucktraffic. Truck traffic introduces risk from vehicularaccidents.

! Protection of Workersduring Remedial Action

None required. Potential risk to workers through inhalationand direct contact during grading andexcavation of hot spots. Proper dust controland health and safety protection will mitigaterisk.

Potential risk to workers through inhalationand direct contact during grading andexcavation of hot spots. Proper dust control andhealth and safety protection will mitigate risk.

Greatest potential for safety-related problems because itinvolves the excavation of contaminated materials. Directexposure and inhalation is the safety risk to workers.Although detailed planning, design, and implementationcan minimize the potential safety problems to onsite andoffsite personnel, they cannot be totally eliminated.

! Environmental Impacts No remedial action. Potential for exposure to waste or runoff ofcontaminants to Polk River duringimplementation. Potential negative impactfrom possible secondary migration ofcontaminated surface water sediments duringremoval for consolidation under cap.

Potential for exposure to waste or runoff ofcontaminants to Polk River duringimplementation. Potential negative impact frompossible secondary migration of contaminatedsurface water sediments during removal forconsolidation under cap.

Potential negative impact due to air emissions fromincineration. Potential for exposure to waste or runoff ofcontaminants to Polk River during implementation.


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EXAMPLE SITE

Page 4 of 6


No Action
















Evaluation Criteria

Short-Term Effectiveness(continued)

• Time Until RemedialAction Objectives areAchieved

No time requirements. Less than 2 years should be required toimplement components of the remedy. If a lowflow extraction rate (e.g., 200 gpm) is selectedthe goal for achieving groundwaterremediation would be 15 years. If a high flowextraction rate (e.g., 500 gpm) is selected thegoal for achieving groundwater remediationwould be 5 years. This assumes continuedcollection of leachate and a completelyeffective leachate collection system controllingoffsite migration of contaminated groundwater.

Less than 2 years should be required toimplement components of remedy. Goal forachieving remediation is the same asAlternative 2.

Groundwater remediation will be the same as Alternative 2.However, incineration of hot spots and dredging of surfacewater sediments will require additional time to implementthe source control components of this remedy. The sourcecontrol components should be implemented in less than 4years.


6-6


EXAMPLE SITE

Page 5 of 6


No Action
















Evaluation Criteria

Implementability

! Technical Feasibility

- Ability to constructand operatetechnology

- Reliability of

technology

- Ability to monitoreffectiveness ofremedy

- Ease of undertakingadditional remedialaction, if any

No action taken. Relatively easy to implement. Implementationof this alternative uses conventionalequipment and technologies.

Monitoring effectiveness would be relativelyeasy, based on visual inspection andgroundwater monitoring.

Monitoring and evaluating effectiveness ofsediments removal will have to considerpotential adverse impacts from secondarymigration and physical disruption of biotaduring excavation activities.

Synthetic liner is difficult to install. Otherwise,this remedy uses conventional equipment andtechnologies.

Since two barriers are installed, a composite-barrier cap would be more reliable than a single-barrier cap.

Monitoring effectiveness would be based onvisual inspection and groundwater monitoring.

Monitoring and evaluating effectiveness ofsediments removal will have to considerpotential adverse impacts from secondarymigration and physical disruption of biotaduring excavation activities.

Incineration is highly questionable due to theheterogeneous nature of the waste material and its mixturewith large quantities of soil and debris. Reliableconfirmation sampling after excavation of sediments maybe difficult.

Monitoring effectiveness would be based on visualinspection and groundwater monitoring.

Same as Alternative 2 and 3 for monitoring and evaluatingeffectiveness of sediments removal.

! Availability of Servicesand Materials

Not applicable. Materials to construct cap readily available.Dewatering and dredging equipment mayrequire some lead time to secure but should beavailable.

Materials to construct cap are readily available.Dewatering and dredging equipment mayrequire some lead time to secure but should beavailable.

Materials to construct cap are readily available. Dewateringand dredging equipment may require some lead time tosecure but should be available. Likewise, incinerationequipment should be available but will require some leadtime, including time for pilot testing.


6-7


EXAMPLE SITE

Page 6 of 6


No Action
















Evaluation Criteria

Implementability(continued)

! Administered Feasibility

- Ability to coordinateand obtain approvalfrom other agencies

Administrative problemsaffecting alternativefeasibility are not expected.However, no action willlikely be unacceptable sincethe remedy is not protectiveand there will not becompliance with ARARs.

Discussions with the state for an NPDESpermit for discharge of treated groundwater tothe unnamed tributary to the Polk River areuncertain and may extend into design.

Discussions with the state for an NPDESpermit for discharge of treated groundwater tothe unnamed tributary to the Polk River areuncertain and may extend into design.

Sufficient space must be available onsite to buildincinerator. More difficult to implement than otheralternatives.

Same as Alternative 2 and 3 for discharge of treatedgroundwater.

COST None. Medium. Medium-high. High.


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6.1 Example Site ARARs

In addition to the potential federal ARARs listed inSection 5, state requirements for the example site thatare promulgated, more stringent than federalrequirements, and applicable or relevant and appropriateare discussed below. It is emphasized that thisdiscussion on specific state ARARs applies only to theExample Site. The purpose of this discussion is topresent some typical state requirements that may affectthe development and evaluation of remedial alternatives.

6.1.1 Chemical-Specific ARARs

6.1.1.1 Groundwater

Chemical-specific state standards for the Example Siteinclude state groundwater enforcement clean-upstandards and preventive action limits. A list of thespecific state groundwater enforcement standards andpreventative action limits that apply to the example sitecan be found in Appendix A. Typically, correctiveactions may be more extensive if enforcementstandards are exceeded. In general, preventive actionlimits apply wherever groundwater is monitored. Stateenforcement standards apply at the following locations:

• Any point of groundwater use

• At or beyond the property boundary of thefacility

• Any point within the property boundary beyondthe three-dimensional design management zone,if one is established by the state

The design management zone is an imaginary boundaryat some horizontal distance from the waste boundarythat extends downward through all saturated geologicformations. For land disposal facilities with feasibilitystudies that were approved by the state after October1, 1985, a horizontal distance of 150 feet is used for thedesign management zone.

6.1.1.2 Surface Water

Potential state ARARs for the Example Site forprotection of aquatic life include state ambient waterquality criteria for aquatic life protection. A list of thespecific state ambient water quality criteria that apply tothe Example Site can be found in Appendix A. Anydirect discharge of treated water (includinggroundwater or leachate) to the unnamed tributary ofthe Polk River would likely have to achieve thesestandards to comply with NPDES requirements.

6.1.2 Location-Specific ARARs

No location-specific state ARARs exist that are stricterthan the federal ARARs listed in Table 5-2. Mostsignificantly, the site is not located within the 100-yearfloodplain nor have wetlands been impacted by theExample Site.

6.1.3 Action-Specific ARARs

6.1.3.1 Soils/Landfill Contents

The Example Site has more stringent action-specificstate ARARs than the federal ARARs for theconstruction of a solid waste landfill cover. Portions ofthese cover requirements specify including a 2-foot claylayer with a 1.5- to 2.5-foot cover layer and 0.5 foot oftopsoil on the surface. The purpose of this requirementis to assure that adequate freeze-thaw protection isincluded in the design of the cap. Otherwise, expansionand contraction during freeze-thaw events could resultin the formation of cracks in the landfill cover.

6.2 Development of Alternatives

When developing alternatives, it is important toreevaluate pathways from the conceptual site modelthat may not represent a significant threat to humanhealth or the environment at this site. For example,landfill gas does not appear to be a significant threat tohuman health and the environment at the Example Sitebecause the area is rural and only a small


6-9

amount of gas is generated. Therefore, future useof the site may allow some access (such as forhunting). Because some landfill gas is likely to begenerated, it may be appropriate to include passivevents in the design of a landfill cap.

For municipal landfill sites with minimal hazardouswaste and no known hot spots, it may not benecessary to consider a composite-barrier cap orsoils treatment and consolidation. An exceptionmight be sites where erosion has dispersed somecontaminated soils without any discernable hotspots. In these instances, some consolidation ofsurficial soils may reduce the area that needs to becapped.

The range of alternatives developed for theExample Site is composed of the four alternativesdescribed below.

6.2.1 Alternative 1--No Action Alternative

Under Alternative 1, no action would be taken. Theno-action alternative is required as part of the NCPand provides a baseline against which otheralternatives can be compared.

6.2.2 Alternative 2

Alternative 2 is composed of the four componentslisted below.

Component 1. Containment

• Construction of a single-barrier cap (tocover entire landfill). Freeze-thawprotection would be included as part of thedesign of the cap. Passive vents would beinstalled to vent landfill gas. Long-termmonitoring of landfill gas would also beincluded as part of the remedy.

• Surface controls (as part of capconstruction)

S GradingS Revegetation

Component 2. Consolidation of the hot spot underthe clay cap

• Since the hot spot is generally within thelandfill contents, consolidation would onlybe required to the extent necessary tominimize the size of the landfill cap.

Component 3. Groundwater extraction andtreatment

• High-strength groundwater (leachate)collection by perimeter wells, and onsitetreatment with discharge to the unnamedtributary to the Polk River

• Low-strength groundwater (offsite)extraction (by wells) and onsite treatmentwith discharge to the unnamed tributary tothe Polk River

Component 4. Consolidation of surface watersediments under landfill cap

• Consolidation of surface water sedimentsfrom the unnamed tributary would includedredging the sediments and consolidatingthem with other material under the landfillcap.

Component 5. Institutional controls

• Deed restrictions to:

S Limit site accessS Prohibit groundwater use

Component 6. Five-year review

Alternative 2 would minimize infiltration of surfacewater and potential for direct contact with thelandfill contents. Passive vents would be installed toprevent accumulation of landfill gas.Perimeter wells would be installed aroundthe landfill to capture high-strength groundwater(leachate) resulting from onsite contamination.Downgradient extraction wells would be


6-10

installed to capture offsite groundwater. Theselection of a groundwater extraction rate forcollection and treatment of offsite groundwaterwould be determined during design. It is estimatedthat, if a total offsite groundwater extraction rate of500 gpm is selected, it would require at least 5years to achieve MCLs at the landfill boundary. Ifa total offisite groundwater extraction rate of 200gpm is selected, it is estimated that at least 15 yearswould be required to achieve MCLs at the landfillboundary. These estimates assume that the onsiteperimeter groundwater extraction wells would becompletely effective at controlling offsite migrationof leachate. Extracted groundwater would betreated onsite and discharged to the unnamedtributary to the Polk River.

High-strength (onsite) groundwater would requireremoval of inorganics using metals precipitation,removal of oxygen demand (BOD, COD) usingactivated sludge biological treatment, and removalof VOCs and semivolatiles using air stripping orGAC. Low- strength (offsite) groundwater wouldonly require removal of VOCs and semivolatiles.Because the site is rural and because the threat dueto direct contact would be minimized, constructionof a fence has not been included in this alternative.Deed restrictions, however, would be placed,prohibiting onsite groundwater use or sitedevelopment.

Sediment consolidation (from the unnamedtributary) could reduce the potential for offsitemigration of contamination in the long term.However, sediment dredging could haveunacceptable short-term impacts due toresuspension of contaminated sediments. Tominimize short-term impacts, temporary dewateringof the excavation areas should be performed beforesediment removal.

6.2.3 Alternative 3

Alternative 3 is composed of the six componentslisted below.


• Composite-barrier cap

S The layers of the composite-barriercap may include (from the top): avegetative layer, a drainage layer, aflexible membrane liner (first barrier),a clay layer (second barrier), and abedding layer. As with a clay cap,freeze/thaw protection (that is, 3 feetof soil) would be part of the design ofthe composite-barrier cap. The designwould also include the installation ofpassive vents to vent landfill gas.Long-term monitoring of landfill gaswould also be included as part of theremedy.



Component 2. Consolidation of the hot spot underthe landfill cap

• Since the hot spot is generally within thelandfill contents, consolidation would berequired only to the extent necessary tominimize the size of the landfill cap.


• Collection via perimeter wells and onsitetreatment of high-strength groundwater(leachate). Effluent would be discharged tothe unnamed tributary to the Polk River.

• Offsite extraction (by wells) and onsitetreatment of low-strength groundwater.Effluent would be discharged to theunnamed tributary to the Polk River.


6-11


• Consolidation of surface water sedimentsfrom the unnamed tributary would includedredging the sediments and consolidatingthem with other material under the landfillcap.





Alternative 3 is similar to Alternative 2 except acomposite-barrier cap would be constructed insteadof a single-barrier cap. A composite-barrier capwould provide maximum protection against directcontact and would minimize potential infiltration. Acomposite-barrier cap would also adhere to thedesign requirements of RCRA guidance for newlandfill cells. As with Alternative 2, the selection ofa pumping rate for extraction of offsite groundwaterwould be determined during design.

6.2.4 Alternative 4

Alternative 4 is composed of the six componentslisted below.


• Single-barrier cap

S Includes installation of passive ventsfor landfill gas and long-termmonitoring of landfill gas



Component 2. Treatment of the hot spot

• Onsite incineration• Consolidation of ash under landfill cap


• Collection and onsite treatment ofhigh-strength groundwater (leachate).Effluent would be discharged to theunnamed tributary to the Polk River.

S Perimeter wells

• Low-strength groundwater extraction andonsite treatment. Effluent would bedischarged to the unnamed tributary to thePolk River.

S Offsite wells


• Consolidation of surface water sedimentsfrom the unnamed tributary would includedredging the sediments and consolidatingthem with the other material under thelandfill cap.





In addition to the components outlined forAlternative 2, Alternative 4 includes treatment ofmaterial excavated from the hot spot area by onsiteincineration. Consolidation of the ash under thelandfill cap is anticipated. By including treatment,this alternative would provide some reduction intoxicity, mobility, or volume. Because the hot spotarea would be treated rather than consolidatedunder the cap, a single-barrier cap is consideredadequate.


6-12

6.3 Comparative Analysisof Alternatives

As part of the feasibility study, an individual analysisis conducted where each of the remediationalternatives is compared to the nine criteriadescribed in Section 5 of this document (see Table6-1). A comparative analysis of alternatives isconducted following the individual analysis. Thecomparative analysis focuses on the significantdifferences between the alternatives. Because allthe alternatives (except no action) include collectionand treatment of leachate and offsite contaminatedgroundwater, the comparative analysis does notfocus on this aspect of the remedial action. A pumpand treat alternative is more effective, protective,expensive, and reliable than no action, and reducesthe volume of contaminants. It is also more difficultto implement.

A comparative analysis of the alternatives withrespect to the threshold criteria and balancingcriteria follows. As with the individual analysis, themodifying criteria of state acceptance andcommunity acceptance are not included becausethey are used to modify an alternative based onformal state and community comments once theproposed plan has been released.

6.3.1 Overall Protection of Human Health andthe Environment

Alternatives 2 through 4 are protective of humanhealth and the environment. Ingestion ofcontaminated groundwater is prevented bygroundwater collection and treatment. Directcontact with waste and release of VOCs fromwaste would be mitigated by either of the proposedcaps. The combination of the leachate collectionsystem (perimeter wells), offsite groundwaterextraction wells, and either a single- orcomposite-barrier cap would mitigate groundwatercontamination.

The decrease in permeability of the composite-barrier cap does not increase its protectiveness, justits effectiveness and reliability. The potentialincrease in infiltration from using a single-barriercap instead of a composite-barrier cap mayincrease the amount of leachate that is collectedand treated but will not necessarily reduceprotectiveness. Incineration of the hot spot may

increase protectiveness by reducing thecontaminant source and subsequent contaminantload to groundwater, thereby potentially reducinggroundwater and leachate treatment costs.

The no-action alternative is not consideredprotective since risk from the various pathways isnot controlled.

6.3.2 Compliance With ARARS

The state in which the Example Site is locatedrequires sanitary landfills to be closed with a capconsisting of 2 feet of clay as a minimum barrierlayer and sufficient cover material to protect againstfreeze/thaw damage. Alternatives 2, 3, and 4 will bedesigned to meet this requirement. The incineratorand groundwater pump and treat system would alsobe designed to meet all action- andchemical-specific ARARs.

The objective of Alternatives 2 through 4 would beto meet chemical-specific ARARs for groundwater(for example, MCLs, MCLGs, state groundwaterenforcement standards) at the landfill boundary. Forthese standards to be maintained (once they areachieved), the leachate collection system (perimeterwells) and the landfill cap would have to bemaintained.

The no-action alternative would not be incompliance with ARARs.

6.3.3 Short-Term Effectiveness

Effects on the community during remedial actionsare related to the degree of truck traffic needed toimport cap materials and the amount of earthmoved during cap construction. The truck traffic ofAlternative 3 (composite-barrier cap) is anticipatedto be slightly greater than Alternatives 2 and 4, andsignificantly greater than the no-action alternative.The truck traffic would cause nuisances from noiseand dust and increase the risk of vehicularaccidents.

Adverse health effects on the community may beincreased by Alternative 4 (treatment of hot spot)as a result of waste disturbance and the possibilityof improper air emissions from incineratormalfunctions or poor destruction efficiency.Although air emission controls and


6-13

monitoring can limit risk from incinerator airemissions, it would be more difficult to control VOCreleases as a result of disturbing the waste. Therural nature of the site should make the effectsnegligible.

Adverse health effects on workers during capconstruction and groundwater remediationconstruction are not expected to be significant.Incineration of soils in the hot spot (Alternative 4)may pose a greater risk to workers thanconsolidation of the hot spot under the landfill cap(Alternatives 2 and 3). Alternatives 2, 3, and 4 allinvolve excavation of the hot spot, which may poserisks to workers from potential VOC emissions.However, since the hot spot is generally within thelandfill, consolidation (Alternatives 2 and 3) mayinvolve only a small amount of excavation tominimize the size of the landfill cap, whereasexcavation and incineration (Alternative 4) wouldinvolve excavation of the entire hot spot area andmay result in a greater risk from VOC emissions.Alternative 4 may also result in greater risk ofconstruction injuries from assembly of the materialshandling and incinerator system, and excavation andconsolidation of surface water sediments.Compared to the no-action alternative, all threealternatives have a significant increase in risk toworkers.

Environmental impacts for Alternatives 2, 3, and 4do not differ significantly. There is a possibility ofwaste or runoff affecting the Polk River duringimplementation of these alternatives.

The time required for implementation of sourcecontrols is the only time variation betweenAlternatives 2, 3, and 4. Design and constructionwould require from 2 years for Alternatives 2 and3 (consolidate hot spot and cap) to 4 years forAlternative 4 (incinerate hot spot and cap).

6.3.4 Long-Term Effectiveness

All alternatives leave the landfill in place and rely oninstitutional controls, such as state prohibition ofconstruction on landfills, to prevent development. Ifthe landfill is developed, hazardous materials couldbe deposited on the surface from earth-movingactivities (grading or excavation), resulting in

exposure to users of the site or transport ofcontaminants to the unnamed tributary of the PolkRiver. Assuming regular cap maintenance,Alternatives 2, 3, and 4 are roughly equivalent intheir ability to prevent direct contact and erosion.

The amount of residuals is typically gauged by thecontaminant mass that would reach thegroundwater. While this is difficult to estimate, theeffect of the residuals is related to the infiltrationrate and the remaining contaminant mass.Alternative 4 removes and treats the hot spot,thereby removing a significant portion of thecontaminant mass. Alternative 3 uses acomposite-barrier cap, which would reduceinfiltration more effectively than the single-barrierclay cap proposed for Alternatives 2 and 4. It isestimated that infiltration could be reduced by asmuch as 75 percent by using a composite-barriercap instead of a single-barrier clay cap.Alternatives 2, 3, and 4 all offer a significanteffectiveness advantage over the no-actionalternative.

The composite-barrier cap is more reliable than aclay cap because of the extra barrier. Maintainingthe long-term reliability and effectiveness of bothtypes of caps would require continued operationsand maintenance. Incineration of the hot spot byAlternative 4 may reduce the critical need ofmaintaining cap reliability by reducing the source ofcontamination.

6.3.5 Reduction of Toxicity, Mobility, andVolume Through Treatment

All of the alternatives, except the no-actionalternative, have groundwater treatment. Thereduction in toxicity, mobility, or volume fromgroundwater treatment would be the same forAlternatives 2, 3, and 4. The only significantdifference concerning treatment is the use ofincineration in Alternative 4. Compared to thelandfilled material, the amount of hazardous materialtreated is not estimated to be large. Yet, becausethe treated area represents the most contaminatedmaterial, the toxicity of the remaining materialwould be significantly reduced. Incineration is apermanent, nonreversible treatment process.


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6.3.6 Implementability

While Alternatives 2, 3, and 4 have no seriousimplementability issues, there are differencesbetween the alternatives. The synthetic liner forAlternative 3 requires special handling duringinstallation to ensure integrity. The incinerator forAlternative 4 may take some effort to locate. Trialburns will then be necessary. Considerableoperating attention will be required because of theheterogeneous nature of the waste. In addition, thetechnical intent of relevant emission permits willhave to be met and demonstrated before theincinerator can operate.

6.3.7 Costs

The costs of the alternatives increase incrementallyfrom no-action to Alternative 4. The relative costsof the alternatives are shown in Table 6-1.


This section has been developed to illustrate howthe evaluation process is applied to a typicalCERCLA municipal landfill site. The previoussections focused primarily on technologies that aremost practicable for landfill sites. This sectiondemonstrates how these technologies might becombined into alternatives and evaluated.


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Section 7BIBLIOGRAPHY

Adamus, P.E. et al. Wetland Evaluation Technique (WET): Volume II--Methodology. U.S. ArmyCorps of Engineers. 1987.

American Public Health Association et al. Standard Methods for the Examination of Water andWastewater. 16th ed. 1985.

American Society for Testing and Materials. ASTM Standard D420, Standard Guide for Investigatingand Sampling Soil and Rock.

American Society for Testing and Materials. ASTM Standard D 1587, Standard Practice forThin-Walled Tube Sampling of Soils.

American Society for Testing and Materials. ASTM Standard D4220, Standard Practices for Preservingand Transporting Soil Samples.

American Society for Testing and Materials. ASTM Standard D5084, Hydraulic Conductivity ofSaturated Porous Materials Using a Flexible Wall Permeameter.

Argonne National Laboratory. An Annotated Bibliography: Environmental Impacts of SanitaryLandfills and Associated Gas Recovery Systems. ANL/CNSV-27. February 1982.

Battelle, Pacific Northwest Laboratories. Comparison of Two Groundwater Flow Models: UWSATIDand HELP. Richland, Washington. 1984.

Battelle, Pacific Northwest Laboratories. Physiochemical Measurements of Soils at Solid-WasteDisposal Sites. Electric Power Research Institute. Final Report. EPRI EA-4417, Project 2485-3. January1986.

Bear, J. Hydraulics of Groundwater. New York: McGraw-Hill. 1979.

Bevan, B.W. Quantitative Magnetic Analysis of Landfills. Geosight. 1983.

Bouwer, H., and R.C. Rice. A Slug Test for Determining Hydraulic Conductivity of UnconfinedAquifers with Completely or Partially Penetrating Wells. Phoenix, Arizona: Agricultural ResearchService, U.S. Department of Agriculture. 1976.

Cedergren, H. Seepage, Drainage, and Flow Net. New York: John Wiley and Son. 1989.


7-2

Chamberlain, E.J., and A.J. Gow. Effect of Freezing and Thawing on the Permeability and Structure ofSoils. Engineering Geology 13 (1979): pp. 73-92.

Cheremisinoff, P.N., and F. Ellerbush. Carbon Adsorption Handbook. Ann Arbor, Michigan: Ann ArborScience. 1980.

Clark, Viessman, and Hammer. Water Supply and Pollution Control. New York: IEP-Dun-Donnell.1977.

Cooper, H.H., Jr., J.D. Bredehoeft, and I.S. Papadopulos. Response of a Finite Diameter Well to anInstantaneous Charge of Water. Water Res. Res. 3 (1967): pp. 263-69.

Daniel, D.E. “In Situ Hydraulic Conductivity Tests for Compacted Clay.” Journal of GeotechnicalEngineering, 115:9 (1989), pp. 1205-1226.

Emcon Associates-Ann Arbor Science. Methane Generation and Recovery from Landfills. Ann Arbor,Michigan: Ann Arbor Science. 1980.

England, C.B. Land Capability: A Hydrologic Response Unit in Agricultural Watersheds. AgriculturalResearch Service. U.S. Department of Agriculture. 1970. pp. 41-172

Fowler, J.W., and D.L. Pasicznyk. Magnetic Survey Methods Used in the Initial Assessment of aWaste Disposal Site. New Jersey Department of Environmental Protection.

Freeze, R.A., and J.A. Cherry. Groundwater. New York: Prentice-Hall. 1979.

Ghassemi, M. Assessment of Technology for Constructing and Installing Cover and Bottom LinerSystems for Hazardous Waste Facilities: Volume I. Ghassemi EPA Contract No. 68-02-3174. U.S.Environmental Protection Agency. May 1983.

Hammer, D.A. Constructed Wetlands for Wastewater Treatment. Chelsea, Michigan: Lewis Publishers.1989.

Hantush, M.S. and C.E. Jacob. Non-Steady Radial Flow in an Infinite Leaky Aquifer.Trans. Am. Geophys. Union 36 (1955): pp. 96-100.

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Javandel, I., and C.F. Tsang. Capture-Zone Type Curves: A Tool for Aquifer Cleanup. Groundwater 24(September-October 1986): p. 5.


7-3

Keely. Optimizing Pumping Strategies for Containment Studies and Remedial Actions. GroundwaterMonitoring Review. Summer 1984. pp. 63-74.

Keely and Tsang. Velocity Plots and Capture Zones of Pumping Centers for Ground-water Investigations.Groundwater. 21 (1983): pp. 701-14.

Kmet, P., K.J. Quinn, and C. Slavik. Analysis of Design Parameters Affecting the CollectionEfficiency of Clay Lined Landfills. University of Wisconsin. September 1981.

Lutton, R.J. Evaluating Cover Systems for Solid and Hazardous Waste. SW867. U.S. EnvironmentalProtection Agency. 1982.

Lyman, W.J. Handbook of Chemical Property Estimation Methods. New York: McGraw-Hill. 1982.

Metcalf & Eddy, Inc., revised by Tchobanoglous. Wastewater Engineering. Treatment, Disposal, Reuse. 2nd ed. New York: McGraw-Hill. 1979.

Michaels, P.A., and M.K. Stinson. Technology Evaluation Report, Vacuum Extraction System .Groveland, Massachusetts: Risk Reduction Engineering Laboratory. Ordinance EA68-03-3255. 1989.

Milne-Thomson, L.M. Theoretical Hydrodynamics. New York: Macmillan Company. 1968.

Montgomery, R.J. et al. Use of Downhole Geophysical Methods in Determining the Internal Structure ofa Large Landfill. The Surface and Borehole Proceedings. Fort Worth, Texas. 1985.

Morel-Seytoux, H.J., and C.J. Daly. A Discrete Kernel Generator for Stream Aquifer Studies. Water Res.Res. 11 (1975): pp. 253-60.

Morrison, W.R., and L.R. Simmons. Chemical and Vegetative Stabilization of Soil: Laboratory andField Investigations of New Materials and Methods for Soil Stabilization and Erosion Control. U.S.Bureau of Reclamation Report No. 7613. 1977.

National Institute of Occupational Safety and Health. Occupational Safety and Health Guidance Manualfor Superfund Activities. 1984.

Neuman, S.P. Theory of Flow in Unconfined Aquifers Considering Delayed Responses of the Water Table.

Noyes Data Corporation. Landfill Methane Recovery. Energy Technology Review 80. 1983.


7-4

Papadopulos, I.S., J.D. Bredehoeft, and H.H. Cooper, Jr. On the Analysis of Slug Test Data. Water Res.Res. 9 (1973): pp. 1087-89.

Residuals Management Technology, Inc. Field Measurement Methods for HydrogeologicInvestigations: A Critical Review of the Literature. Electric Power Research Institute. EPRI EA-4301,Project 2485-7. October 1985.

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Theis, C.V. The Relation between the Lowering of the Piezometric Surface and the Rate and Duration ofa Well using Groundwater Storage. Trans. Am. Geophys. Union 16 (1935): pp. 519-24.

Thiem, G. Hydrologische Methoden. Leipzig: Gebhardt. 1906.

Treybal, R. Mass Transfer Operations. 3rd ed. New York: McGraw-Hill. 1983.

U.S. Army Corps of Engineers. Dewatering and Groundwater Control for Deep Excavations. U.S.Army Engineers Waterways Experiment Station. Technical Manual No. 5-818-5. 1971.

U.S. Army Corps of Engineers. Wetland Evaluation Technique (WET). U.S. Army EngineersWaterways Experiment Station. 1987.

U.S. Environmental Protection Agency. Design and Construction of Covers for Solid Waste Landfills.EPA/600/2-79/165. August 1979a.

U.S. Environmental Protection Agency. Water Related Environmental Fate of 129 Priority Pollutants.EPA/440/4-79/029A. December 1979b.

U.S. Environmental Protection Agency. RCRA Guidance Document Landfill Design, Liner Systems andFinal Cover (Draft). July 1982a.

U.S. Environmental Protection Agency. Fate of Priority Pollutant in Publicly Owned Treatment Works.EPA/440/1-82/303. 1982b.

U.S. Environmental Protection Agency. Handbook for Sampling and Sampling Preservation of Waterand Wastewater. EPA/600/4-82/029. 1982c.

U.S. Environmental Protection Agency. Methods for Analysis of Water and Waste. EPA/600/4-79/020.March 1983a.


7-5

U.S. Environmental Protection Agency. Lining of Waste Impoundment and Disposal Facilities. SW870.1983b.

U.S. Environmental Protection Agency. Permit Guidance Manual on Hazardous Waste LandTreatment Demonstrations (Draft). EPA/530/SW-84/015. December 1984a.

U.S. Environmental Protection Agency. Procedures for Modeling Flow through Clay Liners toDetermine Required Liner Thickness. EPA/530/SW-84/001. 1984b.

U.S. Environmental Protection Agency. Standard Operating Safety Guides. 1984c.

U.S. Environmental Protection Agency. Handbook of Remedial Action at Waste Disposal Sites(Revised). EPA/625/6-85/006. October 1985a.

U.S. Environmental Protection Agency. Leachate Plume Management. EPA/540/2-85/004. November1985b.

U.S. Environmental Protection Agency. Guide for Identifying Cleanup Alternatives at HazardousWaste Sites and Spills. EPA/600/3-83/063. December 1985c.

U.S. Environmental Protection Agency. Covers for Uncontrolled Hazardous Waste Sites.EPA/540/2-85/002. 1985d.

U.S. Environmental Protection Agency. Guidance on Remedial Investigations under CERCLA. 1985e.

U.S. Environmental Protection Agency. Standard Operating Procedures and Quality AssuranceManual. Region IV Water Surveillance Branch. April 1986a.

U.S. Environmental Protection Agency. Quality Criteria for Water. EPA/44/5-86/001. May 1986b.

U.S. Environmental Protection Agency. Groundwater Monitoring Technical Enforcement GuidanceDocument. OSWER-9950.1. September 1986c.

U.S. Environmental Protection Agency. RCRA Groundwater Monitoring Technical EnforcementGuidance. OSWER-9950.1. September 1986d.

U.S. Environmental Protection Agency. Systems to Accelerate In Situ Stabilization of Waste Deposits.EPA/540/2-86/002. September 1986e.

U.S. Environmental Protection Agency. Test Methods for Evaluating Solid Waste, Physical/ChemicalMethods. 3rd ed. November 1986f.

U.S. Environmental Protection Agency. Technology Briefs, Data Requirements for Selecting RemedialAction Technology. EPA/600/2-87/001. January 1987a.


7-6

U.S. Environmental Protection Agency. Data Quality Objectives for Remedial Response Activities:Example Scenario: RI/FS Activities at a Site with Contaminated Soils and Groundwater.EPA/540/G-87/004 (OSWER Directive 9355.0-7B). March 1987b.

U.S. Environmental Protection Agency. Data Quality Objectives for Remedial Response Activities.Volume I. Development Process. EPA/540/G-87/003. March 1987c.

U.S. Environmental Protection Agency. Data Quality Objectives for Remedial Response Activities.Volume II. RI/FS Activities at a Site with Contaminated Soils and Groundwater. EPA/540/G-87/004.March 1987d.

U.S. Environmental Protection Agency. A Compendium of Technologies Used in the Treatment ofHazardous Wastes. EPA/625/8-87/014. September 1987e.

U.S. Environmental Protection Agency. Characterization of MWC Ashes and Leachates from MSDLandfills, Monofills, and Co-Disposal Sites. EPA/530/SW-87/028A. October 1987f.

U.S. Environmental Protection Agency. Revised Procedures for Implementing Off-Site ResponseActions. OSWER 9834.11. November 1987ff.

U.S. Environmental Protection Agency. Contract Laboratory Program Statement of Work (SOW) forInorganic Analysis. Multimedia, Multiconcentration. December 1987g.

U.S. Environmental Protection Agency. A Compendium of Superfund Field Operations Methods.EPA/540/P-87/001. 1987h.

U.S. Environmental Protection Agency. Contract Laboratory Program Statement of Work (SOW) forOrganics Analysis: Multimedia, Multiconcentration. February 1988a.

U.S. Environmental Protection Agency. Superfund Exposure Assessment Manual. EPA/540/1-88/001.April 1988b.

U.S. Environmental Protection Agency. CERCLA Compliance with Other Laws Manual.EPA/540/G-89/006. August 1988c.

U.S. Environmental Protection Agency. Technology Screening Guide for Treatment of CERCLA Soilsand Sludges. EPA/540/2-88/004. September 1988d.

U.S. Environmental Protection Agency. Guidance for Conducting Remedial Investigations andFeasibility Studies under CERCLA. Interim Final. EPA/540/G-89/004. October 1988e.

U.S. Environmental Protection Agency. Guidance on Remedial Actions for ContaminatedGroundwater at Superfund Sites. EPA/540/6-88/003. December 1988f.


7-7

U.S. Environmental Protection Agency. Constructed Wetlands and Aquatic Plant Systems forMunicipal Wastewater Treatment. EPA/625/1-88/022. 1988g.

U.S. Environmental Protection Agency. Experience in Incineration Applicable to Superfund SiteRemediation. EPA/625/9-88/008. 1988g.

U.S. Environmental Protection Agency. Statistical Methods for Evaluating the Attainment ofSuperfund Cleanup Standards. Volume I. Soils and Solid Media. NTIS PB-89-234-959. February1989a.

U.S. Environmental Protection Agency. Ecological Assessment of Hazardous Waste Sites: A Field andLaboratory Reference. EPA/600/3-89/013. March 1989b.

U.S. Environmental Protection Agency. Risk Assessment Guidance for Superfund. Volume II.Environmental Evaluation Manual. Interim Final. EPA/540/1-89/001. March 1989c.

U.S. Environmental Protection Agency. Final Covers on Hazardous Waste Landfills and SurfaceImpoundments. EPA/530/SW-89/047. July 1989d.

U.S. Environmental Protection Agency. Exposure Factors Handbook. EPA/600/8-89/043. July 1989e.

U.S. Environmental Protection Agency. Technical Guidance Document: Final Covers on HazardousWaste Landfills and Surface Impoundments. EPA/530/SW-89/047. July 1989f.

U.S. Environmental Protection Agency. Evaluation of Groundwater Extraction Remedies, Volume I,Summary Report. EPA/540/2-89/054. September 1989g.

U.S. Environmental Protection Agency. Determining Soil Response Action Levels Based on PotentialContaminant Migration to Groundwater: A Compendium of Examples. EPA/540/2-89/057. October1989h.

U.S. Environmental Protection Agency. The Superfund Innovative Technology Evaluation Program:Technology Profiles. EPA/540/5-89/013. November 1989i.

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U.S. Environmental Protection Agency. Risk Assessment Guidance for Superfund. Volume I. HumanHealth Evaluation Manual (Part A). Interim Final. EPA/540/1-89/002. December 1989k.

U.S. Environmental Protection Agency. Summary of Treatment Technology Effectiveness forContaminated Soil. EPA/540/2-89/053. December 1989m.


7-8

U.S. Environmental Protection Agency. Performance Evaluations of Pump and Treat Remediations:Groundwater Issue Paper. EPA/540/4-89/005. 1989n.

U.S. Environmental Protection Agency. Handbook on In Situ Treatment of Hazardous Waste-Contaminated Soils. EPA/540/2-90/002. January 1990a.

U.S. Environmental Protection Agency. Basics of Pump-and-Treat Groundwater RemediationTechnology. EPA/600/8-90/003. March 1990b.

U.S. Environmental Protection Agency. Basics of Pump-and-Treat Remediation Technology.EPA/600/8-90/003. March 1990c.

U.S. Environmental Protection Agency. Criteria for the Evaluation of RCRA Groundwater DetectionMonitoring Systems (Draft). June 1990d.

U.S. Environmental Protection Agency. Terra Vac In Situ Vacuum Extraction System, ApplicationsAnalysis Report. EPA/540/A5-89/003. July 1990e.

U.S. Environmental Protection Agency. CERCLA Site Discharges to POTWs. EPA/540/6-90/005.August 1990f.

U.S. Environmental Protection Agency. International Waste Technologies/Geo Con In SituStabilization/Solidification, Applications Analysis Report. EPA/540/A5-89/004. August 1990g.

U.S. Environmental Protection Agency. High Temperature Treatment for CERCLA Waste: Evaluationof Onsite and Offsite Systems. EPA/540/4-89/006. 1989f.

U.S. Environmental Protection Agency. Stabilization/Solidification of CERCLA and RCRA Wastes--Physical Tests, Chemical Testing Procedures, Technology Screening and Field Activities.EPA/625/6-89/022. 1989g.

U.S. Environmental Protection Agency. State of Technology Review: Soil Vapor Extraction Systems.EPA/600/2-89/024. 1989h.

U.S. Fish and Wildlife Service et al. Federal Manual for Identifying and Delineating JurisdictionalWetlands: An Interagency Cooperative Publication. 1989.

U.S. Geological Survey. Application of Drilling, Coring, and Sampling Techniques to Test Holes and Wells.Techniques of Water-Resource Investigations of the United States Geological Survey. U.S.Department of the Interior.

U.S. Geological Survey. WATSTORE files.

U.S. Steel Corporation. Steel Sheet Piling Handbook: Reference Data on Shapes, Materials,Performance and Applications. Pittsburgh: United States Steel. 1976.


7-9

Viessman et al. Introduction to Hydrology. New York: Harper and Row. 1977.

Warner, R.C. et al. Demonstration and Evaluation of the Hydrologic Effectiveness of a Three-LayerLandfill Surface Cover under Stable and Subsidence Conditions: Phase I Final Project Report. U.S.Environmental Protection Agency.

Xanthakos, P. Slurry Walls. New York: McGraw-Hill. 1979.


Appendix A

Site Characterization Strategyfor an Example Site


A1-1

CONTENTS OF APPENDIXPage

1. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A1-3

2. EVALUATION OF EXISTING DATA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A2-1

2.1 Site Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A2-12.2 Site History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A2-12.3 Regional and Site-Specific Geology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A2-3

2.3.1 Regional Geology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A2-32.3.2 Site-Specific Geology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A2-4

2.4 Hydrology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A2-42.4.1 Surface Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A2-42.4.2 Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A2-42.4.3 Surface Water-Groundwater Relationship . . . . . . . . . . . . . . . . . . . . . . . A2-4

2.5 Hazardous Materials Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A2-62.5.1 Source Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A2-62.5.2 Waste Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A2-6

2.6 Cap Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A2-62.7 Description and Results of Past Sampling and

Analysis Activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A2-7

3. SITE DYNAMICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A3-1

3.1 Limited Field Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A3-13.2 Conceptual Site Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A3-13.3 Preliminary Exposure Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A3-7

3.3.1 Chemicals Previously Detected at the Site . . . . . . . . . . . . . . . . . . . . . . . A3-73.3.2 Contaminant Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A3-73.3.3 Release Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A3-73.3.4 Contaminant Transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A3-73.3.5 Contaminant Migration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A3-83.3.6 Contaminant Fate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A3-83.3.7 Exposure Pathways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A3-8

4. PRELIMINARY IDENTIFICATION OF REMEDIAL ACTION ALTERNATIVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A4-1

4.1 Potential ARARs for the Example Site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A4-14.2 Review of Analytical Results and Comparison to ARARs . . . . . . . . . . . . . . . . . A4-2

4.2.1 Baseline Risk Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A4-24.3 Preliminary Remedial Action Objectives and Goals . . . . . . . . . . . . . . . . . . . . . . A4-8


A1-2

CONTENTS (cont.)Page

4.4 Preliminary Remedial Action Alternatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A4-84.4.1 Landfill Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A4-94.4.2 Hot Spots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A4-94.4.3 Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A4-104.4.4 Landfill Gas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A4-114.4.5 Surface Water and Sediments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A4-11

5. REMEDIAL INVESTIGATION AND FEASIBILITYSTUDY OBJECTIVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A5-1

6. DATA QUALITY OBJECTIVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A6-1

7. RI/FS TASKS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A7-1

7.1 RI/FS Tasks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A7-17.1.1 Task 1--Project Planning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A7-17.1.2 Task 2--Community Relations Activities . . . . . . . . . . . . . . . . . . . . . . . A7-27.1.3 Task 3--Field Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A7-27.1.4 Task 4--Sample Analysis and Data Validation . . . . . . . . . . . . . . . . . . A7-217.1.5 Task 5--Data Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A7-257.1.6 Task 6--Risk Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A7-257.1.7 Task 7--Remedial Investigation Report . . . . . . . . . . . . . . . . . . . . . . . A7-257.1.8 Task 8--Remedial Action Alternative Report . . . . . . . . . . . . . . . . . . . A7-257.1.9 Task 9--Alternatives Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . A7-267.1.10 Task 10--Feasibility Study Report . . . . . . . . . . . . . . . . . . . . . . . . . . A7-267.1.11 Task 11--Treatability Studies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A7-27

8. COST AND KEY ASSUMPTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A8-1

9. SCHEDULE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A9-1

10. PROJECT MANAGEMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A10-1

11. BIBLIOGRAPHY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A11-1


A1-3

Section 1INTRODUCTION

This appendix has been developed to illustrate howinformation provided in the body of thisreport--specifically, in Sections 2, 3, and 4 ofConducting Remedial Investigations/FeasibilityStudies for CERCLA Municipal LandfillSites--could be used to develop a scope of work fora specific landfill site. The example provided in thisappendix should be useful to EPA, states, potentiallyresponsible parties (PRPs), and remedialinvestigation contractors.

Specifically, the purpose of this appendix is:

• To present the scope of work to becompleted at an example site including asite description, objectives of the RI/FS,and task-by-task breakdowns of theplanned work

• To illustrate an example of the level ofcharacterization for a CERCLA municipallandfill site necessary to supportsubsequent decisions (This level ofcharacterization is based on previousexperience and best engineering judgment.)

• To identify preliminary remedial actionalternatives that are practicable for theexample landfill site based on the NCPexpectations, site conditions, and review ofremedial alternatives most often used atlandfill sites (see Section 4 of this report onDevelopment and Selection of RemedialAction Alternatives.)

This RI/FS characterization strategy is developedfor a specific municipal landfill site, hereafterreferred to as the example site. This document willfocus on hot spots, seeps, landfill gas, andgroundwater/leachate as the principal media ofconcern. These were selected because they

are generally the media directly associated withmunicipal landfills. By focusing on these four media,the example scope of work can be less complicatedand applied to other media. The omission of otherpotentially affected media, such as wetlands, in thisexample does not imply that they should be omittedfrom investigation and remediation at sites wherethey are present.

The example site used for preparing this work planis described in detail in Section 2 of this appendix.In order to present technically supportableconditions for the example site, the geology andhydrology used were taken from the work plan ofan actual municipal landfill site located in the Stateof Wisconsin. Some of the characteristics, such asthe names of the river basins, rivers, and distancesto hydrologic features, have been changed. Inaddition, an assumption has been made that theRI/FS at the example site is federally funded.

This appendix begins with a description of theexample site and its history. It then presents thedecisions made from evaluating existing data,conducting limited field investigations, anddeveloping data quality objectives. Future tasksrequired for conducting the RI/FS are describednext. These tasks follow the standardized RI/FStasks described in Appendix B of the RI/FSGuidance (U.S. EPA, 1988a).

The example site is a municipal landfill that islocated in a primarily rural area of County X,Wisconsin. The site was proposed for the NPL in1982 after site inspection and HRS scoring by anEPA Field Investigation Team (FIT). Investigationby FIT indicated elevated levels of volatile organiccompounds (VOCs) and metals in groundwatersamples taken from nearby residential wells.


A1-4

The overall goals of the RI/FS for the example siteare:

• To complete a field program at the site forcollecting data to determine the nature andextent of contamination at the site and thehuman health and environmental risks

associated with contaminants found at the site

• To develop and evaluate remedialalternatives for the site if there areunacceptable human health orenvironmental risks


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Section 2EVALUATION OF EXISTING DATA

This section presents a summary of the availableinformation on the example site. Information wasobtained from the HRS package, state files,interviews with past employees of the landfill,records kept by the landfill, and available engineers’reports for closure of the landfill. This sectionincludes the following subsections:

• Site Description• Site History• Regional and Site-Specific Geology• Hydrology• Hazardous Materials Characterization• Cap Characterization• Description and Results of Past Sampling

and Analysis Activities

2.1 Site Description

The example site, shown in Figure 2-1, isapproximately 60 acres and is located in County X,Wisconsin, an area that is primarily rural. There aresix residences located within one-half mile of thesite and a community of 300 people is located 5miles northwest of the landfill. The primary use ofthe land near the site is farming.

Approximately 20 acres of the 60-acre site arecomposed of a landfill which accepted bothchemical wastes and municipal trash. Existingstructures on the site include a gate house and anoffice. There is a small tributary running within 200feet west of the site which discharges into the PolkRiver. Private drinking water wells, screened withina sand and gravel aquifer, are located downgradientof the site. The landfill was closed by the state in1980 when contamination was found in theseresidential wells.

Industrial, commercial, and municipal wastes aregenerally mixed throughout the fill area, with theexception of liquid industrial solvent wastes whichwere generally restricted to the southeastern half ofthe landfill. Between 1980 and 1982, exposed areas

in the southern half of the landfill were temporarilycovered with a partial cap consisting of 2 feet ofcompacted clay. The remainder of the landfill hasa temporary soil cover although there are someareas of exposed waste. Some of the contaminantsof concern are trichloroethene (TCE) and vinylchloride (VC) in the soil and groundwater; lead,arsenic, and total chromium in the soil; and methanegas.

2.2 Site History

A summary of the landfill’s history was formulatedafter reviewing relevant site records andcorrespondence for information regarding siteoperations, waste disposal practices, wastedescriptions, site engineering studies, historicalaerial photographs, and potentially responsible partyoperations. A condensed version of the site historyfollows.

The landfill, which is privately owned, was licensedby the State of Wisconsin to operate from 1969 to1980, when the state ordered its closure. State filesindicate that in 1969 the landfill began operations,receiving residential, commercial, and industrialrefuse and liquid wastes. In 1971, the state requiredthat an area be designated specifically for thedisposal of liquid industrial solvents. Interviews withsite operators indicated that the solvents weredisposed of in the southeastern portion of the landfillto satisfy the state’s requirements; however,disposal was generally done throughout the landfillprior to this time. Landfill operations during the firstthree years of operation were conducted without anattendant. Thereafter, operating hours were postedand an operator was present to record incomingwaste and to measure the nonresidential waste forrecord-keeping and billing purposes.

Daily landfill operation records indicate that twomajor industrial companies began solvent wastedisposal in 1970. The solvent wastes were


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Figure 2-1SITE PLANEXAMPLE SITE


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stored in 55-gallon drums, which were left or buriedat the site if they were damaged or leaking or couldnot be easily emptied. A large number of drumswere also buried in the southeastern portion of thelandfill.

In 1971, the site began receiving paint, paintthinners, paint residues, lacquers, plating sludges,and industrial process sludges. In 1975, a ConsentOrder issued by the County Circuit Court prohibitedthe disposal of these materials.

In 1979, the state sampled nearby domestic wellsfor compliance with drinking water standards. Theinvestigations indicated that groundwatercontamination had occurred and as a result thelandfill was ordered to stop its operation in 1980.Between 1980 and 1981, closure plans wereprepared by a contractor hired by the owner. Wells,shown by Figure 2-1, were drilled to the base of thelandfill content to provide data for the closurescenarios. In 1981, a partial cap, consisting of 2 feetof compacted clay, was placed over thesoutheastern half of the landfill to cover major areasof exposed wastes and the liquid solvent disposalarea. The remaining portion of the landfill previouslyhad been covered with soil from an unknownsource.

Investigations by FIT in 1986 indicated elevatedlevels of volatile organic compounds (VOCs) andmetals in groundwater samples taken from nearbyresidential wells. Elevated levels of methane gaswere also found. To date the primary contaminantsof concern have been 1,1-dichloroethene(1,1-DCE), cis-1,2-dichloroethene (cis-1,2-DCE),tetrachloroethene (PCE), 1,1,1-trichloroethane(1,1,1-TCA), trichloroethene (TCE), vinyl chloride(VC), toluene, ethylbenzene, bis(2-e/h)phthalate,polychlorinated biphenyls (PBCs), lead, arsenic, andtotal chromium.

This appendix outlines the technical approach andassociated activities to complete the RI/FS for thesite. It is based on data gathered by the state and byFIT. These data were analyzed to develop theconceptual site model, identify additional data needs,and determine the scope of the RI/FS activities.The site received a Hazard Ranking Score of 30.0which exceeded the 28.5 scoring and therefore was

high enough to be proposed for the NPL.

Limited field investigations were conducted by theremedial contractor in 1988 to provide data neededto fully scope the RI. Detailed discussions of theseinvestigations are in Section 3.

2.3 Regional and Site-SpecificGeology

The following sections describe the regional andsite-specific geology of the area.

2.3.1 Regional Geology

The example site lies within the lower valley of theJames River Basin, which was a major glacialdrainage way across the “driftless area” to theMississippi River. Consequently, the site containsthick deposits of unpitted outwash comprising ofstratified sand and gravel to an estimated depth of135 feet. Bedrock in the James River Basinconsists mainly of sedimentary rock of Cambrianand Ordovician ages. Sandstone is predominant, butthe Prairie du Chien Group and Galena-Plattevilleunits are primarily dolomite and limestone,respectively. The greatest thickness of Cambrianand Ordovician rock, approximately 1,700 feet,occurs in the southern tip of the basin where theyoungest bedrock formations cap high ridges. TheCambrian sandstone has a broad outcrop areabecause it is nearly flat lying and has been exposedby erosion as indicated by Soil Conservation datafor this county.

Igneous and metamorphic crystalline rocks ofPrecambrian age form the basement and are thebedrock surface in the northern part of the basin.

Erosion of the sandstone and dolomite bedrock hasoccurred in this unglaciated region throughoutgeologic time. The erosion has cut numerous deepvalleys into what was once a fairly level plateauforming a dissected upland with steep relief. Insome parts of the county, the difference in elevationbetween the valley bottoms and the adjacent ridgetops is as much as 500 feet.


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2.3.2 Site-Specific Geology

The soil underlying the example site belongs to thePlainfield series, which consists of fine to loamyfine sand, that are prevalent on alluvial terraces.This soil exhibits excessive drainage and is easilyeroded by the wind.

The unconsolidated deposits at the site areapproximately 135 feet thick and consist primarilyof sand and gravel of glaciofluvial and alluvialorigin. The site is located within an eroded bedrockvalley that was filled with outwash transported bythe James and Polk Rivers near the end of theWisconsin Stage Glaciation. Atterberg limit testswere performed by the closure contractor on thesurface silt and clay and results indicate that thesestrata are nonplastic. The hydraulic conductivity ofthe silt and clay was estimated to range from 1 x10-3 to 1 x 10-6 cm/sec (Contractor, 1979). Theother strata observed at the site consistspredominantly of very fine to coarse sand withtrace amounts of gravel, silt, and clay. Thehydraulic conductivity of this strata was estimatedto range from 1 x 10-2 to 1 x 10-3 cm/sec(Contractor, 1979).

Bedrock in the vicinity of the site consists ofundifferentiated Cambrian sandstone up to 1,200feet thick. This undifferentiated sandstone includesthe St. Lawrence Formation, Jordan, Franconia,Galesville, Eau Claire, and Mount SimonSandstones. These sandstones are fine tocoarse-grained and contain a small amount of shale.

Bedrock was encountered at a depth of 134 feet ina residential well south of the site.

2.4 Hydrology

The location of the landfill in relation to the PolkRiver is critical in understanding the surfacewater-groundwater flow regime at the site.

2.4.1 Surface Water

The Polk River flows south-southwesterly to within600 feet of the site. An unnamed tributary to thePolk River flows within 200 feet west of the site

(Figure 2-1). As the river flows past the site, itschannel branches into channels that are tributariesto the James River. The main channel of the JamesRiver flows southeast within 2 miles of the site. TheJames River is dammed approximately 4 milessouth of the site, forming Lake Ohio (Figure 2-2). Aleachate seep has been identified that flows fromthe western position of the toe of the landfill to theunnamed tributary of the Polk River.

2.4.2 Groundwater

Groundwater flow directions were determined onthe basis of water levels at nearby residential wellscompleted in the unconsolidated deposits of sandand gravel, and one existing monitoring well nestcompleted to the base of the landfill. These waterlevels have been measured quarterly since 1979.Horizontal groundwater flow is to thesouth-southwest for the majority of the year.However, during the spring runoff period the flowis altered, and groundwater flows to thesouth-southeast away from the river.

The horizontal groundwater gradient, calculatedfrom available quarterly data during the period 1979to 1986, ranged from 2.2 x 10-3 to 2.2 x 10-4 andaveraged 5.3 x 10-4, remaining relatively flatthroughout the year. This variation in horizontalgroundwater gradients is a result of seasonalvariation associated with spring runoff. Verticalgroundwater gradients measured during theinvestigation indicate that there is a slight downwardgradient of 1 x 10-2

2.4.3 Surface Water-Groundwater Relationship

A review of the measurements of groundwaterlevel indicates that the direction of groundwaterflow displays variation. The groundwater flowregime at the site is predicated on the seasonalsurface water fluctuations in the Polk and JamesRivers. These fluctuations are directly related to thePolk River and Lake Ohio, which either rechargesthe adjacent sand-and-gravel aquifer or receivegroundwater discharge as the river and lakelevels fluctuate. During the majority of theyear, groundwater is discharging to theriver, however, during spring runoff, whensurface water levels are high, the riverrecharges the sand-and-gravel aquifer. This


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Figure 2-2SURFACE WATER FOREXAMPLE SITE


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modifies the direction of groundwater flow from thesouth-southwest to the south-southeast, away fromthe river.

2.5 Hazardous MaterialsCharacterization

Since landfill operations began, the 20-acre landfillhad received a variety of municipal, commercial,and industrial wastes. Landfill records (gate slips)kept by the operators identified the waste haulers,indicated whether or not the delivery was amunicipal or industrial waste, and listed theapproximate quantities deposited. The gate slips didnot provide waste descriptions nor did they includedeliveries that occurred outside of the landfilloperating hours. Consequently, a completeinventory of the wastes disposed of at the landfill isnot available. Other records, however, from thecounty, the state, EPA, and past employees of thelandfill were used to develop a partial list of thewaste deposited at the landfill. Waste disposed atthe site consisted primarily of solid waste, includingpaint cans, bottles, plastic, paper, degreasers, andother commercial and municipal garbage. Thewastes of concern generally consisted ofchlorinated and nonchlorinated organics,water-based and oil-based paints, paint thinners andlacquers, waste oil, automobile and householdbatteries, and industrial process sludges.

Available records show no indication of segregationof wastes. Industrial, commercial and municipalwastes are generally mixed throughout the fill areaexcept for liquid industrial solvent wastes. In 1971,the state restricted disposal of the liquid industrialwaste to the southern portion of the landfill. Thewastes were generally buried as soon as it wasreceived and the cover material compacted.

2.5.1 Source Description

Records indicate that a nearby electroplatercontributed the greatest quantities of liquid wastes,consisting primarily of naphtha-based solvents usedin the metal-cleaning process and wastes from paintspray and machine shop cleaning fluids. Paintresidues and solvents were also delivered to the

landfill in 55-gallon drums. These drums wereburied intact at the site if the drums could not beeasily emptied or if they were damaged or leaking.A large portion of the drums were buried in thesoutheast portion of the landfill. There are no otherknown industrial liquid wastes at the site.

2.5.2 Waste Description

Review of existing records suggests that variousindustrial process sludges brought to the facility mayhave contained high concentrations of inorganicssuch as chromium, arsenic, and lead. Review ofexisting records also suggests that waste solventsalso were brought to the site. Waste solventsconsisted primarily of naptha, toluene, ethanol, andpaint residues. The naphtha-based solvents wereprimarily mineral spirits, which are the least volatileof the napthas. Mineral spirits are a watery,colorless liquid with a gasoline-like odor. Theircomponents are slightly soluble in water. Recordsindicate that waste ethanol (ethyl alcohol) broughtto the site had previously been used as a solvent forresins, oils, hydrocarbons, surface castings, andcleaning preparations. Ethanol is a colorless, volatileliquid with a pungent taste. It has an ethereal,wine-like odor and is miscible in water.

The records also suggest that the solventcomponents of the paint wastes include highflashpetroleum and toluene. Toluene is a methylbenzene(C7H8), which is a colorless, mobile liquid with adistinct aromatic odor and is immiscible in water.

2.6 Cap Characterization

In 1980, the state ordered the landfill closed. Theowner then hired a contractor to prepare a closureplan for the landfill. In early 1981, closureinvestigations indicated that a partial cap wasrequired over the southern portion of the landfillwhere the industrial liquid solvent wastes wereburied and where there were areas of exposedwastes. In 1982, the owner submitted a closure planto the state indicating that a cap, consisting of 2 feetof compacted clay with 6 inches of topsoil, was tobe placed over the southern portion of the landfill.The remaining portion of the landfill had been


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previously covered with soil from an unknownsource (Figure 2-3).

As-built or final grading plans for the clay cap arenot known to be available. The existing cap wasvisually observed for cracking and erosion during aninspection that was performed during the site visit.There were no major signs of cracking or failure ofthe existing clay cap, however, there was someminor sideslope erosion.

2.7 Description and Results ofPast Sampling andAnalysis Activities

Organic and inorganic data, shown in Table 2-1(well locations shown in Figure 2-1), are availablefor five residential wells near the site and two onsitemonitoring wells installed by the owner of thelandfill for closure investigations in 1981. All wellsare completed in the unconsolidated deposits ofsand and gravel. Based on drillers’ logs, the fiveresidential wells range in depth from 45 to 58 feetand are completed as open-end steel pipes.Monitoring well GWIS has an open interval from 36to 46 feet and GWID has an open interval from 62to 72 feet. Both monitoring wells are PVC with theopen interval being slotted PVC.

The site has a variety of organic contaminants inthe groundwater and soil that appear on the TargetCompound List (TCL) and the Target Analyte List(TAL), including VOCs such as TCE and VC;semivolatile organic compounds such asbis(2-e/h)phthalate and phenol, and metals such as

lead, arsenic, and chromium. VOC concentrationswere highest at the southeast corner of the landfill.Methane gas was detected at concentrations abovethe lower explosive limit at the eastern end of thelandfill. Low levels of VOCs were found in all ofthe residential wells. These wells are all located tothe south of the site.

Sampling of the seven wells was conducted by thecontractor hired by the owner and the analysis wasdone by a private laboratory not participating in theContract Laboratory Program. The QA/QCprocedures of the sampling and analysis are notreadily available. Sample analysis methodologieswere inappropriate for some contaminants; thedetection limit for VC in groundwater was abovethe maximum contaminant level (MCL) of 2 ppb.Therefore, conclusions with regard to health risksfor this contaminant cannot be made because thechoice of analytical methods and reliability of thegroundwater data are suspect. For purposes of thiswork plan, the above data will be used only forproject planning and to identify preliminaryremediation goals.

Only limited conclusions can be drawn from theexisting data. The full areal and vertical extent ofgroundwater contamination can not be determinedbecause all of the wells sampled showed VOCcontamination. Well R-5, however, did not showexceedances, of primary MCLs. The depth ofcontamination, and the extent of contaminantmigration to the south and west of the site have notbeen determined. Upgradient concentrations arealso unknown. These data gaps need to be filled inthe RI.


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Figure 2-3LOCATION OF EXISTING CAPEXAMPLE SITE


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Table 2-1SUMMARY OF GROUNDWATER SAMPLING AND ANALYTICAL RESULTSa

(Fg/l)

ContaminantResidential Wells Onsite Wells

(R-1) (R-2) (R-3) (R-4) (R-5) (GWIS) (GWID)

1,1-DCE 2.0 2.0 9.9 3.2 <5 8.5 4.5

cis-1,2-DCE 11.0 13.0 17.0 15.0 NA 16.0 10.0

PCE 2.6 3.3 33.5 3.9 <5 28.9 18.6

1,1,1-TCEA 36.0 36.0 90.0 5.5 <5.0 85.0 40.0

TCE 72.0 120.0 100.0 100.0 2.3J 110.0 75.0

VC <5.0 <5.0 5.1 5.3 <5.0 55 4.2

Toluene 1,100 980 1,020 640 400 5,000 1,500

Ethylbenzene 700 850 920 200 200 10,500 500

bis(2-e/h)phthalate 820 640 580 120 45 980 780

Lead 17.3 <1.0 1.3b <1.9 NA 16.5 14.0

Arsenic 2.9 <4.0 2.7 3.2 NA 3.2

Total Chromium 7.0 17.0 27.0 <5.0 <5.0 25.1 18.2aSamples were collected in January 1981 as part of a closure investigation conducted bythe contractor hired by the owner.bEstimated value.


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Section 3SITE DYNAMICS

Understanding the dynamics between the site andits environs including potential receptors, is essentialto successfully scoping the RI/FS. This sectiondiscusses the limited field activities conductedduring development of this work plan to betterunderstand the site dynamics; the conceptual sitemodel describing the site’s dynamics; and thepreliminary remediation goals that have beendeveloped as a result of this information.

3.1 Limited Field Investigation

Insufficient data were available to adequatelydefine the dynamics at the site and, hence, todevelop the conceptual site model and design the RIprogram. Therefore, a limited field investigation wasperformed to collect data to further determine theRI scope. Prior to the limited field investigation, asite visit was conducted. The general features ofthe landfill were observed and documented. Theperimeter of the landfill itself was identified, alongwith access and egress to and from the site.Nearby residents were interviewed, andphotographs were taken. During the site visit, dataon VOCs, radioactivity, and explosivity hazardswere obtained using field analytical equipment (theHNu, radiation meter, and explosimeter) todetermine appropriate health and safety levels. Siteconditions differing from those reported in existingreports were also documented.

A summary of the limited field investigationobjectives, activities, and results are shown byTable 3-1. The limited field investigation wasconducted for several reasons. The site boundarieswere not defined and maps of the site were notavailable. Reports indicate that there are sevenonsite wells. Two of the existing wells, GWIS andGWID, were located during the site visit. The otherfive wells could either not be located during the sitevisit or the limited field investigation or wereunusable. The viable well nest (GWIS and GWID)penetrates through the landfill contents.

In-situ hydraulic conductivity tests were conductedby the RI contractor in May, 1988, on three (R1,R2, and R3) of the five residential wells and the oneonsite well nest (Figure 2-1). Based on the resultsof these tests, the hydraulic conductivity of thissand-and-gravel aquifer ranges from 9.8 x 10-3

cm/sec to 2.1 x 10-1 cm/sec with a geometric meanof 7.4 x 10-2 cm/sec. Table 3-2 summarizes resultsof the in-situ hydraulic conductivity testing. Ingeneral, this aquifer is very transmissive. Thisinformation aids in the placement of the newmonitoring wells and provides an early indication ofcontaminant migration.

Water level measurements were taken from thenearby residential and onsite wells. The water levelat the onsite well was slightly higher than the otherwells, indicating a possible local groundwatermound.

3.2 Conceptual Site Model

Figure 3-1 summarizes the conceptual site modelfor the example site. The entire landfill will beconsidered as the source of the contaminants;however, disposal records indicate that high levelsof VOCs are present in the waste disposed ofprimarily in the southeastern corner (solvent drumsand liquid solvents) of the landfill.

Table 3-3 shows the preliminary exposure path-ways under current and future use at the site.Organics and inorganics are released from thelandfill to the groundwater by leaching caused bycompression and/or by percolation. Thecontaminated groundwater is used as an offsitewater supply source. Leachate discharges via seepsto the small tributary of the Polk River. Landfill gaspresent at the landfill can migrate and pose on- andoffsite fire and explosion hazards. Landfill gas canalso become soluble in groundwater.


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Table 3-1LIMITED FIELD INVESTIGATION OBJECTIVES FOR

THE EXAMPLE SITE

Page 1 of 2

Activity Objectives Action Results

GeneralInvestigation

Delineate site boundaries,estimate uncertainties inboundaries.

Conduct property survey oridentify property ownershipfrom tax records.

Site boundaries defined.

Evaluate present siteconditions.

Visually inspect site for gas/fire/explosion damage, run-off pathways, leachate seeps,exposed wastes, coverconditions, access concerns.

No evidence of gas/fire/explosion damage was observed.Several areas of exposed wastesare present. Additionallyleachate seepage from thelandfill was observed. Runoffpathways to the unnamedtributary of the Polk River werelocated.

Locate existingmonitoring wells.

Perform a topographicsurvey and location andelevation survey of existingmonitoring wells.

Two of the seven existing onsitewells were located.

Evaluate site drainagepatterns.

Perform a topographicsurvey.

Site drainage patterns weredefined.

Locate preliminarylocations for newmonitoring wells.

Perform a topographicsurvey.

Preliminary locations of newmonitoring wells weredetermined.

Locate surface waters,wetlands, sensitiveenvironments.

Conduct site visit. An unnamed tributary of thePolk River flows within 200 ft ofthe west side of the landfill.

Evaluate site-cappingconditions and surfacewater drainage.

Perform visual surfaceinspection with topographicmaps.

Capping and drainage appearedto be in fair condition with minorsideslope erosion.Leachate was observed seepingfrom the side of the landfill.

Initiate measurements oflandfill settlement rate.

Install benchmarks. Benchmarks installed; quarterlyreadings will be taken.

Site preliminary locationsfor trailer, decon pad, andsecured storage area.

Conduct site visit. Locations were identified.

Evaluate site access towater, utilities, andtelephone.

Conduct site visit. Water may be available near thesite from an upgradient well; ifnot, water will need to betrucked to the site, Also, a utilitypole and a telephone line areneeded.


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Table 3-1LIMITED FIELD INVESTIGATION OBJECTIVES FOR

THE EXAMPLE SITE

Page 2 of 2

Activity Objectives Action Results

GeotechnicalInvestigation

Describe geologicfeatures, classify soil.

Conduct visual observationof mechanical erosion, slopeinstability, and pondingcaused by subsidences andcracking.

Minor sideslope erosion of thecap was observed.

HydrogeologicInvestigation

Evaluate usefulness ofexisting monitoring wellnetwork.

Determine accessibility ofexisting wells.

Determine, by sounding tothe bottom of the well, ifexisting wells are obstructed.

Five of the seven wells couldnot be found; however, one wellnest was located.

Of the two wells located, bothwere judged suitable for futuresampling.

Reviews preliminarylocations for newmonitoring wells.

Review topographic map andconduct site survey.

Preliminary locations for newmonitoring wells were observed.

Conduct well inventory:determine localgroundwater uses andconstruction of wells.

Perform well survey for allwells (residential, commercial,industrial) adjacent to, anddowngradient from, thelandfill. Obtain permission foruse.

The majority of the residentialwells are in use and informationregarding their constructionexists. There were no commercialor industrial wells identified.

Confirm direction ofgroundwater flow andestimate gradients.

Record water levelmeasurements from existingwells.

A monitoring well located in thelandfill showed a slight water-level elevation compared toother wells, indicating thepossibility of a local ground-water mound.

Determine rate ofgroundwater flow instrata and bedrockfractures.

Perform hydraulicconductivity tests onexisting wells.

Permeability of hydrogeologicunits was estimated; rate ofgroundwater flow wascalculated; groundwaterextraction seems feasible.

Estimate interactionbetween groundwater andsurface water.

Conduct an investigation ofthe unnamed tributary onfoot to determine if there isgroundwater infiltration.

It appears that the groundwateris recharging the unnamedtributary.


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Table 3-2RESULTS OF IN-SITU HYDRAULIC CONDUCTIVITY TESTS

Well Number Test Number K Geometric Mean

R1 1 2.1 x 10-1 cm/sec2 1.9 x 10-1 cm/sec3 1.5 x 10-1 cm/sec 1.8 x 10-1 cm/sec



GWIS 1 9.5 x 10-2 cm/sec2 9.5 x 10-2 cm/sec3 1.1 x 10-1 cm/sec 1.0 x 10-1 cm/sec

GWID 1 1.2 x 10-2 cm/sec2 9.8 x 10-3 cm/sec 1.1 x 10-2 cm/sec

Geometric Mean 7.4 x 10-2 cm/sec


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Table 3-3PRELIMINARY POTENTIAL EXPOSURE PATHWAYS UNDER CURRENT AND

FUTURE USE FOR THE EXAMPLES SITE

SourceRelease

MechanismTransportMedium

ExposurePoint

ExposureRoute

PotentialReceptors

Exposure Potential

Pathways Retained

Existing Potential

Chemicals infill and/or indrums

Erosion Direct Contact Onsite IngestionDermal Absorption

Site workersFuture site workersTrespassers

Exposed wastes in southeast sectionof landfill.

Yes No, if covered

Excavation Direct Contact Onsite IngestionDermal AbsorptionInhalation

Site workersFuture site workers

Landfill not likely to be excavated infuture. Land value is not expected tobe high enough to justify expense ofdeveloping site.

No No, if notexcavated

Leaching Groundwater Onsite IngestionDermal AbsorptionInhalation

Groundwater users No current use of groundwater onsite.Potential for future use of onsitegroundwater is minimal because oflandfill.

No No

Leaching Groundwater Onsite IngestionDermal AbsorptionInhalation

Groundwater users Use of sand and gravel aquifer. Wellscould be installed in the future.

Yes Yes

Leaching Leachate Seep Stream BioconcentrationIngestion

Aquatic organisms Depends on degree of attenuationand dilution.

Unknown Yes

Leaching Leachate Seep Stream Ingestion of fish thatbioconcentratedchemicals

People whoconsume fish

Depends on degree and frequency ofexposure and amount ingested.

Unknown Yes

Leaching Leachate Seep Stream IngestionDermal AbsorptionInhalation

Recreational waterusers

Depends on dilution with surfacewater and degree of exposure.

Unknown Yes

Leaching Landfill Gas Onsite InhalationExplosion

Site workersFuture site workers

Potential exists for migration into thegroundwater. Potential for exposureduring site investigation.

Yes Yes

Leaching Landfill Gas Onsite InhalationExplosion

ResidentsArea workers

Potential exists for migration into thegroundwater.

No Yes


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Receptors at the site include site workers, futuresite workers, trespassers, residents, and areaworkers. Site workers, future site workers, andtrespassers can make dermal contact with theexposed wastes. Residents and area workers cancome into contact with the groundwater throughingestion, inhalation, and/or dermal contact; andwith landfill gas through inhalation. Explosion is alsoa concern for landfill gas.

3.3 Preliminary ExposureAssessment

Exposure pathways must be identified in order toadequately define the preliminary remediation goals.Exposure pathways describe how a chemical canmove from its source to a receptor. Components ofan exposure pathway include a contaminant source,release mechanism, and the transport, migration,and fate of the contaminant.

3.3.1 Chemicals Previously Detected at theSite

The known types of waste disposed of at the landfilland their chemical characteristics are brieflydiscussed in Section 2.5.2 of this appendix.Chemical analytical data for these compounds are,however, available only for a limited set ofcontaminants. The type of contaminants and levelsdetected in the groundwater are shown by Table2-1. The contaminants detected are:

1,1-DCE leadPCE arsenic1,1,1-TCA total chromiumTCE ethylbenzenecis-1,2-DCE tolueneVC bis(2-e/h)phthalate

3.3.2 Contaminant Source

The contaminant sources at the site are the wastesdisposed of in the landfill. They include:

• Chemicals and drums containing chemicalsdistributed throughout the landfill

• A large number of drums disposed of in the

southeastern portion of the landfill

• The “designated area” where liquid solventwastes were also dumped in thesoutheastern section of the landfill

• Media now contaminated by wastes (e.g.,groundwater, possibly surface water, andsediments of the unnamed tributary)

3.3.3 Release Mechanism

The mechanisms for contaminant release at the siteinclude:

• Leaching of contaminants into thegroundwater

• Leachate seeps discharging to adjacentsoils and surface water

• Erosion of cover material, exposing landfillcontents so they are released by runoff

Release of landfill gas containing volatile organics

3.3.4 Contaminant Transport

The primary transport mechanisms are:

• Movement with groundwater• Movement of leachate seeps• Movement with surface water runoff• Movement of landfill gas

Leaching of contaminants from the landfill materialshas occurred as indicated by the groundwatercontamination and the possible presence of a moundunder the landfill. This is the release mechanism ofgreatest concern at the site because with noadditional action, it has the potential to add thegreatest amount of contaminants to the environmentand to affect receptors via drinking water wells.Continued release, however, may occur fromleaking drums, continued low-rate infiltration fromcontaminated soils, wastes in contact with thegroundwater, or exposure of waste to surfacerunoff as a result of erosion. Migration of landfillgas is also of concern at the site because


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of both explosion potential by a buildup of methanein enclosed spaces and air-quality degradation byvolatile (vinyl chloride) carcinogens.

3.3.5 Contaminant Migration

After contaminants have entered the ground-water,several migration pathways are possible dependingon their widely varying sorption characteristics.Shallow groundwater could migrate downgradientor to deeper aquifers and eventually to potentialreceptors offsite. Existing data indicate that thecontaminant plume has moved offsite as evidencedby the contamination in the nearby residential wells.

Based on the hydraulic conductivities and gradientsdetermined during the limited field investigations,and an estimated time of 20 years, groundwaterrecharge velocities were calculated. Most of thedetected VOCs are expected to be found withinapproximately 1,000 feet of the site.

Contaminants in the leachate seeps may migrateoffsite to the unnamed tributary to the Polk River.Potential receptors include aquatic and terrestrialorganisms in the stream as well as human receptorswho may consume fish from the stream or use thestream for recreational purposes.

Contaminants in the form of landfill gas may alsomigrate from the site seeking escape into theatmosphere. Microbial decomposition of organicwastes under anaerobic conditions produces a gas,which is generally 50 to 55 percent methane and 40to 45 percent carbon dioxide.

3.3.6 Contaminant Fate

The following discussion describing the fate ofcontaminants detected in the study area is based ona review of literature and relevant site conditions.

VOCs were detected in groundwater within thelandfill and in nearby residential wells. Underexisting site conditions, the VOCs could betransported with groundwater, leachate seeps,

or surface-water runoff to surface waters. Duringtransport in the groundwater, the contaminants maybe subject to adsorption, hydrolysis, and biologicaldegradation under aerobic or anaerobic conditions.Upon transport to surface water the chemicals maybe adsorbed to sediments or taken up by aquaticorganisms, and with exposure to aerobic conditionsand sunlight, subjected to volatilization, biologicaltransformation, hydrolysis, or photolysis. Theprimary mechanisms that affect the migration andfate of the organic compounds are: adsorption onsediments, volatilization, degradation, and uptake byaquatic organisms.

3.3.7 Exposure Pathways

The potential exposure pathways associated withthe site are shown in Table 3-3. The major potentialexposure pathways associated with the site are:

• Release of contaminant to thegroundwater, contaminant migrationthrough the groundwater, and exposurethrough use of the groundwater as adrinking water source

• Release of a contaminant from leachateseeps to surface water (stream) and theexposure to aquatic and terrestrialorganisms in the stream

• Erosion of cover material and exposure oflandfill contents leading to exposure ofnearby residents, site workers, future siteworkers, future site users, trespassers, orterrestrial wildlife

! Landfill gas migration leading to fire andexplosion and air quality degradation whichcan affect residents, area workers, siteworkers, and future site users

Identifying these exposure pathways aids in thedevelopment of the remedial action objectives andpreliminary remediation goals, which are presentedin Section 4.3 of this appendix.


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Section 4PRELIMINARY IDENTIFICATION OF REMEDIAL ACTION

ALTERNATIVES

4.1 Potential ARARs for theExample Site

A description of the federal and state location-andaction-specific ARARs for CERCLA municipallandfill sites can be found in Sections 5 and 6,respectively, of the body of this report (ConductingRemedial Investigation/Feasibility Studies forCERCLA Municipal Landfill Sites). Potentialfederal location-specific ARARs for the examplesite are presented in Table 5-2 in the body of thisdocument; no state location-specific requirements(Section 6) were identified that were more stringentthan the federal location-specific ARARs.

The most significant potential location-specificARARs involve wetlands and floodplains. Althoughthere are no wetland areas presently known to existnear the site, if any are discovered remediation willhave to be implemented in a manner that minimizesthe destruction, loss or degradation of the wetlandareas (Executive Order 11990, Protection ofWetlands--40 CFR 6, Appendix A). Additionally,the Clean Water Act Section 404 prohibitsdischarge of dredged or fill material into a wetlandarea without a permit. If it is determined that theexample site is within the floodplain of the PolkRiver, then remediation will have to avoid adverseeffects and preserve natural and beneficial valuesof the floodplain (Executive Order 11988,Protection of Floodplains--40 CFR 6, Appendix A).

Potential federal action-specific ARARs arepresented in Table 5-3 in the body of this document.The most significant action-specific ARAR will bein compliance with RCRA closure requirements. Ata minimum, remediations will have to comply withRCRA subtitle D closure requirements. Compliancewith RCRA Subtitle C requirements will benecessary if it is determined to be applicable orrelevant and appropriate. Subtitle C will beapplicable if the results of the RI indicate that thewaste in thesoutheast corner of the landfill contains

RCRA characteristic or listed waste and that theresponse action for those wastes constitutestreatment, storage, or disposal as defined byRCRA. A determination of relevance andappropriateness will depend on a number of factors,including the nature of the waste, its hazardousproperties, and the nature of the requirement itself.Since it is probable that a cap will be constructed atthe example site, compliance with state coverdesign requirements will be necessary. The staterequires sufficient freeze-thaw protection withminimum cover requirement including a 2-foot claylayer with a 1.5 to 2.5-foot cover layer and 0.5 footof topsoil.

In situations where RCRA requirements arepotential ARARs, disposal of contaminated soils willbe influenced by the RCRA Land DisposalRestrictions (LDRs). The LDRs may be applicableto contaminated soils if it is determined that the soilshave been contaminated by a restricted, listedRCRA waste or if the contaminated soils are aRCRA characteristic hazardous waste. The LDRsmay require that a specific concentration level beachieved or that a specified technology be used fortreatment prior to offsite disposal at a RCRAfacility.

Some of the alternatives for the example site mayinclude technologies that result in discharge ofcontaminants to the air. Technologies that typicallyresult in air emissions include air stripping, collectionand treatment of landfill gas, excavation andconsolidation of contaminated soils; andincineration. Table 5-3, in the body of this documentsummarizes the requirements concerning airemissions for these technologies, which may beimplemented at the example site.

State and federal chemical-specific ARARs (e.g.,MCLs, state groundwater enforcement standards)will have to be complied with when


A4-2

determining appropriate cleanup levels forgroundwater. The MCLGs, established under theSafe Drinking Water Act, that are set at levelsabove zero, should be attained by remedial actionsfor ground or surface waters that are current orpotential sources of drinking water. Where theMCLG for a contaminant has been set at a level ofzero, the MCL for that contaminant should beattained. More stringent state standards that havebeen promulgated, are identified in a timely manner,and have been applied consistently by the state, willhave to be attained unless a waiver is used. Tables4-1 through 4-4 of this appendix present thepotential chemical-specific ARARs for the examplesite. Water quality criteria have been included in thetables along with drinking water standards since itis likely these criteria would be the basis forestablishing discharge requirements for dischargesto the unnamed tributary to the Polk River.

4.2 Review of Analytical Resultsand Comparison to ARARs

Table 2-1 in this appendix provides a summary ofthe groundwater sampling and analytical results forboth residential and onsite wells. The sampling datafor these seven wells are described as not being ofCLP quality, with QA/QC procedures not available,and with a detection limit higher than the MCLs forsome chemicals. However, it is clear that all wellsshow some VOC contamination.

To show how the streamlined approach describedin Section 3.7.2 of this document may suggest thata certain remedial action (such as capping) beinitiated, the contaminant concentrations actuallydetected in residential wells are compared to theARARs for each contaminant. Because ingestionof groundwater is a direct exposure route, anycontaminant concentration above its ARAR(federal non-zero MCLGs or MCLs) would indicatethat remedial action is warranted. After comparingTables 2-1 (contaminant levels in residential wells)and 4-1 (potential chemical-specific ARARs), it isobvious that several residential wells havecontaminant concentrations above ARARs,

particularly well R-3 where 1,1-DCE, PCE, TCE,VC, and ethylbenzene concentrations are all abovetheir federal MCLs. Therefore, based on thisreview of preliminary groundwater data, thefollowing conclusions can be made to expediteremediation:

1. Initial RI fieldwork should include obtainingdata that can be utilized to make thiscomparison and determination. If validated RIdata confirms that contaminant levels inresidential wells clearly exceed ARARs,remediation to address contamination inresidential wells as an early action or interimaction is warranted.

2. Based on the volume and heterogeneity ofwaste within the landfill, capping can beidentified as the only practicable alternative forthe landfill contents (discussed in Section4.4.1). Therefore, in order to reduce thecontinued contaminant loading to groundwatercapping alternatives for the example site maybe evaluated as an early action.

A more thorough quantitative baseline riskassessment is required for other exposure pathwayssince there is not clear exceedance of ARARs.These areas include risks associated with hot spotareas, landfill gas, and surface water andsediments.

4.2.1 Baseline Risk Assessment

The approach described above for the baseline riskassessment of the example site deals only withresidential groundwater data, ingestion ofgroundwater as the route of exposure, andcomparison to federal MCLs for the toxicityassessment. The purpose is to expedite remediationof groundwater since ARARs appear to be clearlyexceeded. A more thorough baseline riskassessment, considering all potential exposurepathways for both human and environmentalexposure, will be necessary to show that the finalremedies will protect human health and theenvironment. The following documents provideguidance regarding more thorough baseline riskassessments:


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Table 4-1POTENTIAL FEDERAL CHEMICAL-SPECIFIC ARARs FOR THE EXAMPLE SITE a

Chemicalb MCLµg/l

MCLGµg/l

Secondary MCLµg/l

Trichloroethylene 5final 1987

0proposed 1985

N/A

Vinyl Chloride 2c

final 19870d

final 1985N/A

1,1-Dichloroethylene 7final 1985

7final 1985

N/A

cis-1,2-Dichloroethylene 70e

proposed 198970e

proposed 1989N/A

Benzene 5final 1987

0final 1985

N/A

Ethylbenzene 700e

proposed 1989680

proposed 198530e

proposed 1989

Toluene 2,000e

proposed 19892,000e

proposed 198540e

proposed 1989

Xylenes (total) 10,000e

proposed 1989440

proposed 198520e

proposed 1989

Tetrachloroethylene 5e

proposed 19890

proposed 1984N/A

1,1,1-Trichloroethane 200Final 1987

200Final 1985

N/A

Bis(2-ethylhexyl)phthlate N/A N/A N/A

Lead 50f,g 20f N/A

Arsenic 50g 50proposed 1985

N/A

Chromium III 50g,h

final 1986120h

proposed 1985N/A

Chromium VI 50g,h

final 1986120h

proposed 1985N/A

Copper 1,300proposed 1988

1,300proposed 1988

1,000e

proposed 1989

Mercury (Inorganic) 2e

proposed 19892e

proposed 1989N/A

Manganese N/A N/A 50

Iron N/A N/A 300aSource, unless otherwise note - Integrated Risk Information System (IRIS), March 1990bSome of the ions that may be used for plume mapping at the example site (e.g., chloride, sodium, sulfate) donot have chemical-specific ARARs associated with them. These parameters are being analyzed for use as conservative indicators in determining theextent of groundwater contamination.cFederal Register 45 CFR (141)dU.S. EPA Health AdvisorieseFederal Register 54 CFR (97)fFor water entering the distribution system, not at the tapgFederal Register 40 CFR (141)hProposed 100 µg/l for total chromium (III and VI), 54 CFR (97)iFederal Register 53 (160), 8/18/88N/A = not available


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Table 4-2POTENTIAL FEDERAL CHEMICAL-SPECIFIC TBCs FOR THE EXAMPLE SITE a

Page 1 of 2

Chemicalg

Ambient Water Quality CriteriaHealth Advisory

Longer Term Adultand Children

µg/R

Human Health Aquatic Organisms (Freshwater) Oral Reference Dose Oral Potency

Water & Fish µg/R

Fish Onlyµh/R

Acute LCµg/R

Chronic LCµg/R

mg/kg-day Cancer Classification (mg/kg-day) -1

Trichloroethylene 2.710-6 cancer risk

80.710-6 cancer risk

45,000 None 0.00735b No suitable data B2c 0.011c

Vinyl Chloride 2d

10-6 cancer risk525d

10-6 cancer risk-- -- -- 46b Ab 2.3 b

1,1-Dichloroethylene 0.03310-6 cancer risk

1.8510-6 cancer risk

11,600 None 0.009 3,500b C 0.6

cis-1,2-Dichloroethylene -- -- -- -- 0.01b 3,500b D None

Ethylbenzene 1,400 3,280 32,000 None 0.1 3,400 D None

Toluene 14,300 424,000 17,500 None 0.3(assume 0.5

absorption factor)

3,460b D None

Xylene (total) -- -- N/A N/A 2 27,300b D None

Tetrachloroethylene 0.8 10-6 Cancer Risk

8.8510-6 Cancer risk

5,280 840 0.01 5,000 Pending N/A

1,1,1-Trichloroethane 18,400 1,030,000 None None 0.09 (assume 0.3

inhalation retention (factor)

125,000c D None

Bis(2-ethylhexyl)phthlate 1.75e 5.88e 940 3 0.02 N/A B2 0.014

Lead 50 N/A 82 3.2 Inappropriate N/A B2 N/A

Arsenic 0.0022 0.175 360 190 Pending N/A A 1.5 f

Chromium III 170,000 3,433,000 980 120 1 840 N/A N/A

Chromium VI 50 N/A 16 11 0.005 840 Aby inhalation only

N/A

Benzene 0.6610-6 cancer risk

4010-6 cancer risk

5,300 None Pending Not calculated due to carcinogenicity

A 0.029from inhalation data

Copper -- -- 6.5 j -- -- -- D None


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Table 4-2POTENTIAL FEDERAL CHEMICAL-SPECIFIC TBCs FOR THE EXAMPLE SITE a

Page 2 of 2

Chemcialg

Ambient Water Quality CriteriaHealth Advisory

Longer Term Adultand Children

µg/R

Human Health Aquatic Organisms (Freshwater) Oral Reference Dose Oral Potency

Water & Fish µg/R

Fish Onlyµh/R

Acute LCµg/R

Chronic LCµg/R

mg/kg-day Cancer Classification (mg/kg-day) -1

Mercury -- -- 4.857h 1.302h – -- D None

aSource, unless otherwise noted - Integrated Risk Information System (IRIS), March 1990bU.S. EPA Health AdvisoriescEPA Health Effects Assessment Summary Tables (HEAST) Fourth Quarter FY 1989dFederal Register 45 (231)eInterim Addendum to DEHP CriteriafRisk Assessment Forum Document, 1988gSome of the ions that may be used for plume mapping at the example site (e.g., chloride, sodium, sulfate) do not have chemical specific ARARs associated with them. These parameters are being analyzedfor use as conservative indicators in determining the extent of groundwater contamination. hMercury (II). Ambient Water Quality Criteria for Mercury - 1984, EPA jAt a hardness of 50 mg/L Federal Register, Vol. 50 p. 30784, July 29, 1985 N/A - not available LC - lethal concentration --- = no value found

U.S. EPA Cancer Classification Group A Human carcinogen -- sufficient evidence of carcinogenicity in humans Group B1 Probable human carcinogen -- limited evidence of carcinogenicity in human Group B2 Probable human carcinogen -- sufficient evidence of carcinogenicity in animals Group C Possible human carcinogen -- limited evidence of carcinogenicity in animals Group D Not classifiable as to human carcinogenicity -- there is no animal evidence, or human or animal evidence is inadequate Group E Evidence of noncarcinogenicity for humans


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Table 4-3STATE GROUNDWATER STANDARDS

FOR THE EXAMPLE SITE

Chemical aEnforcement

Standardb

(µg/l)

Preventative Action Limitb

(µg/l)

Arsenic 50 5Chromium 50 51,2-dichloroethylene 100 10 (cis)1,1-Dichloroethene 0.24 0.024Ethybenzene 1,360 272Lead 50 5Manganese 50 5Selenium 10 1Silver 50 5Toluene 343 68.6Tetrachloroethylene 1.0 0.11,1,1-Trichloroethane 200 40Trichloroethene 1.8 0.18Vinyl chloride 0.015 0.0015Xylene 620 124Zinc 5,000 2,500aChemicals are those to which state standards apply. Typically, there will not bestate groundwater standards for all the chemicals detected in the groundwater.bThe list presented is based on a review of Wisconsin groundwater standards–NR140.


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Table 4-4STATE AMBIENT WATER QUALITY CRITERIA

FOR AQUATIC LIFE PROTECTIONFOR THE EXAMPLE SITE

Chemical

State Water QualityCriteriaa

Acuteb ToxicityCriteria (ug/l)

Chronicc ToxicityCriteria (ug/l)

Arsenic d 363.8 153.0

Benzoic acid -- --

bis-2-Ethylhexylphthalate -- --

chromium(hexavalent)d 14.2 9.7

Chromium(trivalent) 3,301.1 95.4

1,1-Dichloroethene -- --

1,2-Dichloroethene (cis) -- --

Ethylbenzene -- --

Tetrachloroethylene -- --

1,1,1-Trichloroethane -- --

Trichloroethene -- --

Vinyl chloride -- --

Xylenes -- --

Notes:aBased on Wisconsin Water Quality Criteria for Protection of Freshwater Aquatic Life (WarmWater Sportfish Classification). From Wisconsin Administrative Code NR 105.

bAcute Toxicity Criteria is the maximum daily concentration of a substance which ensuresadequate protection of sensitive aquatic species and may not be exceeded more than onceevery 3 years.

cChronic Toxicity Criteria is the maximum 4-day concentration of a substance which ensuresadequate protection of sensitive aquatic species and may not be exceeded more than onceevery 3 years. CTC are based on acute/chronic toxicity ratios as defined in NR 105.06(5).

dCriteria listed is applicable to the “total recoverable” form. Typically, state water qualitycriteria will not exit for all the contaminants found at the site.


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• U.S. EPA. Risk Assessment Guidance forSuperfund--Human Health EvaluationManual, Part A. Interim Final. EPA/540/1-89/002. December 1989.

• U.S. EPA. Risk Assessment Guidance forSuperfund. Volume H. EnvironmentalEvaluation Manual. EPA/540/1-89/001.March 1989.

4.3 Preliminary Remedial ActionObjectives and Goals

Preliminary remedial action objectives and goalshave been developed for the example site to assistin identifying preliminary remedial actionalternatives and RI data requirements. The remedialaction objectives for the example site are asfollows:

• Provide adequate protection to humanhealth and the environment from directcontact or ingestion of the hazardousconstituents in wastes or soil from landfill

• Provide adequate protection to humanhealth and the environment from directcontact, ingestion, or inhalation of thehazardous constituents in groundwaterbeneath the landfill or groundwater that hasmigrated from the landfill

• Provide adequate protection to humanhealth and the environment from directcontact or ingestion of the hazardousconstituents in surface water andsediments of the unnamed tributary

• Provide adequate protection to humanhealth from inhalation of explosion oflandfill gases

Preliminary remediation goals were developedbased on the remedial action objectives, existingdata (Section 2.7), preliminary ARARs (Section4.1), and the exposure assessment (Section 3.3).Because of the limited usability of the data (seeSection 2.7), these goals will be revised as moreinformation on the site becomes available. Thepreliminary remedial action goals are follows:

• Prevent ingestion of contaminatedgroundwater exceeding non-zero MCLGsor MCLs (where MCLGs are set at zero).

• Prevent direct contact with landfill contentsand minimize continued contaminantloading to groundwater.

• Prevent direct contact and ingestion ofcontaminated soils from hot spot areas.

• Provide adequate protection to humanhealth from inhalation or explosion oflandfill gas. Potential collection andtreatment requirements will be establishedbased on an analysis of the data to becollected in the RI (including a riskassessment).

• Provide adequate protection to humanhealth and the environment from directcontact or ingestion of contaminatedsurface waters or sediments of theunnamed tributary. Specific remediationrequirements will be established based onrisk after an analysis of the data to becollected in the RI.

4.4 Preliminary Remedial Action Alternatives

Several technologies and/or alternatives are unlikelyto survive screening in the FS for technical,implementation, or cost reasons. As an example, theexcavation of the landfill with subsequent treatmentor disposal onsite or offsite is not a feasiblealternative for the example site because of thesubstantial cost that would be associated with alandfill of this size (20 acres, or approximately750,000 cubic yards), the significant health andsafety concerns that would arise during excavationin areas of solvent disposal, and the potential for fireor explosion of the landfill gases. Likewise,containment of groundwater with a cutoff such asa slurry wall is not considered practicable becausean aquitard does not appear to be present at thesite. The following sections discuss the practicableremedial actions for the media of concern at thesite.


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As required by the NCP, the no-action alternativeis included and involves no additional activities byEPA, thereby providing a baseline for evaluatingother alternatives.

4.4.1 Landfill Contents

The most practicable remedial action alternative forthis medium is containment with or withoutinstitutional controls. The containment alternativesmight include: (1) regrading and revegetation ofexisting cap and implementation of institutionalcontrols, (2) construction of a single-barrier capwith or without institutional controls, or (3)construction of a composite-barrier cap with orwithout institutional controls. The purpose of thefirst alternative would be to provide some protectionagainst direct contact and would improve surfacewater drainage, thereby reducing infiltration. Thesecond two alternatives would provide superiorprotection against further groundwatercontamination by minimizing the potential forinfiltration and would provide a barrier to preventcontaminated soil from eroding during precipitationevents. Reducing infiltration and subsequentleachate generation would also mitigate leachateseeps. Capping can also provide gas control,particularly if implemented in conjunction with a gascollection system. A composite-barrier cap will bemore effective and reliable in preventing infiltrationthan a single-barrier cap, however, both designsmay satisfy applicable or relevant and appropriaterequirements (ARARs). All three caps may beviable, depending on the remedial objectives and theresults of the RI. The factors that may affect thetype of cap to be used are presented in Figure 4-1of the body of this report (Conducting RemedialInvestigations/Feasibility Studies for CERCLAMunicipal Landfill Sites). These alternatives couldbe used in conjunction with a fence and a restrictivecovenant on the landfill property to prevent futuresite development.

If RI data indicate that landfill gas presents ahazard to human health and the environment, thendeed restrictions may also be imposed on areas inthe vicinity of the site to limit exposure to the landfillgas. Another measure may be to vent and treat thelandfill gas as described in Section 4.3.4.

4.4.2 Hot Spots

The practicable alternatives for the contaminatedsoils in the southern portion of the site include: (1)excavation and disposal, (2) excavation, treatment,and disposal (onsite or offsite) of treated material,or (3) consolidation of hot spot areas under a landfillcap.

The first two alternatives would involve excavation,possible treatment, and disposal of the soil/waste inthe solvent disposal area of the landfill. Bothalternatives would protect against furthercontamination of the groundwater and surfacewater and against direct contact. Excavation couldbe accomplished using conventional constructionequipment (e.g., backhoe); the risks to localresidents and site workers during executionactivities will be evaluated during the analysis ofremedial action alternatives. Treatment ofcontaminated soil/waste, if necessary, would likelybe done onsite (offsite treatment of soils frommunicipal landfill sites is rarely done because ofavailability and cost). The most viable onsitetreatment options include incineration andsolidification/stabilization. The most common type ofincineration process is rotary kiln, but often thedecision is made during design or by the remediationcontractor based on performance criteria.Solidification/stabilization involves adding pozzolanicagents such as lime, cement, and fly ash to thesoil/waste in situ or in a batch process. The selectedtreatment method may be largely dependent onwhether the waste is a RCRA-restricted waste ornot, and therefore whether the land disposalrestrictions apply.

Disposal of excavated soil/waste should occuronsite and be incorporated under the landfill’s finalcover. All soil/waste treated onsite would probablybe disposed of in the same place from which it wasremoved if the treated wastes are not consideredRCRA wastes.

The required level of treatment of RCRA-restricted wastes before disposal is dependent onthe RCRA land disposal restrictions (LDRs) thatapply to the specific contaminant. In order todetermine the level of treatment required, theprocess(es) generating the contaminants must beidentified and the appropriate RCRA hazardouswaste number determined.


A4-10

In addition to information on the process thatgenerated the hazardous waste, information neededto select a treatment and disposal option includes:the type and concentrations of contaminants in thesoil, the volume of contaminated soil, the moisturecontent of the soil, and the soil type. Also,information on the types and population densities ofresident micro-organisms suitable for biodegradationof contaminants may be needed if contaminantconcentrations are sufficiently high. Potentialexposures from dermal contact, entrainment of soilparticles in air, and release of volatiles duringremediation would be evaluated and necessaryactions taken.

The third alternative for this area would beconsolidation of the hot spots to reduce the area ofthe final landfill cap. This alternative is similar to thefirst alternative, except that, when a landfill cap isconstructed, the hot spot areas would be includedunder the cap, or material from the hot spot areaswould be excavated to the extent necessary toconsolidate these materials under the landfill cap.This alternative would prevent direct contact withthe contaminated soil and prevent contamination ofsurface water. Further contamination ofgroundwater would be reduced by preventinginfiltration of runoff through the contaminated soil.

4.4.3 Groundwater/Leachate

The existing data shows that four of the fiveresidential wells tested exceeded primary MCLs, aspresented in Table 2-1 of this appendix. Practicablealternatives for groundwater remediation willinclude extraction, treatment, and disposal of thecontaminated groundwater. The two strategiesassociated with groundwater extraction includeplacement of perimeter wells to capture leachateand placement of downgradient wells to capturecontaminated groundwater that has migratedoffsite. Leachate extraction wells in conjunctionwith a landfill cap may also be used to stop leachateseeps. Collection trenches are also an option forgroundwater/leachate extraction; however,extraction wells are more likely to be used becauseof the depth of groundwater contamination.

Extraction, treatment, and disposal of contaminatedgroundwater would help stabilize the contaminantplume and provide for ground-water remediation.

Groundwater samples should also be analyzed tocharacterize the contaminant types andcharacteristics and the conventionalparameters--such as hardness and ironcontent--needed to design a treatment system.

Extraction wells would be located in areas thatwould maximize the yield of contaminatedgroundwater. Perimeter wells could be placedaround the landfill to capture leachate and providea containment system to minimize offsite migrationof contaminants via groundwater and leachateseeps. Placement of wells down-gradient within thecontaminated plume would be used to remediatecontaminated groundwater that has alreadymigrated offsite. The extracted groundwater wouldthen be treated before discharge, either onsite or ata POTW. The information needed to design a morecomprehensive groundwater extraction systemincludes the chemical parameters associated withthe contaminated plume and the hydrauliccharacteristics of the aquifer.

Either onsite or offsite treatment of contaminatedgroundwater will likely be feasible. Typically,leachate or high strength contaminated groundwaterfrom municipal landfill sites will be high inconcentrations of organic matter. Treatment isusually by conventional means such as biologicaltreatment (e.g., activated sludge), physicaltreatment (e.g., granular activated carbon (GAC) orair stripping), and/or chemical treatment (e.g.,metals precipitation).

Based on known data, onsite treatment might beaccomplished using air stripping for VOC removaland/or GAC for removal of semi-volatilecontaminants. Depending on the contaminants andtheir concentrations, GAC columns could also beused without air stripping to remove VOCs, as wellas sentivolatile contaminants.

Average and peak flow rates and contaminantconcentrations and properties would need to beidentified to design the treatment system.Information on the hardness, biochemical oxygendemand (BOD), chemical oxygen demand (COD),total suspended solids (TSS), iron, and otherconventional pollutant parameters would be neededas well in order to determine if othertreatment processes (such as biological or


A4-11

chemical treatments) are necessary in addition to,or as a replacement for, the air stripping and/orGAC treatment. At the landfill, the BOD tests couldbe prone to interferences from metals and othermaterials present. COD is therefore usually morerepresentative of the leachate. This informationcould be used to determine the probability andseverity of sealing and fouling occurring in the bedof an air stripper and GAC column. Sand filters orcartridge filters may be necessary to preventsealing and fouling of the GAC columns. Also, if airstripping is used, vapor-phased GAC may berequired to remove VOCs from the air stripperemissions.

For onsite remedial actions, the substantativerequirements of the ARARs, but not theadministrative requirements, must be met. Effluentfrom an onsite treatment system could bedischarged to the Polk River; an NPDES permitcould be required for this disposal method andappropriate ARARs (such as MCLs or waterquality criteria) would be met.

As an interim action, or to supplement agroundwater extraction and treatment system, analternate water supply could be provided to affectedor potentially affected residents to limit exposure tocontaminated groundwater. The water authoritycould provide the alternate water supply byextending the existing distribution system orinstalling a new deep well. Alternatively, bottledwater could be used for temporary drinking andcooking. A comprehensive well inventory andsubsequent sampling of nearby residential wells isneeded to conduct a risk assessment to determinewhether providing an alternate water supply iswarranted.

4.4.4 Landfill Gas

The potential alternatives for this medium includescollection and possible treatment of landfill gas. Thisalternative involves intercepting the methane gasusing passive vents, which typically consist of freeventing structures; active vents if air emissions are

locally controlled; or collection of the gas by onsiteextraction wells for treatment. Passive ventsystems require that a highly permeable material beplaced in the path of gas flow to intercept thelandfill gas and discharge it to the air. An activevent system is used to control the venting of gasesinto the atmosphere when the constituents of thegas are of concern from an air quality standpoint.After collection, if necessary, landfill gas can thenbe incinerated using enclosed ground flares.Enclosed ground-flare systems consist of arefractory-lined flame enclosure (or stack) with aburner assembly at its base. Because of the ruralnature of the example site, a passive venting systemwithout treatment may be acceptable.

Information needed to determine the need for gascollection and treatment would be collected byplacement of monitoring gas probes within thelandfill as well as along the landfill perimeter andanalyzed for methane, TCE, and vinyl chloride. Thepotential for pressure build-up below a landfill capand potential for damage to a vegetative cover willbe evaluated based on the quality and quantity oflandfill gas estimated to be generated at the site.

4.4.5 Surface Water and Sediments

Contaminated sediments in the nearby unnamedtributary to the Polk River may require remediation.The most practicable alternatives for remediatingcontaminated sediments include excavation andconsolidation under the landfill cap or leavingsediments in place and relying on naturalattenuation. Sediment removal can be accomplishedwith conventional dredging or excavation equipmentoperated from shore.

The advantage of relying on natural attenuation toremediate sediments is that dredging activities canoften cause secondary migration of contaminantswhich can potentially have significant environmentalimpacts. If dredging is done, these impacts shouldbe minimized by dewatering during excavationactivities.


A5-1

Section 5 REMEDIAL INVESTIGATION AND FEASIBILITY

STUDY OBJECTIVES

The overall goals of the RI/FS are to:

• Complete a field program for collectingdata to quantify the extent and magnitudeof contamination in the groundwater,subsurface soils, surface water/sediments,and landfill gas

• Determine if unacceptable risk exists tohuman health and the environment

• Develop and evaluate remedial actionalternatives if unacceptable risks areidentified

Table 5-1 shows the objectives of the Phase I RIfor the Example Landfill site. After evaluation ofthe Phase I data, it may be necessary to conduct aPhase II. A Phase II would be conducted if theobjectives of the Phase I R1 are not accomplished.For example, if the Phase I RI groundwatersampling results indicate a contaminant plume butnot enough data was collected to determine theextent of the plume, then further investigations willbe warranted.

The objectives and actions listed in Table 5-1 onlyapply to the example site. These may vary foractual sites where the contaminated media and siteconditions differ from the example site.


A5-2


THE EXAMPLE SITE

Page 1 of 3



Site Mapping/Dynamics Map site and determine topography;determine site boundaries, drainagepatterns, and other geophysical features.

Use photogrammetric methods fromaerial photography; conduct fly-over,if necessary.

Geophysical Investigation Investigate probable presence of buriedferromagnetic materials (drums) insouthern portion of the landfill.

Conduct magnetometer and/or groundpenetrating radar survey.

Geotechnical Investigation Evaluate the physical propertiesgoverning transport of contaminantsthrough identified pathways.

Collect data on permeability, porosity,hydraulic head, percent organic carbon,etc.

Collect data on soil characteristics todetermine if onsite soil can be used as fillmaterial and to determine placement of apotential cap.

Measure soil characteristics such asplasticity index, moisture content,porosity, and permeability.

Evaluate existing cap to determinephysical properties.

1) Collect data on permeability,porosity, and measure thickness.

2) Determine Atterberg limits.

3) Determine extent of vegetationcover, any vegetative stress, anderosion.

Measure current landfill settlement rate. Monitor landfill benchmarks.

Hydrogeologic Investigation Determine selection of screen settings inboth the shallow and deep wells.

Obtain soil classification or geologicdata.

Identify and characterize hydrogeologicunits.

1) Place monitoring wells at pointsaround the landfill to better define theaquifers and confining layers.

2) Perform down-hole geophysicalsurvey.

Determine direction of groundwater flowand estimate gradients.

1) Install monitoring wells and takewater level measurements from newand existing wells.

2) Investigate yield of private andpublic wells.


Install monitoring wells and performhydraulic conductivity tests on newand existing wells; check water levelsat a maximum of once a month duringthe RI.

Meteorological Investigation Determine prevailing wind direction andair speed to evaluate remedial alternatives.

Collect and analyze wind speed anddirection data.


A5-3


THE EXAMPLE SITE

Page 2 of 3




Groundwater Identify extent and type of groundwatercontamination to perform an assessmentof human health and environmental risksto determine if remedial action isnecessary.

Install monitoring wells in aquifers ofconcern; design monitoring wellnetwork to determine the extent of theplume (wells should also be locateddowngradient in “clean” area toconfirm that the end of the plume islocated); collect and analyze samples.

Identify upgradient water quality for eachgeologic unit.

Install upgradient monitoring wells inaquifers of concern and collect andanalyze samples.

Determine source of groundwatercontamination.

Collect and analyze groundwatersamples and compare results to thelandfill waste characteristics andbackground levels.

Determine whether seasonal fluctuationsoccur in contaminant concentrations in thegroundwater and in hydrauliccharacteristics.

Sample and analyze groundwater witha minimum of two rounds of samplingfrom the same location(s).

Evaluate feasibility of groundwatertreatment systems.

Obtain COD, BOD, and otherconventional water quality data.

Leachate Identify extent and type of leachate seepsto evaluate feasibility of groundwatertreatment system.

Collect and analyze leachate and seepdata.

Estimate amount of leachate productionfrom landfill.

Install leachate wells around land-filland measure leachate head.

Perform water balance calculation onlandfill.

Surface Water and Sediment Determine viability of treatmenttechnologies

Collect field measurements on DO andtemperature.

Determine effect of groundwater onsurface water.

Collect and compare up- anddowngradient surface water andsediment samples to downgradientgroundwater samples.

Compare stream and groundwater levelsduring several periods during the RI.

Install staff gauges onsite, surveygauges, measure surface water levelsand groundwater levels concurrently.


A5-4


THE EXAMPLE SITE

Page 3 of 3



Surface Water and Sediment(Continued)

Determine background concentration ofsurface water and sediment.

Collect and analyze upstream waterand sediment samples; includetoxicity testing.

Surface Water and Sediment Determine surface runoff impact onsurface water quality; determine the typeand extent of contamination in nearbysurface waters and sediments.

1) Collect and analyze samples fromnearest leachate seeps and compareto stream water quality.

2) Collect and analyze surface waterand sediment samples at increasingdistances away from the landfill andcompare results to landfill wasteand background levels.

Landfill Gas/Air Identify areas within the landfillcontaining high concentrations ofexplosive or toxic landfill gas to performan assessment of human health risks dueto air toxics and explosive hazards, toevaluate the feasibility of gas collectionand treatment, and to evaluate otherremedial actions.

Obtain flow-related data fromnewly installed gas vents, estimateemission rates, and perform airmodeling.

Collect and analyze landfill gassamples from onsite and perimetersampling points.

Estimate concentrations of selected VOCsbeing emitted to the atmosphere.

Collect and analyze ambient airsamples.

Landfill Gas/Groundwater Identify areas within the landfillcontaining high concentrations ofexplosives or toxic landfill gas todetermine if VOCs act or may act as asource of groundwater contamination

Obtain flow-related data fromnewly installed gas vents, estimateemission rates, and perform airmodeling.

Hot Spots (Soil) Investigate areal extent, depth, andconcentration of contaminants at hotspots in the landfill’s soil.

Collect and analyze perimetersamples with more extensivesampling around known hot spotarea.

Environmental Evaluation Determine impact of landfill on nearbystream.

Collect and analyze surface waterand sediment from nearby stream.

Describe aquatic and terrestrialcommunity in vicinity of site and aquaticcommunity downstream of site

Observe aquatic or terrestrialorganisms in the vicinity of the site.

Determine impact of remedial action onstream.

Collect biota samples from streamadjacent to site.


A6-1

Section 6 DATA QUALITY OBJECTIVES

The data to be collected during the RI will be usedfor site characterization, risk assessment, andremedial action alternative evaluation. Theobjectives of the RI and the necessary actions toaccomplish the objectives are shown in Table 5-1.The number and types of samples of soil,groundwater, leachate, sediments, surface water,and landfill gas to be collected for a sufficientrepresentation of the conditions at the site; thechemicals of concern for which the samples are tobe analyzed; and the precision, accuracy,representativeness, completeness, and comparability(PARCC) parameters to be used are summarizedin Tables 6-1 through 6-3.

In order to achieve the established DQOs, acombination of laboratory services will be used fora more efficient use of time and money. All fivelevels of data quality will be used during the RI asdescribed below:

• Level I--Field screening. This level ischaracterized by the use of portableinstruments that can provide real-time datato assist in the optimization of samplingpoint locations and for health and safetysupport. Data can be generated regardingthe presence or absence of certaincontaminants (especially volatiles) atsampling locations. An HNu will be usedfor Level I analysis for soil samples and tomonitor concentration of VOCs in air forhealth and safety considerations duringdrilling. Additionally an explosimeter will beused during drilling and soil probeinstallation; a radiation meter will be usedinitially to determine if harmful levels ofradioactivity exist at the site.

• Level II--Field analysis. This level ischaracterized by the use of portableanalytical instruments that can be used

onsite or in mobile laboratories stationednear a site (close-support labs). Dependingon the types of contaminants, samplematrix, and personnel skills, qualitative andquantitative data can be obtained. Anonsite mobile laboratory will be used duringwell installation to provide analytical resultsthat will be used to re-evaluate theproposed monitoring well network.Groundwater samples will be analyzed forselected VOCs and inorganic ions (chlorideand sulfate) to aid in determining the extentof the groundwater plume. Soil gas sampleswill also be analyzed for VOCs todetermine the extent of the solvent disposalarea.

• Level III--Laboratory analysis usingmethods other than the CLP RoutineAnalytical Services (RAS). This level isused primarily in support of engineeringstudies using standard EPA approvedprocedures. Some procedures may beequivalent to CLP RAS, without the CLPrequirements for documentation. Analysiswill include COD, BOD, TOC, and TSS ingroundwater and leachate samples.

• Level IV--CLP RAS. This level ischaracterized by rigorous QA/QCprotocols and documentation and providesqualitative and quantitative analytical data.Some regions have obtained similar supportvia their own regional laboratories,university laboratories, or other commerciallaboratories. This level will be used forconfirmatory sampling of groundwater, hotspots, surface water, and sediments.Analyses performed will include TCLorganics and TAL metals.


A6-2

• Level V--Nonstandard methods. These areanalyses that may require methodmodification and/or development. CLPSpecial Analytical Services (SAS) areconsidered Level V. This level will be usedfor vinyl chloride in groundwater andleachate where lower detection limits arewarranted.

• Other--Geotechnical testing to determinesoil characteristics and other data, such aspH and conductivity, will be conducted toaid in the engineering design ofalternatives. Geotechnical analysis will bedone by a commercial laboratory.Conductivity and pH will be analyzed in thefield.


A6-3

Table 6-1DATA QUALITY OBJECTIVES SUMMARY FOR GROUNDWATER/LEACHATE

OF THE EXAMPLE LANDFILL SITE

Page 1 of 3

Data Quality Objective Elements Site Characterization Risk Assessment

Engineering Design of Alternative

Objective • Identify extent and type ofcontamination

• Determine if contaminantsare present in residentialwells

• Assess risks due toingestion

• Evaluate feasibilityof groundwatertreatment system

Data Quality Factors

Prioritized Data Use(s) Site characterization Risk assessment Engineering design ofalternative

Contaminants of Concern TCE, vinyl chloride, lead,arsenic, chloride, chromium

TCE, vinyl chloride, lead,arsenic, chromium

COD, BOD, pH,conductivity

Level of Concern (ARARs)a

TCEVinyl chlorideLeadArsenicChlorideSulfateChromium

5 ppb2 ppb50 ppb50 ppbN/AN/A50 ppb


N/AN/AN/AN/AN/AN/AN/A

Reporting Limitb

TCEVinyl chlorideLeadArsenicChlorideSulfateChromium

5 ppb10 ppb5 ppb10 ppb50 ppb50 ppb10 ppb


N/AN/AN/AN/AN/AN/AN/A

Appropriate Analytical Levels I, II, IV IV and V III and Other

Critical Samples Residential wells Residential wells Monitoring wells

Data Quality Needs

Sampling/Analysis Procedures

• Sample Collectionc

• Sample Analysis

Level I--Field Screeningd Use of HNu

N/A--Not applicable

a These are federal MCLs from the SDWA. While federal ARARs are stated for this example, state ARARs maypreclude the federal ARARs.

b The listed values are the Contract Required Quantitation Limits (CRQLs) taken from the CLP SOWs (Level IV).Since reporting limits in some cases are at or above levels of concern, special analytical services (SAS) reporting limits(Level V) may be required to achieve lower detection limits (e.g., vinyl chloride). This CRQL is matrix dependent andmay not be achievable in every sample,

c Sample collection procedures are outlined in the A Compendium of Superfund Field Operations Methods, August 1987.d Level I analytical methods are not compound specific, only quantitative for total organics.


A6-4



Page 2 of 3



Level II--Field Analysise

TCEVinyl chlorideLeadArsenicChlorideSulfateChromiumf

GC/ECD/PIDGC/ECD/PIDAtomic AbsorptionAtomic AbsorptionIon ChromatographIon ChromaographAtomic Absorption

Level III--Non-CLP Lab Methodsg

CODBODTSSTOC

EPA 405.1EPA 410.1EPA 209

Level IV--CLP RAS

TCELeadArsenicChromium

CLP Organic SOWCLP Inorganic SOWCLP Inorganic SOWCLP Inorganic SOW

CLP Organic SOWCLP Inorganic SOWCLP Inorganic SOWCLP Inorganic SOW

N/AN/AN/AN/A

Level V–CLP SASh

Vinyl chloride EPA 601

Other

pHSpecific Conductance

pH meterConductivity meter

PARCC Parameters

• Precisioni

- TCE- Vinyl chloride- Lead- Arsenic- Chromium

<14+25%±20%±20%±20%

• Accuracyi

- TCE- Vinyl chloride- PCB- Lead- Arsenic- Chromium

71-120%75-125%N/A75-125%75-125%75-125%

N/A–Not applicable

e Method used by the onsite mobile laboratory.f Only total chromium will be detected.g Level II analysis is only for parameters not on the CLP TLC and TAL lists and for cases where QC requirements are less

stringent than that of the CLP methods. Level III analysis is not applicable for the selected contaminants of concern listedexcept for COD and BOD in groundwater and TCE and vinyl chloride in landfill gas.

h Level V-CLP SAS methods may include modified versions of CLP RAS methods to achieve lower detection limits, to provideproject-specific QC, to analyze for non-CLP parameters or to use non-CLP methods but still provide the levels and types ofQA/QC and deliverables prevented by CLP RAS.

i The listed values precision and accuracy in analysis of water samples are based on CLP RAS SOW requirements and do notnecessarily reflect actual method performance.


A6-5



Page 3 of 3



• Representativesj

• Completenessk

• Comparabilityl

j Qualitative parameter, which considers the project as a whole. No numerical criteria can be set.k Can be expressed as a quantitative assessment of the percentage of valid data received. Also includes a qualitative parameter and

must be assessed after all data are reviewed.l A qualitative parameter that can be maximized through the use of standard sampling, analysis, and data review techniques.


A6-6

Table 6-2DATA QUALITY OBJECTIVES SUMMARY FOR HOT SPOTS, FILL, AND CAP INVESTIGATION

OF THE EXAMPLE LANDFILL SITEPage 1 of 3

Data Quality Objective Elements Hot-Spot Areas Fill Cap Investigation

Objective • Identify highly contaminatedareas that may be presentonsite

• Assess risk due to directcontact

• Determine if fill can be used forcapping

• Determine existing capcharacteristics


Prioritized DataUse(s)

Site characterization, riskassessment, and engineeringdesign of alternatives

Engineering design of alternative Engineering design ofalternative

Contaminants ofConcern

TCE, PCB, lead, arsenic,chromium, treatabilityparameters

Geotechnical parameters Permeability, porosity,depth


TCEVinyl chloridePCBLeadArsenicChromium

636 ppb0.3 ppb0.091 ppb105 ppb3 ppb(III) 75,000, (VI) 375 ppb

Reporting Limit b


5 ppb10 ppb80 ppb500 ppb1,000 ppb1,000 ppb

Appropriate AnalyticalLevels

Site characterization: II, III, IVRisk assessment: IV and V

Engineering design of alternative,III

Engineering design ofalternative, Other

Critical Samples Clean samples at outerboundary of contaminated area

Collect samples from perimeter ofwaste area to determine arealextent of waste

Data Quality Needs

Sample/AnalysisProcedures• Sample Collectionc

• Sample Analysis

Level I–Field Screeningd

a While federal ARARs are stated for this example, state ARARs may preclude the federal ARARs. Numbers listed should beupdated to incorporate current guidance. For carcinogens, numbers are based on the 10-6 cancer risk. For noncarcinogens,numbers are based on the reference dose. All numbers are calculated for a 17-kg child ingesting 0.2 gms of soil per day.

b The listed values are the Contract Required Quantitation Limits (CRQLs) taken from the CLP SOWs (Level IV). The CRQL ismatrix dependent and may not be achievable in every sample. The actual reporting limit will also be affected by moisturecontent for soil and sediment samples. Some samples are analyzed as received but reported on a dry-weight basis. Since reportinglimits in some case are at or above levels of concern, SAS reporting limit (Level V) may be required to achieve lower detectionlimits (e.g., vinyl chloride).

c Sample collection procedures are outlines in the A Compendium of Superfund Field Operations Methods, August 1987.d Level I analytical methods are not compound specific, only quantitative for total organics. Not used for soil investigation.


A6-7


OF THE EXAMPLE LANDFILL SITEPage 2 of 3


Level II–Field Analysise

TCEVinyl chlorideLeadArsenicChromiumf

GC/ECD/PIDGC/ECD/PIDX-ray FluorescenceX-ray FluorescenceX-ray Fluorescence

Level III–Non-CLP LabMethodsg

Level IV–CLP RAS


CLP Organic SOWCLP Organic SOWCLP Organic SOWCLP Inorganic SOWCLP Inorganic SOWCLP Inorganic SOW

Level V–CLP SASh

Other

Moisture ContentPermeabilityIn Situ Densityi

Atterberg LimitsGrain Size AnalysisBTU contentTCLP

ASTM 2216-80SW 846, Method 9100

ASTM D4318ASTM D422

N/ASW 846, Method 9100N/AN/AN/A

PARCC Parameters

• Precisionj

- TCE- Vinyl Chloride- PCB- Lead- Arsenic- Chromium

<20±25%±25%±20%±20%±20%

• Accuracyj

- TCE- Vinyl chloride- PCB- Lead- Arsenic- Chromium

62-137%75-125%75-125%75-125%75-125%75-125%

e Level II methods used by the onsite mobile laboratory and soil gas analysis. f Only total chromium will be detected. g Level II analysis is only for parameters not on the CLP TLC and TAL lists and for cases where QC requirements are less

stringent than those of the CLP methods. Level III will not be used for these media. h Level V–CLP SAS methods may include modified versions of CLP RAS methods to achieve lower detection limits, to provide

project-specific QC, to analyze for non-CLP parameters, or to use non-CLP methods, but they still provide the levels and typesof QA/QC and deliverables prevented by CLP RAS. Level V will not be used for these media.

i Method report in Methods for Soil Analysis, Section 13.2j The listed values for precision and accuracy in analysis of soil, sediment, and water samples are based on CLP RAS SOW

requirements and do not necessarily reflect actual method performance. Precision and accuracy performance for landfill gassamples are method dependent and should be determined on a project-specific basis.


A6-8



Page 3 of 3


• Representativenessk

• Completenessl

• Comparabilitym

k Qualitative parameter, which considers the project as a whole. No numerical criteria can be set. l Can be expressed as a quantitative assessment of the percentage of valid data received. Also includes a qualitative parameter and

must be assessed after all data are reviewed. m A qualitative parameter that can be maximized through the use of standard sampling, analysis, and data review techniques.


A6-9

Table 6-3DATA QUALITY OBJECTIVES SUMMARY FOR SURFACE WATER, SEDIMENT

AND LANDFILL GAS OF THE EXAMPLE LANDFILL SITEPage 1 of 3

Data Quality Objective Elements Surface Water Sediment Landfill Gas

Objective Evaluate impact of surfacewater runoff from the site to theunnamed tributary

Evaluate impact of surface waterrunoff from the site to thesediment of the unnamed tributary

Identify areas within thelandfill containing highconcentrations of selectedVOCs. Identify landfill gascontaminant concentrationat perimeter of site toevaluate impact fromoffsite migration.


Prioritized DataUse(s)

Site characterization, riskassessment

Site characterization Site characterization

Contaminants ofConcern

TCE, PCB, lead, arsenic,chromium

TCE, PCB, lead, arsenic,chromium

Methane, TCE, vinylchloride


TCEVinyl chloridePCBLeadArsenicChromiumMethane

2.7 ppb2.0 ppb0.000079 ppb50 ppb0.0002 ppb50 ppbN/A

636 ppb0.3 ppb0.091 ppb105 ppb0.35 ppb(III) 75,000, (IV) 375 ppbN/A

N/AN/AN/AN/AN/AN/ANo federal ARARb

Reporting Limit c

TCEd

Vinyl chlorided

PCBLeadArsenicChromiumMethaned

5 ppb10 ppb0.5 ppb5 ppb10 ppb10 ppbN/A

5 ppb10 ppb80 ppb500 ppb1,000 ppb1,000 ppbN/A

N/AN/AN/AN/A

Appropriate AnalyticalLevels

Site characterization and riskassessment: IV and V

Site characterization: IV Site characterization: III

Critical Samples Samples from the groundwaterand leachate seeps

Samples from the groundwater andleachate seeps

Samples from areas of thelandfill where it issuspected that methane gasis produced

a Surface water–These are based on the Federal Ambient Water Quality Criteria , a nonenforceable guidance document under theCWA and are either based on toxicity protection (lead, chromium) or the 10 cancer risk level. The selected criteria are thechronic criteria for protection of Aquatic life. The level of concern for chromium is for both the total and hexavalent species.While federal ARARs are stated for this example, state ARARs may preclude federal ARARs if they are more stringent.

b Several states have air toxics emissions regulations. Guidance on air ARARs can be found in the National Air ToxicsInformation Clearinghouse Database Report on state, local, and EPA air toxics.

c The listed values are the Contract Required Quantitation Limits (CRQLs) taken from the CLP SOWs (Level IV). This CRQL ismatrix dependent and may not be achievable in every sample. The actual reporting limit will also be affected by sample moisturecontent for sediment samples. Some samples are analyzed as received but reported on a dry-weight basis. Since reporting limitsin some cases are at or above levels of concern, SAS reporting limits (Level V) may be required to achieve lower detection limits(e.g., vinyl chloride).

d The reporting limit for TCE, vinyl chloride and methane is dependent upon the volume of gas sampled and should be establishedfor each sampling event.


A6-10


AND LANDFILL GAS OF THE EXAMPLE LANDFILL SITE

Page 2 of 3


Data Quality Needs

Sample/AnalysisProcedures• Sample Collectione

• Sample Analysis

Level I–Field Screeningf

Level II–Field Analysisg

Level III–Non-CLP LabMethodsh

MethaneTCEVinyl chlorideTSSAlkalinityHardnessTOCGrain Size Analysis% Moisture% Solids

N/AN/AN/AEPA 209

N/AN/AN/AN/A

N/AN/AN/AN/AN/AN/A

ASTM D422

T014T014T014N/AN/AN/AN/AN/AN/AN/A

Level IV–CLP RASi

TCEVinyl ChloridePCBLeadArsenicChromium



Level V– CLP SASj

Toxicity Testsk

Other

EhpHSpecific Conductance

Eh MeterpH MeterConductivity Meter

EPA 9045pH MeterEPA 126.1

N/AN/AN/A

N/A–Not applicable.

E Sample collection procedures are outlined in the A Compendium of Superfund Field Operations methods, August 1987. f Level I analytical methods are not compound specific, only quantitative for total organics. Level I will not be used for the

surface water sediment, and landfill gas media. g Level II will not be used for analysis of the surface water, sediment, or landfill gas samples. h Level III analysis is only for parameters not on the CLP TLC and TAL lists and for cases where QC requirements are less

stringent than that of the CLP methods. Level III analysis is not applicable for the selected contaminants of concern listedexcept for TCE and VC in landfill gas.

i CLP RAS methods are not currently available for landfill gas. These samples will always be analyzed by Level III methods.j Level V-CLP SAS methods may include modified versions of CLP RAS methods to achieve lower detection limits, to provide

project-specific QC, to analyze for non-CLP parameters, or to use non-CLP methods but still provide the levels and types ofQA/QC and deliverables prevented by CLP RAS. Some standard SAS methods are reported for landfill gas.

k Acute and chronic bioassays are done for surface water with invertebrate, vertebrate and plant species. For sediments, EPtoxicity test are done.


A6-11


AND LANDFILL GAS OF THE EXAMPLE LANDFILL SITE

Page 3 of 3


PARCC Parameters

• Precisionl

- TCE- Vinyl Chloride- PCB- Lead- Arsenic- Chromium- Methane

<14±25%±25%±20%±20%±20%N/A

<20±25%±25%±20%±20%±20%N/A

• Accuracym

TCEVinyl chloridePCBLeadArsenicChromiumMethane

75-125%N/AN/AN/AN/AN/AN/A

62-137%75-125%75-125%75-125%75-125%75-125%N/A

• Representativenessn

• Completenesso

• Comparabilityo

N/A–Not applicable.

l The listed values for precision and accuracy in analysis of water samples are based on CLP RAS SOW requirements and do notnecessarily reflect actual method performance. Precision and accuracy performance for landfill gas samples are methoddependent.

m Qualitative parameter, which considers the project as a whole. No numerical criteria can be set.n Can be expressed as a quantitative assessment of the percentage of valid data received. Also includes a qualitative parameter and

must be assessed after all data re reviewed. o A qualitative parameter that can be maximized through the use of standard sampling, analysis, and data review techniques.


A7-1

Section 7RI/FS TASKS

The field investigation is conducted to provide datathat can be used to determine the type and extent ofcontamination at the site and to identify if the siteposes risks to human health and the environment.The RI/FS tasks described in this work plan havebeen developed to meet these objectives. Thissection of the work plan follows the standardformat outlined in the RI/FS Guidance (U.S. EPA,1988a). Several of these activities were conductedbefore developing this work plan. These activitiesinclude the evaluation of existing data and theperformance of limited field investigations. Theresults of both of these activities are reported inSection 2 and 3, respectively, of this appendix.

7.1 RI/FS Tasks

The following tasks have been identified for theRI/FS:

• Task 1--Project Planning

• Task 2--Community Relations Activities

• Task 3--Field Investigations

! Subtask 3A--Fieldwork Support

! Subtask 3B--Surveying and Mapping

! Subtask 3C--Geophysical Investigation

! Subtask 3D--Soil Gas Survey

! Subtask 3E--Cap Investigation

! Subtask 3F--Source Testing, Test Pits,Soil Samples (perimeter)

! Subtask 3G--Hydrogeologic Investigation

! Subtask 3H--Groundwater Sampling

! Subtask 3I--Residential Well Sampling

! Subtask 3J--Surface Water and Sediment Sampling

! Subtask 3K--Landfill Gas EmissionsSampling

! Subtask 3L--RI-Derived WasteDisposal

• Task 4--Sample Analysis/Data Validation

• Task 5--Data Evaluation

• Task 6--Risk Assessment

• Task 7--Remedial Investigation Report

• Task 8--Remedial AlternativeDevelopment

• Task 9--Alternatives Evaluation

• Task 10--Feasibility Study Report

• Task 11--Treatability Studies

7.1.1 Task 1--Project Planning

Included in this task are limited field investigationactivities, existing data evaluation, development ofthe work plan; obtaining appropriate approvals forthe work plan, budget, and schedule; preparation ofthe sampling and analysis plan (SAP), whichconsists of the Quality Assurance Project Plan(QAPP) and the Field Sampling Plan (FSP);preparation of the Site Safety Plan (SSP); projectmanagement and agency coordination; obtainingeasements and permits, if necessary; and meetingsamong EPA, the State, and the contractor.


A7-2

Development of the RI/FS work plan includesformulation of DQOs, identification of thenecessary RI/FS tasks, and preparation of budgetsand schedules for implementing the proposed RI/FStasks. Results of the existing data evaluation arepresented in Section 2 of this document and resultsof the limited field investigation activities reported inSection 3 were utilized to develop the scope of RIactivities. Potential ARARs and remedial actionalternatives for the example site are discussed inSection 4 of this document. This information wasalso utilized to develop the RI scope.

A SAP will be prepared in conjunction with thework plan that will include a QAPP, FSP, and anSSP for the proposed field activities. The QAPPwill specify the analytical procedures and themethods for analytical choices and data reduction,validation, and reporting. The FSP will indicateproposed sampling locations, collection procedures,and the equipment necessary for sampling andtesting. The procedures outlined in theCompendium of Superfund Field OperationsMethods (U.S. EPA, 1987c) and the Users Guideto the Contract Laboratory Program (U.S. EPA,1988b) will be used to develop the. FSP. Samplecustody procedures, including those related tochain-of custody, also will be delineated in the FSPand will conform to the procedures detailed in theNational Enforcement Investigation Center’sPolicies and Procedures for Sample Control.Preparation of the SSP will also be based onhistorical information, OSHA regulations, andcorporate health and safety policies.

At critical junctures of the project, it will also benecessary to conduct meetings between EPA, thecontractor, and other appropriate parties to discussproject deliverables and the schedule and toevaluate the need for additional studies. Table 7-1summarizes the subject, frequency, participants, andlocations of proposed meetings for all tasks.

7.1.2 Task 2--Community Relations Activities

A community relations plan will be preparedaddressing activities that EPA will conduct withresidents and government officials involved with

the site. The plan will contain the following sections:

• Site description

• History of the site

• Community issues

• Objectives of the community relations plan

• Community relations activities

• Schedule of community relations activitiesthrough ROD

Information presented in the plan will be developedfrom previous work conducted at the site andinterviews conducted with federal, state, and localofficials and residents, as appropriate.

Public meeting contractor support can be providedby issuing Agency-approved public notices,supplying court recorders, and preparation of visualaids. In addition, project updates will be developedto provide information regarding project status. Anupdate will be distributed at the beginning of thefield investigation, and a second once the fieldinvestigation is complete. A proposed plansummarizing the alternative selection process andthe preferred remedial action alternative will beprepared for public comments. A final fact sheetwill be prepared after the ROD is signed to explainthe remedial action alternative selected for the site.

7.1.3 Task 3--Field Investigation

All efforts to prepare for onsite work, with theexclusion of sample analysis, are included in thistask.

7.1.3.1 Subtask 3A--Fieldwork Support

Fieldwork support includes those activities that arenecessary before the field activities can beimplemented. The following sections describe theseactivities and include those associated withsubcontractor and equipment procurement and sitesetup.


A7-3

Table 7-1PROJECT MEETING SUMMARY FOR THE RI/FS AT THE EXAMPLE SITE

Meeting Participants*

TaskBudgeted

UnderSubject ofMeeting

No. of Meetings

Anticipated Pointin Schedule Contractor EPA Region Other

AnticipatedMeeting Location

1 Project kickoff meeting 2 Before initiation of projecttasks

Project manager(PM), task leaders

Remedial projectmanager (RPM),technical advisors,project officer

State representative,Natural ResourceTrustees, ifappropriate

EPA office and thesite

1 Project progressmeetings

6 Quarterly for duration ofRI/FS

PM, task leaders RPM and technicaladvisors (asappropriate)


3 in EPA office3 in contractor’soffice

1 Public meetings 2 Before RI/FS initiation andfollowing EPA issuance of FSreport, and public reviewperiod and comment period

PM RPM, technicaladvisors

PRP and Staterepresentatives

Site

2 Community relationsorganizational meeting

3 Before RI/FS initiation, beforeissuing proposed plan, andbefore issuing final fact sheet

PM, communityrelations specialist

RPM, risk assessmentspecialist

State representative EPA office

3 Discuss field activities 2 During field activities PM, seniorhydrogeologist

RPM hydrogeologist State representative EPA office or at site,if necessary

7 RI Outline Report 1 After RI field data is available

7 Draft RI Report 1 After EPA review of draft RIreport

PM, seniorhydrogeologist, riskassessment specialist

RPM, technicalspecialists


EPA office

8 RA screening 1 During RA screening PM, process engineer RPM, technicalspecialists

State representative Remedialcontractor’s office

10 FS Outline 1 After RA screening

10 Draft FS report 1 After EPA review of draft FSreport

PM, process engineer RPM, technicalspecialist


EPA office

Note:

* Meeting participants may vary depending on the EPA Region.


A7-4

Subcontractor Procurement. Several of theinvestigative activities that will be conducted duringthe course of the RI will require services typicallyprovided by contractors other than those scopingand performing the RI/FS. Services expected to besubcontracted are:

• Construction of decontamination pad

• Provision of trailer for onsite office andmobile laboratory and hookups of electricityand telephone

• Obtaining sample bottles

• Surveying and topographic mapping

• Drilling and installation of monitoring wells

• Geophysical studies

• Excavation of hot spot area test pits

• Fencing of investigation waste storage area

• Commercial laboratory for engineeringdesign analysis (BOD, COD, etc.)

• Geotechnical laboratory analysis

• Removal of RI-derived waste, if necessary

• Treatability studies, as appropriate

Equipment Procurement and Site Setup. Thiselement involves securing and shipping fieldequipment and health and safety equipment/materials onsite and setting up an onsite field officetrailer and support area. A mobile trailer will berented for use as an onsite office and for storingequipment and supplies. This trailer will also housethe onsite mobile laboratory. The trailer will beequipped with air conditioning (fieldwork plannedfor the summer), telephone, water, and electricity.A decontamination pad will also be constructed.

7.1.3.2 Subtask 3B--Surveying and Mapping

A preliminary search for existing maps and aerialphotographs from sources such as the Departmentof Transportation and the U.S. Geological Surveywas made during the evaluation of existing data. Anaerial topographic survey of the site andsurrounding area will be conducted. This aerialsurvey will be field checked by a ground surveycrew who will establish a localized baseline andbenchmark for future sampling and to tie-in newwell locations. Stream contours will also beestablished from water depths. The topographic sitemap covering the 60 acres of the site andimmediate surrounding area will consist of contourlines on 1-foot intervals and use a scale of 1" = 75'.A topographic map with a contour interval of 2 feetand a scale of 1" = 100' will be developed for amuch broader area of 145 acres and will include thesurface-water drainage system. The locations ofsurface features such as power lines, fences, andsewers will also be located on the site map to aid inthe geophysical investigations.

7.1.3.3 Subtask 3C--Geophysical Investigation

Surface geophysical surveys will be performed inthe southeast section of the landfill. The purpose ofthese studies is to confirm suspected landfill areasthat may contain buried hazardous waste drums, toaid in selecting test pit sites, and to delineate theextent of the fill. The need for the geophysicalinvestigation was determined during the scopingactivities where indications of a buried drum areawere identified through review of existing aerialphotographs and interviews with former employees.A magnetometer survey (total field and verticalgradient) will be used to meet these objectives. Itshould be noted, however, that landfills containmany products other than drums that are madeof metal. Therefore, this type of investigationis used only when there is evidence to suggestlarge discrete areas of drum disposal. Whilethe survey cannot specifically distinguishbetween drums and other metal objects,they can delineate areas of buried metalmasses. Subsequent investigations such as the testpits will be used to further explore the specificnature of the buried metal and to investigate


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subsurface soil conditions below areas of wastedisposal.

Magnetometer Survey. A magnetometer surveywill be conducted to determine the location, extent,and relative magnitude of the drum disposal area.Before the survey, a 100-foot by 40-foot grid will belaid out over the southeastern portion of the landfill,which encompasses the area of suspected drumdisposal (Figure 7-1). A magnetometer base stationwill also be established to monitor diurnal changesin the magnetic field (for correction purposes).Once the grid and base station have been located,magnetometer readings will be collected at 20-footcenters using an Magnetometer/Gradiometer. Anyother readings made from locations not marked bya grid flag will be located by positioning a markedtape or rope along the appropriate line.

The magnetometer survey will consist of total fieldmeasurements and vertical magnetic gradientmeasurements. Vertical gradient data are capableof higher resolution than the total field data and willminimize potential noise problems. The total fieldand gradient data will be collected simultaneously.

Upon completion of the magnetometer survey, datawill be corrected for the effects of the diurnalchanges in the local magnetic field. Once this hasbeen done, a magnetic contour map will beprepared to interpret magnetic anomalies.

7.1.3.4 Subtask 3D--Soil Gas Survey

A soil gas survey will be conducted in conjunctionwith the magnetometer survey to locate theboundaries of the drum disposal area. Themagnetometer survey may be inconclusive if thenumber of drums per unit area is low or if thedrums are buried deeply. A soil gas survey will beconcentrated in the southeast corner of the landfill.A soil gas survey, coupled with the mobilelaboratory analysis of the soil gas for a few selectedVOCs, may provide immediate information on thelateral extent of contamination of the soil (primarilyin the liquid solvent disposal area) and possibly thegroundwater. This survey may also minimizethenumber of geotechnical borings and monitoringwells that must be drilled or installed.

Soil gas ground probes will be used to save time andexpense. Ground probes will be driven to thedesired depth and a vacuum pump used to draw asample from the probe. The soil gas samples will becollected in Tedlar bags.

Sample analyses will be furnished by an onsitemobile laboratory. The laboratory will use a gaschromatograph with a photoionization detector.Samples will be analyzed for 1,1-DCE, TCE,1,1,1-TCA, and toluene.

Initially vertical profiles of organic gases present inthe soil pore spaces will be measured and plotted atseveral locations. A sampling depth of at least 4feet will also be selected, based on the measuredvertical profiles. However, sampling probe depthwithin the landfill may be limited by the presence ofburied drums and extreme care must be exercised.Once this constant sampling depth is established,soil gas samples will be collected across a grid.Samples will be collected on a 20-foot by 20-footgrid laid out over an area measuring 200 feet by 200feet. Initially, samples will be collected nearest thesuspected disposal location. Once the location isidentified, sampling on a 10-foot by 10foot grid willbe done to more accurately identify the limits of thearea. In the event that results from the initialvertical profiles do not provide data to sufficientlylocate the solvent plume, the soil gas survey will bediscontinued. A maximum of 80 soil gas sampleswill be taken in the initial effort. An additionalmaximum of 20 soil gas samples will be taken on a100-foot by 100-foot grid to identify the extent ofthe groundwater contamination south of the disposalarea. Depending on the location of the solventdisposal area, this survey may include additionalareas within the landfill.

7.1.3.5 Subtask 3E--Cap Investigation

The cap covers the southern portion of the landfillas shown in Figure 2-1. Because the cap wasengineered and may be used as a component of thefinal cover system, further investigation on itsconstruction is warranted. The objectives of the capinvestigations are to:


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Figure 7-1CAP INVESTIGATIONTEST PIT LOCATIONEXAMPLE SITE


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• Determine the permeability of the existingcap

• Evaluate the susceptibility to damage fromfreezing, drying, and erosion

• Determine thickness of existing cap

Permeability tests performed on undisturbed(Shelby tube) samples will be used to determine theeffectiveness of the cap as it currently exists.Undisturbed and remolded sample permeability anddensity tests will be compared to explore thesusceptibility of the cap soil to damage fromfreezing and drying. Characterization andpermeability testing will also be used to supportevaluation of remedial alternatives such asconstruction of a multilayer cap. These objectivescan be achieved as explained in the followingparagraphs.

A maximum of seven test pits (see Figure 7-1) willbe dug at the site to show the constructed crosssection of the cap. The visual extent of cracking,layering, root-penetration and vegetation successwill be noted when the pits are dug. The test pitswill be hand dug or dug with a narrow-bucketbackhoe and are expected to be about 2 feet deep.A nuclear density gauge will be used to determinein situ density and moisture content at variouslocations across the site. The quantity and locationsof the nuclear density tests will be determined in thefield.

Samples from the test pits will be sent to ageotechnical laboratory for analysis if it isdetermined during the test pit program that the capis a clay cap. A summary of the sampling andanalysis program is presented in Table 7-2. Thesamples will be tested for moisture content and willbe characterized by grain size analysis, andAtterberg limits. One moisture-density relation testwill be performed using a soil sample taken from arepresentative test pit. A flexible-wall permeabilitytest will be performed on a remolded sample,compacted to 95 percent maximum density at theoptimum moisture content. This data will be used todetermine the permeability of the existing cap andwhether the cap has the geotechnical propertiesnecessary to be used as a base if a new cap were

constructed over the existing material.

Shelby tube samples will be taken at each of thetest pit locations. The Shelby tubes will be pushedusing the backhoe bucket that is needed for thehydrogeologic investigation. If the characterizationtests performed on the test pit samples indicatemarkedly different soil types, additional Shelby tubesamples may be necessary. Shelby tube sampleswill be analyzed for in-situ density and moisture.Flexible-wall permeability tests will be performed onsamples taken from the Shelby tubes.

Geotechnical laboratory tests will require monitoringof the procedures and equipment being used.Specifications for each test will be prepared andincluded as part of the drilling subcontract. Thedrilling subcontractor will be responsible forretaining a laboratory (with the remedialcontractor’s approval) who is capable ofconforming to the specifications. A geotechnicalengineer will visit the laboratory at least once toreview the procedures and equipment being used.

Also additional permeability tests on different locallyavailable soils or onsite soil-bentonite clay mixtureswill be performed. This is necessary because it isexpected that a cap will be needed for the currentlyuncapped northern section of the landfill. Andbecause it may be necessary to upgrade the existingcap if it has a high permeability or is geotechnicallyunstable.

After the initial stage of geotechnical investigationand sampling is completed, the results will beevaluated to determine whether or not morefieldwork is needed. Results of the permeabilitytests will be reviewed along with compaction tests.To fully evaluate capping alternatives, it will benecessary to construct test patches of the proposedcover material over the landfill to determine thefeasibility of achieving the desired relativecompaction. Compaction over the landfill may be anissue because of potential problems with the soft(refuse) subgrade.

Landfill settlement will be monitored through-out the RI by surveying changes in benchmarksthat were installed during the Limited FieldInvestigation. If substantial settlement is still


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Table 7-2SUMMARY OF SAMPLING AND ANALYSIS PROGRAM FOR EXISTING CAP AND HOT SPOTS

Medium Analysis

Target Detection

LimitsProposed Analytical

MethodSource of Analysis

No of. Samplesa

Field andRinsateBlanks

TripBlanksb Replicates

AdditionalVolume Needed

forQA/QC Lots

Existing Cap Moisture Contentc,d -- ASTM 2216-80 Geotech Lab 7 -- -- -- –

Permeability Test c,d -- SW 842Method 9100

Geotech Lab 7 -- -- -- –

In Situ Densityc,d – – Geotech Lab 7 -- -- -- --

Atterberg Limitsc,d -- ASTM D4318 Geotech Lab 7 -- -- -- --

Grain Size -- ASTM D422 Geotech Lab 7 -- -- -- --

Hot Spot TCL BNA Extractables CRDL Organic SOW87 CLP-RAS 36 1/dayeach

-- 1/20samples

Double volumeper 20 samples

TCL Pesticides/PCBs CRDL Organic SOW87 CLP-RAS 36 1/dayeach

-- 1/20samples


TCL Volatile Organics CRDL Organic SOW87 CLP-RAS 36 1/dayeach

1/day 1/20samples


TAL Inorganics CRDL Inorganic SOW88 CLP-RAS 36 1/dayeach

-- 1/20samples


Cyanide CRDL Inorganic SOW88 CLP-RAS 36 1/dayeach

-- 1/20samples


Mercury CRDL Inorganic SOW88 CLP-RAS 36 1/dayeach

-- 1/20samples


CRDL -- Contract Required Detection LimitTCL -- Target Compound ListTAL – Target Analyte ListRAS -- Routine Analytical ServiceCLP – Contract Laboratory ProgramBNA -- Base Neutral and AcidaGeotechnical test samples correspond to one sample per cap investigation test pit. Analytical samples for the hot spot area correspond to 12 samples per source (hot spot) test pit.bTrip blanks are only necessary for volatile organic samples.cQC samples are not collected for geotechnical samples. Sample results are reviewed an experienced geotechnical engineer for conformity with the specified ASTM method.dThe proposed analytical method for in situ density is reported in Methods of soil Analysis, Section 13.2.


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occurring, then a temporary cap may need to bedesigned and installed until the settlement rate hasdecreased.

7.1.3.6 Subtask 3F--Source Testing, Test Pits

The objectives of the source testing program are:(1) to evaluate the integrity of the buried drums, (2)determine the extent of contamination ofunsaturated soil in the solvent disposal area, and (3)determine the approximate volume of the hotspot(s). The test pit excavation will be done in theone-half acre area believed to be used for drumdisposal. Personnel will conduct sampling of the testpits in Level B protection.

Test pit depths are limited by the stability ofsubsurface materials and the maximum depth of thebackhoe. Backhoes typically can reach depths of atleast 25 feet below grade, but actual test pit depthsare expected to be less because of soil stabilitylimitations. For this reason, the maximum depth oftest pits is estimated to be 20 feet below grade.Specific excavating equipment cannot be identifieduntil an excavating contractor has been selected,but it will probably be a track-mounted backhoe.Three test pits in the southeastern section of thelandfill will be logged and photographed todocument the subsurface conditions encountered.No attempt will be made to enter the pits, andsamples will be collected directly from the backhoebucket. Excavated portions of the existing cap willbe kept for replacement of the cover and theexcavated waste will be placed on plastic sheets ina separate area from that of the cover material toprevent contamination of surface soils.

If intact or crushed drums are encountered, the fieldexcavation crew will leave them undisturbed.Drums will not be removed from test pits.Drummed materials will not be tested unless drumsare degraded and leaking, as visually evidenced bythe presence of liquids in the test pits around thedrums; samples will be obtained from the backhoe.If a free-floating liquid layer is found, the pit will belined with a sorbent material and closed immediatelyafter samples of the liquid are collected.

Following completion of sampling and test pitlogging, each test pit will be backfilled to grade. Ifa strong contaminant profile is observed in the testpit wall, the field excavation crew will backfill thetest pit to roughly the same condition it was inbefore excavation. The most contaminated materialbased on HNu screening, will be backfilled into thetest pit first with the least contaminated going inlast. Any remaining excavated materials that cannot be placed into the test pit will be left at the testpit location and covered with clean clay fill obtainedfrom an offsite borrow area.

The qualitative data obtained from the fieldscreening will be used in conjunction with visual andstratigraphic information derived from the test pitlogging to select soil samples for submittal to theCLP for analyses. The chemical informationobtained from the CLP analysis will be compared tothe groundwater plume data to identify groundwatercontaminant source areas. The chemicalinformation will also characterize the type andconcentration of contaminants in the source areas.This soil information is necessary to characterizethe potential for future contaminant releases to thegroundwater and to evaluate containment,treatment, and disposal alternatives for the hot spotin the FS.

The proposed location of the test pits is shown inFigure 7-2. A maximum of 36 test pit samples willbe submitted for TCL and TAL analyses. Thisnumber assumes a maximum of 12 samples eachfrom the three test pits. The actual number ofsamples will depend on field observations and actualtest pit depth. Samples will be considered as havinglow or medium concentrations, depending on theHNu readings. Sampling methods and protocol willbe discussed in detail in the SAP. Some or all of thesoil samples may be depth-interval samples.Samples will be selected by depth, based on visualobservations (e.g., soil staining); the concentrationsor types of VOCs detected during the soil gassurvey and stratigraphic relationships. The samplingteam leader will decide on the depth interval afterconsultation in the field with the projecthydrogeologist and chemist. A summary of thesampling and analysis program is presented in Table7-2.


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Figure 7-2SOURCE TEST PITSLOCATIONSEXAMPLE SITE


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information on health and safety concerns for testpit excavations can be found in Compendium ofSuperfund Field Operation Methods (U.S. EPA,1987c).

7.1.3.7 Subtask 3G--HydrogeologicInvestigation

The purpose of the hydrogeologic investigation is toaccomplish the following:

• Refine the conceptual model of thegroundwater flow system in relationship tounderlying hydrostratigraphy

• Evaluate the aquifer properties and itsresponse to pumping

• Locate monitoring wells for the collectionof analytical data to define the type andextent of contamination

• Provide information on pathways for use inthe risk assessment

Based on thorough review of existing data thefollowing investigations are intended to fill in thedata gaps and thereby fulfill the objectives listedabove.

Geotechnical Borings . To refine the conceptualmodel and the subsurface stratigraphic relationships,and to aid in delineating the extent of the VOCplume in the vicinity of the landfill, eight soil borings,will be drilled and sampled (Figure 7-3). Therationale and proposed depth of each boring ispresented in Table 7-3. The number and location ofborings may change depending on the results of theinitial borings. For instance, if soil contamination isfound in borings west or east of the site, based onfield observations and soil gas probe readings,additional borings would be ‘ installed upgradientnorthwest or northeast of the landfill. In the eventthat the stratigraphy is more complex or thegroundwater contamination more extensive thanthat presented in the evaluation of existing data, amaximum of 16 more geotechnical borings may berequired. The location for these borings will bebased on the information developed

from the initial eight soil borings.

All borings will be advanced using a 6.25-inch (ID),screened hollow-stem auger. EPA will beresponsible for obtaining easements and permits atall offsite locations.

Three of the soil borings will be advanced tobedrock, which is expected to be approximately 135feet below ground surface. The other five boringswill be advanced to a depth of about 70 feet belowground surface to determine the stratigraphy of thefill units beneath the south portion of the landfill andsouth of the landfill in the vicinity of the potentialgroundwater migration pathways. Eachgeotechnical boring will be sampled at 5-footintervals using a standard split-spoon samplerfollowing ASTM Standard D-1586 for the StandardPenetration Resistance Test. Boreholes wheremonitoring wells are not installed will be abandonedby injecting a thick bentonite slurry from the bottomof the borings to the ground surface using thetremie method.

Each boring will be logged by an experiencedgeologist, geotechnical engineer, or soil scientist.Samples will be described using the Unified SoilClassification System terminology. Samples will becollected for grain size analysis and/or Atterberglimits based on changes in stratigraphy. Thedecision to submit a sample for geotechnicalanalysis will be made in the field by the supervisinggeologist, engineer, or scientist but in no case willexceed three samples per boring.

Information obtained from the soil boring programwill help to determine the need for additionalmonitoring wells and the depths at which monitoringwells will be installed. This stratigraphic informationis also necessary to identify potential migrationpathways and to evaluate the fate and transport ofreleased contaminants.

Drill cuttings generated during the soil boringprogram will be collected and stockpiled onsite.These cuttings will be covered with clean clay fillobtained from an offsite borrow area. The cuttingswill be consolidated with other waste under the finalcap for the landfill.


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Figure 7-3SOIL BORINGLOCATIONSEXAMPLE SITE


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Table 7-3RATIONALE FOR SOIL BORING LOCATIONS FOR

THE EXAMPLE SITE

Boring Location Proposed Depth Rationale

B-1 Bedrock • Stratigraphy in west side of site where data arescarce, helps determine screen interval formonitoring wells

B-2 70 feet • Stratigraphy in SW portion of the site where dataare scarce, helps determine screen interval formonitoring wells

B-3 70 feet • Helps determine location of downgradientmonitoring nest

B-4 70 feet • Helps determine location of downgradientmonitoring nest, stratigraphy in SW corner of sitewhere data are scarce

B-5 Bedrock • Stratigraphy of potential migration pathways, helpslocate monitoring wells, extent of contamination

B-6 70 feet • Stratigraphy of potential migration pathways, helpslocate monitoring wells, extent of contamination

B-7 70 feet • Downgradient stratigraphy, helps locate monitoringwells, extent of contamination

B-8 Bedrock • Stratigraphy in SE portion of the site, where data arescarce


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Monitoring Well Installation. To better definepotentiometric relationships in the vicinity of the siteand evaluate the extent of groundwatercontamination, 15 new monitoring wells will beinstalled and one existing well nest will be used. Anonsite laboratory will be used during well installationto provide analytical results that will be used toreevaluate the proposed monitoring well network.Groundwater samples will be analyzed for selectedVOCs and inorganic anions (chloride and sulfate) toaid in determining the extent of the groundwaterplume. The inorganic anions are persistentchemicals which can be used as indicators ofleachability and transport. Therefore, mappingelevated levels of these indicator chemicals relativeto upgradient concentrations can give a moreaccurate picture of the movement of thegroundwater and possible extent of the contaminantplume than just VOC analysis. Because ofvolatization, adsorption and degradation, VOCs maydiminish in concentrations more rapidly than theinorganic ions.

Potential locations for the new wells are shown inFigure 7-4. The rationale for each location ispresented in Table 7-4. This rationale is based onthe assumption that subsurface conditions arehomogeneous. If subsurface conditions areheterogeneous, additional wells may be necessary.Also, based on the conceptual site model, it ispossible that the horizontal or vertical extent ofgroundwater contamination may be greater thanthat estimated from existing data and the results ofthe VOC and inorganic ion analysis to be done bythe onsite mobile laboratory, therefore an additionalnumber of monitoring wells may be necessary. Forpurposes of this work plan, a maximum of 15additional wells are estimated. The need for thesewells and their locations will be assessed in the fieldby the project manager in conjunction with EPA’sRPM.

One two-well monitoring well nest will be installedupgradient (background) of the landfill to determineupgradient groundwater quality. A secondmonitoring well nest (with three wells), in additionto the existing onsite landfill well nest, will beinstalled just off the southwest corner of the landfillto evaluate groundwater quality within the landfill.

Because there is an existing well nest onsite, andfor health and safety reasons, installing an additionalwell nest onsite is not proposed. A third (two-well)and a fourth (three-well) nest is proposed tomeasure downgradient groundwater quality. Threesingle wells are proposed to measure the westward,eastward and southerly extent of groundwatercontamination and to investigate the possiblegroundwater mound. One two-well monitoring wellnest is proposed to evaluate the vertical distributionof contaminants downgradient of the landfill and todetermine if a vertical gradient exists.

At least six of the remaining monitoring wells willbe installed in geotechnical borings describedearlier. These monitoring wells will be installedimmediately after completion of the geotechnicalborings at each location. The elevations of eachmonitoring well measuring point will be determinedand water levels recorded. This information isneeded to determine the groundwater flow system.The information obtained from completion of thistask will be important to the analysis of the fate andtransport of constituents released from the landfilland to the identification of contaminant migrationpathways.

The boreholes for the monitoring wells will beadvanced using screened hollow-stem augers(6.25-inch ID). This size allows sufficient annularspace between the well and the auger wall tointroduce a filter pack and seal. If alternative drillingmethods are required, only methods using clearwater, air, or cable tool will be considered.

Following installation, each monitoring well will bedeveloped until substantially free of sediment, anduntil pH and conductivity are stable to thesatisfaction of the project hydrogeologist. Wells willbe developed using the surge-and-bail method. Welldevelopment water will be discharged as describedunder Section 7.1.3.12--RI-Derived WasteDisposal.

During installation of the 15 new wells, groundwatersamples will be collected from three depths(water table, mid-depth, and above bedrock)at each location. These samples will be analyzedby the onsite mobile laboratory for


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Figure 7-4 PROPOSED MONITORING WELL LOCATION EXAMPLE SITE


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Table 7-4RATIONALE FOR MONITORING WELL LOCATIONS

Well Number Proposed Depth Rationale for Location

MW-1S 45 feet Can monitor quality of upgradient groundwater(background)

MW-1M 90 feet

MW-2S 45 feet Can monitor quality of groundwater migratingfrom the landfill (Samples will also be collectedfrom existing onsite well nest.)

MW-2M 90 feet

MW-2D 135 feet

MW-3S 45 feet Can monitor quality of downgradientgroundwater and depth of contamination

MW-3D 135 feet

MW-4S 45 feet Can monitor quality of downgradientgroundwater

MW-4M 90 feet

MW-4D 135 feet

MW-5M 70 feet Can monitor westward extent of groundwatercontamination

MW-6M 70 feet Can monitor eastward extent of groundwatercontamination

MW-7M 70 feet Can monitor southward extent of groundwatercontamination

MW-8S 45 feet Can monitor quality of downgradientgroundwater and depth of contamination

MW-8M 70 feet

Note: Location of monitoring wells are dependent on results from the onsite mobile laboratory and soilgas analysis if performed.


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four selected VOCs--1,1-dichlorethene (1,1-DCE),trichloroethene (TCE), 1,1,1,-trichloroethene (1,1,1-TCA), and toluene, and two inorganic ions--chlorideand sulfate. The results will be plotted on site mapsand will be used to evaluate the new monitoringwell network. If the analytical results indicate highlevels of the four VOCs and the two inorganic ionsfrom the downgradient wells, then additionaldowngradient wells will be installed.

Water Level Monitoring . All new monitoringwells will be surveyed to establish horizontallocation and elevation of the measuring points.Elevation measurements will be taken on the riserpipe with the measuring point designated by a chiselmark. All elevations will be referenced to thebenchmark previously established at the site. Allwells will be located horizontally to within plus orminus 5 feet. Vertical elevations of measuringpoints will be made to the nearest 0.01 foot.

Water levels will be collected at a maximum of onea month from new and existing monitoring wells forthe duration of the RI. This is assumed to be 5months. An electric water-level indicator graduatedin 0.1-foot increments will be used.

Aquifer Tests. The purpose of the aquifer tests isto determine the physical characteristics of theunderlying aquifer sufficiently to allow evaluation ofgroundwater collection alternatives. Both pumpstests and slug tests will be conducted.

This pump test is important for understanding howthe aquifer responds to pumping given the site’sproximity to constant-head boundaries. A 6-inch(minimum) ID, fully penetrating production wellwould be drilled using mud rotary techniques for thepurpose of conducting a 72-hour pump test. Eightmonitoring wells will be used as observation wellsfor this test. Groundwater samples will be collectedduring the pump test for analysis of CLP routineanalysis of TCL organic and TAL inorganicpackages. The layout of the pump and observationwells that will be used for the test is shown byFigure 7-4. The production well will be located in anarea where it could be used later as a groundwaterextraction well. The final location and depth of thescreened interval will be selected in consultation

with the RPM after screening results of thegroundwater and soil samples for the mobilelaboratory are evaluated.

The pump test may generate up to 1,000 gpm for 3days. This volume of water (4.3 million gallons) istoo large to store onsite and will have to bedischarged to the local POTW. Permission willhave to be obtained from the POTW. If permissionis not obtained, the pump test will not be performedand the slug test results will be used to characterizethe hydraulic properties of the aquifer. Thedisadvantage of using only slug tests is that there isa higher degree of uncertainty in the parameterestimates and the influence of constant headboundaries is not determined.

Slug tests will also be performed to measure in-fieldhydraulic conductivity. Slug tests will be completedafter the wells are developed. Tests will beconducted by either withdrawing a known volumeof water or by inserting a cylinder of knowndimension and recording changes in water level atthe time.

7.1.3.8 Subtask 3H--Groundwater Sampling

Information obtained from the new monitoring wellswill be used to study the possible groundwatermound and its effect on contaminant migration, todetermine the vertical and lateral extent of theVOC contamination, and to evaluate sourcecontainment and groundwater extraction andtreatment alternatives.

After well installation and recovery, groundwatersamples will be collected from the new wells andfrom the existing landfill well nest. Groundwatersample collection will begin with the leastcontaminated wells and conclude with the mostcontaminated to prevent cross contamination ofsamples. Samples will be collected from within thehollow-stem auger after purging at least three wellvolumes to remove stagnant water or stratifiedcontaminants and until the pH and conductivity arestable. Purge water will be collected or dischargedon the ground as described in Section 4.2.3.12--RI-Derived Waste Disposal. Groundwaterelevations will be measured before purging wells.Samples from each well will also be


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submitted to the CLP for analysis of routine TCLorganic and TAL inorganic packages, specialanalytical service (SAS) for vinyl chloride as wellas for BOD, COD, TOC, and TDS. Efforts willalso be made to identify Tentatively IdentifiedCompounds (TIC) if they are detected in significantconcentrations since they also could pose a humanhealth risk. Field parameters of pH, temperature,and specific conductance will be measured at thetime of sample collection. Details on samplingmethods, collection of blanks and duplicates,preservation of samples, and sample handling andshipping will be presented in the SAP.

A second round of groundwater sampling will begin4 months after completion of the first round toverify the previous results. Samples will besubmitted to the CLP for the same analysesoutlined above for round one. Field parameters willalso be the same as above. A summary of thesampling and analysis program is presented in Table7-5.

7.1.3.9 Subtask 3I--Residential Well Sampling

Residential wells in the vicinity of the landfill aresampled to verify reported contamination, to provideadditional data as to the extent of contamination,and to identify wells that may not be affected by thecontaminant plume.

To accomplish these objectives, a total of nineresidential wells (shown in Figure 7-5) will besampled during the two rounds of groundwatersampling. Five wells (R1-R5) will be sampled toprovide additional data on the extent of groundwatercontamination; the four remaining residential wells(R6-R9) are not anticipated to be contaminated andwill be sampled only to verify that contaminationhas not migrated to them. Available information onthe 9 wells including well depths and constructiondetails was collected during limited fieldinvestigations.

Grab samples will be obtained from the cold watertaps, at a point prior to treatment, after the wellshave been adequately purged to remove stagnantwater. Samples will be submitted for CLP analysisof routine TCL organic and TAL inorganicpackages, except for the vinyl chloride analysis,

which will require a special analytical service (SAS)request. Efforts will also be made to identify TICs.

Homeowners will be contacted for permission tosample. Their requests with respect to the samplingschedule will be adhered to at all times. A wellinventory form will be completed for each wellsampled.

7.1.3.10 Subtask 3J-Leachate Sampling

There is no existing data on either the observedleachate seep or leachate within the landfill. Theobjectives of the leachate study are to identify theapproximate amount of leachate production and thecomposition of the leachate. Compositioninformation will be used to characterize the leachateand to determine compatibility of leachate treatmentwith groundwater treatment.

The leachate seep located on the west side of thelandfill will be sampled twice. Grab samples will betaken at the toe of the landfill. One sample will betaken at the same time as the surface watersampling presented below. The other sample will betaken in the spring after a wet period when the flowfrom the seep is higher than normal. These twosamples will indicate the range of composition ofthe leachate seep. Leachate seep samples will beanalyzed for TCL organics, TAL inorganics, BOD,COD, pH, TDS, and oil and grease.

Water quality and wellhead data from thegroundwater monitoring wells will be used to aid inthe estimation of leachate composition andproduction. The data from the shallow well withinthe landfill will be a useful source of this data,Sampling of these wells was covered under Subtask3H. A summary of the sampling and analysisprogram is presented in Table 7-5.

7.1.3.11 Subtask 3K--Surface Water andSediment Sampling

No existing data on surface water and sedimentcontamination of the unnamed tributary to the PolkRiver are available. As discussed in Section 4.3 ofthis appendix, site contaminants may have migratedby way of surface runoff and groundwaterrecharge. To determine if this has


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Table 7-5SUMMARY OF SAMPLING AND ANALYSIS PROGRAM FOR GROUNDWATER

Medium Analysis

Target Detection

Limits

ProposedAnalytical Method

Source of Analysis

No. ofSamplesa


TripBlanksb Replicates


forQA/QC Lots

Groundwater TCL BNA Extractables CRDL 625 CLP-RAS 52 1/dayeach

-- 1/20 samples Triple volumeper 20 samples

TCL Pesticides/PCBs CRDL 625 CLP-RAS 52 1/dayeach

-- 1/20 samples Triple volumeper 20 samples

TCL Volatile Organics (prepurgeand purged samples)

0.5 ppb 524.2 CLP-SAS 52 1/dayeach

1/day 1/20 samples Triple volumeper 20 samples

TAL Inorganics - Metals

CRDL 200.7 CLP-RAS 52 1/dayeach

-- 1/20 samples Double volumeper 20 samples

- Cyanide CRDL 335.2 CLP-RAS 52 1/dayeach

1/20 samples Double volumeper 20 samples

Biochemical OxygenDemand (BOD)

-- 507 Non-CLP 34 -- -- 1/20 samples –

Chemical OxygenDemand (COD)

-- 410 Non-CLP 34 -- -- 1/20 samples –

Total dissolvedSolids (TDS)

-- 209 Non-CLP 34 -- -- 1/20 samples –

Total Organic Carbon(TOC)

-- 415.1 Non-CLP 34 -- -- 1/20 samples --

CRDL -- Contract Required Detection LimitTCL -- Target Compound ListTAL – Target Analyte ListSAS -- Special Analytical ServiceRAS -- Routine Analytical ServiceCLP – Contract Laboratory ProgramBNA -- Base Neutral and AcidTOC-- Total Organic CarbonaTwo rounds of sampling from 26 wells (15 new wells, 2 existing wells, 9 residential wells). Only the 17 monitoring wells (not residential wells) will be analyzed for BOD, COD TDS,and TOC.bTrip blanks are only necessary for volatile organic samples.


A7-20

Figure 7-5RESIDENTIAL WELLSAMPLING LOCATIONEXAMPLE SITE


A7-21

happened, four surface water and sediment sampleswill be collected from the stream and submitted forCLP analysis of routine TCL organics and TALinorganics and toxicity testing. One of the samplinglocations will be upgradient of the landfill todetermine background levels in the river. Twolocations will be along the banks of the river closestto the landfill and the remaining location will bedowngradient of the landfill. These locations areshown in Figure 7-6. The sampling will occur inmidsummer during a period of relatively low streamflow to determine maximum groundwater impact onthe stream. A summary of the sampling andanalysis program is presented in Table 7-6.

7.1.3.12 Subtask 3L--Landfill Gas EmissionsSampling

Significant amounts of methane and other gasessuch as vinyl chloride are typically generated bydecomposition of the materials within the landfill.These gases will be sampled during Phase I tosupport an evaluation of the extent of gas migrationinto the soil surrounding the landfill and the rate ofcontaminant emissions to the ambient air. Toaccomplish this objective, eight onsite gas probeswill be installed within the landfill, six offsite gasprobes will be installed along the southern border ofthe site near the residential area, and three offsitegas probes will be installed along the northernborder. The proposed landfill gas sampling locationsare shown in Figure 7-7.

The probes will be placed to a depth of at least 5feet. The collection procedures for methane gas arethe same as those described in Section 7.1.3.4 forsoil gas sampling.

7.1.3.13 Subtask 3M--RI-Derived WasteDisposalWastes derived from the RI field tasks will include:drill cuttings from monitoring well installation; waterproduced from equipment decontamination, welldevelopment, groundwater sampling, and aquifertesting. Field clothes and assorted trash will also bestored, but separately from the other waste, for finaldisposal.

Cuttings will be generated as the monitoring wellsare drilled. Some monitoring wells will be cored fortheir entire length; therefore, most material removedfrom these holes will be as core and will be retainedfor logging and future reference. All cuttings will becollected and stockpiled onsite. These cuttings willneed to be addressed when the final alternative isimplemented.

All water generated during equipmentdecontamination and well development will bestored onsite. Water from the pump test will need tobe discharged to the local POTW because thequantities are too large for onsite Storage.

Drilling equipment decontamination will typicallyconsist of high-pressure steam cleaning. An areawill be designated at the site for this purpose andberms will be built around the area for runoffcontrol. The area will be lined with an HDPE linerand the water collected for storage.

7.1.4 Task 4--Sample Analysis and DataValidation

7.1.4.1 Subtask 4A--Onsite MobileLaboratory

This subtask includes mobilization, operation, anddemobilization of the mobile laboratory at the landfillsite. The mobile laboratory will be used forscreening groundwater and soil samples for targetVOCs using a portable gas chromatograph unit. Allanalytical data will be tabulated and organized foragency review in the field. The screening data willbe used to direct other field operations, includingfuture drilling on monitoring wells and test pitsampling. Samples will be selected for CLP analysisbased on screening results.

7.1.4.2 Subtask 4B--Data Validation

Upon completion of sample analysis, SampleManagement Office (SMO) receives thedata packages from the CLP laboratoriesand distributes them to the Contract ProjectManagement Section (CPMS) of the RegionalEnvironmental Services Division (ESD). The


A7-22

Figure 7-6SURFACE WATERSAMPLING LOCATIONSEXAMPLE SITE


A7-23

Table 7-6SUMMARY OF SAMPLING AND ANALYSIS PROGRAM FOR

SURFACE WATER, SEDIMENT, AND LANDFILL GAS

Medium Analysis

Target Detection

Limits

ProposedAnalytical Method

Source of Analysis

No of. Samples


TripBlanks Replicates


forQA/QC Lots

Leachate (Seep)

TCL BNA Extractables CRDL 625 CLP-RAS 2 1/dayeach

-- 1/20 samples Triple volume per 20 samples

TCL Volatile Organics CRDL 624 CLP-RAS 2 1/dayeach

1/day 1/20 samples Triple volume per 20 samples

TAL Inorganics CRDL 200.7 CLP-RAS 2 1/dayeach

-- 1/20 samples Double volume per 20 samples

Surface Water(Stream)







Sediment (Stream)







Landfill Gas Methane, TCE, VC * T014 non-CLP 17 -- -- 1/20 samples --

CRDL – Contract Required Detection LimitTCL -- Target Compound ListTAL – Target Analyte ListTCE – Trichlorethylene*The target detection limit for methane is dependent on the volumeof gas sampled and should be established for each sampling event.

VC -- Vinyl ChlorideRAS -- Routine Analytical Service CLP – Contract Laboratory ProgramBNA -- Base Neutral and Acid


A7-24

Figure 7-7LANDFILL GAS SAMPLINGTEST PIT LOCATIONEXAMPLE SITE


A7-25

CPMS reviews all data packages resulting fromregional sampling efforts.

After the ESD-reviewed data packages arereceived they will be reviewed before interpretationby the project staff. Any data noted in the reviewthat should be qualified will be flagged with theappropriate symbol. Results for field blanks andfield duplicates will also be reviewed (these may ormay not be considered by the CPMS) and the datafurther qualified if necessary. The data set as awhole will also be examined for consistency,anomalous results, and whether or not the data arereasonable for the samples involved.

Any limitations on the use of the analytical databased on the data review and the CLP QA/QCcomments will be identified. Limitations of theanalytical data will be presented in the RI report.

7.1.5 Task 5--Data Evaluation

Specific analyses and evaluations to be performedunder the Data Evaluation subtask will include:

• Preparing groundwater contour plots for allidentified hydrostratigraphic units

• Computing vertical and horizontal hydraulicgradients and evaluating groundwater flowdirection in each stratigraphic unit

• Generating figures showing spatial and,when applicable, temporal distributions ofcontaminants in soil and groundwater

7.1.6 Task 6--Risk Assessment

The risk assessment will be consistent with EPAmethods as outlined in the documents RiskAssessment Guidance for Superfund, VolumeI--Human Health Evaluation Manual (Part A)(U.S. EPA, 1989b) and Risk AssessmentGuidance for Superfund, Volume II--Environmental Evaluation Manual (U.S. EPA,1989c). The results of the assessment will beincluded as a chapter in the RI Report, Supportingrisk, transport, and fate calculations will beappended, and relevant references will be cited.

Based on the risk assessment, EPA will developcleanup levels to guide the selection of remedialmeasures for media where either ARARs do notexist or where the ARARs are not protective.These proposed criteria will be developed by EPAwith contractor input on the technical issues.

7.1.7 Task 7--Remedial Investigation Report

A report summarizing RI activities and findings willbe prepared and submitted to the EPA for reviewand comment. Early chapters of the reportsummarizing the field investigation activities and theanalytical data will be submitted to U.S. EPA asearly as possible to aid in identification of ARARswhich will be finalized during the FS. The RI reportwill also be submitted to the Agency for ToxicSubstance and Disease Registry to assist in theirhealth assessment of the site. The RI report will beprepared in accordance with the current RI/FSGuidance (U.S. EPA, 1988a).

7.1.8 Task 8--Remedial Action AlternativeDevelopment

The purpose of developing remedial actionalternatives is to produce a reasonable range ofwaste management options to be analyzed morefully in the detailed analysis of alternatives.Developing alternatives includes the followingelements:

• Establishing remedial action objectives

• Developing general response actions

• Identify and screen technologies andprocess options

• Combining medium-specific technologies toform alternatives

• Screening alternatives, if necessary

Section 4.1 of this appendix presents thepreliminary identification of remedial actionsalternatives for the example site. The preliminaryremedial action objectives and subsequent remedialaction alternatives are based on resultsof the limited site investigation, preliminary


A7-26

remedial goals, experience at municipal landfill sites,and engineering judgment.

These preliminary remedial action alternatives willbe refined on the basis of the information collectedduring the RI. Additional alternatives such as directremediation of surface water and sediments mayneed to be developed depending on the findings ofthe risk assessment. As required, a no-actionalternative will also be retained through thedevelopment and evaluation of the alternativesprocess.

Sections 5 and 6 in the body of this report(Conducting Remedial Investigations/FeasibilityStudies for CERCLA Municipal Landfill Sites)should be referred to for additional information onthe development, evaluation, and selection ofremedial action alternatives for the example site.

7.1.9 Task 9--Alternatives Evaluation

The final alternatives will be evaluated to provideEPA with a framework with which to select aremedy for the site. The detailed analysis of thesealternatives will be conducted in three stages:further refinement, individual analysis, andcomparative analysis.

Further refinement of the alternatives will includedeveloping detailed information such as:

• Identifying design parameters fortechnology components such as landfill capand groundwater treatment system

• Quantifying amounts of contaminated soils(and possibly sediments) to be handled

• Estimating time of implementation forconstruction activities

• Estimating O&M requirements, particularlyfor a groundwater pump and treatmentsystem and a landfill gas treatment system

• Process sizing

This information will be used to develop a costestimate to within +50 percent to -30 percent.

During the individual analysis, each alternative will

be evaluated with respect to the following nineevaluation criteria:

• Overall protection of human health and theenvironment

• Compliance with ARARs

• Long-term effectiveness and permanence

• Reduction of toxicity, mobility, or volumethrough treatment

• Short-term effectiveness

• Implementability

• Cost

• State acceptance

• Community acceptance

Detailed descriptions of each of the above criteriaare reported in the RI/FS Guidance (U.S. EPA,1988a).

Following the individual analysis, a comparativeanalysis will be performed. The comparativeanalysis will lead to the development of adescription of the strengths and weaknesses of thealternatives relative to one another. Not all thecriteria will be used in this evaluation; just those thatillustrate significant differences among thealternatives. As part of this evaluation, there will bean analysis of how a change in the uncertainties orassumptions made in the analysis may change theperformance of the alternatives.

7.1.10 Task 10--Feasibility Study Report

Following completion of the detailed evaluation task,the Contractor will prepare and submit a draft FSreport for the example site to EPA for review andcomment. The report will summarize FS activitiesand RI site characterization results and will beprepared in accordance with RI/FSGuidance (U.S. EPA, 1988a). Informationdeveloped during the FS such as identificationof ARARs, detailed description of alternatives,and detailed evaluation of alternatives will


A7-27

be provided to EPA for review as these items arecompleted, in order to obtain input from the Agencyduring the evaluation process.

7.1.11 Task 11--Treatability Studies

Any necessary laboratory, bench, or pilot scaletreatability studies required to evaluate theeffectiveness of remedial technologies and establishengineering criteria will be identified as early aspossible. Should laboratory studies be required, atesting plan for the studies will be prepared andpresented to EPA for review

and approval. This testing plan will identify thetypes and goals of the studies, the level of effortneeded, a schedule for completion, and the datamanagement guidelines. Upon EPA approval, a testfacility and any necessary equipment, vendors, andanalytical services will be procured. Uponcompletion of the testing, the results will beevaluated to assess the technologies with respect tothe goals identified in the test plan. A reportsummarizing the testing program and its results willbe prepared and presented in the final FS report.


A8-1

Section 8COST AND KEY ASSUMPTIONS

The work plan should present a section that contains a cost estimate for conducting the RI/FS.The key assumptions used in preparing this estimate should also be presented. This section willfollow the same approach used in all RI/FS work plans and is not discussed here because it iscovered in the RI/FS guidance (U.S. EPA, 1988a).


A9-1

Section 9SCHEDULE

The schedule preparation for municipal landfill sites does not differ in approach from typicalRI/FS work plans and is therefore not presented in this example.


A10-1

Section 10PROJECT MANAGEMENT

Project management activities, such as staffing and coordination for municipal landfill sites,does not differ in approach from other types of sites and is therefore not covered in thisexample.


A11-1

Section 11BIBLIOGRAPHY

U.S. Environmental Protection Agency, National Enforcement Investigation Center (NEIC).Policies and Procedures for Sample Control. 1986.

U.S. Environmental Protection Agency. Data Quality Objectives for Remedial ResponseActivities. EPA/540/6-87/003. March 1987a.

U.S. Environmental Protection Agency. Health Advisories for 25 Organics . March 1987b.

U.S. Environmental Protection Agency. Compendium of Superfund Field OperationsMethods. EPA/540/P-87/001. December 1987c.

U.S. Environmental Protection Agency. Guidance for Conducting Remedial Investigationsand Feasibility Studies under CERCLA. Interim Final. EPA/540/G-89/004. October 1988a.

U.S. Environmental Protection Agency. User's Guide to the Contract Laboratory Program.EPA/540/8-89/012. December 1988b.

U.S. Environmental Protection Agency. Integrated Risk Information System. June 1989a.

U.S. Environmental Protection Agency. Interim Final, Risk Assessment Guidance forSuperfund, Volume 1, Human Health Evaluation Manual, Part A. December 1989b.

U.S. Environmental Protection Agency. Risk Assessment Guidance for Superfund. VolumeII. Environmental Evaluation Manual. Interim Final. EPA/540/1-89/001. March 1989c.


Appendix B

Remedial Technologies Usedat Landfill Sites


B-1

Appendix B-1RODS REVIEWED FOR THE MUNICIPAL LANDFILL STUDY

Page 1 of 5

Region Site ROD Date(s)

Region I Auburn Road Landfill, NH 9/17/869/29/89

Beacon Heights, CT 9/23/85

Charles George, MA 12/29/837/11/859/29/88

Davis Liquid, RI 9/29/87

Iron Horse, MA 9/15/88

Kellogg-Deering Well Field, CT 9/17/869/29/89

Landfill & Resource Recovery, RI 9/29/88

Laurel Park, CT 6/30/88

Old Springfield, VTa 9/22/88

Winthrop Landfill, ME 11/22/85

Region II Combe Fill North, NJ 9/29/86

Combe Fill South, NJ 9/29/86

Florence Landfill, NJ 6/27/86

GEMS Landfill, NJ 9/27/85

Helen Kramer, NJ 9/27/85

Kin-Buc Landfill, NJ 9/30/88

Lipari Landfill, NJ 8/03/829/30/857/11/88

aSource control ROD has not yet been completed; only groundwater remedy (i.e., management of migration) has been implemented.


B-2


Page 2 of 5


Region II(Continued)

Lone Pine Landfill, NJ 9/28/84

Ludlow Sand & Gravel, NY 9/30/88

Old Bethpage, NY 3/14/88

Port Washington Landfill, NY 9/30/89

Price Landfill, NJa 9/20/839/29/86

Ringwood Mines, NJ 9/29/88

Sharkey Landfill, NJ 9/29/86

South Brunswick Landfill, NJ 9/27/87

Volney Landfill, NY 7/31/87

Region III Army Creek, DE 9/29/86

Blosenski Landfill, PA 9/29/86

Craig Farm Drum, PA 9/29/89

Delaware Sand & Gravel, DE 4/29/88

Dorney Road Landfill, PA 9/29/88

Henderson Road, PA 6/01/889/29/89

Enterprise Avenue, PA 5/10/84

Heleva Landfill, PA 3/22/85

Industrial Lane, PAa 9/29/86

Moyer Landfill, PA 9/30/85

Reeser’s Landfill, PA 3/20/89



B-3


Page 3 of 5


Region III(Continued)

Strasburg Landfill, PA 3/30/89

Tybouts Corner, DE 3/06/86

Wildcat Landfill, DE 6/29/889/30/88

Region IV Airco, KY 6/24/88

Amnicola Dump, TN 3/30/89

Davie Landfill, FL 9/30/85

Goodrich, KY 6/24/88

Hipps Road Landfill, FL 9/03/86

Kassouf-Kimberling, FL 9/30/89

Lees Lane Landfill, KY 9/25/86

NW 58th Street Landfill, FL 9/21/87

Newport Dumpsite, KY 3/27/87

Powersville Landfill, GA 9/30/87

Region V Belvidere Landfill, IL 6/29/88

Bowers Landfill, OH 3/31/89

Cemetery Dumps, MI 9/11/85

Cliff/Dow Dumps, MI 9/27/87

Coshocton City Landfill, OH 6/17/88

E.H. Schilling, OH 9/29/892/29/84

Forest Waste, MI 3/31/88



B-4

Appendix B-1RODS REVIEW FOR THE MUNICIPAL LANDFILL STUDY

Page 4 of 5


Region V(Continued)

Fort Wayne, IN 8/26/88

Industrial Excess, OH 9/30/877/17/89

Ionia City Landfill, MI 9/29/88

Kummer Landfill, MN 6/12/859/30/88

Lake Sandy Jo, IN 9/26/86

Liquid Disposal, MI 9/30/87

Marion/Bragg, IN 9/30/87

Mason County, MI 9/28/88

Metamora Landill, MI 9/30/86

Miami County, OH 6/30/89

Mid-State, WI 9/30/88

New Lyme Landfill, OH 9/27/85

Northside, IN 9/25/87

Oak Grove Landfill, MN 9/30/88

Schmalz Dump, WI 8/13/859/30/87

Spiegelberg, MI 9/30/86

Wauconda Sand & Gravel, IL 9/30/86

Windom Dump, MN 9/29/89



B-5


Page 5 of 5

Region Site RODDate(s)

Region VI Bayou Sorrel, LA 11/14/86

Cecil Lindsey, AR 4/23/86

Cleve Reber, LA 3/31/87

Compass Industries, OK 9/29/87

Industrial Waste Control, AR 6/28/88

Region VII Arkansas City Dump, KS 9/21/89

Conservation Chemical, MO 9/27/87

Doepke Disposal, KS 9/21/89

Fulbright/Sac River Landfill, MO 9/30/88

Todtz, Lawrence Farm, IA 11/4/88

Region VIII Marshall Landfill, CO 9/26/86

Region IX Jibboom Junkyard, CA 5/09/85

Operating Industries, CA 7/31/87

11/16/87

9/30/88

Ordoy Disposal Site, GUAM 9/28/88

Region X Colbert Landfill, WA 9/29/87

Commencement Bay South Tacoma Channel, WA 3/31/88

Northside Landfill, WA 9/30/89

aSource control ROD has not yet been completed; only groundwater remedy (i.e.,management of migration) has been implemented.


11/14/90

B-6

Appendix B2Remedial Technologies Used at Landfill Sites

GENERAL RESPONSE ACTION/ Region I

Remedial Technologies Auburn Beacon Charles Davis Iron Kellogg Landfill & Laurel Old Winthrop Region I

Process Options Road Heights George Liquid Horse Deering Res. Rec. Park Springfield Landfill Total

SOILS/LANDFILL CONTENTS

NO ACTION 0ACCESS RESTRICTION X X X X 4

Deed Restrictions X X 2

Land Use Restrictions X 1

Fencing X X X 3

CONTAINMENT X X X X X X X 7

Surface Controls X X X 3

Grading X 1

Revegetation X X 2

Cap X X X X X X 6

Clay Barrier X 1

Multibarrier X X X X X 5

Soil X 1

Synthetic Membrane X X 2REMOVAL/DISPOSAL X X X X 4

Excavation X X X X 4Mechanical Excav. 0Drum Removal 0Consolidation X 1

Disposal Onsite 0RCRA Type Landfill 0

Disposal Offsite X 1

SOIL TREATMENT 0

Biological Treatment 0

Physical Treatment 0

Thermal Treatment X 1Incineration X 1

Offsite Treatment 0

RCRA Incinerator 0

IN-SITU TREATMENT X 1

Biodegradation X 1

Vitrification 0

Physical Treatment X 1

Solidification/fixation 0

Vapor Extraction X 1


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B-7


GENERAL RESPONSE ACTION/ Region IRemedial Technologies Auburn Beacon Charles Davis Iron Kellogg Landfill & Laurel Old Winthrop Region I


GROUNDWATERAND LEACHATE

NO ACTION 0Attenuation 0Observation 0

MONITORING X X X X X X X 7INSTITUTIONAL CONTROLS X X X X X 5Alternate Water Supply X X X X X 5CONTAINMENT 0Vertical Barriers 0

Slurry Wall 0Horizontal Barriers X 1COLLECTION X X X X X X X 7Extraction X X X X X X X 7

Extraction Wells X X 2Ext/Injection Wells 0

Leachate Collection X X X 3Collection trench X 1Leachate Drain X X 2

Onsite Discharge 0Aquifer Reinjection 0Surface Discharge 0Dewatering 0

Offsite Discharge X 1POTW X 1Land Application 0

TREATMENT X X X X 4Biological Treatment X 1

Activated Sludge 0Chemical Treatment X X X 3

Oxidation X 1Ion Exchange Treatment X 1

Coagulant Addition X 1Metals Preciptation X X 2pH Adjustment 0

Physical Treatment X X X X 4Adsorption X X X X 4Air Stripping X X X 3Sedimentation 0Sand filtration 0Flocculation 0Lime pretreatment 0

Offsite Treatment X 1POTW X 1


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B-8


GENERAL RESPONSE ACTION/ Region IRemedial Technologies Auburn Beacon Charles Davis Iron Kellogg Landfill

&Laurel Old Winthrop Region I


LANDFILL GAS

COLLECTION X X 2Passive Systems X X X X 4

Pipe Vents 0Trench Vents 0

Active Vents X 1Extraction Wells X 1Blowers 0

TREATMENT X 1Thermal Destruction X X 2

Flaring X 1Activated carbon 0MONITORING X X 2

SURFACE WATERAND SEDIMENTS

Stormwater controls X 1Diversion X 1

Removal Disposal (sediments) X 1Excavation X 1

Offsite Disposal (sediments) 0Treatment X 1

Solidification X 1Dewatering X 1Thermal treatment 0


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B-9


GENERAL RESPONSE ACTION/ Region II GloucesterRemedial Technologies Combe Fill Combe Fill Florence Environ. Helen Kin-Buc Lipari Lone Ludlow Old Port Price Ringwood Sharkey South Volney Region II

Process Options North South Land Recon. Mgmt. (GEMS) Kramer Landfill Landfill Pine Sand Bethpage Washington Landfill Mines Landfill Brinswick Landfill Total


NO ACTION 0ACCESS RESTRICTION X X X X X X 6Deed Restrictions 0Land Use Restrictions 0Fencing X X X X X X X X X 9CONTAINMENT X X X X X X X X X X X X 12Surface Controls X X X X X X 6

Grading X X X X 4Revegetation X 1

Cap X X X X X X X X X X X X X 13Clay Barrier X X X X X X 6Multibarrier X X X X X X 6Soil X X 2Synthetic Membrane X 1

REMOVAL/DISPOSAL X 1Excavation X X 2

Mechanical Excav. X 1Drum Removal 0Consolidation 0


Disposal Offsite 1SOIL TREATMENT X 0Biological Treatment 0Physical Treatment 0Thermal Treatment X 1

Incineration 0Offsite Treatment 0

RCRA Incineration 0IN-SITU TREATMENT 0

Biodegradation 0Vitrification 0

Physical Treatment X 1Solidification/fixation X 1

Vapor Extraction 0


11/14/90

B-10



Process Options North South Land Recon. Mgmt. (GEMS) Kramer Landfill Landfill Pine Sand Bethpage Washington Landfill Mines Landfill Brinswick Landfill Total


NO ACTION X 1Attenuation X 1Observation 0

MONITORING X X X X X X X X X X X 11INSTITUTIONAL CONTROLS X 1Alternate Water Supply X X 2CONTAINMENT X X X X X X X 7Vertical Barriers X X X X X X X 7

Slurry Wall X X X X X X X 7Horizontal Barriers 0COLLECTION X X X X X X X X X X X 11Extraction X X X X X X X X X X X X X 13

Extraction Wells X X X X X X X 7Ext/Injection Wells X 1

Leachate Collection X X X X X X X X 8Collection trench X X X 3Leachate Drain X X X X 4

Onsite Discharge 0Aquifer Reinjection X 1Surface Discharge 0Dewatering X X 2

Offsite Discharge X X 2POTW X X 2Land Application 0

TREATMENT X X X X X X X X X 9Biological Treatment X X X 3

Activated Sludge 0Chemical Treatment X X X X 4

Oxidation 0Ion Exchange Addition 0Coagulant Addition 0Metals Preciptation X X X 3PH Adjustment X 1

Physical Treatment X X X X X X X X 8Adsorption X X 2Air Stripping X X X X X X 6Sedimentation X X 2Sand filtration 0Flocculation X X 2Lime pretreatment X 1

Offsite Treatment X X X X X X 6POTW X X X X X X 6


11/14/90

B-11



Process Options North South Land Recon. Mgmt. (GEMS) Kramer Landfill Landfill Pine Sand Bethpage Washington Landfill Mines Landfill Brunswick Landfill Total

LANDFILL GAS

COLLECTION X X X X X X X X 8Passive Systems X X X X X 5

Pipe Vents X 1Trench Vents X X X X 4

Active Vents X X X X X 5Extraction Wells X X X 3Blowers X X X X 4

TREATMENT X X X X 4Thermal Destruction X X X X X 5

Flaring X X X 3Activated carbon X X X 3MONITORING X X X X X 5


Stormwater controls X X X X X 5Diversion 0

Removal Disposal (sediments) X X X 3Excavation X X X 3

Offsite Disposal (sediments) X 1Treatment 0

Solidification 0Dewatering X X 2Thermal treatment X 1


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B-12


GENERAL RESPONSE ACTION/ Region IIIRemedial Technologies Army Blosenski Craig Delaware Dorney Enterprise Heleva Henderson Industrial Moyer Reeser’s Stratsburg Tybouts Wildcat Region III

Process Options Creek Landfill Farm Sand Road Avenue Landfill Road Lane Landfill Landfill Landfill Corner Landfill Subtotal


NO ACTION X 1ACCESS RESTRICTION X 1Deed Restrictions X 1Land Use Restrictions X 1Fencing 0CONTAINMENT X X X X X X X X X X X X 12Surface Controls X X X X 4

Grading X X X 3Revegetation X X 2

Cap X X X X X X X X X X X 11Clay Barrier X X X X 4Multibarrier X X X X X X 6Soil X X 2Synthetic Membrane 0

REMOVAL/DISPOSAL X X 2Excavation X X X X X 5

Mechanical Excav. X X 2Drum Removal X X X 3Consolidation 0

Disposal Onsite 0RCRA Tyoe Landfill 0

Disposal Offsite X 1SOIL TREATMENT X X 2Biological Treatment 0Physical Treatment X 1Thermal Treatment X 1

Incineration X 1Offsite Treatment 0

RCRA Incinerator 0IN-SITU TREATMENT X 1


Physical Treatment X X X 3Solidification/fixation X X 2Vapor Extraction X 1


11/14/90

B-13





NO ACTION X 1Attenuation 0Observation 0

MONITORING X X X X X X 6INSTITUTIONAL CONTROLS X 1Alternate Water Supply X X X X 4CONTAINMENT 0Vertical Barriers 0

Slurry Wall 0Horizontal Barriers 0COLLECTION X X X X 4Extraction X X X X 4

Extraction Wells X X X 3Ext/Injection Wells X 1

Leachate Collection X X X X 4Collection trench X X X X 4Leachate Drain X X X 3


Offsite Discharge 0POTW 0Land Application X 1

TREATMENT X X X 3Biological Treatment X 1

Activated Sludge X 1Chemical Treatment 0

Oxidation 0Ion Exchange Treatment 0Coagulant Addition 0Metals Precipitation 0PH Adjustment 0

Physical Treatment X X X 3Adsorption X X 2Air Stripping X X 2Sedimentation X 1Sand filtration 0Flocculation 0Lime pretreatment X 1



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B-14




LANDFILL GAS

COLLECTION X X X X 4Passive Systems X X X 3

Pipe Vents 0Trench Vents X X 2

Active Vents X X 2Extraction Wells X 1Blowers 0

TREATMENT X 1Thermal Destruction X 1

Flaring 0Activated carbon 0MONITORING X X X 3


Stromwater controls 0Diversion X X X 3

Removal Disposal (sediments) 0Excavation 0

Offsite Disposal (sediments) X 1Treatment 0

Solidification 0Dewatering 0Thermal treatment 0


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B-15


GENERAL RESPONSE ACTION/ RegionIV

Remedial Technologies Airco Amnicola Davie B.F. Hipps Kassouf- Lees NW58th

Newport Powersville Region IV

Process Options Landfill Dump Landsfill

Goodrich Road Kimerling Lane St. LF Dumpsite Landfill Total


NO ACTION 0ACCESS RESTRICTION X X X X 4Deed Restriction X X 2Land Use Restriction X X X X 4Fencing X X X 3CONTAINMENT X X X X X X X 7Surface Controls X X X X X 5

Grading X X 2Revegetation X X 2

Cap X X X X X X X X 8Clay Barrier X X X X X 5Multibarrier X 1Soil X 1Synthetic Membrane 0

REMOVAL/DISPOSAL 0Excavation X X X X 4

Mechanical Excav. X X 2Drum Removal X 1Consolidation X 1

Disposal Onsite X X 2RCRA Type landfill X 1

Disposal Offsite 0SOIL TREATMENT 0Biological Treatment 0Physical Treatment 0Thermal Treatment 0


RCRA Incinerator 0IN-SITU TREATMENT 0


Physical Treatment X X X 3

Solidification/fixationX X 2

Vapor Extraction X X 2


11/14/90

B-16



Remedial Technologies Airco Amnicola

Davie B.F. Hipps Kassouf- Lees NW58th

Newport Powersville Region IV

Process Options Landfill Dump Landfill Goodrich Road Kimerling Lane St. LF Dumpsite Landfill Total



MONITORING X X X X X X X 7INSTITUTIONAL CONTROLS X X X X 4Alternate Water Supply X X X 3CONTAINMENT 0Vertical Barriers 0

Slurry Wall 0Horizontal Barriers 0COLLECTION X X X X 4Extraction X X X X 4

Extraction Wells X X X 3Ext/Injection Wells 0

Leachate Collection X X X X 4Collection trench X 1Leachate Drain X X 2


Offsite Discharge 0POTW 0Land Application 0

TREATMENT X X X 3Biological Treatment X 1

Activated Sludge 0Chemical Treatment 0

Oxidation 0Ion Exchange Treatment 0Coagulant Addition 0Metals Perciptation 0

pH Adjustment 0Physical Treatment X X X 3

Adsorption X X 2Air Stripping X X X 3Sedimentation 0Sand filtration 0Flocculation 0Lime pretreatment 0

Offsite Treatment X X 2POTW X X 2


11/14/90

B-17



Remedial Technologies Airco Amnicola Davie B.F. Hipps Kassouf- Lees NW 58th Newport Powersville RegionIV

Process Options Landfill Dump Landfill Goodrich Road Kimerling Lane St. LF Dumpsite Landfill Total

LANDFILL GAS

COLLECTION X X 2Passive Systems X X 2

Pipe Vents 0Trench Vents X X 2

Active Vents 0Extraction Wells 0Blowers 0

TREATMENT 0Thermal Destruction 0

Flaring 0Activated carbon 0MONITORING X 1


Stormwater controls X 1Diversion 0


Offsite Disposal (sediments) 0Treatment X 1

Solidification X 1Dewatering X 1Thermal treatment 0


11/14/90

B-18


GENERAL RESPONSE ACTION/ Region VRemedial Technologies Belvidere Bowers Cemetery Cliff/Dow Coshocton E. H. Forest Fort Industrial Ionia Kummer Lake Liquid Marion Mason Metamora Miami Mid-State New

Process Options Landfill Landfill Dump Dump Landfill Schilling Waste Wayne Excess City Landfill Sandy Jo Disposal Bragg County Landfill County Landfill Lime


NO ACTIONACCESS RESTRICTION X X X X X X X X X X X X X XDeed Restriction X X X X X X X X X XLand Use Restrictions X X X X X X XFencing X X X X X X X X X X X X XCONTAINMENT X X X X X X X X XSurface Controls X X X X X X X X X X

Grading X X X X X X XRevegetation X X X X

Cap X X X X X X X X X X X X X X X X XClay Barrier X X X X X XMultibarrier X X X X X XSoil X X X X X X X XSynthetic Membrane

REMOVAL/DISPOSAL X XExcavation X X X X X X X X X

Mechanical Excav. X XDrum Removal X X XConsolidation X X X

Disposal Onsite X XRCRA Type Landfill

Disposal Offsite X X X XSOIL TREATMENT X XBiological Treatment X XPhysical Treatment XThermal Treatment X X X X

Incineration X X X XOffsite Treatment

RCRA Incineration

IN-SITU TREATMENT XBiodegradationVitrification X

Physical Treatment X XSolidification/fixation X

Vapor Extraction X


11/14/90

B-19





NO ACTIONAttenuation

ObservationMONITORING X X X X X X X X X X X XINSTITUTIONAL CONTROLS X X X X X XAlternate Water Supply X X X X XCONTAINMENT X X XVertical Barriers X X X

Slurry Wall X X XHorizontal BarriersCOLLECTION X X X X X X X XExtraction X X X X X X X X X

Extraction Wells X X X X XExt/Injection Wells

Leachate Collection X X XCollection trenchLeachate Drain X X X

Onsite DischargeAquifer Reinjection

Surface DischargeDewatering X X

Offsite DischargePOTW

Land Application X XTREATMENT X X X XBiological Treatment

Activated Sludge XChemical Treatment X

Oxidation

Ion Exchange Treatment XCoagulant Addition XMetals Perciptation

pH Adjustment X XPhysical Treatment X X X X X

Adsorption X X XAir Stripping X X XSedimentation X XSand filtration XFlocculation XLime pretreatment

Offsite Treatment X X XPOTW X X X


11/14/90

B-20




LANDFILL GAS

COLLECTION X X XPassive Systems X

Pipe VentsTrench Vents X

Active Vents X XExtraction Wells X XBlowers X

TREATMENT XThermal Destruction X X

Flaring X XActivated carbonMONITORING X X X X


Stormwater controlsDiversion

Removal Disposal (sediments) XExcavation X

Offsite Disposal (sediments)Treatment X X

Solidification X XDewateringThermal treatment


11/14/90

B-21


GENERAL RESPONSE ACTION/ Region V ContinuedRemedial Technologies Northside Oak Schmalz Spiegelberg Wauconda Windom Region V

Process Options IN Grove Dump Landfill Sand Dump Total


NO ACTION 0ACCESS RESTRICTION X X X 17Deed Restriction X X 12Land Use Restrictions 7Fencing X X 15CONTAINMENT X X X 12Surface Controls X X X 13

Grading X X 9Revegetation X X X 7

Cap X X X X X 22Clay Barrier X X 8Multibarrier X X 8Soil X 9Synthetic Membrane 0

REMOVAL/DISPOSAL 2Excavation X X 10



Disposal Offsite X X 6SOIL TREATMENT 3Biological Treatment 1Physical Treatment 1Thermal Treatment 4

Incineration 4Offsite Treatment X 1

RCRA Incineration X 1IN-SITU TREATMENT 1


Physical Treatment 2Solidification/fixation 1

Vapor Extraction 1


11/14/90

B-22






MONITORING X X X X X 17INSTITUTIONAL CONTROLS 6Alternate Water Supply X 6CONTAINMENT 3Vertical Barriers 3

Slurry Wall 3Horizontal Barriers 0COLLECTION X 9Extraction X 10

Extraction Wells 5Ext/Injection Wells 0

Leachate Collection X X 5Collection trench X 1Leachate Drain X X 5



TREATMENT 5Biological Treatment X 2

Activated Sludge X 1Chemical Treatment X 3

Oxidation X 1Ion Exchange Treatment 1Coagulant Addition 0Metals Perciptation X 2pH Adjustment 0

Physical Treatment X 7Adsorption X 5Air Stripping 4Sedimentation 1Sand filtration 1Flocculation 1Lime pretreatment 0



11/14/90

B-23




LANDFILL GAS

COLLECTION 3Passive Systems 1



TREATMENT 1Thermal Destruction X 3

Flaring X 3Activated carbon 0MONITORING X X 6


Stormwater controls 0Diversion X 1

Removal Disposal(sediments)

1

Excavation 1Offsite Disposal(sediments)

0

Treatment 2Solidification 2Dewatering 0Thermal treatment 0


11/14/90

B-24


GENERAL RESPONSE ACTION/ Region VIRemedial Technologies Bayou Cecil Cleve Compass Industrial Region V

Process Options Sorrel Lindsey Reber Industries Waste Total


NO ACTION 0ACCESS RESTRICTION X X X X 4Deed Restriction 0Land Use Restrictions X 1Fencing X X X X 4CONTAINMENT X X 2Surface Controls X 1

Grading X 1Revegetation 0

Cap X X X 3Clay Barrier 0Multibarrier X X 2Soil 0Synthetic Membrane 0

REMOVAL/DISPOSAL 0Excavation X X X 3

Mechanical Excav. X X 2Drum Removal X X X 3Consolidation X X 2


Disposal Offsite X 1SOIL TREATMENT 0Biological Treatment 0Physical Treatment 0Thermal Treatment X 1

Incineration X 1Offsite Treatment 0

RCRA Incineration 0IN-SITU TREATMENT 0


Physical Treatment X X 2

Solidification/fixationX X 2

Vapor Extraction 0


11/14/90

B-25


GENERAL RESPONSE ACTION/Remedial Technologies

Process Options

Region VIBayouSorrel

CecilLindsey

CleveReber

CompassIndustries

Industrial Waste

Region VITotal

GROUNDWATER AND LEACHATE


MONITORING X X X X 4INSTITUTIONAL CONTROLS X 1Alternate Water Supply 0CONTAINMENT X 1Vertical Barriers X X 2

Slurry Wall X X 2Horizontal Barriers 0COLLECTION X 1Extraction X 1


Leachate Collection X 1Collection trench 0Leachate Drain X 1



TREATMENT X X 2Biological Treatment 0

Activated Sludge 0Chemical Treatment 0

Oxidation 0Ion Exchange Treatment 0Coagulant Addition 0Metals Precipitation 0pH Adjustment 0

Physical Treatment 0Adsorption 0Air Stripping 0Sedimentation 0Sand filtration 0Flocculation 0Lime pretreatment 0

Offsite Treatment 0POTW 0


11/14/90

B-26



Process Options

Region VIBayouSorrel

CecilLindsey

CleveReber

CompassIndustries

Industrial Waste

Region VITotal

LANDFILL GAS

COLLECTION X 1Passive Systems X 1

Pipe Vents 0Trench Vents X 1


TREATMENT 0Thermal Destruction 0

Flaring 0Activated carbon 0MONITORING 0




Offsite Disposal (sediments) 0Treatment 0

Solidification 0Dewatering 0Thermal treatment 0


11/14/90

B-27



Process Options

Region VIIArkansasCity

ConservationChemical

DoepkeDisposal

Fulbright/SacRiver

LawrenceTodtz

RegionVIITotal

Region VIIIMarshallLandfill

Region VIIITotal


NO ACTION X 1 0ACCESS RESTRICTION X X 2 X 1Deed Restrictions X X 2 0Land Use Restrictions X 1 0Fencing X 1 X 1CONTAINMENT X 1 0Surface Controls X X 2 X 1

Grading X 1 X 1Revegetation X 1 X 1

Cap X X X 3 0Clay Barrier X 1 0Multibarrier X 1 0Soil X X 2 0Synthetic Membrane 0 0

REMOVAL/DISPOSAL X X 2 0Excavation X 1 0

Mechanical Excav. 0 0Drum Removal X 1 0Consolidation 0 0

Disposal Onsite X 1 0RCRA Type Landfill 0 0

Disposal Offsite X X 2 0SOIL TREATMENT 0 0Biological Treatment 0 0Physical Treatment 0 0Thermal Treatment 0 0

Incineration 0 0Offsite Treatment 0 0

RCRA Incinerator 0 0IN-SITU TREATMENT 0 0

Biodegradation 0 0Vitrification 0 0

Physical Treatment 0 0Solidification/fixation 0 0Vapor Extraction 0 0


11/14/90

B-28



Process Options



DoepkeDisposal

Fulbright/SacRiver

LawrenceTodtz

RegionVIITotal

Region VIIIMarshallLandfill

Region VIIITotal

GROUND WATERAND LEACHATE

NO ACTION X X 2 0Attenuation 0 0Observation X 1 0

MONITORING X X X X 4 0INSTITUTIONAL CONTROLS 0 0Alternate Water Supply X 1 0CONTAINMENT X 1 0Vertical Barriers X 1 0

Slurry Wall X 1 0Horizontal Barriers 0 0COLLECTION X 1 0Extraction X 1 0

Extraction Wells X 1 0Ext/Injection Wells 0 0

Leachate Collection 0 X 1Collection trench 0 0Leachate Drain 0 X 1

Onsite Discharge 0 0Aquifer Reinjection 0 0Surface Discharge X 0 0Dewatering 1 X 1

Offsite Discharge 0 0POTW 0 0Land Application 0 0

TREATMENT X 1 X 1Biological Treatment X 1 0

Activated Sludge 0 0Chemical Treatment X 1 0

Oxidation 0 0Ion Exchange Treatment 0 0Coagulant Addition 0 0Metals Preciptation X 1 0pH Adjustment 0 0

Physical Treatment X 1 X 1Adsorption X 1 X 1Air Stripping 0 X 1Sedimentation 0 X 1Sand Filtration X 1 0Flocculation 0 0Lime pretreatment 0 0

Offsite Treatment X 1 0POTW X 1 0


11/14/90

B-29



Process Options



DoepkeDisposal

Fulbright/SacRiver

LawrenceTodtz

RegionVIITotal

RegionVIII

MarshallLandfill

Region VIIITotal

LANDFILL GAS

COLLECTION 0 0Passive Systems 0 0

Pipe Vents 0 0Trench Vents 0 0

Active Vents 0 0Extraction Wells 0 0Blowers 0 0

TREATMENT 0 0Thermal Destruction 0 0

Flaring 0 0Activated carbon 0 0MONITORING 0 0


Stormwater controls 0 X 1Diversion 0 0

Removal Disposal (sediments) 0 0Excavation 0 0

Offsite Disposal (sediments) 0 0Treatment 0 0

Solidification 0 0Dewatering 0 0Thermal treatment 0 0


11/14/90

B-30

Appendix B2


Process Options

Region IXJibboomJunkyard

Operating Industries

Ordot Disposal

Region IXTotal


NO ACTION X 1ACCESS RESTRICTION 0Deed Restrictions 0Land Use Restrictions 0Fencing 0CONTAINMENT 0Surface Controls 0

Grading 0Revegetation 0

Cap 0Clay Barrier 0Multibarrier 0Soil 0Synthetic Membrane 0

REMOVAL/DISPOSAL 0Excavation X 1



Disposal Offsite X 1SOIL TREATMENT 0Biological Treatment 0Physical Treatment 0Thermal Treatment 0


RCRA Incinerator 0IN-SITU TREATMENT 0


Physical Treatment 0Solidification/fixation 0Vapor Extraction 0


11/14/90

B-31

Appendix B2


Process Options



Ordot Disposal

Region IXTotal

GROUNDWATER AND LEACHATE


MONITORING 0INSTITUTIONAL CONTROLS 0Alternate Water Supply 0CONTAINMENT 0Vertical Barriers 0

Slurry Wall 0Horizontal Barriers 0COLLECTION 0Extraction 0


Leachate Collection 0Collection trench 0Leachate Drain 0



TREATMENT X 1Biological Treatment 0

Activated Sludge 0Chemical Treatment X 1

Oxidation 0Ion Exchange Treatment 0Coagulant Addition X 1Metals Preciptation 0pH Adjustment 0

Physical Treatment X 1Adsorption X 1Air Stripping X 1Sedimentation 0Sand Filtration 0Flocculation 0Lime pretreatment 0

Offsite Treatment 0POTW 0


11/14/90

B-32

Appendix B2


Process Options



Ordot Disposal

Region IXTotal

LANDFILL GAS

COLLECTION 0Passive Systems 0


Active Vents X 1Extraction Wells X 1Blowers 0

TREATMENT X 1Thermal Destruction X 1

Flaring X 1Activated carbon 0MONITORING X 1




Offsite Disposal (sediments) 0Treatment 0

Soldification 0Dewatering 0Thermal treatment 0


11/14/90

B-33



Process Options

Region XColbertLandfill

CommencementBay

NorthsideWA

Region XTotal

GRANDTOTAL


NO ACTION 0 3ACCESS RESTRICTION X 1 40Deed Restriction X 1 20Land Use Restrictions X 1 16Fencing 0 36CONTAINMENT X 1 54Surface Controls 0 35

Grading 0 22Revegetation 0 16

Cap X X 2 68Clay Barrier 0 25Multibarrier X 1 30Soil 0 17Synthetic membrane 0 3

REMOVAL/DISPOSAL 0 11Excavation 0 30

Mechanical Excav. 0 11Drum Removal 0 11Consolidation 0 8

Disposal Onsite 0 5RCRA Type Landfill 0 1

Disposal Offsite 0 13SOIL TREATMENT 0 5Biological Treatment 0 1Physical Treatment 0 2Thermal Treatment 0 8

Incineration 0 7Offsite Treatment 0 1

RCRA Incinerator 0 1IN-SITU TREATMENT 0 3

Biodegradation 0 1Vitrification 0 1

Physical Treatment 0 12Soldification/fixation 0 8Vapor Extraction 0 5


11/14/90

B-34

Appendix B2Remedial Technologies Used at Landfill

Sites


Process Options


CommencementBay

NorthsideWA

Region XTotal

GRANDTOTAL


NO ACTION 0 6Attenuation 0 1Observation 0 1

MONITORING X X X 3 59INSTITUTIONAL CONTROLS X X X 3 21Alternate Water Supply X X X 3 24CONTAINMENT 0 12Vertical Barriers 0 13

Slurry Wall 0 13Horizontal Barriers 0 1COLLECTION X X X 3 40Extraction X X X 3 43

Extraction Wells X X X 3 24Ext/Injection Wells 0 2

Leachate Collection X 1 27Collection trench 0 10Leachate Drain X 1 19

Onsite Discharge 0 0Aquifer Reinjection 0 1Surface Discharge 0 0Dewatering 0 6

Offsite Discharge 0 3POTW X X X 3 6Land Application 0 1

TREATMENT X X X 3 32biological Treatment 0 9

Activated Sludge 0 2Chemical Treatment 0 12

Oxidation 0 2Ion Exchange Treatment 0 2Coagulant Addition 0 2Metals Preciptation 0 8pH Adjustment 0 1

Physical Treatment X 1 29Adsorption 0 18

Air Stripping X X X 3 23Sedimentation 0 5Sand Filtration 0 2Flocculation 0 3Lime pretreatment 0 2

Offsite Treatment 0 15POTW 0 15


11/14/90

B-35

Appendix B2Remedial Technologies Used at Landfill

Sites


Process Options


CommencementBay

NorthsideWA

Region XTotal

GRANDTOTAL

LANDFILL GAS

COLLECTION 0 20Passive Systems X 1 17

Pipe Vent 0 1Trench Vents 0 10

Active Vents 0 11Extraction Wells X 1 9Blowers 0 5

TREATMENT 0 8Thermal Destruction 0 12

Flaring X 1 9Activated carbon 0 3MONITORING X X X 3 21


Stormwater controls 0 10Diversion 0 5

Removal Disposal (sediments) 0 5Excavation 0 5

Offsite Disposal (sediments) 0 2Treatment 0 4

Solidification 0 4Dewatering 0 4Thermal treatment 0 1


B-36

Appendix B-3BREAKDOWN BY REGION OF REMEDIAL TECHNOLOGIES USED AT LANDFILL SITES

Page 1 of 2

EnvironmentalMedia

General ResponseActions

RemedialTechnologies

Region 1(10 sites)

Region 2(16 sites)

Region 3(14 sites)

Region 4(10 sites)

Region 5(25 sites)

Region 6(5 sites)

Region 7(5 sites)

Region 8(1 site)

Region 9(3 sites)

Region 10(3 sites)

Total (92 sites)

Soils/LandfillContents

No Action 0 0 1 0 0 0 1 0 1 0 3

Access Restriction Deed Restrictions 2 0 1 2 12 0 2 0 0 1 20Fencing 3 9 0 3 15 4 1 1 0 0 36

Land Use Restrictions 1 0 1 4 7 1 1 0 0 1 16

Containment Surface Controls 3 6 4 5 13 1 2 1 0 0 35

Cap 6 13 11 8 22 3 1 0 1 2 68

Soils/HotsSpots

Removal/Disposal Excavation 4 2 5 4 10 3 1 0 1 0 30

Disposal Onsite 0 0 0 2 2 0 1 0 0 0 5

Disposal Offsite 1 1 1 0 6 1 2 0 1 0 13

Onsite Treatment Thermal Treatment 1 1 1 0 4 1 0 0 0 0 8

In Situ Treatment Biological Treatment 0 0 0 0 1 0 0 0 0 0 1

Physical Treatment 1 1 3 3 2 2 0 0 0 0 12

Offsite Treatment Thermal Destruction 0 0 0 0 1 0 0 0 0 0 1Groundwaterand Leachate

No action 0 1 1 0 1 1 2 0 0 0 6

InstitutionalControls

Alternate WaterSupply

5 2 4 3 6 0 1 0 0 3 24

Containment Vertical Barriers 0 7 0 0 3 2 1 0 0 0 13

Horizontal Barriers 1 0 0 0 0 0 0 0 0 0 1

Collection Extraction 7 13 4 4 10 1 1 0 0 3 43

Leachate Collection 3 8 4 4 5 1 0 1 0 1 27


B-37

Appendix B-3BREAKDOWN BY REGION OF REMEDIAL TECHNOLOGIES USED AT LANDFILL SITES

Page 2 of 2

EnvironmentalMedia

General ResponseActions

RemedialTechnologies

Region 1(10 sites)

Region 2(16 sites)

Region 3(14 sites)

Region 4(10 sites)

Region 5(25 sites)

Region 6(5 sites)

Region 7(5 sites)

Region 8(1 site)

Region 9(3 sites)

Region 10(3 sites)

Total (92 sites)

Groundwaterand Leachate(Continued)

Treatment Biological Treatment 1 3 1 1 2 0 1 0 0 0 9

Chemical Treatment 3 4 0 0 3 0 1 0 1 0 12

Physical Treatment 4 8 3 3 7 0 1 1 1 1 29

Offsite Treatment(at POTW)

1 6 1 2 4 0 1 0 0 0 15

Disposal Onsite Discharge 0 0 0 0 0 0 0 0 0 0 0

Offsite Discharge 1 2 0 0 0 0 0 0 0 0 3 Monitoring Monitoring Wells 7 11 6 7 17 4 4 0 0 3 59

Landfill Gas Collection Passive Vents 4 5 3 2 1 1 0 0 0 0 17

Active Systems 1 5 2 0 2 0 0 0 1 0 11

Treatment Thermal Destruction 2 5 1 0 3 0 0 0 1 0 12

Activated Carbon 0 3 0 0 0 0 0 0 0 0 3

Monitoring Monitoring wells 2 5 3 1 6 0 0 0 1 3 21

Surface Waterand WetlandsSediments

Containment Stormwater Controls 1 5 0 1 1 1 0 1 1 0 10

Removal Disposal Excavation 1 3 0 0 1 0 0 0 0 0 5

Offsite Disposal 0 1 1 0 0 0 0 0 0 0 2

Treatment Solidification 1 0 0 1 2 0 0 0 0 0 4

Dewatering 1 2 0 1 0 0 0 0 0 0 4

Thermal Treatment 0 1 0 0 0 0 0 0 0 0 1


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