prepared for: art brass plating, inc. e a r t h w a t e...

REMEDIAL INVESTIGATION REPORT Art Brass Plating

Prepared for: Art Brass Plating, Inc.

Project No.050067‐005C September 27, 2012 Agency Review Draft

REMEDIAL INVESTIGATION REPORTArt Brass Plating Prepared for: Art Brass Plating, Inc.

Project No.050067‐005C September 27, 2012 Agency Review Draft

Aspect Consulting, LLC

Dana Cannon, LHG Senior Project Hydrogeologist [email protected]

Doug Hillman, LHG Principal Hydrogeologist [email protected]

V:\050067 Art Brass Plating\RI Report\Sept 27 Agency Review Draft\RI Report_AgencyDraft 9-26-12.docx

e a r t h + w a t e r Aspect Consulting, LLC 401 2nd Avenue S. Suite 201 Seattle, WA 98104 206.328.7443 www.aspectconsulting.com

ASPECT CONSULTING

PROJECT NO.050067-005C SEPTEMBER 27, 2012 AGENCY REVIEW DRAFT i

Contents

Executive Summary ...................................................................................... ES-1 ABP Facility and the RI Study Area ................................................................. ES-1 Mapped Extent of Solvent and Metals Impacts ............................................... ES-1 Interim Cleanup Action at the ABP Facility ...................................................... ES-2 Human Health Currently Protected ................................................................. ES-3 Recommended Next Steps ............................................................................. ES-3

1 Introduction ................................................................................................. 1 1.1 Purpose and Objectives ............................................................................... 1 1.2 Site Background and Study Area ................................................................. 1 1.3 Report Organization ..................................................................................... 2

2 Facility Background .................................................................................... 3 2.1 Facility Location and Description ................................................................. 3 2.2 Facility Operations ....................................................................................... 3 2.3 Past and Current Land Use .......................................................................... 4

3 Environmental Setting ................................................................................ 4 3.1 Topography and Surface Water Features .................................................... 4 3.2 Vegetation .................................................................................................... 5 3.3 Climate ......................................................................................................... 5 3.4 Hydrogeologic Conditions ............................................................................ 5

3.4.1 Geology .................................................................................................. 5 3.4.2 Groundwater .......................................................................................... 6

4 Summary of Completed Investigations ................................................... 10 4.1 Pre-RI Investigations .................................................................................. 10

4.1.1 Soil and Groundwater Sampling (PSI, 1999) ....................................... 10 4.1.2 Preliminary Site Investigation (Aspect, 2005a) .................................... 10 4.1.3 Follow-up Site Investigation (Aspect, 2005b) ....................................... 11 4.1.4 Data Gaps Investigation (Aspect, 2006a) ............................................ 12 4.1.5 SVE and Air Sparging Pilot Test (Aspect, 2007) .................................. 12 4.1.6 Downgradient Groundwater Investigation (Aspect, 2008).................... 13 4.1.7 Soil Sampling during Interim Action Implementation (Aspect, 2008) ... 13

4.2 RI Investigations ......................................................................................... 14 4.2.1 Groundwater Monitoring Well Installations........................................... 14 4.2.2 Groundwater Monitoring ...................................................................... 14 4.2.3 Groundwater Sampling with Probes .................................................... 14 4.2.4 Porewater Sampling ............................................................................. 15 4.2.5 Soil Sampling ....................................................................................... 15

4.3 Indoor Air and Soil Vapor Sampling ........................................................... 16 4.4 Data Quality Assessment and Usability ..................................................... 16

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5 Environmental Regulations and Potential Cleanup Levels .................... 17 5.1 Potential Applicable Regulatory Requirements ......................................... 17

5.1.1 Potentially Applicable Federal Requirements ...................................... 18 5.1.2 Potentially Applicable State and Local Requirements ......................... 18

5.2 Potential Exposure Pathways .................................................................... 20 5.3 Screening Levels ....................................................................................... 22 5.4 Groundwater Potability Analysis ................................................................ 24

6 Interim Actions ........................................................................................... 25 6.1 Vapor Intrusion Mitigation Program ........................................................... 25 6.2 Source Control ........................................................................................... 28

7 Nature and Extent of Contamination ........................................................ 28 7.1 Chemicals of Concern ............................................................................... 28 7.2 Soil Quality ................................................................................................. 29

7.2.1 Chlorinated Solvents ............................................................................ 29 7.2.2 Metals .................................................................................................. 31

7.3 Groundwater Quality .................................................................................. 32 7.3.1 Chlorinated Solvents ............................................................................ 32 7.3.2 Metals .................................................................................................. 37 7.3.3 1,4-Dioxane .......................................................................................... 41

7.4 Sediment Porewater Quality ...................................................................... 42 7.5 Soil Vapor and Indoor Air Quality .............................................................. 43

8 Fate and Transport of COCs ..................................................................... 43 8.1 Chlorinated COCs ...................................................................................... 43

8.1.1 Attenuation/Transport Evaluation ......................................................... 43 8.2 Metal COCs ............................................................................................... 50

9 Conceptual Site Model and Exposure Pathway Assessment ................ 52 9.1 Summary of Contaminant Source and Extent ........................................... 52 9.2 Pathways of Exposure ............................................................................... 53

9.2.1 Soil ...................................................................................................... 53 9.2.2 Groundwater ........................................................................................ 55 9.2.3 Air ...................................................................................................... 56 9.2.4 Sediment/Surface Water ...................................................................... 57

10 Conclusions and Recommendations ....................................................... 58

References ......................................................................................................... 62

Limitations ......................................................................................................... 64

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List of Tables 1 Aquifer Hydraulic Conductivity Estimates from Slug Tests

2 Well Completion Summary

3 Summary of Monitoring Objectives for Individual Wells

4 Summary of Chemical Analyses Completed to Date for Groundwater Monitoring

5 Summary of Data Gaps

6 Summary of Potential Exposure Pathways

7 Soil Screening Levels

8 Groundwater and Surface Water Screening Levels

9 Indoor Air and Groundwater IPIMALs for Residential and Commercial Scenarios

10 BIOCHLOR Model Inputs

11 Summary of Literature Biodegradation Rate Half Lives

12 Summary of BIOCHLOR Model Results

13 Evaluation of Potential Exposure Pathways

List of Figures 1 Vicinity map

2 Facility Map

3 Historical and Present Commercial/Industrial Land Use

4A Exploration Locations – Area-wide

4B Exploration Locations – Art Brass Plating Facility Detail

4C Exploration Locations – Duwamish Shoreline

5 Cross Section A-A’

6 Cross Sections B-B’, C-C’, D-D’, E-E’

7 Site Stratigraphy and Sampling Intervals

8 Groundwater Elevations, August 2012 – Water Table Interval

9 Groundwater Elevations, August 2012 – Shallow Interval

10 Groundwater Elevations, August 2012 –Intermediate Interval

11 TCE Data in Vadose Zone Soil

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12 TCE Data in Saturated Soil

13 Nickel Data in Vadose Zone Soil

14 Nickel Data in Saturated Soil

15 Plume Delineation: Trichloroethene (TCE)

16 Plume Delineation: Tetrachloroethene (PCE)

17 Plume Delineation: cis-1,2-Dichloroethene (DCE)

18 Plume Delineation: Vinyl Chloride

19 Plume Delineation: Total Chlorinated Ethenes

20 Seasonal Groundwater Quality: Tetrachloroethene (PCE) – Water Table Interval

21 Seasonal Groundwater Quality: Tetrachloroethene (PCE) – Shallow Interval

22 Seasonal Groundwater Quality: Tetrachloroethene (PCE) – Intermediate Interval

23 Seasonal Groundwater Quality: Trichloroethene (TCE) – Water Table Interval

24 Seasonal Groundwater Quality: Trichloroethene (TCE) – Shallow Interval

25 Seasonal Groundwater Quality: Trichloroethene (TCE) – Intermediate Interval

26 Seasonal Groundwater Quality: cis-1,2-Dichloroethene (DCE) – Water Table Interval

27 Seasonal Groundwater Quality: cis-1,2-Dichloroethene (DCE)– Shallow Interval

28 Seasonal Groundwater Quality: cis-1,2-Dichloroethene (DCE) – Intermediate Interval

29 Seasonal Groundwater Quality: Vinyl Chloride – Water Table Interval

30 Seasonal Groundwater Quality: Vinyl Chloride – Shallow Interval

31 Seasonal Groundwater Quality: Vinyl Chloride – Intermediate Interval

32 Nature and Extent of Dissolved Cadmium in Groundwater

33 Nature and Extent of Dissolved Copper in Groundwater

34 Nature and Extent of Dissolved Nickel in Groundwater

35 Nature and Extent of Dissolved Zinc in Groundwater

36 Groundwater pH

37 Subsurface Utilities with Sewer Camera Survey Observations

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38 Nature and Extent of Total Iron in Groundwater

39 Nature and Extent of Total Manganese in Groundwater

40 Nature and Extent of Total Arsenic in Groundwater

41 Nature and Extent of Total Barium in Groundwater

42 Nature and Extent of 1,4-Dioxane in Groundwater

43 Porewater Salinity

44 Trichloroethene (TCE) in Porewater

45 Cis-Dichloroethene (cis-DCE) in Porewater

46 Vinyl Chloride in Porewater

47 Buildings Where ABP is Responsible for Interim VI Activities

48 Modeled Concentrations Near the Waterway, Base Case Model Parameters

49 Modeled Concentrations Near the Waterway, Velocity x2 Case

50 Modeled Concentrations Near the Waterway, Velocity x2, Revised Half Life Case

51 Modeled Concentrations Near the Waterway, Velocity x2, Incr. Conc., Rev. Half Life Case

52 Modeled Concentrations Near the Waterway, Velocity x10, Revised Half Life Case

53 Areas Exceeding Screening Levels for Potential Exposure Pathways

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List of Appendices

A Boring Logs

B Data Tables

C Facility Background

D Hydraulic Studies

E Vapor Intrusion Assessment

F Interim Measures Evaluation

G Mann-Kendall Trend Tests and Plots

H BIOCHLOR Modeling Results

I Geochemical Modeling Results

J Duwamish Waterway Porewater Risk Assessment – Anchor QEA

K Data Usability with Lab and Data Validation Reports on CD

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Executive Summary

The purpose of this Art Brass Plating (ABP) Remedial Investigation report (RI) is to present sufficient information to characterize site conditions attributed to releases of chemicals from the ABP Facility, to assess area conditions that could affect ABP’s selection of a remedy, and to evaluate the effectiveness of interim remediation actions. Information collected for the RI will enable ABP to prepare a feasibility study and select a remedy to address contamination. Aspect Consulting, LLC prepared this RI on behalf of ABP and in accordance with the Washington State Department of Ecology (Ecology) Agreed Order No. DE5296.

ABP Facility and the RI Study Area The ABP Facility (Facility) is the property located at 5516 3rd Avenue South (the northwest corner of South Findlay Street and 3rd Avenue South). The RI Study Area (Study Area) extends from the ABP Facility to the Duwamish Waterway (Waterway), a distance of about 2,200 feet towards the west-southwest. The Study Area is a subset of a broader area that includes soil and groundwater contaminated by historical releases at several facilities: Philip Services Corporation located at 734 South Lucile Street; Capital Industries located at 5801 3rd Avenue South; and Blaser Die Casting located at 5700 3rd Avenue South.

Since 1983, the Facility has been operated exclusively for metal plating and related work (e.g., metal polishing and powder coating). Metal plating has included nickel, chrome, brass (an alloy of copper and zinc), copper, and gold. The chlorinated solvent trichloroethene (TCE) was formerly used at the Facility for vapor degreasing from approximately 1983 to February 2004.

Environmental investigations confirm the likely release of chlorinated solvents and plating metals from the Facility to soil and groundwater. The investigation data show the downgradient migration of TCE and its degradation products cis-DCE and vinyl chloride via groundwater flow. These data also indicate the historical release of plating solutions resulting in depressed pH and elevated concentrations of cadmium, copper, nickel, and zinc in soil and groundwater beneath, and in close proximity to, the Facility.

Mapped Extent of Solvent and Metals Impacts Screening levels protective of human health and environmental exposures are used in this RI to evaluate the investigation data and map the extent of impacts. The screening levels are based on protection against direct contact (soil, groundwater), consumption of organisms (surface water), ecological receptors (surface water), and vapor inhalation (air, soil/dust).

Chlorinated Solvents The primary chemical of concern in the Study Area is the chlorinated solvent TCE. However, under certain conditions observed in the Study Area, TCE undergoes reductive dechlorination and forms less chlorinated ethenes: dichloroethenes (cis-DCE, 1,1-DCE, trans-DCE) and vinyl chloride. The highest concentrations of TCE in soil have been

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ES-2 AGENCY REVIEW DRAFT PROJECT NO.050067-005C SEPTEMBER 27, 2012

detected beneath the western portion of the Facility and at depths close to the water table. TCE appears to have migrated downward but has not been detected in soils at depths greater than 20 feet beneath the Facility.

The groundwater TCE plume migrates slightly downward and towards the southwest, consistent with the vertical and horizontal groundwater gradients in this area, until around 1st Avenue South where it reaches its maximum depth (approximately 75 feet). West of 1st Avenue South, the plume migrates upward to the southwest (consistent with the upward gradients observed in this area) and extends to the Waterway. Vinyl chloride concentrations exceeding the screening levels for protection of human health via fish consumption are located throughout the plume, including wells located adjacent to the Waterway.

Because TCE, cis-DCE, and vinyl chloride contamination in groundwater extends to the Waterway, sediment porewater within the potential groundwater discharge zone was characterized to evaluate potential impacts to surface water. Vinyl chloride was detected in sediment porewater exceeding screening levels based on protection of human health via consumption of surface water organisms. Currently, recreational uses in the area are limited due to the industrial nature of this area of the Waterway and subsistence shellfish harvesting activities are limited due to limited available populations.

Metals In addition to chlorinated solvents, data indicate the likely historical release of plating solutions at the Facility. These past releases result in depressed pH and elevated concentrations of copper, nickel, and zinc in soil and groundwater beneath the Facility. The highest concentrations in soil and groundwater have been detected beneath and downgradient of the former plating area located in the southwest corner of the Facility. In contrast with the chlorinated solvents, the extent of plating metals impacts appears limited to a distance of approximately 400 feet downgradient of the Facility.

Interim Cleanup Action at the ABP Facility Interim cleanup actions at the Facility and in the likely source areas are underway and have significantly reduced chlorinated COC concentrations. Since starting the interim action in 2008, the TCE concentrations in groundwater have decreased by over 90 percent near the Facility and declining trends are now observable at wells located more than 100 feet downgradient. The interim cleanup action consists of an air sparging/soil vapor extraction system capable of removing volatile organic compounds (including chlorinated solvents) from both soil and groundwater.

With groundwater quality conditions improving at the Facility, the highest concentrations of TCE are now detected mid-plume (which is around 1st Avenue South). Using reasonably conservative fate and transport parameters, modeling predicts that groundwater concentrations near the Waterway will not increase over time. However, given the uncertainty in model inputs, it is also conceivable that concentrations could increase over time, and neither potential future outcome can be rejected. Continued monitoring is warranted to empirically evaluate trends.

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PROJECT NO.050067-005C SEPTEMBER 27, 2012 AGENCY REVIEW DRAFT ES-3

Human Health Currently Protected Based on existing data, most of the potential human health and environmental exposure pathways are not complete. The exposure pathways that are potentially complete are currently mitigated as follows:

Vapor migration from groundwater to indoor air is mitigated by monitoring and/or sub-slab depressurization/SVE systems within areas of vadose-zone soil and water table groundwater contamination. Downgradient property owners have been cooperative in providing access for vapor intrusion monitoring and mitigation;

Impermeable covers (asphalt and concrete) prevent contact with contaminated soil; and

Utility companies have been contacted to inform them of areas of shallow groundwater contamination to protect against potential exposure to underground workers.

Recommended Next Steps The RI provides sufficient technical information to delineate the nature and extent of contamination associated with the ABP Facility. These data should be used to prepare a Feasibility Study (FS) that develops remedial action objectives and evaluates a range of potential alternatives to achieve these objectives. Based on this alternatives evaluation, a Cleanup Action Plan (CAP) detailing the selected remedy should be developed. Quarterly groundwater monitoring should continue during FS/CAP preparation, but an analysis of the monitoring data may warrant a reduction in sampling frequency beginning in spring 2013.

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PROJECT NO.050067-005C SEPTEMBER 27, 2012 AGENCY REVIEW DRAFT 1

1 Introduction

1.1 Purpose and Objectives The Art Brass Plating (ABP) Remedial Investigation report (RI) has been prepared in accordance with the Agreed Order between Department of Ecology (Ecology) and Art Brass Plating, Inc dated January 8, 2008 (Agreed Order No. DE5296). The purpose of the RI is to collect sufficient information to characterize site conditions attributed to releases of chemicals from the ABP Facility; characterize area conditions that affect ABP’s selection of a remedy; and evaluate the effectiveness of interim remediation actions. This data includes the distribution of contaminants at the site and the associated potential threat to human health and the environment. Information collected for the RI will enable ABP to prepare a feasibility study and select a remedy to address contamination under a subsequent Agreed Order.

The RI Work Plan (Aspect, 2008) summarized data available at that time and identified data needed to complete site characterization for the RI. The RI Work Plan was approved by Ecology on October 17, 2008. From October 2008 through the present, Aspect Consulting, LLC (Aspect) has been implementing the RI Work Plan. In addition to the data needs identified in the RI Work Plan, additional data needs have been identified and the data collected in accordance with Ecology-approved work plans. This report presents the data collected throughout the RI period and discusses all relevant data collected to date.

1.2 Site Background and Study Area To complete the RI, ABP has conducted investigations in the area of the ABP Facility extending to the Duwamish Waterway (Waterway). The ABP Facility (Facility) is the property located at 5516 3rd Avenue South (the northwest corner of South Findlay Street and 3rd Avenue South) as illustrated on Figure 1. Figure 1 also shows the ABP Study Area (Study Area). The Study Area was originally confined to the area east of East Marginal Way South in the RI Work Plan, but the boundaries were extended to the Waterway based on data collected during the RI.

The Study Area is a subset of a broader area that includes soil and groundwater contaminated by historical releases at several facilities. As part of their own remedial investigation, Philip Services Corporation (PSC) has conducted groundwater investigations throughout the Georgetown neighborhood (PSC, 2003). Chlorinated solvent releases from the PSC Georgetown facility have migrated downgradient of their facility located at 734 South Lucile Street and may impact groundwater in the area west of 4th Avenue. Based on the PSC’s area-wide groundwater investigations, other potential sources of solvent contamination were identified west of Fourth Ave South including the ABP Facility, Capital Industries (Capital) located at 5801 3rd Avenue South, and Blaser Die Casting (Blaser) located at 5700 3rd Avenue South. Ecology concluded there were significant releases associated with these facilities and as a result, required separate agreed orders. Ecology has named ABP, Capital, Blaser, and PSC as PLPs for

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groundwater contamination west of 4th Avenue South. In this report, ABP, Blaser, Capitol, and PSC are collectively referred to as the West of Fourth (W4) Group.

Capital and Blaser have conducted similar RI activities at the same time as ABP. During the course of the RI, investigation activities and data sharing were coordinated among ABP, Blaser, Capitol, and PSC. Data collected by the W4 Group relevant to the ABP RI, including area groundwater chemistry, plume delineation, and hydrogeologic characterizations, has been included in this report and referred to as ‘area-wide’ data.

The Study Area illustrated on Figure 1 is based on data collected by ABP and others in the W4 group. Figures and text in Section 7 will provide additional details about the available data.

1.3 Report Organization This RI includes 10 sections and 8 appendices. The main text is organized as follows:

Section 1 – The Introduction presents information regarding the objectives and approaches for the ABP RI;

Section 2 – The Facility Background section provides information about the facility location and history, and past and current land use;

Section 3 – The Environmental Setting section summarizes environmental information relevant to the ABP RI including topography and surface water features, vegetation, climate, and hydrogeology;

Section 4 – A Summary of Completed Investigations describes the purpose and scope of each investigation conducted in the area of the Facility;

Section 5 – Environmental Regulations and Potential Screening Levels are identified for the purposes of comparing chemical concentrations and identifying potential exposure pathways;

Section 6 – Interim Actions summarizes interim remedial measures, including vapor intrusion mitigation and source control that have been implemented to date;

Section 7 – The Nature and Extent of Contamination describes the distribution of chemicals in environmental media within the Study Area;

Section 8 – The Fate and Transport of COCs (chemicals of concern) describes the mechanisms of contaminant transport through groundwater, and the potential future migration of chemicals in the Study Area;

Section 9 – The Conceptual Site Model Summary and Exposure Pathway Assessment evaluates potential exposure pathways resulting from COC occurrences;

Section 10 – Conclusions of the RI are summarized and recommendations for future actions are provided; and

References are provided at the end of the main report text.

The RI includes multiple appendices to support the analyses and discussions in the main body of the text. These appendices include:

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Appendix A – Boring Logs;

Appendix B – Data Tables grouped by analyte group and sampling interval;

Appendix C – Facility Background;

Appendix D –Hydraulic Studies;

Appendix E – Vapor Intrusion Assessment;

Appendix F – Interim Measures Evaluation;

Appendix G – Mann-Kendall Trend Tests and Plots;

Appendix H – BIOCHLOR Modeling Results;

Appendix I – Geochemical Modeling Results;

Appendix J – Duwamish Waterway Porewater Risk Assessment – Anchor QEA; and

Appendix K – Data Usability with Lab and Data Validation Reports on CD.

2 Facility Background

2.1 Facility Location and Description The ABP Facility is located at 5516 3rd Avenue South in the Georgetown neighborhood in Seattle, Washington, as shown on Figure 1. The Facility and surrounding area are generally flat, with a gradual slope to the west. The Facility surface is completely covered with either buildings or pavement. According to King County assessor records, the Facility covers 20,000 square feet. The property is owned by Dean Allstrom.

2.2 Facility Operations Based on a review of historical records, including Sanborn Fire Insurance Maps and city directories, the property now occupied by the Facility was used as a residence or undeveloped prior to 1983. Addresses of residences located on the property, as identified on City of Seattle sewer cards, were 5516 3rd Avenue South, 306 South Findlay Street, and 318-1/2 South Findlay Street.

The site was purchased by the current property owner in 1983 and has been used for metal finishing since that time. The current property owner, Dean Allstrom, owned and operated Art Brass Plating, Inc. between 1983 and 2001. Since 2001, Mike Merryfield has owned and operated Art Brass Plating, Inc., which leases the property.

A facility map showing locations of various operations is provided on Figure 2. The existing ABP building was constructed in three phases: the westernmost building was constructed in 1983, the easternmost building in 1987, and the central portion in 1991. Site process areas have slowly expanded to the current layout since metal finishing operations began in 1983. A more detailed discussion of the building expansion and use

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is provided in Appendix C, which is a reproduction of an earlier submittal to Ecology dated June 6, 2005.

Since 1983, the Facility has been operated exclusively for metal plating and related work (e.g., metal polishing and powder coating). Metal plating has included nickel, chrome, brass (an alloy of copper and zinc), copper, and gold. A former plating area in the southwest corner of the Facility was closed in 1999 and is currently used for storage. Plating operations currently take place in the central portion of the Facility within a secondary containment area. Plating bath schematics of the former and current plating lines are provided in Appendix C. For dangerous waste reporting, ABP is classified by Ecology as a Large Quantity Generator and submits dangerous waste reports and Toxic Release Inventory reports that detail chemical and waste volumes used. Following on-site treatment, aqueous wastes are discharged to King County sanitary sewer under a King County Industrial Waste Permit.

Trichloroethene (TCE) was formerly used at the Facility for vapor degreasing from approximately 1983 to February 2004. Since 1983, the vapor degreaser has been located at its current location just south of the polishing area, labeled “Former TCE Degreaser No. 1” on Figure 2. A second vapor degreaser, located in what is now the Time-Saver Room, was temporarily used between 1988 and 1993, labeled “Former TCE Degreaser No. 2” on Figure 2.

2.3 Past and Current Land Use The Facility is located within the Georgetown neighborhood that has a long history of mixed industrial, commercial, and residential land use. While industrial is the predominant land use in the area, commercial and residential uses are present, and the mixed-use pattern is anticipated to remain in the long-term. Land use surrounding the Facility includes a residence to the north, an autobody shop and restaurant to the east, a plastics fabricator and warehouse to the south, and a supplier of point-of-use sales equipment to the west.

During the RI, Aspect conducted a historical review of properties adjacent to and downgradient of the Facility. The purpose of the research was to identify potential sources of chlorinated solvent contamination. Historical sources that were consulted included Polk City Directories, Sanborn Fire Insurance Maps, and building records at the City of Seattle Department of Planning and Development. Figure 3 provides a summary of some of the historical and present commercial/industrial land use activities adjacent to and downgradient of the Facility.

3 Environmental Setting

3.1 Topography and Surface Water Features The Facility is located within the floor of the north-south-trending Duwamish River Valley, where the land surface is relatively level. The valley floor is approximately 6,000 feet wide in this area, and bounded to the east and west by steeply sloped uplands that

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rise to elevations of 300 to 500 feet above mean sea level. The ground surface elevation of the Facility is approximately 15 feet mean sea level.

The Lower Duwamish Waterway is located approximately 2,200 feet west-southwest of the Facility. No other surface water bodies are known to be present in the area. The Lower Duwamish Waterway was dredged and straightened in the early 1900s. Prior to that time, the Duwamish River meandered as it flowed north through the Duwamish River Valley toward Elliott Bay. The abandoned meanders reportedly were filled with dredged material during the waterway straightening project.

3.2 Vegetation Vegetation in the area is generally sparse, which is consistent with the predominantly industrial setting. The area is typical of urban, developed land, with vegetation limited to landscaped planting areas, street-side trees, and plantings on the dispersed residential properties.

3.3 Climate The climate is characterized by mild temperatures and a rainy season, with considerable cloudiness during the winter months. The following description is excerpted from the PSC (2003) RI Report. Average winter daytime temperatures are in the 40s (degrees Fahrenheit) and nighttime readings in the 30s. During the summer, daytime temperatures are usually in the 70s, with nighttime lows in the 50s.

The middle of the dry season occurs in July or early August, with July being the driest month of the year. The rainy season extends from October to March, with December normally the wettest month. However, precipitation is rather evenly distributed throughout the winter and early spring months. More than 75 percent of the yearly precipitation falls during the rainy season. At the King County Airport (located approximately 2 miles south), an average annual precipitation of 36.55 inches is reported (PSC, 2003).

3.4 Hydrogeologic Conditions The hydrogeology provides a framework for understanding the subsurface conditions and groundwater flow system in the Study Area, which is entirely located in the Duwamish River Valley. This section provides a description of the local hydrogeology based on area borings and an area-wide interpretive report called the Duwamish Basin Groundwater Pathways Study (Booth and Herman, 1998). Boring locations are presented on Figures 4A (Area-wide), 4B (Facility), and 4C (Duwamish Shoreline).

3.4.1 Geology The hydrogeologic units encountered in borings completed in the vicinity of ABP include a Younger Alluvium and Older Alluvium. The upper portion of the Younger Alluvium has been modified and is referred to as the Fill Unit. A description of these units is provided below.

Figures 5 and 6 provide geologic cross sections: one along the approximate centerline of the plume oriented northeast-southwest (Figure 5, A-A’) and four others that are drawn

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perpendicular to the plume and oriented northwest-southeast (Figure 6, B-B’, C-C’, D-D’ and E-E’). Cross section locations are shown on Figure 6.

Fill Unit The Fill unit consists of heterogeneous layers of gravelly sand, silt, and silty sand with scattered bits of inert debris such as glass shards or brick fragments. This unit extends up to a depth of 8 feet. In some cases, the boundary between the Fill Unit and the Younger Alluvium is difficult to distinguish. Therefore, in most discussions and figures these units are grouped together.

Younger Alluvium The Younger Alluvium (Qyal) represents channel and overbank/floodplain deposits from the Duwamish River (Booth and Herman, 1998). Based on borings in the vicinity of the Facility, the Younger Alluvium consists of two subunits, a sandy silt or silty sand unit overlying slightly silty fine-medium sand unit. Scattered bits of wood and organic debris are also present. This unit is typically found within a few feet above or below the current sea level and extends to a depth of approximately 25 to 30 feet beneath the Facility. West of the Facility, starting near 2nd Avenue South, the Younger Alluvium extends to a depth of approximately 55 feet.

The upper sandy silt/silty sand unit typically extends to a depth of 8 to 12 feet and includes a 4- to 6-foot thick silt unit beneath the Facility and adjacent right-of-ways. The sand in the underlying slightly silty sand unit has a characteristic ‘salt and pepper’ appearance. This lower portion of the Qyal also includes silt stringers that range up to a few inches thick.

Older Alluvium The Older Alluvium (Qoal) represents materials deposited in an estuarine and deltaic environment. Based on borings in the vicinity of the Facility, the Older Alluvium consists of interbedded sequences of silty fine sand and sandy silt. While not observed in ABP borings, this unit can also contain discontinuous gravel lenses and locally abundant shells and some wood (Booth and Herman, 1998).

A silt aquitard, likely a subunit of the Older Alluvium, and bedrock have been identified in deeper borings east of 4th Avenue (PSC, 2003). These additional units were not encountered in the borings located in the Study Area, where the deepest borings were completed to a depth of 74 feet. Based on a review of the Duwamish Valley cross sections available in Booth and Herman (1998), it is expected that the silt aquitard and bedrock are present at a depth greater than 150 feet.

3.4.2 Groundwater Groundwater in the Study Area is encountered at a depth of 4 to 10 feet below grade. Groundwater flow is towards the Waterway, which is west-southwest of the Facility. Appendix D provides a summary of the groundwater hydraulic characterization studies that have been completed during the RI, including slug tests, tidal studies and water level measurements. This section summarizes the conclusions of these studies. Please refer to the appendix for details.

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3.4.2.1 Groundwater Sampling Intervals The lithologic units discussed above correspond to the hydrogeologic units encountered in the Study Area. However, PSC (2003) adopted a standardized nomenclature for groundwater monitoring and sampling intervals that does directly correspond to the lithologic units. For consistency, this convention has been maintained in describing groundwater conditions within the Study Area. These sampling intervals are illustrated on Figure 7 and are described below:

Water Table Interval. This interval includes monitoring wells screened above 20 feet below ground surface (bgs) and reconnaissance groundwater samples collected above 20 feet bgs.

Shallow Interval. This interval includes monitoring wells screened below 20 feet and above 40 feet bgs, and reconnaissance groundwater samples collected between 21 feet and 40 feet bgs.

Intermediate Interval. This interval includes monitoring wells and reconnaissance groundwater samples screened below 40 feet bgs.

3.4.2.2 Aquifer Characteristics The discussion below provides a characterization of aquifer characteristics based on the data collected during the RI. Methodologies and data analysis techniques are reviewed in Appendix D.

Groundwater Flow Direction and Gradients The W4 Group completed multiple coordinated water level measurements during the RI. The events completed between May 2010 and August 2012 represent the most comprehensive data set for the W4 Group. Groundwater elevations were contoured for these events and are provided in Appendix D. Little seasonal variability in flow direction was observed. The August 2012 groundwater elevations with contours are provided in Figures 8, 9, and 10 for the Water Table, Shallow, and Intermediate Intervals, respectively.

Some localized and anomalous high water levels have been noted at the Water Table Interval in wells MW-16 and PSC-CG-143-WT. Groundwater mounding at PSC-CG-143-WT is sporadically observed and the cause has not been determined. Groundwater mounding at MW-16 has been observed during winter months and may be related to recharge from a leaking combined sewer. A sewer survey identified potential leaking joints in the Findlay Street sewer upgradient of MW-16 (see Section 7.3.2). In addition to the two anomalous readings noted at the Water Table Interval, the remaining anomalous reading was from October 2010 in well MW-16-75. The October 2010 reading is likely a field error since all other water levels from this well were consistent with readings from surrounding wells.

Findings from the May 2010 through August 2012 events indicate the following:

Water Table Interval. The approximate direction of groundwater flow was southwest. The gradient for the Water Table Interval ranges from 0.0004 to 0.0016 feet per foot;

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Shallow Interval. The approximate direction of groundwater flow is west-southwest. The gradient for the Shallow Interval ranges from 0.0013 to 0.0021 feet per foot; and

Intermediate Interval. The approximate direction of groundwater flow is west-southwest. The gradient for the Intermediate Interval ranges from 0.0007 to 0.0018 feet per foot.

Vertical gradient between the Water Table and Shallow Intervals are typically downward. Vertical gradients between the Shallow and Intermediate Intervals fluctuate between upward and downward except in the well clusters close to the Waterway, west of East Marginal Way. Upward gradient were typical in these well pairs.

Hydraulic Conductivity Measurements Hydraulic conductivity measurements are based on slug tests completed at multiple wells for each sampling interval. Hydraulic conductivities estimated using slug test results are generally biased low compared to those hydraulic conductivity values calculated from pumping tests. Estimated hydraulic conductivities at each well location are summarized in Table 1. The following provides a summary of the data:

Water Table Interval. Based on data from 6 wells, the geometric mean is 0.003 cm/sec;

Shallow Interval. Based on data from 8 wells, the geometric mean is 0.03 cm/sec; and

Intermediate Interval. Based on data from 8 wells, the geometric mean is 0.002 cm/sec.

The hydraulic conductivity values measured in the Shallow and Intermediate Intervals by ABP are consistent with those values from the other W4 Group. It should be noted that the hydraulic conductivity values measured at the Water Table Interval were an order of magnitude lower compared to the geometric mean of the entire W4 Group data set for Water Table Interval slug test (0.022 cm/sec). Water Table Interval wells MW-8, MW-10, MW-11, and MW-13, which are part of the ABP slug test data set, have a four- to six-foot thick silt layer within the screened intervals, which would result in lower hydraulic conductivity measurements.

3.4.2.3 Groundwater Flow and Tidal Variability ABP has completed four tidal studies during the following periods: May/June 2010, October 2010, January 2011, and August 2012. Appendix D provides a summary of the analyses that were completed on the tidal data. A discussion of some of the results is provided below.

Groundwater from upland areas generally flows toward the Waterway. Water levels in the Waterway are influenced by river flow and tidal effects from Puget Sound. The typical tidal range in Seattle’s Elliott Bay is approximately 11 feet, based on the difference between mean higher high water (MHHW) and mean lower low water (MLLW) (http://tidesandcurrents.noaa.gov). Monitoring wells completed near the waterway in the Shallow and Intermediate Intervals (MW-22-30/-50, MW-23-30/-50 and, PSC-CG-151-25) had a tidal range of 6 to 8 feet. Monitoring wells in the same interval

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but 300 feet from the Waterway (MW-24-30/-50) had a recorded tidal range of approximately 3 feet. Tidal influences on water levels diminish to 0.5 feet or less east of East Marginal Way, approximately 800 feet east of the Waterway.

High tides result in localized groundwater flow gradient reversal, although the time-averaged net groundwater flow direction is still toward the Waterway (Booth and Herman, 1998). The occurrence of localized and transient flow reversals is consistent with site characterization data collected at other similar sites in the Waterway, and with the ABP RI data. For the four RI tidal studies completed, the magnitude and direction of the gradient were calculated using a solution to the “three-point problem” using a three-well configuration: MW-23-30, PSC-CG-151-25, and MW-24-30. Gradients ranged between 0.006 and 0.009 feet per foot with groundwater flows to the southwest and 0.003 feet per foot or less with groundwater flows to the northeast.

In the two nearshore well clusters (MW-22-30/-50 and MW-2-30/-50), the tidally-averaged vertical gradients were slightly upward: +0.004 at MW-22 and +0.008 at MW-23. This slightly upward gradient is consistent with the regional flow path of groundwater discharge from adjacent uplands into the Waterway. The relatively dense saline water wedge that occurs in and below the Waterway results in an upward gradient of groundwater discharge into the river. In the Waterway, fresh surface water moving downstream overlies this tidally oscillating saltwater wedge. These conditions result in the occurrence of saline water in the groundwater zone beneath the channel. Less dense, low salinity groundwater does not readily mix or migrate into these deeper saline zones. As a result, fresh groundwater migrating beneath upland areas discharges upward primarily into shallower areas of the Waterway when it meets the saline groundwater wedge located directly beneath the channel. The size and shape of the saltwater wedge within this section of the Waterway is dependent upon local groundwater flux, aquifer permeability, and seasonal upstream river flows and stages.

3.4.2.4 Geochemical Conditions During the RI, select groundwater samples were analyzed for nitrate, sulfate, ferrous iron, and methane. With the field parameters, these data provide an understanding of the oxidation-reduction potential (redox) conditions in groundwater. Reducing conditions have been documented by PSC as ubiquitous in groundwater in the Georgetown area (PSC, 2003). The likely reason for widespread reducing conditions is the presence of naturally occurring organic materials in the Younger and Older Alluvial deposits. These organics act as a food source (electron donor) for indigenous microbial consumption. Anthropogenic releases of chemicals that can be used as a microbial food source (e.g., petroleum or non-chlorinated solvents) can locally exacerbate area-wide reducing conditions.

The remediation system at the Facility, which includes air sparging of the shallow aquifer, has resulted in localized oxidized redox conditions at the water table. The RI data indicate that as redox conditions became oxidized, methane concentrations decreased and sulfate concentrations increased.

Conditions remain reducing in the Shallow and Intermediate Intervals and in the Water Table Interval away from the air sparging area. This is evidenced by low dissolved oxygen and Eh, elevated ferrous iron, and moderate sulfate concentrations. The presence

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and persistence of methane indicates some localized areas of methanogenesis; however, the continued presence of sulfate suggests methanogenesis does not occur everywhere in the Study Area.

4 Summary of Completed Investigations

This section provides a discussion of the environmental investigations completed by ABP. The first part details the investigations completed prior to finalizing the RI Work Plan (Aspect, 2008). This is followed by a summary of the site characterization completed during the RI.

4.1 Pre-RI Investigations ABP conducted several subsurface and indoor air investigations at and around the Facility between 1999 and 2008, prior to the RI. The reports for each investigation are compiled in Volume II and Appendix B of the Draft Interim Cleanup Action Plan (Aspect, 2007). The purpose and scope of these investigations are summarized below; the exploration locations are depicted on Figure 4. Boring and well construction logs are provided in Appendix A.

4.1.1 Soil and Groundwater Sampling (PSI, 1999) In March 1999, PSI conducted a subsurface investigation to evaluate whether plating solution releases from ABP operations had impacted soil or groundwater at the Facility. Work included the following:

Advancing 2 direct-push borings to a depth of 9 feet at the southwestern (downgradient) corner of the Facility;

Collecting continuous soil samples and 1 groundwater grab sample from the Water Table Interval, from each boring; and

Submitting 2 soil and 2 grab groundwater samples for analysis for cyanide, chromium, copper, lead, nickel, and zinc.

This investigation did not identify any constituents in soil or groundwater above Model Toxics Control Act (MTCA) Method A cleanup levels, except for a slight exceedance of chromium in groundwater. There were reported detections of chromium, copper, nickel, and zinc in groundwater exceeding the proposed cleanup levels. One soil sample exceeded the proposed cleanup level for protection of groundwater for zinc.

4.1.2 Preliminary Site Investigation (Aspect, 2005a) In June 2005, Aspect conducted a subsurface investigation to evaluate whether TCE detected in groundwater at PSC explorations 217F and N15 may have originated from the Facility. Work included the following:

Reviewing operations at the Facility and identifying potential areas where TCE was used or handled;

Reviewing historical records to identify potential background sources of TCE;

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Advancing 12 direct-push soil borings in and around the Facility to depths from 12 to 16 feet bgs;

Collecting continuous soil samples and 1 grab groundwater sample from the Water Table Interval, from each boring;

Collecting soil gas samples from the 1- to 4-foot bgs depth interval at 3 borings located inside the building at the Facility;

Submitting 18 soil and 12 groundwater samples for analysis for volatile organic compounds (VOCs) by EPA Method 8260; and

Submitting 3 soil gas samples for analysis for VOCs by EPA Method TO-15.

This work confirmed the probable release of TCE from the two vapor degreasers located on the Facility. Elevated concentrations of TCE were detected in soil and grab groundwater samples collected in close proximity to each degreaser and extending to the downgradient property line.

4.1.3 Follow-up Site Investigation (Aspect, 2005b) In October 2005, based on the results of the Preliminary Site Investigation, Aspect conducted a follow-up investigation to characterize local hydrogeology and identify vertical and horizontal boundaries of the contamination plume. Work included the following:

Installing monitoring wells MW-1 through MW-4 adjacent to and downgradient of two vapor degreasers that formerly used TCE. Monitoring wells were screened across the Water Table Interval to a depth of 14 feet bgs;

Surveying monitoring well top-of-casing elevations into the PSC well network, measurement of water levels, and estimation of local groundwater flow direction;

Advancing 7 direct-push borings downgradient of the Facility to depths from 11 to 15 feet bgs;

Advancing 2 direct-push borings downgradient of the former TCE-using degreasers to depths between 42 and 45 feet bgs;

Collecting continuous soil samples from each soil boring;

Collecting 1 grab groundwater sample from the Water Table Interval of each shallow boring, and collecting 3 grab groundwater samples at approximately 15-foot intervals from each of the two deep borings;

Collecting 1 groundwater sample from each of the fur monitoring wells;

Submitting 13 groundwater samples for analysis for VOCs by EPA Method 8260 and total suspended solids by EPA Method 160.2; and

Submitting 6 soil samples from the two deep borings for analysis for VOCs by EPA Method 8260.

Monitoring wells installed at the Facility were used to investigate and confirm the prior analytical results for probe-based sampling. Two deeper probe explorations located in the downgradient right-of-way were used to evaluate the vertical extent of impacts. No

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VOCs were detected in groundwater collected from depths of approximately 40 feet bgs in either location. Neighborhood-area probe-collected groundwater samples also were used to bound the extent of TCE migration at the Water Table Interval, with non-detectable results to the west at 2nd Avenue South and to the south at Orcas Street when coupled with PSC-collected data.

4.1.4 Data Gaps Investigation (Aspect, 2006a) In June 2006, Aspect conducted a data gaps investigation to define the vertical and horizontal extent of soil and groundwater contamination at the Facility. Work included the following:

Installing 3 monitoring wells, screened across the Water Table Interval to a depth of 14 feet bgs, to provide permanent monitoring points downgradient of the former TCE storage area (MW-5), upgradient of the Facility (MW-6), and between the two degreasers (PMW-1);

Installing air sparging wells AS-1 and AS-2 adjacent to the former degreasers, screened from 25 to 28 feet bgs at the base of the shallow sand unit, to vertically delineate contamination in potential source areas, and to provide points to pilot test air sparging;

Advancing direct-push borings SP-14 to SP-17 to depths from 12 to 20 feet bgs;

Collecting continuous soil samples at each boring and monitoring well location;

Collecting 1 grab groundwater sample from the Water Table Interval of each direct-push boring;

Collecting groundwater samples from the five new monitoring and air sparging wells;

Submitting 9 groundwater samples for analysis for VOCs by EPA Method 8260; and

Submitting 19 soil samples from the two deep borings for analysis for VOCs by EPA Method 8260.

Interpretation of the data collected by this investigation refined the understanding of the distribution of TCE-impacted soil and groundwater on the Facility, enabling more focused source-control remediation efforts. The data also indicated a potential historical release of TCE in the former solvent storage area near the northwestern corner of the Facility building. Two air sparging wells were installed in close proximity to the degreasers. Groundwater samples collected from each well yielded non-detectable TCE results at a depth of 30 feet.

4.1.5 SVE and Air Sparging Pilot Test (Aspect, 2007) In August 2006, Aspect conducted a pilot test for soil vapor extraction and air sparging to evaluate the potential applicability of these technologies for source control of VOCs, and to determine design parameters. Work included the following:

Applying SVE at existing monitoring wells MW-1, MW-2, and MW-5 for 1 to 5.5 hours each;

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Applying air sparging at existing air sparging wells AS-1 and AS-2 for 1.5 to 2 hours each; and

Monitoring of performance parameters, including pressure/vacuum at active and surrounding wells, dissolved oxygen at surrounding monitoring wells, air injection and extraction flow rates, and VOC concentrations in off-gas.

On the basis of the pilot test results, Aspect concluded that SVE and air sparging are viable technologies for interim source control remediation, and the results have provided further site-specific performance data for system design.

4.1.6 Downgradient Groundwater Investigation (Aspect, 2008) In 2008, Aspect completed five geoprobe borings southwest of the Facility to provide additional lateral and vertical definition of the contaminant plume. Work included the following:

Advancing direct-push borings SPO-10 through SPO-14 to a depth of 70 feet bgs.

Collecting 1 grab groundwater sample from the Water Table Interval of borings SPO-11, SPO-13, and SPO-14.

Collecting 2 grab groundwater samples from the Shallow Interval from borings SPO-11, SPO-13, and SPO-14.

Collecting 3 grab groundwater samples from the Intermediate Interval from borings SPO-11, SPO-13, and SPO-14 and two grab groundwater samples from SPO-10 and SPO-12.

Submitting 22 groundwater samples for analysis for chlorinated VOCs by EPA Method 8260.

Submitting 1 groundwater sample from SPO-13 for analysis of total and dissolved iron and manganese by EPA Method 6010B and 1,4-dioxane by EPA Method 8270.

Results from these investigations were incorporated into the RI Work Plan and used to guide additional RI investigations.

4.1.7 Soil Sampling during Interim Action Implementation (Aspect, 2008)

In 2008, Aspect conducted soil sampling during implementation of the interim action. Thirteen soil samples were collected for analysis of chlorinated VOCs by EPA Method 8260B, and two soil samples were also analyzed for 1,4-dioxane by EPA Method 8270. The samples analyzed for TCE were collected from shallow soils at air sparging wells along the underground piping alignment to characterize soil removed from trenching for disposal. The samples submitted for dioxane analysis were collected from boring AS-25 at 6 feet bgs and from the pipe trench near MW-1 at a depth of 2 feet. The sample from the trench was also analyzed for TCE. Soil sampling data collected during implementation of the interim action have been incorporated into this RI Report.

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4.2 RI Investigations This section provides a description of the investigation work completed during the RI period (October 2008 through August 2012). Investigations were completed to characterize soil, groundwater, porewater, and hydrogeologic conditions. All work was completed in accordance with the Agreed Order and done under multiple Ecology approvals, as summarized in the quarterly progress reports. Exploration locations are depicted on Figure 4A, 4B, and 4C. Boring logs and well completion diagrams are provided in Appendix A.

4.2.1 Groundwater Monitoring Well Installations During the RI period, a multi-well monitoring network was installed. Table 2 provides a summary of the well completion information for all wells located in the ABP monitoring network. Work completed during the RI included the following:

Installing one piezometer in the Water Table Interval.

Installing 48 monitoring wells:

18 wells completed in the Water Table Interval;

12 wells completed in the Shallow Interval; and

18 wells completed in the Intermediate Interval.

Surveying of the monitoring well top-of-casing elevations into the PSC well network. Surveying was completed by Professional Land Surveyors, Inc in June 2010. The survey was completed with an accuracy of +/- 0.01 feet. Wells installed in spring 2011 were surveyed by Aspect with an accuracy of +/- 0.01 feet.

4.2.2 Groundwater Monitoring ABP has implemented a quarterly groundwater quality monitoring program to obtain data for this RI and the subsequent FS. Groundwater monitoring was completed to meet various objectives of the RI, sentinel monitoring near the Waterway, interim actions performance monitoring, and vapor intrusion (VI) assessment. Table 3 provides a summary of the monitoring objectives per individual well (e.g., wells sampled to monitor the plume centerline). Table 4 provides a summary of the groundwater sampling chemical analyses completed during the RI investigation period.

4.2.3 Groundwater Sampling with Probes The primary purpose of the groundwater samples collected from probes was to better delineate the vertical and horizontal boundaries of the chlorinated solvent plume and guide placement of monitoring wells. The secondary purpose of the groundwater probe sampling was to identify other potential sources of chlorinated solvents in the vicinity of the Facility. Sample locations identified for the secondary objective were based on historical research and the facilities identified on Figure 3.

The following probe work was completed during the course of the RI:

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Advancing direct-push borings SPO-15 through SPO-52 up to a depth of 74 feet bgs, with one exception. Probe SPO-43 was not completed due to access issues on the Saint-Gobain Containers property;

Collecting 53 grab groundwater samples from the Water Table Interval;

Collecting 68 grab groundwater samples from the Shallow Interval;

Collecting 84 grab groundwater samples from the Intermediate Interval;

Submitting 190 groundwater samples for analysis of chlorinated VOCs by EPA Method 8260;

Submitting 16 samples for analysis of dissolved arsenic, manganese, and iron by EPA Methods 200.8 or 6010B;

Submitting 20 samples for analysis of dissolved cadmium, copper, nickel, and zinc by EPA Method 200.8; and

Submitting 3 groundwater samples for analysis of 1,4-dioxane by EPA Method 8270, 1 from SPO-16 and 2 from SPO-18.

4.2.4 Porewater Sampling Groundwater monitoring data suggested the potential discharge of the chlorinated volatile organic compound TCE, and its degradation products cis-1,2-dichloroethene (cis-DCE) and vinyl chloride along the eastern side of the Waterway. The purpose of the porewater sampling program was to measure concentrations of chlorinated ethenes in sediment porewater discharging into the biologically active zone of Waterway sediments (Aspect, 2011a & 2011b). The program was completed in two phases:

Phase 1 – Sediment Sampling (February 2011)

Collecting 67 VanVeen grab samples. Samples were collected from both a “coarse-grid” spacing (50-foot) and a “fine-grid” spacing (15-foot) to assess whether reduced sediment porewater sampling spacing is likely to improve the resolution of preferential groundwater discharge locations.

Measuring salinity in sediment grab sample.

Measuring grain size composition (e.g., percent fines) of the individual samples.

Phase 2 – Porewater Sampling (May 2011)

Collecting porewater samples at 25 locations in the Waterway. Porewater sample locations were determined based on Phase 1 results.

Submitting 27 samples (2 field duplicates) for analysis of chlorinated VOCs by EPA Method 8260.

4.2.5 Soil Sampling The purpose of the soil sampling proposed for the RI was to provide further definition of the lateral and vertical distribution of contaminants in close proximity to the suspected source areas as well as support contaminant fate and transport modeling. The sampling program included the following:

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Collecting 40 soil samples for analysis of total organic carbon by Method Plumb 1981: 25 from the Water Table Interval, 8 from the Shallow Interval, and 7 from the Intermediate Interval.

Collecting 97 soil samples by EPA Method 5035 for analysis of chlorinated VOCs by EPA Method 8260: 72 from the Water Table Interval, 20 from the Shallow Interval, and 5 from the Intermediate Interval.

Collecting 28 soil samples for analysis of iron and manganese by EPA Method 6010B: 19 from the Water Table Interval, 5 from the Shallow Interval, and 4 from the Intermediate Interval.

Collecting 95 soil samples for analysis of cadmium, copper, nickel, and zinc by EPA Method 200.8: 83 from the Water Table Interval, 8 from the Shallow Interval, and 4 from the Intermediate Interval.

4.3 Indoor Air and Soil Vapor Sampling ABP completed several investigations involving indoor air and/or soil vapor sampling under the vapor intrusion (VI) assessment program, to evaluate whether indoor air in nearby buildings was being unacceptably impacted by VI. Sampling was conducted at the following addresses:

214 S. Findlay St. – Indoor air sampling was conducted at this residence on two occasions, in August and December 2009. Results are documented in Aspect, 2010a.

215/217 S. Findlay St. – Indoor air sampling was conducted at this building in December 2005. Results are documented in Aspect, 2006b.

218½ S. Findlay St. – Indoor air sampling was conducted at this residence in December 2009. Results are documented in Aspect, 2010a.

222 S. Orcas St. – Indoor air sampling was conducted at this building in December 2009, followed by sub-slab soil vapor sampling in April 2010. Results are documented in Aspect, 2010a and Aspect, 2010b, respectively.

The results of indoor air sampling at 222 S. Orcas St. were inconclusive. The results of all other sampling events listed above indicated that indoor air in the respective buildings was not being unacceptably impacted by VI. Refer to Section 6.1 and Appendix E for a detailed discussion of the VI assessment program.

ABP also conducted indoor air and soil vapor sampling associated with implementation of the interim cleanup action discussed in Section 6.2 and Appendix F.

4.4 Data Quality Assessment and Usability This section provides a summary of the analytical and field data quality and usability. Appendix K provides a more detailed assessment of the data quality as well as the laboratory certificates of analysis and data validation reports.

Analytical Data Assessment. EcoChem, Inc., a data validator, performed third-party validation of the soil and groundwater analytical results collected during the RI. The data

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validation was conducted in accordance with the Ecology approved RI Work Plan (Aspect, 2008). The validation process was performed to provide a determination of whether the data meets the project specific criteria for data quality and data use. All data were deemed acceptable by the data validator, incorporating data qualifiers as appropriate.

To complete the RI and FS, two critical data needs are identified: 1) definition of the boundary of contamination; and 2) evaluation and monitoring of potential current exposure risks. An analysis of the spatial and temporal representativeness of the data set has identified some data gaps as summarized in Table 5. Existing data has been used to interpolate through these data gaps. Uncertainties are inherent in such extrapolations; however, the existing data are sufficient to complete the RI and FS.

Field Data Assessment. Field data are considered data collected in the field that did not require laboratory analysis. Data included in this category are groundwater elevation data, field parameters collected during groundwater monitoring, and hydraulic tests. Standard field protocols (e.g., sampling procedures and documentation, sample handling, sample custody, hydraulic conductivity testing) are defined in the Standard Field Methods plan located in Appendix B of the RI Work Plan (Aspect, 2008). Adherence to these methods has ensured the quality of data generated. Furthermore, a Washington State-licensed hydrogeologist has reviewed field activities and generated data. Field data were acceptable for use in this RI with the exception of pH data collected in December 2010 and March 2011, which were not included due to a faulty pH probe that was subsequently replaced.

5 Environmental Regulations and Potential Cleanup Levels

Many environmental laws may apply to cleanup actions at the Facility. A number of these laws identify chemical concentrations in environmental media that are determined to be protective of human health and the environment under specified exposure conditions (i.e., cleanup levels). In this section, we identify potentially applicable environmental regulations and cleanup levels, and select screening levels based on the lowest cleanup level for a particular media and exposure pathway. In Section 6, chemical concentrations detected in the Study Area are compared to screening levels to determine chemicals of concern (COCs). Preliminary cleanup levels for site COCs will be developed in the FS and finalized by Ecology in the Cleanup Action Plan (CAP).

5.1 Potential Applicable Regulatory Requirements The following provides a summary of potentially applicable or relevant and appropriate requirements (ARARs) based state and federal laws. Because the RI is being conducted under an Agreed Order with Ecology, permits that would otherwise be required for certain actions (for instance, air emissions) are not required, but the substantive requirements of the applicable regulations must still be met.

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5.1.1 Potentially Applicable Federal Requirements The Clean Water Act (CWA) (33 USC Section 1251 et seq.) requires the establishment of guidelines and standards to control the direct or indirect discharge of pollutants to waters of the United States. Section 304 of the CWA (33 USC 1314) requires the U.S. Environmental Protection Agency (EPA) to publish Water Quality Criteria, which are developed for the protection of human health and aquatic life. Federal water quality criteria are published as they are developed, and many of them are included in Quality Criteria for Water 1986, EPA 440/5-86-001, May 1, 1986 (51 FR 43665), commonly known as the "Gold Book". Publications of additional criteria established since the Gold Book was printed are announced in the Federal Register. Federal water quality criteria are used by states, including Washington, to set water quality standards for surface water. These standards are adopted by the state under the Washington Water Pollution Control Act (see Section 5.1.2).

Since the Waterway is an estuary, fresh, brackish, and/or marine water body, Water Quality Criteria may also be potentially applicable at different locations and under different seasonal conditions within the area. Surface water quality criteria may be applicable to the sediment/porewater interface. Because estuary water is considered non-potable, potentially applicable Water Quality Standards for protection of human health are based on consumption of organisms only.

Resource Conservation and Recovery Act. The Resource Conservation and Recovery Act (RCRA) addresses the generation and transportation of hazardous waste, and waste management activities at facilities that treat, store, or dispose of hazardous wastes. Subtitle C (Hazardous Waste Management) mandates the creation of a cradle to grave management and permitting system for hazardous wastes. RCRA regulates "solid wastes" that are hazardous because they may cause or significantly contribute to an increase in mortality or serious illness, or that pose a substantial hazard to human health or the environment when improperly managed. In Washington State, RCRA is implemented by EPA and/or Ecology under the State’s Dangerous Waste Regulations, Chapter 173-303 WAC. For this RI, RCRA regulations potentially apply1 to wastes (i.e., soil or water) generated at the Facility during investigation and interim measure activities.

Federal and State Clean Air Acts (42 USC 7401 et seq.; 40 CFR 50; RCW 70.94; WAC 173-400, 403). The Clean Air Act regulates emissions of hazardous pollutants to the air. Controls for emissions are implemented through federal, state and local programs. The Clean Air Act is implemented in the state of Washington through the Washington Clean Air Act (RCW 70.94). The regional air pollution contract authorities, activated under the Washington Clean Air Act, have jurisdiction over regulation and control of the emission of air contaminants and the requirements of state and federal Clean Air Acts in their districts. Both the federal and Washington state Clean Air Acts regulate air emissions generated during interim measures implemented at the Facility (i.e., soil vapor extraction and vapor mitigation).

5.1.2 Potentially Applicable State and Local Requirements Washington Model Toxics Control Act (MTCA; Chapter 70.105D RCW). This Act authorized Ecology to adopt cleanup standards for remedial actions at sites where 1 Depending on the presence and/or concentration of hazardous chemicals regulated under RCRA.

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hazardous substances are present. The processes for identifying, investigating, and cleaning up these sites are defined and cleanup standards are set for groundwater, soil, surface water, and air in Chapter 173-340 WAC. MTCA does not contain standards for the cleanup of contaminated sediments but instead references the requirements in the Washington State Sediment Management Standards (SMS; Chapter 173-204 WAC), discussed below.

MTCA procedures employ a risk-based evaluation of potential human health and environmental exposures to site COCs. To establish cleanup standards, it is necessary to determine both the cleanup level that will apply as well as the point of compliance. For a given COC detected in soil, groundwater, surface water, and/or air, cleanup levels must be at least as stringent as established state or federal standards or other laws (i.e., ARARs) developed for human health and environmental protection. Not all COCs have state or federal standards. If a state or federal standard is available, that ARAR is evaluated to ensure that it is protective under MTCA. If the ARAR is not protective, the cleanup level is adjusted to a lower value to ensure its protectiveness.

The cleanup level for one media must also be protective of the beneficial uses of other affected media. For example, since Study Area groundwater eventually discharges into the Waterway, site-specific MTCA groundwater cleanup levels need to consider the protection of surface water. The procedures for developing cleanup levels for groundwater, surface water, soil, and air are outlined in the MTCA Cleanup Regulation Sections 173-340-720, -730, -740, and -750 WAC, respectively. Included in these sections are the specific rules for evaluating cross-media protectiveness.

Washington Sediment Management Standards (SMS; Chapter 173-204 WAC). When contaminated sediments are involved, the primary regulations governing cleanup levels and other procedures are the SMS. The SMS were developed to establish cleanup standards for marine, low salinity, and freshwater environments for the purpose of reducing and/or eliminating adverse effects on biological resources and significant health threats to humans from surface sediment contamination. Both the SMS and MTCA regulations require that cleanup actions must protect human health and the environment, meet environmental standards in other applicable laws, and provide for monitoring to confirm compliance with cleanup levels.

Contaminated groundwater discharges from the Study Area to the Waterway. Since there are no promulgated sediment cleanup standards for the primary COCs (chlorinated ethenes), the SMS allows for development of alternative sediment cleanup levels based on ARARs. In this case, surface water quality criteria promulgated under the federal CWA (33 USC Section 1251 et seq.) and Washington Water Pollution Control Act (Chapter 90.48 RCW; Chapter 173 201A WAC) may be ARARs for the sediment/surface water interface. As discussed above, MTCA requires that these ARARs be further evaluated to ensure they are adequately protective under MTCA (e.g., cumulative cancer risk of less than 10-5 under reasonable maximum exposure conditions; WAC 173-340-708). If the ARAR is not protective, the cleanup level is adjusted to a lower value to ensure its protectiveness.

State Environmental Policy Act (SEPA; RCW 43.21C; WAC 197-11). The SEPA is intended to ensure that state and local government officials consider environmental

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values when making decisions. The SEPA process is required for any government “action” as defined in SEPA Rules (WAC 197-11-704) that is not categorically exempt (WAC 197-11-800 through 890). Under SEPA, agencies must follow specific procedures to ensure that appropriate consideration has been given to the environment. For this RI, which is under an Agreed Order, Ecology is the lead agency for SEPA, and conducted SEPA review prior to beginning the RI. Additional SEPA review may be required prior to conducting the FS or implementing future cleanup actions.

Washington Water Pollution Control Act (Chapter 90.48 RCW; Chapter 173 201A WAC). This Act provides for the protection of surface water and groundwater quality. Chapter 173-201A WAC establishes water quality standards for surface waters of the state. As with the CWA, this RI considers marine surface water standards to be potentially applicable because of the potential for discharge of COCs to a marine surface water body (the Duwamish Waterway).

Washington Hazardous Waste Management Act (Chapter 70.105 RCW; Chapter 173-303 WAC). This regulation implements the State Hazardous Waste Management Act of 1976 as amended, and also implements RCRA. Unlike RCRA, which defines hazardous wastes as those solid wastes designated by 40 CFR Part 261 and regulated as hazardous and/or mixed waste by EPA, Chapter 173-303 WAC distinguishes between different types of wastes, including dangerous, extremely hazardous, and mixed waste. As with RCRA, for this RI these regulations apply to wastes (i.e., soil or water) generated at the site during investigation and interim measure activities.

5.2 Potential Exposure Pathways Potential receptors and exposure pathways are described below for the purposes of identifying screening levels. Screening levels based on potential pathways are identified in Section 5.3. In Section 9, these pathways are evaluated relative to pathway-specific screening levels for current and potential future uses on and off the ABP property.

Potential Receptors The Study Area includes upland and aquatic areas. Potential receptors in the upland areas include:

Above-ground workers (e.g., employees at commercial facilities);

Below-ground workers (e.g., construction workers conducting digging or trenching operations); and

Residents.

Potential receptors in aquatic areas include:

Recreational beach users;

Recreational fisher/shellfish harvesters;

Subsistence fisher/shellfish harvesters; and

Aquatic organisms.

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Because of the developed nature of the area, the site qualifies for an exclusion from a terrestrial ecological evaluation, on the basis that there are less than 1.5 acres of contiguous undeveloped land on the site or within 500 feet of the site (WAC 173-360-7491). This condition is not likely to change in the foreseeable future. Therefore, terrestrial ecological receptors were not considered in determining potential screening levels.

Potential Exposure Pathways Potentially impacted media in the Study Area include soil, groundwater, air, and surface water. Potential exposure pathways for each medium are identified below. Potential exposure pathways under current or potential future uses for potential receptors on and off the ABP Property are summarized in Table 6. An evaluation based on available data and area conditions, and of whether these exposure pathways are currently complete or could be complete in the future is provided in Section 9.

As discussed in Section 2, no residents are currently located on the ABP property. Off the ABP property, the Study Area includes a mixture of industrial, commercial, and residential uses. For the purposes of identifying potential exposure pathways, it is assumed that any of the properties in the Study Area, including the ABP property, could potentially be used for industrial, commercial, or residential purposes in the future.

Soil

Potential direct exposure pathways for soil contamination include:

Direct contact; and

Dust inhalation.

Although existing surface materials (asphalt and concrete) prevent contaminated soils from being inhaled or contacted, this is a potential future exposure pathway in the event that coverings are removed or below-ground work is conducted. Therefore, these pathways are considered potential current and/or future exposure pathways for all potential upland receptors.

Soil contamination may also contribute to contamination in other media through intermedia transport, as follows:

Air contamination, via the soil-to-air migration pathway (i.e., volatilization); and

Groundwater contamination, via the soil-to-groundwater migration pathway (i.e., leaching).

Potential groundwater and air exposure pathways are discussed below.

Groundwater. Based on the results of a potability analysis (see Section 5.4), groundwater in the Study Area is not considered a current or potential future source of drinking water. Therefore, ingestion of groundwater was not considered in identifying potential screening levels for the RI2.

2 It is expected (based on the East-of-4th CAP for the PSC-Georgetown Site (Geomatrix 2010)) that the FS and CAP will need to consider a possible future scenario where groundwater, at least in some areas, may become viewed as a drinking water resource.

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Potential direct exposure pathways for groundwater contamination include:

Incidental direct contact.

This pathway is considered a potential current and/or future exposure pathway only for below-ground workers. Above-ground residents and workers are not expected to contact groundwater, which is located 4 to 10 feet below ground surface.

Groundwater contamination may also contribute to contamination in other media, as follows:

Air contamination, via the groundwater-to-air migration pathway (i.e., volatilization); and

Surface water contamination, via the groundwater-to-surface water migration pathway (i.e., discharge to surface water).

Air. VOCs in contaminated soil and groundwater may volatilize into soil gas, which in turn may migrate into indoor or outdoor air (i.e., vapor intrusion). Contaminated soil gas is also captured by the SVE system, treated, and the treated soil gas discharged to ambient air. Potential exposure pathways for VOCs in air include:

Inhalation of outdoor air; and

Inhalation of indoor air.

Inhalation of indoor and outdoor air contaminated via vapor intrusion is a potential current and/or future exposure pathway for all potential receptors. Outdoor inhalation of VOCs is considered a potential exposure pathway for below-ground workers. Off-property, outdoor inhalation of VOCs from the SVE system is not considered a potential exposure pathway because the SVE system discharge is monitored to prevent exposure above acceptable levels as an operational requirement.

Surface Water/Sediments. The nearest surface water/sediment receptor, the Waterway, is a brackish water body that is not a potential drinking water source. Potential exposure pathways for contaminated3 surface water and sediment include:

Incidental direct contact to humans;

Direct contact by aquatic organisms;

Aquatic or terrestrial organism ingestion of contaminated aquatic organisms; and

Human ingestion of contaminated aquatic organisms.

5.3 Screening Levels Screening levels were identified based on potential current and potential future exposure pathways. Screening levels for each medium take into account not only direct exposure to that media but also exposure resulting from intermedia transport. In particular, the following transport pathways were considered in identifying potential screening levels:

3 The pathways noted for surface water and sediments refer to exposure to media or biota that have been contaminated by discharge of contaminated Study Area groundwater – not contaminated via other sources.

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Soil screening levels based on protection of groundwater;

Groundwater screening levels based on protection of indoor air; and

Groundwater screening levels based on protection of surface water.

The ABP Study Area is a subset of the region evaluated by PSC when establishing their cleanup levels for the PSC Georgetown Facility. Therefore, the screening levels for the ABP Study Area are based on the potential cleanup levels identified for the PSC Georgetown Facility in the Site Wide Feasibility Study (Geomatrix, 2006). The discussion below and Tables 7 and 8 provide a summary of the basis of these screening levels. PSC’s Site Wide Feasibility Study provides a more detailed analysis. Updated cleanup levels are provided in PSC’s east-of-4th Cleanup Action Plan (Geomatrix, 2010). The screening levels for soil and groundwater in Tables 7 and 8 have been modified from those presented in Geomatrix reports as follows:

The Facility is an industrial facility in an area zoned industrial, but is bordered by a mixture of industrial, commercial, and residential uses. Therefore, soil screening levels for the Study Area consider potential residential exposure; and

To account for recent changes in risk-based cleanup level assumptions, including fish consumption rates and toxicological information.

Screening levels for soil are provided in Table 7, as follows:

Screening levels based on direct contact under residential use (Method B Direct Contact) and industrial use (Method C Direct Contact). Screening levels based on direct contact under residential use and industrial use are provided for both carcinogenic and non-carcinogenic effects. The lowest of these screening levels based on the direct contact pathway is considered protective of the direct contact pathway for all potential receptors on and off the Facility property. This level is also considered protective of the dust inhalation pathway for all potential receptors on and off the property for two reasons:

COCs at the Facility are either volatile organic compounds (e.g., TCE) that would volatilize and not adhere to airborne dust particulates, or metals with very low human toxicity values (e.g., nickel, copper, and zinc).4

VOCs in dust are very unlikely to contribute significantly to risk when present at concentrations below the direct contact screening level. For example, an environment containing soil particulates at the Occupational Safety and Health Administration’s Permissible Exposure Limit (OSHA PEL) for dust (15 mg/m3) that are contaminated with TCE at the residential direct contact screening level (12 mg/kg) would contain TCE at a concentration in air of 0.18 µg/m3, which is lower than the air screening level based on residential exposure.

The screening level based on groundwater protection (Method B Groundwater Protection). The groundwater protection screening level is based

4 For example, the PSC Risk Assessment (PSC, 2001) only considered arsenic, cyanide, and carcinogenic PAHs when evaluating the risks from dust inhalation.

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on the lowest potential groundwater screening level, which considers protection of indoor air (under residential exposure assumptions); therefore, the groundwater protection screening level for soil is considered protective of the soil-to-air pathway for above-ground receptors. This screening level is also considered protective of the soil-to-air pathway for below-ground workers.

Groundwater screening levels are provided in Table 8 and are dependent on the sampling interval. Screening levels for the Water Table Interval are the lower of levels for two potential exposure pathways: 1) groundwater to surface water, and 2) indoor vapor inhalation. Groundwater screening levels for the Shallow and Intermediate Intervals are based on the groundwater to surface water pathway. Surface water screening levels are the same as groundwater screening levels for the Shallow and Intermediate Intervals presented on Table 8. Based on the PSC Risk Assessment, which identified the highest potential risk from contaminated groundwater to be residential indoor air when compared to potential commercial, industrial and trench worker exposure scenarios (PSC 2001, Table 2-15), groundwater to indoor air screening levels are also considered protective of the groundwater direct contact pathway for below-ground workers.

Screening levels for indoor and outdoor air were calculated in accordance with WAC 173-340-750. Indoor air screening levels depend on the specific exposure scenario, which varies within the Study Area. Screening levels under residential and commercial exposure scenarios are presented in Table 9.

Screening levels for sediments and porewater are based on the lowest potential screening level for potential ecological or human receptors. Potential screening levels for human health are based on the subsistence fisher pathway for the Asian-Pacific Islander (API-Fisher) population5 or ARARs. These screening levels are assumed to also be protective of recreational fisher and recreational direct contact.

Where appropriate, screening levels are adjusted to natural background or the practical quantitation limit (PQL), whichever is higher, in accordance with WAC 173-340-700 through 750. PQLs, and natural background concentrations if applicable, are included in Tables 7, 8, and 9.

5.4 Groundwater Potability Analysis Under MTCA, groundwater cleanup levels must be based on the highest beneficial use of groundwater. The highest beneficial use would be drinking water unless the criteria outlined in the MTCA definition are not met as detailed in WAC-173-340-720-2. PSC completed a potability analysis as part of their Remedial Investigation Report (PSC, 2003). The ABP Study Area is a subset of the region evaluated by PSC when completing their potability analysis. PSC concluded that cleanup standards for groundwater based on the use of groundwater as drinking water would not be applicable. ABP concurs with this conclusion and these cleanup standards have not been included in the discussion of the data.

5 Note that fish consumption rate assumptions are currently being reviewed by Ecology.

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PSC’s potability analysis provided the following summary for their analysis which concluded that the cleanup standards for groundwater based on the use of groundwater as drinking water would not be used for the PSC-Georgetown facility:

“The groundwater is not currently used as a source of drinking water and would not be classified as a potential future source of drinking water under WAC 173-340-720 (2). Furthermore, it is highly unlikely that the groundwater contamination in the shallow and intermediate aquifers at the site is hydraulically connected to any groundwater or surface water that is a potential future source of drinking water. Various state and local regulations prohibit the installation and use of drinking water wells in the vicinity of the facility. Several other sites in the Duwamish Basin have been granted a “non-potable” designation under MTCA or federal law. These sites include, but are not limited to: Harbor Island, Southwest Harbor Project, Great Western Chemical, Fostoria Business Park, Spencer Industries, Holnam Markey Site and the Myrtle Street Property, shown in Figure 6-3. Cleanup standards developed for these sites are based on the protection of surface water as a non-potable water body. Consequently, the cleanup levels for the contaminated groundwater in the vicinity of the site will not include standards based on the use of groundwater as a source of drinking water. Because groundwater from the shallow and intermediate aquifers discharges to the Duwamish River and the Duwamish River is classified for use as wildlife habitat and for shellfish harvesting, groundwater cleanup standards will be protective of these uses.”

ABP has not identified any changes to land use in the area. As stated above, regulations prohibit the installation and use of drinking water wells in the vicinity of the Facility. In 2000 and 2001, PSC completed several surveys of businesses and residences located in the area and no drinking water wells existed on the responding properties (PSC, 2003). Aspect reviewed well logs available on the Ecology website as of July 2012 and no drinking water wells were identified in the vicinity of ABP.

6 Interim Actions

Chlorinated solvents in Study Area groundwater at the water table exceed screening levels for the vapor intrusion pathway. Because of the concern for this pathway, two interim actions were implemented prior to the completion of the RI: 1) a vapor intrusion mitigation program; and 2) source control remediation. These actions are described below.

6.1 Vapor Intrusion Mitigation Program In June 2001, EPA and Ecology modified PSC’s corrective action permit and required that PSC implement groundwater interim measures. The interim measures focused primarily on protecting indoor air quality in areas where shallow groundwater was contaminated with VOCs. VOCs can volatilize and migrate upwards in the soil vapor space above the water table. Where contaminated shallow groundwater lies beneath a building, VOCs have the potential to move indoors through cracks or other openings,

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contaminating indoor air in a phenomenon known as vapor intrusion (VI). VI from groundwater was evaluated under MTCA, pursuant to WAC 173-340-350, 173-340-720(1)(c), 173-340-720(1)(d)(iv), and 173-340-750.

In 2002, PSC developed and began implementing an Inhalation Pathway Interim Measure (IPIM) Program (presented in PSC, 2002) to determine whether individual buildings or building “clusters” warrant further investigation or mitigation through an interim measure. The following tiered decision process is used to implement the IPIM Program:

Tier 1 – Quarterly groundwater quality data are evaluated with respect to volatilization potential to determine whether residential buildings located in areas of impacted groundwater merit further evaluation under Tier 3 (or proceed directly to Tier 4).

Tier 2 – Quarterly groundwater quality data are evaluated with respect to volatilization potential to determine whether commercial/industrial buildings located in areas of impacted groundwater merit further evaluation under Tier 3 (or proceed directly to Tier 4).

Tier 3 – Building-specific sampling is conducted (potentially including indoor air, ambient air, groundwater, and soil/sub-slab vapor sampling) to empirically determine whether installation of a VI mitigation system (under Tier 4) is warranted.

Tier 4 – A sub-slab depressurization (SSD) or sub-membrane depressurization (SMD) system is installed and operated. These systems are designed to mitigate VI in buildings with floor slabs and crawl spaces, respectively. Similar to systems used for keeping out radon gas, they induce a small vacuum under the building and thereby minimize any movement of soil vapor indoors.

During implementation of the IPIM Program and in order to finalize the PSC Georgetown Facility RI, PSC conducted groundwater investigations in the Georgetown neighborhood west of 4th Avenue South (W4 Investigation Area). These investigations identified TCE in groundwater downgradient of the PSC facility at higher concentrations than were detected upgradient of that facility. As a result, ABP initiated the subsurface investigations documented in this RI. Based on investigation results, ABP replaced PSC as the lead business for interim VI measures for certain properties in the vicinity of the Facility. PSC investigations in the W4 Investigation Area also identified VOC source areas at Blaser (5700 3rd Avenue S) and Capital (5801 2nd Avenue S). As with ABP, Blaser and Capital became the lead businesses for interim VI measures for certain properties in the vicinity of their facilities.

To establish a consistent interim process to assess and mitigate potential VI threats in the W4 Investigation Area, PSC, ABP, Blaser, and Capital jointly prepared (at Ecology’s request) an Interim VI Plan (Arrow et al., 2007). The Interim VI Plan lists the Ecology-identified buildings to be addressed by each of the four lead businesses, presents a proposed interim VI approach, and specifies that the Ecology-approved methodologies of PSC’s IPIM Program be adopted by the lead businesses.

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The Interim VI Plan lists 23 buildings where ABP is responsible for conducting interim VI activities. These buildings, the locations of which are shown on Figure 47, can be categorized as follows:

Twelve of the buildings (colored green on Figure 47) were at various stages of VI assessment when the Interim VI Plan was prepared. VI assessment activities associated with these buildings are discussed in Appendix E.

Nine of the buildings (colored purple on Figure 47) already had VI mitigation systems installed (by PSC) and operating when the Interim VI Plan was prepared. System installation is briefly discussed in Appendix E. Inspection, monitoring, and maintenance (IM&M) activities associated with those systems are discussed in Appendix E.

VI mitigation was planned but not yet implemented at the Facility itself and the office building directly across 3rd Avenue South (colored peach on Figure 47). An air sparging (AS) and soil vapor extraction (SVE) system was subsequently installed and is currently operating (as an interim cleanup action) at the Facility. The primary purpose of the AS/SVE system is source removal, but it also provides VI mitigation. That system is discussed in Section 6.2 and Appendix F. A SSD system was installed and is currently operating in the office building across the street. SSD system installation is briefly discussed in Appendix E, and IM&M activities associated with that system are discussed in Appendix E.

For other (unshaded) buildings shown on Figure 47 that are adjacent to those noted above, subsurface investigations completed prior to preparation of the Interim VI Plan indicated that interim VI activities were not needed. Changes to subsurface conditions since those investigations were completed include the following:

VOC concentrations in water table groundwater have improved considerably, largely due to the operation of the AS/SVE system discussed in Section 6.2. Lower VOC concentrations in water table groundwater result in a reduced potential for VI threats.

Operation of the AS/SVE system causes pressure gradients in the vadose zone soil that could potentially result in the migration of vapor-phase contaminants into areas that were not previously impacted. For example, positive pressure caused by air sparging beneath the ABP building could potentially push contaminated soil vapor eastward towards the adjacent buildings along 4th Avenue South. To address this concern, differential pressures are monitored in the vicinity of the AS/SVE system and vapor migration potential is evaluated, as discussed in Appendix F.

Therefore, subsurface conditions are only expected to improve over time, and follow-up VI investigations should not be needed at the unshaded buildings on Figure 47.

Details of the VI assessment and mitigation work conducted by ABP are compiled in Appendix E. This appendix also includes an assessment that supports shutdown of current mitigation systems where conditions are now protective of indoor air quality.

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6.2 Source Control In September 2008, ABP installed an AS/SVE system to remove chlorinated COCs from soil and groundwater at and around the Facility. The system includes 28 AS wells, 13 SVE wells and 10 trenches. Extracted vapors are treated with granular activated carbon (GAC).

The objectives of the AS/SVE system were as follows:

Prevent vapor intrusion at the Facility and the adjacent 220 Findlay office building; and

Reduce soil and groundwater concentrations of TCE, cis-DCE, and vinyl chloride to levels that significantly reduced the restoration time frame and were protective of the indoor air pathway.

The AS/SVE system has operated continuously (except for periodic shutdowns for monitoring and maintenance) since being installed. In late 2011, the AS portion of the system was shutdown to conduct a rebound analysis. The system has removed approximately 72 pounds of TCE from the subsurface, and groundwater concentrations of TCE have declined 90 to 99 percent at wells in and around the treatment area. A full description of system monitoring and an analysis of system performance are provided in the Interim Measures Evaluation (Appendix F).

7 Nature and Extent of Contamination

7.1 Chemicals of Concern The Agreed Order identified the following chemicals of potential concern to be investigated:

Trichloroethene (TCE)

Dichloroethenes (DCEs)

Vinyl chloride

1,4-Dioxane

Iron

Manganese

In the RI Work Plan, data collected at and around the Facility from pre-RI investigations was compared to preliminary screening levels. Based on that evaluation, the RI Work Plan also identified the following chemicals that needed further evaluation to determine if they were present at levels of potential concern:

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Arsenic Copper

Barium Nickel

Cadmium Zinc

Chromium Tetrachloroethene (PCE)

Through a comparison of the available data with the screening levels identified in Tables 7 and 8, these constituents were retained as COCs, with one exception. Chromium was not identified above screening levels. Occurrences of COCs in each media are described below.

7.2 Soil Quality This section provides a discussion of the soil quality data collected by ABP. A majority of the soil data has been collected near the Facility to define the nature and extent of the contaminant source area. Soil samples in the vicinity of the Facility have mainly been analyzed for VOCs and metals. Two samples from the vadose zone were analyzed for 1,4-dioxane. One sample was collected from a depth of 6 feet at AS-25 and the other collected from a trench near the vapor degreaser during installation of the interim remedial action. These soil samples were non-detect for 1,4-dioxane. The soil sample discussion below has been divided into two parts, chlorinated solvents and metals.

7.2.1 Chlorinated Solvents Prior to installation and operation of the AS/SVE system, 61 soil samples were collected from 39 locations (pre-remediation samples). Samples were collected from depths up to 45 feet. An additional 54 soil samples from 13 borings were collected in 2012 after the AS system was shut down to conduct a rebound analysis (see Appendix F). The post-remediation6 samples were collected to further define the extent of contamination and to evaluate AS/SVE system effectiveness in reducing solvent concentrations in soil. As described in Appendix F, the data show an improvement in both vadose and saturated zone soil quality from remediation. However, most post-remediation samples were located near, but not directly adjacent to, pre-remediation sample locations, and the heterogeneity of shallow soils adds uncertainty when comparing sample results. In general, both pre- and post-remediation samples have been used to identify the extent of contamination, except where more recent data appear more representative as noted in the discussion below.

Of the chlorinated solvent COCs, only TCE has been detected in soil above proposed soil screening levels for groundwater protection or direct contact (0.058 mg/kg and 12 mg/kg, respectively). Soil TCE data are illustrated on Figure 11 for soil above the water table and on Figure 12 for soil below the water table. Results for each of these intervals are discussed below.

Vadose Zone. TCE concentrations above the seasonal high water table (sample depths of 6 feet or less) have ranged up to 14 mg/kg. The highest concentrations were detected in

6 These samples are identified as post-remediation for the purposes of this RI Report; however, remediation via SVE is still ongoing, and additional AS remediation is contemplated (see Appendix F).

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the southwest corner of the facility near Vapor Degreaser No. 1 that formerly used TCE. The highest concentration detected in post-remediation sampling was 0.13 mg/kg; however, the area south of Vapor Degreaser No. 1 was not sampled due to access constraints.

One pre-remediation sample (14 mg/kg at SP-9) slightly exceeded the TCE direct contact screening level (12 mg/kg). The estimated area of TCE exceeding the direct contact screening level is a localized area southwest of the Vapor Degreaser No. 1, on the Facility property (see Figure 11).

Exceedances of the groundwater protection screening level (0.058 mg/kg) for TCE in both pre- and post-remediation samples are limited to the area below the western half of the Facility. No samples collected above the water table off the ABP property exceeded the groundwater protection screening level. Only one post-remediation sample (0.13 mg/kg at SP-25, adjacent to the former degreaser) on the ABP property exceeded the groundwater protection screening level.

Saturated Zone. TCE concentrations below the seasonal high water table (sample depths greater than 6 feet) have ranged up to 55 mg/kg. However, the highest concentration (55 mg/kg at SP-1) was detected prior to remediation; post-remediation sampling at SP-20 close to the same location indicated a maximum TCE concentration of 0.012 mg/kg. Furthermore, TCE concentrations in groundwater at MW-4 (installed at the location of SP-1) have declined more than 99 percent since remediation began. Therefore, the pre-remediation data from this location was not used to estimate the current extent of contamination.

The estimated area of soil in the saturated zone exceeding the direct contact screening level is a localized area southwest of Vapor Degreaser No. 1, on the Facility property (see Figure 12).One pre-remediation sample (21 mg/kg at SP-9) exceeded the TCE direct contact screening level (12 mg/kg). Groundwater concentrations in the well installed at this location (MW-1) have declined more than 90 percent since remediation began; however, soil at this location was not sampled post-remediation due to access constraints. The highest TCE concentration in post-remediation sampling (12 mg/kg at SP-18, just north of SP-9) was detected at the direct contact screening level.

Soil samples exceeding the TCE groundwater protection screening level (0.058 mg/kg) are generally located within the groundwater plume beneath the Facility and downgradient of the Facility beneath the adjacent street rights-of-way. Three exceptions are pre-remediation soil samples collected from borings just east of the Facility that slightly exceeded the screening level (0.065 mg/kg at SP-4; 0.24 mg/kg at SP-7; and 0.021 mg/kg at SP-13). Groundwater concentrations measured at these borings were below the groundwater screening level.

The highest TCE concentrations in the saturated zone have generally been detected around the 9-foot depth interval, which is the approximate depth where soils transition from silt and silty sands to a more uniform sand. The deepest soil sample exceeding the groundwater protection screening level was collected from a depth interval of 12 to 16 feet at AS-1 (0.066 mg/kg). No soil samples below 16 feet have exceeded groundwater protection screening level.

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7.2.2 Metals Metals analyses were completed for soil samples collected from probe borings completed in and around the ABP Facility. For cadmium, copper, nickel, and zinc, 95 soil samples were collected from 17 locations from within and around the Facility (SP-18 through SP-33 and SPO-46). For iron and manganese, 28 soil samples were collected from 4 locations (SP-18 through SP-20 and SPO-46). No data exceed direct contact screening levels. The following provides a summary of the analytical data relative to State background concentrations (Ecology, 1994):

Cadmium was detected in 9 samples with concentrations ranging between 0.1 and 0.5 mg/kg. All data were below the State background concentration of 1 mg/kg.

Copper was detected in all 95 samples ranging between 4.8 and 77 mg/kg. One sample collected from location SP-18, inside the Facility, exceeded the State background concentration of 36 mg/kg with a concentration of 77 mg/kg. This sample was collected from a depth of 6 to 7 feet and is co-located with nickel exceedances.

Iron was detected in all 28 samples with concentrations ranging between 8,150 and 18,600 mg/kg. All detections are below the State background concentration of 42,100 mg/kg.

Manganese was detected in all 28 soil samples with concentration ranging between 62 and 170 mg/kg. All detections are above the State background concentration of 11 mg/kg.

Nickel was detected in all samples with concentrations ranging between 4.1 and 830 mg/kg. Nickel data is depicted on Figures 13 and 14 for the vadose zone and saturated soils, respectively.

Eighteen of the 95 collected samples exceed the State background concentration of 38 mg/kg. Three of these soil samples were from the vadose zone (6 feet or shallower) with concentrations ranging between 57 and 830 mg/kg. These soil samples were collected from borings located near the former plating area on the west side of the building (SP-18, SP-24 and SP-25). The remaining 14 exceedances were from below the water table with concentrations ranging between 520 and 68 mg/kg. These exceedances are located at depth in borings with vadose zone exceedances (SP-18, SP-24, and SP-25) or downgradient of the vadose zone exceedances (SP-19, SP-31, and SP-32).

Zinc was detected in all 95 samples ranging between 15 and 223 mg/kg. One sample collected from location SP-22 exceeded the State background concentration of 86 mg/kg with a concentration of 223 mg/kg. This sample was collected from a depth of 3 to 4 feet and is located in the waste storage area on the north side of the building.

Several soil samples have analytical data for cadmium, copper, nickel, and zinc that exceed MTCA Method B screening levels for groundwater protection. It should be noted that Method B calculated values are based on a soil partitioning quotient (Kd) that assumes a neutral pH. Depressed pH values have been measured in groundwater near the

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Facility. Since the Method B screening levels are based on a geochemical condition that does not exist at the Facility, a detailed discussion of the results relative to these standards is not appropriate in this section. Section 8 provides a discussion of the fate and transport of these metals within the context of the geochemical conditions near the Facility.

7.3 Groundwater Quality This section provides a discussion of the groundwater quality data collected from the Study Area. The Facility is located in an area where chlorinated solvents and other COCs originate from multiple different commercial and industrial sources, including the PSC property that is located upgradient of ABP. Data outside the Study Area collected by the W4 Group is provided on the figures for reference.

7.3.1 Chlorinated Solvents The primary chlorinated solvent COC is TCE; however under certain conditions, TCE can undergo reductive dechlorination and forms less chlorinated ethenes: dichloroethenes (cis-DCE, 1,1-DCE, trans-DCE) and vinyl chloride. Conditions that support reductive dechlorination do exist in the Study Area as exhibited by the presence of TCE and its daughter products at and downgradient of the Facility.

Plume Delineation Plume boundaries have been drawn based on the most stringent screening level for the given parameter at the sampling interval depicted. Multiple lines of evidence were used in delineating plumes for the various COCs that include groundwater data from monitoring wells, groundwater grab sample data from probes, and hydrogeologic conditions.

Figures 15 through 18 illustrate the data and plume boundaries for PCE, TCE, cis-DCE, and vinyl chloride, respectively, for the three groundwater intervals. The monitoring well data depicted in these figures represent the most recent recorded data from June 2012 or prior. Previous results from groundwater grab samples and data from Blaser and Capital are also presented on the figures. If multiple grab samples were collected within a given sampling interval, the highest reported value for that interval is depicted on the figure. At locations where both a well sample and grab sample were collected, the well sample is used for plume delineation.

Since multiple sources of chlorinated solvent contamination exist west of 4th Avenue South, the TCE plume provides a reliable technical illustration of the ABP plume footprint. Cis- DCE follows a similar trend as TCE however the extent of contamination has a smaller footprint. Vinyl chloride is an area-wide issue and has been more difficult to determine sources and source contributions, especially in those areas downgradient of other PLPs. As illustrated in Figures 15 and 19, the TCE plume footprint and total chlorinated ethene data identify the discrete areas of groundwater contamination resulting from different upgradient sources in an area where vinyl chloride concentrations become comingled. These data collectively enable us to differentiate the ABP plume from those originating from other source areas.

The following provides a more detailed discussion of the occurrences of TCE, PCE, cis-DCE, vinyl chloride, and total chlorinated ethenes.

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TCE The extent of TCE contamination is illustrated in plan view on Figure 15 for the three groundwater depth intervals. At the Water Table Interval, the most stringent screening level is based on protection of residential indoor air (6.8 µg/L). TCE contamination at the Water Table Interval extends approximately 300 feet southwest of the Facility, with recent detection ranging between 0.2 and 760 µg/L.

Within the Shallow Interval, TCE contamination has a narrow plume width of about 200 to 250 feet wide that extends from the Facility to the Waterway. Groundwater monitoring data from the Study Area exceed the most stringent groundwater screening level based on protection of surface water, Federal Ambient Water Quality Criteria for protection of human health (30 µg/L). Recent data range up to 2,000 µg/L, with the higher values located between East Marginal Way and 1st Avenue South.

The TCE plume extent at the Intermediate Interval has a similar narrow pattern, but is approximately 1,000 feet in length, between the Facility and the Waterway. Groundwater monitoring data from the Study Area exceed the most stringent groundwater screening level based on protection of surface water, Federal Ambient Water Quality Criteria for protection of human health (30 µg/L). Recent data range up to 8,200 µg/L with the higher values, like within the Shallow Interval, located between East Marginal Way and 1st Avenue South.

Figures 5 and 6 provide cross section representations of the TCE plume: one section along the approximate centerline of the plume oriented northeast-southwest (Figure 5, A-A’) and four others that are drawn perpendicular to the plume and oriented northwest-southeast (Figure 6, B-B’, C-C’, D-D’ and E-E’). Cross section locations are shown on Figure 4. From the southwest corner of the Facility the plume sinks and reaches its deepest point of approximately 75 feet between 2nd Avenue South (SPO-16; MW-16-40/-60) and East Marginal Way (SPO-41). Where the plume has a sinking pattern, downward gradients were typically observed in the ABP well network. Consistent with the upward gradient measured in wells near the Waterway, the plume depth is shallower (between 35 and 50 feet) within 600 feet of the Waterway.

PCE PCE has been detected in 19 groundwater samples within the Study Area, with exceedances only occurring at the Shallow Interval as shown on Figure 16. Four groundwater probe samples with concentrations between 3.8 and 31 µg/L exceed the most stringent groundwater screening level based on protection of surface water, Federal Ambient Water Quality Criteria for protection of human health (3.3 µg/L). PCE groundwater results do not exceed any other screening levels.

When reviewing the available RI data for all sampling intervals (Appendix B), PCE detections in groundwater are located north of the ABP TCE plume centerline at monitoring wells MW-16, MW-18-50 and PSC-138-WT and groundwater probes SPO-39 and SPO-47, with one exception at SPO-31 discussed below. Probe SPO-31 is a Water Table Interval sample with a PCE concentration of 2.8 µg/L; however, PCE was not detected in co-located (SPO-11) or surrounding probes or wells. Similarly the other PCE detections have surrounding data below screening levels or non-detect, thus indicating that these detections north of the ABP plume centerline are isolated from the ABP TCE plume (see cross section D-D’ and Figure 16). Since ABP has not used PCE in its

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manufacturing processes, the localized detections of PCE suggest the potential for a source other than ABP.

Cis-DCE At the Water Table Interval, cis-DCE detections are located within and slightly downgradient of the ABP TCE plume area, with some low detections also located near the Waterway as shown on Figure 17. The only results that exceed screening levels for protection of aquatic organisms (590 µg/L) are located at the Facility. Exceedances at monitoring wells range between 800 and 880 µg/L and have only been reported at wells MW-1 and PMW-1. No data exceed the screening level for protection of human health-via fish consumption.

At the Shallow Interval, as shown on Figure 17, cis-DCE detections are located throughout the Study Area from Lucille Street and southward, however only a limited number of samples within the Study Area exceed the screening level for protection of aquatic organisms (590 µg/L). Of the monitoring well data one recent sample (April 2012) at MW-22-30, located next to the Waterway, exceeded the screening levels at a concentration of 660 µg/L. The exceedance illustrated on Figure 17 near the Waterway is probe data collected in 2002/2003. No data from the Shallow Interval exceed the screening level for protection of human health-via fish consumption.

No cis-DCE data in the Intermediate Interval exceed screening levels.

Vinyl Chloride At the Water Table Interval, vinyl chloride detections within the ABP TCE plume area are located near the Facility and along Fidalgo near the Waterway as shown on Figure 18. Of the 14 detections near the Facility, results are typically around 1 µg/L or below, with one exception from probe SP-24 collected from a depth of 16 to 20 feet (4.8 µg/L). Only the 4.8 µg/L result exceeds screening levels for protection of indoor air and protection of human health via fish consumption (1.3 and 1.7 µg/L, respectively). Detections from the Waterway area along Fidalgo range between 0.2 and 108 µg/L and are from groundwater probe samples collected in 2002/2003. Well MW-24 was completed in the area of the probe that had the highest exceedance of 108 µg/L. Since 2010, 7 groundwater samples have been collected from this well and all results from been non-detect. No groundwater monitoring well data from the Water Table Interval exceeds screening levels.

As illustrated on Figure 18, vinyl chloride is an issue throughout the Study Area at the Shallow and Intermediate Intervals. At the Shallow Interval, detections in monitoring wells (not including probe data) range between 0.1 and 120 µg/L with the highest concentrations located along the southern edge of the TCE plume centerline around 1st Avenue South. Higher vinyl chloride concentrations in this area may result from the fact that groundwater conditions are generally more reducing than further north in the ABP TCE plume area. More reducing conditions may support faster biodegradation of TCE (via reductive dechlorination) and slower biodegradation of vinyl chloride (which is typically more rapidly degraded under aerobic conditions).

At the Shallow Interval, vinyl chloride concentrations exceeding the screening levels for protection of human health via fish consumption are located throughout the plume, including wells located adjacent to the Waterway. Porewater samples have been collected in the Waterway and these results are discussed in Section 7.4.

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In the Intermediate Interval, the extent of the vinyl chloride detections has a smaller footprint compared to the Shallow Interval. Exceedances of the screening levels for protection of human health via fish consumption are bounded at East Marginal Way, thus not reaching the Waterway. In the Intermediate Interval, monitoring well concentrations (not including probe data) range between 0.1 and 110 µg/L. Like the Shallow Interval, the higher values concentrates are typically located along the southern edge of the TCE plume centerline around 1st Avenue South.

Total Chlorinated Ethenes Like TCE, a depiction of the total chlorinated ethene data provides a reliable technical illustration of the ABP plume. Figure 19 shows total chlorinated ethene data. Well and groundwater probe data south of the ABP TCE plume boundary indicate a concentration ‘trough’ for total chlorinated ethenes between the ABP plume and other W4 PLPs Capital and Blaser, both at the Shallow and Intermediate Intervals. This trough helps identify the areas of groundwater contamination resulting from different upgradient sources in an area where vinyl chloride concentrations are comingled.

Seasonal and Long-Term Trends Monitoring well data were used to evaluate seasonal and long-term trends in chlorinated solvent concentrations. When looking at the temporal trends of the data, it is important to note the installation dates of wells in the Study Area. Wells east of 1st Avenue were installed in early 2009 or earlier and have at least 3 years of data. Wells located west of 1st Avenue were installed in early 2010 and have approximately 2 years of data, with the exception of well clusters MW-20, MW-25, and MW-26 installed in early 2012. Due to the limited data set, a statistical analysis for seasonality is limited. Additional groundwater monitoring data will help identify seasonal trends in the data.

Figures 20 through 31 provide quarterly results for PCE, TCE, cis-DCE, and vinyl chloride with each figure illustrating Water Table, Shallow or Intermediate Interval. The data presented are from June 2010 through March 2011 because this time interval had the most consistently complete set of data in each of four consecutive quarters. Appendix B provides a full summary of the data collected.

Near Facility Seasonal and long-term trends in the data are affected by implementation of the interim action in 2008. Near the Facility the highest detections of TCE and cis-DCE are located at the Water Table Interval. Prior to implementation of the interim action, concentrations of TCE at the facility were up to 4,300 g/L at the Water Table Interval. During the past 4 quarters of monitoring, the maximum detected TCE concentration was 760 g/L. Appendix F provides an evaluation of the interim measures with a more detailed discussion of the change in solvent concentrations that have been observed near the facility since 2008.

Downgradient of Facility

LONG-TERM TRENDS

A statistical evaluation of longer-term concentration trends was used to assess quarterly monitoring data from wells located approximately on the plume centerline (well clusters MW-16, MW-17, MW-24, and MW-22). This evaluation indicates stable or decreasing VOC concentrations in well cluster MW-16 located at 2nd Avenue South, a mix of

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increasing and decreasing trends at well cluster MW-17 located at 1st Avenue South, and a mix of increasing, stable, and decreasing trends in wells located closer to the Waterway.

Trends in TCE, cis-DCE, and vinyl chloride concentrations at wells along the centerline of the plume, moving southwestward from the Facility, are evaluated using Mann-Kendall Trend Test analyses and trend plots are copied in Appendix G. These analyses indicate:

East of 1st. The highest concentrations of TCE and cis-DCE in the Shallow and Intermediate Intervals are at well clusters MW-16 and MW-17. At well cluster MW-16 (2nd Avenue and Orcas), TCE concentrations in the Shallow Interval range between 980 and 1,600 g/L and 0.3 to 170 g/L at the Intermediate Interval. At well cluster MW-17 (1st Avenue between Orcas and Mead), TCE concentrations are higher at the Intermediate Interval ranging between 5,100 to 3,300 g/L and concentrations at the Shallow Interval are 770 to 2,350 g/L. TCE concentrations from well cluster MW-16 and well MW-17-60 appear to be decreasing, while TCE concentrations from well MW-17-40 appear to be increasing. TCE concentrations at MW-16-40 have decreased from a high of 1,600 g/L in June 2009 to 980 g/L in April 2012 and TCE concentrations at MW-17-60 have decreased from 5,100 g/L in March 2009 to 3,600 g/L in June 2012. Conversely, the TCE concentration at MW-17-40 was initially 1,600 g/L in March 2009, but after decreasing in the following two sampling rounds has since increased to as high as 2,350 g/L in April 2012, although the June 2012 sample returned to a concentration of 1,600 g/L. The analyses indicate that these are statistically significant trends.

West of 1st. At well cluster MW-24, located about 350 feet upgradient from the Waterway, COC exceedances are limited to TCE and vinyl chloride at the Shallow Interval. Since March 2010 when this well cluster was first sampled, TCE concentrations from well MW-24-30 have ranged from 71 to 140 g/L and vinyl chloride concentrations have ranged from 13 to 34 g/L. The vinyl chloride concentrations at this well appear to be stable, while TCE and cis-DCE concentrations show statistically significant decreasing trends.

At the Waterway. Mann-Kendall Trend Test analyses were performed for TCE, cis-DCE, and vinyl chloride at well MW-22-30, located on the plume centerline adjacent to the Waterway. Vinyl chloride concentrations appear to be stable, with no statistically significant trend. TCE and cis-DCE are trending in opposite directions, with cis-DCE concentrations increasing and TCE concentrations decreasing. An additional trend evaluation was performed by converting the TCE, cis-DCE, and vinyl chloride concentrations at well MW-22-30 into molar equivalents (e.g., micromoles per liter, rather than g/L) and summing those values for each sampling round. This allows for evaluation of trends in total chlorinated VOCs in groundwater approaching the Waterway. Total chlorinated VOC concentrations appear to be stable, with no statistically significant trend.

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SEASONAL VARIATIONS

At most well locations there does not appear to be strong seasonal variability in COC concentrations. Observed seasonal behavior along the centerline of the plume, moving southwestward from the Facility, is as follows:

East of 1st. The nine and twelve quarterly data sets from well clusters MW-16 and MW-17, respectively, appear to have little seasonal variability except that the highest concentrations detected at MW-17-40 were typically from the March sampling events.

At the Waterway. For wells adjacent to the Waterway, COC exceedances are limited to TCE and vinyl chloride at the Shallow Interval. Trends for these two analytes at wells adjacent to the Waterway are as follows:

TCE. Only MW-22-30 has exceedances for TCE and these concentrations have ranged from 71 to 630 g/L since March 2010. Data from the months of June and September have ranged between 100 and 630 g/L. Concentrations from the months of March and December are lower between 71 and 320 g/L.

Vinyl Chloride. Vinyl chloride concentrations at MW-22-30 and MW-23-30 show little seasonal variability. A wider range of variability has been observed at PSC-CG-151-25, with concentrations ranging between 1.7 (in September 2011) and 51 g/L (in September 2010).

7.3.2 Metals Arsenic, barium, copper, iron, manganese, cadmium, copper, nickel, and zinc are metals that have been detected above screening levels in the Study Area. These metals are discussed below in two general categories:

Plating metals. Four of these metals (cadmium, copper, nickel and zinc) have been detected above screening levels in the vicinity of the Facility at the Water Table Interval. These metals that have been historically or are presently used at the Facility.

Redox-Sensitive Metals. Four of these metals (arsenic, barium, iron, manganese) have been detected above screening levels throughout the Georgetown area. These metals occur naturally in soil and their occurrence in groundwater depends on local groundwater redox conditions7. In general, elevated concentrations of these metals occur with more reducing conditions (as indicated by low Eh or low dissolved oxygen). Geochemical conditions in the Study Area and the surrounding area are generally reducing, as described in Section 3.4.2.4.

Figures 32 through 35 illustrate the most recent data available for each metal. Table B-3 summarizes all metals data. Field parameters that have a potential effect on metal mobility, including Eh, dissolved oxygen, and pH, are included in Table B-3 for reference. Field-measured groundwater pH for the Water Table Interval is shown on Figure 36.

7 Although not directly sensitive to redox, arsenic and barium are strongly adsorbed to iron oxides and oxyhydroxides or manganese oxides and can be released under reducing conditions.

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Plating Metals Dissolved cadmium, copper, nickel, and zinc have been detected at the Water Table Interval exceeding screening levels for protection of aquatic organisms (0.25, 3.1, 8.2, and 81 g/L, respectively). The highest concentrations are located within or immediately adjacent to the Facility. Elevated concentrations of copper, nickel, and zinc have also been detected at well MW-16 located approximately 350 feet downgradient of the Facility. These two areas of plating metals occurrences are discussed below.

Near Facility Groundwater data from temporary probes and monitoring wells provides the lateral and vertical bounding of plating metals occurrences near the Facility. Data indicate that exceedances of cadmium, copper, and zinc were limited to the Water Table Interval and generally located within the nickel groundwater plume, except as noted below. Therefore the discussion of the lateral and vertical extent of the metals is mostly within the nickel section.

NICKEL

The highest concentrations of nickel (33,100 to 119,000 g/L) were observed at Water Table Interval wells MW-1 and MW-3. Well MW-8, located approximately 100 feet downgradient of MW-3, had nickel concentrations ranging between 3.4 to 7.4 g/L in 2009 and 2010. Concentrations have increased to 1,850 and 4,750 g/L in 2011 and 2012, respectively. As discussed in Appendix F, this increase may be due to the air sparging system creating lateral spread of metals contamination. A preliminary analysis of this hypothesis is provided in Appendix F, but additional data will be collected to further evaluate this hypothesis. Concentrations above screening levels at other Water Table Interval wells in and near the Facility range between 703 and 8.6 g/L. With the exception of one historical sample collected from MW-16, discussed below, nickel has not exceeded screening levels in wells downgradient of MW-8. Based on the most recent data, the lateral extent of the nickel plume at the Water Table Interval is estimated to extend less than 350 feet downgradient of the Facility.

At the Shallow Interval, wells MW-8-30 and MW-3-30 have exceedances of the screening level for protection of aquatic organisms (8.2 g/L). Concentrations from MW-8-30 were below the screening level prior to 2011, but have increased up to 19,500 g/L in September 2011. Similar to the increase in concentration observed at MW-8, this increase may be due to lateral spreading from air sparge operation (see Appendix F). Well MW-3-30 was installed in March 2012 and has been sampled two times (April and June 2012) results ranging between 0.9 and 18.1 g/L.

At the Intermediate Interval, monitoring well results are below screening levels with detections ranging between 0.6 and 3.8 g/L.

CADMIUM

Detected concentrations of cadmium at the Water Table Interval that exceed criteria for protection of aquatic organisms (0.25 g/L) range between 0.3 to 1.7 g/L. Results from the Shallow and Intermediate Intervals were non-detect. No data exceed the criteria for protection of human health via fish consumption (19 g/L).

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COPPER

Detected concentrations of copper at the Water Table Interval range between 0.5 and 136 g/L with the highest concentrations at wells MW-1 and MW-3. As illustrated on Figure 33, multiple monitoring wells near the Facility exceed screening levels for protection of aquatic organisms (3.1 g/L). Three results between 122 and 136 g/L (all from MW-3) exceed screening criteria for protection of human health via fish consumption (114 g/L).

In general, copper exceedances are located in wells at or immediately downgradient of the Facility. The exception is at MW-16, which is further discussed below.

Detected concentrations at the Shallow and Intermediate Intervals range between 0.5 and 0.9 g/L, with one exception. Results from well MW-16-75 have ranged up to 6.2 g/L, exceeding the screening level for protection of aquatic organisms (3.1 g/L).

ZINC

Detected concentrations of zinc range between 4 and 440 µg/L. Concentrations exceeding the screening level for protection of aquatic organisms (81 g/L) were measured at the Facility wells MW-1, MW-3, MW-4, MW-5 and well MW-7, just west of the Facility. No data exceed the screening level for protection of human health via fish consumption (705 g/L).

Concentrations at the Shallow and Intermediate Intervals range between 4 and 75 g/L, below zinc screening levels.

DEPRESSED PH VALUES

Low pH measurements have been recorded at the same wells where elevated concentrations of copper, nickel, and zinc have been detected. Figure 36 provides and illustration of the pH measurements completed in September 2011 and April 2012. The highest concentrations of copper, nickel, and zinc were detected at MW-1 and MW-3, which are located in and just downgradient, respectively, of the former plating area that was closed in 1999. The pH measurements from these wells have been between 4.8 and 2.6. The high levels of plating metals, and the co-located low pH, suggest a historical release of plating solutions may have occurred in this area. Section 8.2 provides a discussion of the geochemical modeling that has been completed to assess mechanisms controlling the fate and transport of copper, nickel, and zinc in groundwater at and downgradient from the Facility.

Monitoring Well MW-16 Slightly elevated concentrations of copper, nickel, and zinc, and slightly depressed pH, have been measured in groundwater at the Water Table Interval at well MW-16, located approximately 400 feet downgradient of the facility. However, several wells between the Facility and this location were below screening levels. Possible causes of the occurrences at MW-16 include:

A historical release that created a ‘pulse’ moving downgradient of the Facility. However, this is unlikely given the generally high affinity for metals with soils, which would retard movement and limit the occurrences of isolated ‘pulses’.

A leaky sewer pipe could release water elevated in metals. The sewer from ABP runs down Findlay near this well, but the condition has not been inspected. In addition to the elevated metals concentrations, anomalously high water levels

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have been measured at this well. The Findlay sewer was inspected as part of the RI; the results of the inspection are shown on Figure 37. The inspection identified several locations where leaks potentially could occur, including a 100-foot long section upgradient of well MW-16 that had been replaced with PVC but had separated from the adjacent clay pipe, leaving a gap at both ends.

Redox Sensitive Metals Occurrences of redox sensitive metals are depicted on Figures 38 through 41 and are summarized as follows:

Iron. At the Water Table Interval, detected iron concentrations at and within 100 feet of the Facility range between 280 and 72,700 g/L. Concentrations at the remaining Water Table Interval wells range between 1,010 and 46,900 g/L. Concentration at upgradient well MW-6 range between non-detect and 690 g/L.

At the Shallow Interval, the highest iron concentrations were detected at MW-8-30 where concentrations ranged between 22,100 and 239,000 g/L. At all other wells, concentrations ranged between 4,410 and 45,200 g/L, with the exception of one measurement at PSC-CG-151-25 (600 g/L). This variability is observed across the Study Area and was also measured over multiple sampling events at some individual wells. Upgradient concentrations measured at MW-6-30 were within a similar range (16,300 to 25,100 g/L).

At the Intermediate Interval, iron concentrations range between 2,670 and 41,000 g/L with the exception of one value from MW-21-75 (810 g/L). Values from the upper end of the range provided have been detected both upgradient (PSC-CG-135-50) and downgradient of the Facility.

Manganese. Detected manganese concentrations have the greatest variability at the Water Table Interval where results range between 12.5 to 4,700 g/L. Those concentrations greater than 1,000 g/L are located within 100 feet of the Facility. At the Shallow and Intermediate Intervals, manganese concentrations both upgradient and downgradient of the Facility range between 100 and 1,120 g/L with the exception of well MW-8-30. At MW-8-30, concentrations have increased from 378 g/L in 2008 to 7,190 g/L in 2012, with the highest results from 2010 at 10,700 g/L.

Arsenic. Detected arsenic concentrations at all three sampling intervals range between non-detect and 4.2 g/L with the exception of data collected from MW-9 where concentrations were 52.4 and 56.3 g/L. Since concentrations upgradient and downgradient of the Facility are similar, it is unlikely that the elevated concentrations at MW-9 are due to releases from ABP.

Barium. Detected barium concentrations at the upgradient well cluster MW-6 range between 3.7 and 5.4. Concentrations at other wells ranged between 5.7 and 86.6 µg/L with little difference between sampling intervals. The higher barium concentrations were measured at MW-8 and MW-8-30 (51.8 to 86.6 g/L).

The oxidation-reduction potential is an important factor when evaluating the occurrence of these metals. Microbial degradation of organic materials in the aquifer matrix (either

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naturally occurring or anthropogenically released) has resulted in generally anaerobic conditions in groundwater8. Table B-3 provides a summary of the Eh and dissolved oxygen measurements completed in ABP wells. Field parameters that have influence on the fate and transport of metals include the redox potential (Eh), dissolved oxygen, and pH.

As described above, elevated concentrations of arsenic, barium, iron, and manganese are present throughout the Study Area. Similar conditions have been reported by PSC in their discussions of data from the PSC-Georgetown facility (Geomatrix, 2006). It should be noted that these metals are not used at the ABP Facility. The low redox conditions as well as the simultaneous presence of the four metals indicate that the geochemical conditions in the aquifer have resulted in the dissolution of these metals from the native aquifer materials.

Geochemical conditions upgradient and downgradient of the facility are similar and support dissolution of metals from native materials. At the Shallow and Intermediate Intervals, Eh ranges between 200 and -260 and dissolved oxygen is less than 1 mg/L. The pH is typically between 5.5 and 6.8 with some slightly higher measurements (up to 7.5) in the Intermediate Interval. Within this range of Eh, manganese and iron reduction is typical resulting in increasing concentrations of these metals. Arsenic and barium are strongly adsorbed to the iron oxides and oxyhydroxides or manganese oxides. Thus dissolution of these compounds would result in an increase in concentration of arsenic and barium as well as iron and manganese.

Near the Facility, iron, manganese, and barium concentrations in the Water Table Interval are higher than concentrations just upgradient of the Facility. Although Eh and dissolved oxygen are similar or slightly higher than surrounding groundwater, this is likely due to the operation of the air sparging system which would increase these values. The pH is significantly lower (as low as 2.5) at the Water Table Interval at the Facility than in surrounding groundwater. Concentrations of these metals may be elevated because of the low pH.

The highest concentrations of iron and manganese in the Study Area were detected just downgradient of the Facility in the Shallow Interval at MW-8-30. Concentrations of iron and manganese at this well increased dramatically since the installation of air sparging wells upgradient of MW-8-30, but it is unclear why since the addition of air would be expected to reduce the amount of soluble iron.

7.3.3 1,4-Dioxane As illustrated on Figure 42, 1,4-dioxane has not been detected above the groundwater screening level in the Study Area. Most of the monitoring well data is from one round of sampling in December 2008. Groundwater grab samples were also collected from probes SPO-16 and SPO-18 at the Shallow Interval and probe SPO-18 at the Intermediate Interval. The groundwater screening level for 1,4-dioxane is 69 g/L. The same screening level applies to the Water Table, Shallow, and Intermediate Intervals.

The following summary is for results: 8 Except in the vicinity of the ABP remedial system, where air injection appears to have raised ORP while the system is operating.

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Water Table Interval. 1,4-Dioxane was not detected.

Shallow Interval. All results were below the proposed screening level. 1,4-Dioxane was detected in five of the six groundwater samples at concentrations ranging between 3.1 and 18 g/L.

Intermediate Interval. 1,4-dioxane was detected at four locations, with concentrations ranging between 20 and 40 g/L with the exception of upgradient well PSC-CG-135-50. One sample collected during this RI at PSC-CG-135-50 slightly exceeded the proposed screening level at a concentration of 70 g/L.

These data and the fact that 1,4-dioxane is not a component of any chemicals known to have been used at the Facility (and was not detected in two soil samples collected beneath the Facility) confirm that ABP has not contributed to the release of 1,4-dioxane in the area. With Ecology approval, ABP has not monitored for 1,4-dioxane since 2008.

7.4 Sediment Porewater Quality Because TCE, cis-DCE, and vinyl chloride contamination in groundwater extends to the Waterway, sediment porewater within the potential groundwater discharge zone was characterized to evaluate potential impacts to surface water. As discussed in Section 4.2.4, sediment porewater at the nearshore discharge zone was characterized using a two phase program. In the first phase of work, porewater salinity and sediment grain size were analyzed at points along a ‘coarse grid’ and ‘fine grid’ in the nearshore area. The spatial distribution of porewater salinity is shown on Figure 43. A complete analysis of the Phase 1 results is provided in the memorandum titled Phase One Spatial Variability in Groundwater Discharge (Aspect, 2011b). The conclusions from the Phase 1 sampling are summarized as follows:

The saltwater wedge in the Waterway is directing groundwater discharge into the intertidal and shallow subtidal areas (i.e., between MLLW and -14 ft NAVD88). This is consistent with other observations in the region (Windward, 2004). The salinity results in plan view (with bathymetry) convey this same relationship (Figure 44); and

Tidal stage and sediment grain size have a minor influence on groundwater discharge compared to the saltwater wedge relationship.

Based on the results and conclusions of the Phase 1 program, a sampling plan was developed to measure VOC concentrations in sediment porewater in the potential area of groundwater discharge (i.e., Phase 2 of the program). Results from the passive porewater samplers are illustrated on Figures 44, 45, and 46 for TCE, cis-DCE, and vinyl chloride, respectively. PCE was not detected in the porewater samplers therefore no figure was drafted to illustrate the results. Occurrences for each TCE, cis-DCE, and vinyl chloride are as follows:

TCE was detected in four samples at concentrations ranging between 0.4 and 3.9 µg/L (Figure 44). Concentrations are below screening levels protective of organisms (47 µg/L) and human health (30 µg/L). Detections were above an elevation of -4 ft and centrally located relative to the sampling grid. Detections were bounded by non-detect sampling locations to the west, north and south;

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Cis-DCE was detected in 8 samples ranging between 160 and 0.2 µg/L, well below screening levels. While cis-DCE was detected in the westernmost sampling transect (Figure 45), the highest concentrations were located above elevation -2 ft and decrease significantly in the western-most transect with detections between 0.6 and 0.2; and

Vinyl chloride was detected in nine samples at concentrations ranging between 23 and 0.2 µg/L (Figure 46). Six results with concentrations between 28 and 3.4 µg/L exceed the MTCA Method B screening level of 2.4 µg/L. The locations of the detections are consistent with the TCE detections. One porewater sample along the western transect exceeded the screening level for vinyl chloride. While the western boundary of the extent of vinyl chloride in sediment porewater is not known, the area of potentially-impacted groundwater discharging to the river farther to the west is constrained by the saltwater wedge, as identified with the salinity results from the Phase 1 event.

7.5 Soil Vapor and Indoor Air Quality The indoor air quality of buildings in the immediate vicinity and downgradient of ABP was evaluated as part of the vapor intrusion mitigation program discussed in Appendix E. Soil vapor quality was also evaluated to a lesser extent. Buildings associated with ABP vapor intrusion activities are identified on Figure 47.

8 Fate and Transport of COCs

The following sections present an evaluation of the fate and transport of chlorinated COCs in groundwater downgradient from the Facility to the Waterway followed by an evaluation of the attenuation of plating metals COCs in groundwater focused on the area between the Facility and 1st Avenue South.

8.1 Chlorinated COCs

8.1.1 Attenuation/Transport Evaluation A screening level fate and transport evaluation of chlorinated COCs was performed using the BIOCHLOR (ver. 2.2) spreadsheet model. BIOCHLOR simulates the natural attenuation of common chlorinated solvents, including TCE, cis-DCE, and vinyl chloride. BIOCHLOR is a Microsoft® Excel programmed spreadsheet that simulates one-dimensional advection, three-dimensional dispersion, linear adsorption to the soil matrix, and biotransformation via reductive dechlorination for dissolved-phase chlorinated solvents. This model has been accepted by the EPA and is available for downloading from the EPA CLU-IN web site. Ecology indicated the model was appropriate to evaluate screening level fate and transport of chlorinated COCs for this RI.

The primary purposes of this modeling, in combination with evaluation of groundwater quality monitoring data, are to:

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Evaluate whether concentrations of chlorinated COCs in groundwater approaching the Waterway are likely to increase over time, and if so to estimate potential maximum future concentrations; and

Estimate the potential timing when maximum concentrations of chlorinated COCs would arrive at the Waterway.

Groundwater quality monitoring data indicate that the chlorinated COCs TCE and vinyl chloride are currently present in shoreline wells at concentrations exceeding surface water screening levels. Sediment porewater sampling was performed to assess whether COCs are present at the point of discharge to the Waterway at concentrations that would present an environmental risk, or if there is sufficient attenuation between the near shore wells and the Waterway to reduce concentrations to acceptable levels. Results of the porewater sampling are presented above in Section 7.4; an evaluation of the exposure pathways and associated environmental risk is presented in Section 9.

8.1.1.1 Modeled Area and Depth Interval As shown on Figures 15 through 18, the highest concentrations of chlorinated COCs apparently associated with a release at the Facility are in the Shallow and Intermediate Intervals at well cluster MW-17, about 900 feet downgradient from the Facility. For the purposes of this modeling and the discussion in this section, the MW-17 area was treated as the “source area” to evaluate potential future evolution of the chlorinated COC plume.

In plan view, the model area extends 1,400 feet along the centerline of the plume from the MW-17 well cluster, through the MW-24 and MW-22 well clusters to the Waterway. Modeling was limited to evaluation of the Shallow Interval. Except near the Facility, chlorinated COCs in groundwater have not been detected above screening levels in the Water Table Interval. Although TCE concentrations in the Intermediate Interval at the MW-17 well cluster are about twice the concentrations in the Shallow Interval, chlorinated COC impacts to the Intermediate Interval do not appear to extend as far downgradient as in the Shallow Interval. This may be due to the hydraulic conductivity in the Intermediate Interval being about an order of magnitude lower than in the Shallow Interval, resulting in about an order of magnitude longer travel time through the Intermediate Interval or it could be the result of upward gradients closer to the Waterway forcing impacted water from the Intermediate Interval to the Shallow Interval. Given these observations, modeling is based on evaluation of the Shallow Interval, with the effects of possible COC migration from the Intermediate Interval addressed by applying a higher source area concentration term to the Shallow Interval during model sensitivity analyses.

8.1.1.2 Input Parameters Parameters describing advective and dispersive transport, sorption to soil matrix, degradation of dissolved constituents, and overall model geometry are required inputs to the model. These input parameters were selected from a combination of site-specific data, values from the published literature, and values available from Ecology guidance documents. Site investigation data from the Capital and Blaser sites were used, as appropriate, and selection of certain model inputs, particularly biodegradation rates, was coordinated with these parties to ensure consistency in general modeling approach and input values between this report and remedial investigations being completed for those

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sites. Required model input parameters and sources of data are summarized on Table 10 and include:

Hydraulic gradient. Average hydraulic gradient between the Facility and the downgradient points of interest was based on contoured maps of groundwater elevation measurements from existing and planned site monitoring wells. The average gradient of 0.002 for the shallow depth interval was used.

Hydraulic conductivity. The hydraulic conductivity for the Shallow Interval of 24 ft/day was based on the geometric mean of hydraulic conductivity values estimated from 26 slug tests at wells completed in the Shallow Interval at the ABP, Blaser, and Capital sites. As discussed below, additional model runs were performed using a higher hydraulic conductivity value of 48 ft/day.

Effective porosity. An effective porosity of 0.25 was assumed, based on typical specific yield values for sand aquifers. Specific yield, or gravity drainage from aquifer materials, is assumed to be representative of the interconnected pore space, or effective porosity.

Dispersivity. This parameter was calculated based on the flow path length between the “source area” and the furthest downgradient discharge point (the Waterway). Several methods are available to calculate longitudinal dispersivity (x). The empirical method of Xu and Eckstein (1995) available within the BIOCHLOR model was used. Transverse dispersivity (y) was set equal to one-tenth of x. Because the vertical extent of the plume does not appear to be increasing downgradient, vertical dispersivity (z) was set to zero.

Soil bulk density. A value of 1.51 kg/L was used, based on the recommended soil bulk density value in MTCA (WAC 173-340-747).

Fraction organic carbon in soil. Twelve soil samples collected during well drilling were analyzed for fraction organic carbon. The average measured value of 0.0025 (0.25 percent) was used.

Soil organic carbon-water partitioning coefficients (Koc). Values of Koc for TCE, cis-DCE, and vinyl chloride were selected from Ecology’s Cleanup Levels and Risk Calculations (CLARC) database.

Source area concentrations. Concentrations of COCs in “source area” groundwater were based on the April 2012 round of groundwater quality samples from well MW-17-40, which had the highest recent TCE concentration. A single, uniform set of COC concentrations were applied across the “source area”. These concentrations were held constant over time (i.e., no source decay).

Source area dimensions. The 200 foot width the “source area” at MW-17-40 was estimated based on the lateral delineation of the TCE plume in this area. The thickness of the “source area” of 25 feet was based on the vertical delineation of the plume above the Intermediate Interval in this area.

Biodegradation rates. Biodegradation rates (as half-lives) were selected from review of literature sources. Average biodegradation half-lives from the literature sources are summarized on Table 11. These include compilations of

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biodegradation half-lives from field and laboratory scale studies (Aronson and Howard, 1997; Newell, et al., 2002), recommended half-lives from the BIOCHLOR model documentation, and half-lives estimated using a mass balance approach in the site-wide feasibility study for the PSC Georgetown facility. As discussed in Section 3.4.2.4, groundwater at the site appears to be under iron and sulfate reducing conditions. Half-lives for TCE and vinyl chloride from field scale studies under similar iron- to sulfate-reducing conditions reported in Aronson and Howard were reviewed and the average values are shown on Table 11. The 25th percentile values from Newell, which are somewhat higher (lower degradation rate) than the average from field sites with similar reducing conditions, were selected as reasonable initial estimates for half-lives at the site. As discussed below, an additional model run was performed using the biodegradation half-lives developed for the PSC site-wide feasibility study.

8.1.1.3 Model Results This section provides a summary and discussion of the various model runs that were completed. Copies of the spreadsheets with the input parameters and results are provided in Appendix H.

8.1.1.3.1 Base Case Model An initial model run (Base Case) was performed using the parameters listed on Table 10. Modeled TCE, cis-DCE, and vinyl chloride concentrations approaching the Waterway over a 50 year time frame are shown on Figure 48. Modeled concentrations approaching the Waterway after 50 years are also summarized on Table 12 with the average concentrations from groundwater quality data from wells MW-22-30 and MW-24-30.

As shown on Figure 48, using the Base Case model inputs, the leading edge of a plume extending from the MW-17 area would be expected to reach the Waterway after about 20 years, would require about 35 years to reach half the maximum modeled concentration, and would reach the maximum concentration after more than 50 years.

The maximum modeled TCE and cis-DCE concentrations are less than 5 percent of what has on average been detected in wells MW-22-30 and MW-24-30, although the vinyl chloride concentration is reasonably similar. This large under-prediction of observed concentrations is potentially due to use of too slow of a groundwater velocity in the model, too high of a degradation rate in the model, historical release of a much higher concentration slug of TCE that has already migrated past the MW-17 well cluster and reached wells MW-22-30/MW-24-30, migration of impacted water with higher concentrations from the Intermediate Interval at well MW-17-60 to the Shallow Interval, or some combination of these possibilities.

If the explanation is that a much higher concentration slug of COCs has already moved past the MW-17 well cluster and reached wells MW-22-30/MW-24-30, then concentrations near the Waterway would be expected to decrease as water with lower concentrations of chlorinated COCs flush through the system. Existing data are inconclusive as to whether this is the case. As discussed in Section 7.3 COC concentrations at well MW-17-40 appear to be slightly increasing, while concentrations at near shore wells MW-22-30 and MW-24-30 are stable or slightly decreasing. Given the conflicting trend data at these well locations this possibility was not evaluated.

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Three additional model runs were performed to assess whether a better fit between modeled and observed concentrations at the near shore wells could be achieved by using: 1) a higher groundwater velocity (hydraulic conductivity); 2) a higher “source area” concentration term to account for higher concentrations observed at Intermediate Interval well MW-17-60 potentially migrating into the Shallow Interval; and 3) a higher groundwater velocity and revised half-lives. To address Ecology comments to the ABP Draft RI dated July 15, 2011, a fourth model run was performed using the revised half-lives and an even higher groundwater velocity. Results of these model runs are summarized in the following sections.

8.1.1.3.2 Increased Groundwater Velocity x2 Model A second model run was performed using the Base Case model inputs from Table 10, but doubling the hydraulic conductivity from 24 to 48 ft/day. Modeled TCE, cis-DCE, and vinyl chloride concentrations approaching the Waterway over a 50 year time frame are shown on Figure 49. Maximum modeled concentrations approaching the Waterway are also summarized on Table 12 with recent groundwater quality data from wells MW-22-30 and MW-24-30.

As shown on Figure 49, using these model inputs the leading edge of a plume extending from the MW-17 area would be expected to reach the Waterway after about 12 years, would require about 18 years to reach half the maximum modeled concentration, and would reach the maximum concentration in about 30 years. The maximum modeled TCE and cis-DCE concentrations are similar to the average concentrations at well MW-24-30 and about half of the average concentrations at well MW-22-30, while the vinyl chloride concentration is about 6 to 10 times higher than the concentrations observed near the Waterway (Table 12). Additionally, the modeled vinyl chloride concentration is greater than the cis-DCE concentration and about twice the TCE concentration. This is the opposite of what is observed in groundwater within the plume, where TCE and cis-DCE concentrations are typically several times to more than an order of magnitude greater than vinyl chloride concentrations.

8.1.1.3.3 Increased Groundwater Velocity x2 and Revised Half-Life Model A third model run was performed using the Base Case model inputs from Table 10, but doubling the hydraulic conductivity and modifying the half-lives to better maintain typical ratios of TCE and cis-DCE concentrations to vinyl chloride concentrations. For this model run half-lives for TCE and vinyl chloride of 3.0 and 0.8 years, respectively, were selected based on biodegradation half-lives developed for the PSC site-wide feasibility study. The cis-DCE half-life of 1.6 years was not changed.

Modeled TCE, cis-DCE, and vinyl chloride concentrations approaching the Waterway over a 50 year time frame are shown on Figure 50. Maximum modeled concentrations approaching the Waterway are also summarized on Table 12. Using these model inputs the leading edge of a plume extending from the MW-17 area would be expected to reach the Waterway after about 12 years, would require about 18 years to reach half the maximum modeled concentration, and would reach the maximum concentration in about 30 years.

Modeled ratios of TCE and cis-DCE concentrations to the vinyl chloride concentration are more consistent with observed ratios of these constituents in the plume than results

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from the other model runs, although the modeled proportion of vinyl chloride remains high at about 3 to 4 times observed concentrations near the Waterway.

8.1.1.3.4 Increased Groundwater Velocity x2, Revised Half-Life, and increased Source Concentration Model

A fourth model run was performed using the increased velocity and revised half-life model described above, but increasing the “source area” concentrations to those measured in well MW-17-60 to account for migration of COCs from the Intermediate Interval. The model source concentration terms were selected based on the June 2012 sample from well MW-17-60, with TCE, cis-DCE, and vinyl chloride concentrations specified as 3,600, 92, and 41 µg/L, respectively.

Modeled TCE, cis-DCE, and vinyl chloride concentrations approaching the Waterway over a 50 year time frame are shown on Figure 51. Maximum modeled concentrations approaching the Waterway are also summarized on Table 12. Using these model inputs the leading edge of a plume extending from the MW-17 area would be expected to reach the Waterway after about 12 years, would require about 18 years to reach half the maximum modeled concentration, and would reach the maximum concentration in about 30 years.

As would be expected, with increased “source area” concentrations the modeled concentrations near the Waterway also increase, in this case by about 50 percent compared to the prior model run differing only in the source concentrations.

8.1.1.3.5 Increased Groundwater Velocity x10 and Revised Half-Life Model A final model run was performed using the previous increased groundwater velocity and revised half-life model, but increasing the hydraulic conductivity by another factor of 5 (i.e., a total increase of 10 times over the initial Base Case model).

Modeled TCE, cis-DCE, and vinyl chloride concentrations approaching the Waterway over a 50 year time frame are shown on Figure 52. Maximum modeled concentrations approaching the Waterway are also summarized on Table 12. Using these model inputs the leading edge of a plume extending from the MW-17 area would be expected to reach the Waterway after only a few years and would reach the maximum concentration within 5 to 10 years.

Modeled concentrations of TCE far exceed any concentration that has been measured near the Waterway since wells were installed in 2010.

8.1.1.3.6 Summary of Model Results The Base Case model results do not appear to accurately represent attenuation between the MW-17 well cluster and the Waterway, based on the long predicted travel time and modeled maximum concentrations that are well below observed concentrations in wells near the Waterway. Although it is possible that a higher concentration slug of TCE from the Facility or another source has already migrated past the MW-17 well cluster and arrived at wells MW-22-30 and MW-24-30, concentration trends at MW-17-40 do not support this hypothesis. A more likely explanation is that groundwater velocities and/or biodegradation rates used in the Base Case model do not accurately reflect actual conditions.

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Increasing the groundwater velocity by a factor of 2 in the second model run increases the predicted chlorinated COC concentrations, but using the Base Case model biodegradation half-lives produces ratios of TCE and cis-DCE concentrations to vinyl chloride concentrations that are the opposite of what is observed in the field. Revising the TCE and vinyl chloride biodegradation rates to those developed for PSC’s site-wide feasibility study better matches the observed concentration ratios. Results of this third model run, combined with water quality monitoring data, are used in the evaluation in the following section of potential future evolution of the plume near the Waterway.

The two additional model runs, applying a higher “source area” concentration and applying a much higher groundwater velocity, do not improve model results. As expected, an increased “source area” TCE concentration results in increased modeled TCE, cis-DCE, and vinyl chloride concentration at the Waterway. These results imply that if the Intermediate Interval is contributing significant mass to groundwater that ultimately discharges to the Waterway through the Shallow Interval, then either the modeled degradation rates are too low and/or the modeled groundwater velocities are too high. In either case, the overall observation that COC concentrations at the MW-17 well cluster are likely to reach the Waterway at concentrations exceeding screening levels still holds.

Results of the model run using ten times the base case groundwater velocity is not consistent with empirical data from the Study Area, grossly over predicting TCE concentrations and, to a lesser extent, over predicting cis-DCE and vinyl chloride concentrations. If this model were accurately representing site conditions, we would expect to see a significant increase in COC concentrations, especially TCE, over the two years of monitoring at well MW-24-30, located about 300 feet from the shoreline. Instead, over the monitoring record there has been a gradual decrease in TCE and cis-DCE concentrations at this well, with no change in vinyl chloride concentrations.

8.1.1.4 Evaluation of Future Plume Evolution There are two primary issues in evaluating potential future evolution of the plume near the Waterway. The first is whether concentrations approaching the Waterway are likely to increase over time. The second is, if concentrations near the Waterway do increase, what is the timeframe over which the increase would occur.

Predicted COC concentrations near the Waterway from the revised half-life model (Section 8.1.1.3.3) are generally similar to what has recently been observed in wells near the Waterway. This general similarity between model-predicted and observed COC concentration indicates that there is a reasonable likelihood that concentrations in groundwater approaching the Waterway will not increase over time. This is tentatively supported by two years of monitoring data from wells near the shoreline, which show decreasing or stable COC concentrations at MW-24-30 and stable total COC concentrations (the sum of individual COCs as molar equivalents) at well MW-22-30. The revised half-life model used reasonably conservative model input parameters, including a hydraulic conductivity twice what was estimated from field slug tests, a moderately slow TCE biodegradation rate for the iron- and sulfate reducing conditions in the Study Area, and assuming a constant concentration over time at the MW-17 well cluster “source area”. However, given the uncertainty in model inputs, particularly

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biodegradation rates, it is also conceivable that concentrations could increase over time, and neither potential future outcome can be rejected.

The modeling can be used to assess the timeframe over which a potential change in concentrations approaching the Waterway would occur. The revised half-life model uses a hydraulic conductivity higher than was estimated from slug tests, resulting in faster travel times and a conservatively shorter estimated timeframe over which increases would be expected to occur. The concentration breakthrough curves shown on Figure 50 indicate that the leading edge of a plume (or higher concentration slug of COCs) migrating past the MW-17 well cluster would arrive near the Waterway in about 12 years, and would be observed in the near-Waterway wells as a rapid increase in concentrations.

If future monitoring data indicate a significant increase in concentrations at well MW-24-30, it would take several years before those concentrations would arrive at the shoreline. The estimated groundwater linear velocity, assuming a hydraulic conductivity of 48 ft/day, is about 165 feet per year (ft/yr). Accounting for the average retardation factor of the chlorinated COCs of 2.4, the average contaminant migration rate is about 70 ft/yr. If a significant increase in COC concentrations were observed at well MW-24-30, located about 300 feet upgradient from the Waterway, there would be about a 4 year period before those concentrations would approach the shoreline of the Waterway.

8.2 Metal COCs Geochemical modeling was performed to assess mechanisms controlling the fate and transport of copper, nickel, and zinc in groundwater at and downgradient from the Facility. Model results indicate that although these metals are not being significantly attenuated in the low pH groundwater at the Facility, significant attenuation through mineral precipitation and sorption of metals to mineral surfaces is likely occurring between about 2nd Avenue and 3rd Avenue as pH increases to more neutral conditions. The modeling results are consistent with the observed metals concentrations in groundwater showing a marked decrease in concentrations within about 120 feet of the Facility. The following summarizes the modeling approach and results; details of the modeling approach, inputs, assumptions, and results are presented in Appendix I.

Based on the groundwater quality investigations, the extent of the plating metals plume (copper, nickel, and zinc) in groundwater downgradient from the Facility is significantly retarded relative to the extent of the chlorinated solvent plume. Plating metals concentrations exceeding groundwater screening levels extend to well MW-16 located on 2nd Avenue (see Figures 34, 35, and 36), while VOCs apparently extend to the Waterway. Assuming the release of plating metals to groundwater was concurrent with the release of VOCs, the more limited extent of the metals plume indicates that metals are being attenuated in groundwater.

There are several mechanisms known to naturally attenuate metals in groundwater. These include readily reversible reactions (e.g., weak adsorption to mineral surfaces) that would slow metals migration but not permanently remove metals from groundwater, as well as generally non-reversible reactions that are capable of permanently immobilizing metals (precipitation and co-precipitation reactions). Our hypothesis is that the observed attenuation and limited extent of plating metals is largely due to changes in pH and, to a

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lesser extent, Eh in groundwater downgradient from the Facility. The changes in pH and Eh create conditions favorable for removal of metals from groundwater through irreversible mineral precipitation and co-precipitation reactions, and also enhance sorption of metals to mineral surfaces.

Geochemical modeling was performed to evaluate the hypothesis of metals attenuation and assess what mechanisms are controlling the fate and transport of plating metals. Modeling was performed using PHREEQC (Parkhurst and Apello, 1999), a thermodynamic equilibrium model available from the United States Geological Survey. Attenuation mechanisms evaluated in the PHREEQC modeling include:

Precipitation reactions, where metals are immobilized through direct precipitation of mineral solids (e.g., metal sulfides or carbonate minerals);

Co-precipitation reactions, where plating metals are incorporated as trace elements in precipitation of iron or manganese oxyhydroxides or sulfides; and

Adsorption of metals to mineral surfaces.

Geochemical modeling was performed by evaluating mineral stability or saturation indices (SIs) along an approximate flow path from the Facility to 1st Avenue South. Mineral SIs describe the equilibrium between the aqueous solution and mineral solids in a geochemical system, and indicate if conditions are favorable for mineral precipitation (oversaturated conditions) or dissolution (undersaturated conditions). The model was applied for three areas to calculate SIs using groundwater chemistry data from monitoring wells. Chemistry data included metals concentrations; conventional parameters such as alkalinity, sulfate, and sulfide concentrations; and field parameters, such as pH and Eh. The three modeled areas are:

Source Area, using data from wells MW-2 and MW-3. These wells are located at the Facility and exhibit high concentrations of copper, nickel, and zinc, low pH (<4), and low alkalinity (i.e., acid buffering capacity);

Attenuation Area, using data from wells MW-8 and MW-16-40. These wells are located about 120 and 440 feet southwest of the Facility, respectively. This area exhibits higher pH (>6), increased alkalinity, lower Eh, and lower plating metals concentrations than the Source Area; and

Downgradient Area, using data from well MW-17-40. This well is located about 1,100 feet southwest of the Facility. A full suite of plating metals data was not available for this well, but available data indicate near neutral pH, increased alkalinity, and slightly oxidizing (positive Eh) conditions.

Modeled SIs were evaluated to determine whether metal-bearing mineral phases are expected to precipitate, dissolve, or are in equilibrium with groundwater geochemical conditions at each of the areas. The model results indicate that minerals are not expected to precipitate or otherwise attenuate at the Facility, due largely to the acidic pH. This result is consistent with the observed high metals concentrations in groundwater at the Facility.

Downgradient at wells MW-8 and MW-16-40, observed pH and alkalinity increase, while copper, nickel, and zinc concentrations in groundwater decrease by at least one to two

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orders of magnitude compared to the source area. Consistent with the observed significant decrease in aqueous metals concentrations, metals-bearing minerals are modeled to be more stable at these wells primarily due to the increased pH. Based on the SIs, metal-sulfide and metal-oxyhydroxides minerals are likely to precipitate, removing metals from groundwater and limiting downgradient migration.

Further downgradient from wells MW-8 and MW-16-40 conditions are favorable for the precipitation of stable iron and manganese oxide minerals that can sorb trace metals, further reducing concentrations of copper, nickel, and zinc. The modeling further indicates that the sorption capacity and strength increases as pH increases from acidic to more neutral conditions.

The PHREEQC modeling supports the hypothesis that plating metals are attenuating in groundwater downgradient from the Facility due to a combination of precipitation, co-precipitation, and sorption reactions. Although there is strong evidence based on groundwater monitoring data and supported by the modeling that these attenuation mechanisms are effective at reducing metals concentrations to below screening levels or background conditions, the modeling cannot conclusively demonstrate that the plating metals plume will not expand beyond the current observed extent. Based on the limited current extent of the plating metals plume relative to the chlorinated solvent plume it is clear that metals are migrating at a significantly slower rate than the VOCs and it is expected that future expansion of the plume, if any, would occur slowly.

9 Conceptual Site Model and Exposure Pathway Assessment

9.1 Summary of Contaminant Source and Extent The Facility is located in an area where chlorinated solvent COCs originate from multiple different commercial and industrial sources. TCE was used at the Facility until 2004. Environmental investigations confirm the likely release of TCE from the Facility to soil and groundwater and downgradient migration of TCE and its degradation products cis-DCE and vinyl chloride via groundwater flow.

The highest concentrations of TCE in soil have been detected beneath the western portion of the Facility and at depths close to the water table. TCE appears to have migrated downward through shallow fill soils to the water table. However, TCE has not been detected in soils at depths greater than 20 feet beneath the Facility. The maximum TCE concentration in groundwater is less than 1 percent of its solubility, suggesting that TCE as a dense non-aqueous phase liquid (DNAPL) is not present at the Facility.

Groundwater quality data used to map the chlorinated COC plumes originating from the Facility are described in Section 7.3.1. The groundwater TCE plume migrates slightly downward and towards the southwest, consistent with the vertical and horizontal groundwater gradients in this area, until around 1st Avenue South where it reaches its maximum depth (approximately 75 feet). West of 1st Avenue South, the plume migrates

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upward to the southwest (consistent with the upward gradients observed in this area) and extends to the Waterway.

Interim source control remedial actions have significantly reduced chlorinated COC concentrations at the Facility. Since source control began, the highest concentrations of TCE have been detected mid-plume (around 1st Avenue South). Concentrations downgradient of the Facility are expected to attenuate via natural processes; however, the data indicate slow biodegradation throughout much of the plume. Contaminant fate and transport modeling suggests that there is a reasonable likelihood that concentrations in groundwater approaching the waterway will not increase over time.

Data also indicate the likely historical release of plating solutions resulting in depressed pH and elevated concentrations of copper, nickel, and zinc in soil and groundwater beneath the Facility. The highest concentrations in soil and groundwater have been detected beneath and downgradient of the former plating area located in the southwest corner of the Facility. Concentrations of two redox sensitive metals – iron and manganese – are slightly higher at the Facility than in surrounding groundwater, possibly due to locally depressed pH or local variations in redox conditions. Concentrations of these five metals relative to area-wide concentrations are elevated in the vicinity of the Facility but impacts relative to the screening levels (for copper, nickel, and zinc) or the area-wide levels (for iron and manganese) do not extend far downgradient of the Facility.

9.2 Pathways of Exposure Potential exposure pathways for contaminants in the Study Area are identified in Section 5.2. In this section we evaluate the potential for these exposure pathways to be complete under current or possible future conditions on and off the ABP property based on the data presented in the preceding sections and the pathway-specific screening levels identified in Section 5.3.

Exposure pathways identified in Section 5.2 that are applicable to metal contaminants are limited. These contaminants are not volatile, have limited mobility, and do not reach, nor appear likely to reach, the Waterway. The five metal COCs (iron, manganese, copper, nickel, and zinc) also exhibit very low toxicity to humans and therefore have very high screening levels (if any) for the direct contact pathway. Maximum detected concentrations of metals were below applicable screening levels for the direct contact pathway under residential exposure assumptions. Therefore, no potentially complete current or future exposure pathways for metals in the Study Area were identified.

Potential exposure pathways identified in Section 5 for chlorinated COCs under current and potential future uses are discussed below by medium. A summary of potential exposure pathways under current and future uses is provided in Table 13, and areas exceeding screening levels for potential exposure pathways are shown on Figure 53.

9.2.1 Soil Potential exposure pathways for VOCs in soil include direct contact, dust inhalation, and transport to air and groundwater. Each of these pathways is discussed below for soil from ground surface to the water table. Below the water table, potential exposure pathways are evaluated based on groundwater data, consistent with the PSC East-of-4th CAP (Geomatrix 2010).

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Direct contact. The residential direct contact screening level (Table 7) was used to evaluate the direct contact pathway. Only TCE has been detected above direct contact screening levels. Soil containing concentrations of TCE above the direct contact screening level is confined to the area beneath the Facility. Most recent data do not indicate any exceedances of the direct contact soil screening level; however, access limitations prevent full characterization of potentially contaminated soil on the Facility property. Therefore, for the purposes of this RI, it is assumed that soil near Vapor Degreaser No. 1, as shown on Figure 53, may exceed the direct contact screening level.

The Facility is covered by impervious pavement or building foundations that prevent direct contact with affected media. Furthermore, as described in Section 5, company policy prohibits subsurface work; in the event that subsurface work is required, the company would assume soil encountered is potentially contaminated and would implement mitigation methods to prevent unacceptable exposures. Therefore, this exposure pathway is not currently complete. Because soil beneath the Facility may exceed the direct contact screening level, this pathway is considered a potential future exposure pathway that would need to be addressed in the FS.

Dust inhalation. As discussed in Section 5, dust inhalation is an unlikely exposure pathway due to tendency of VOCs to volatilize from airborne particles. The residential direct contact screening level (Table 7) was used as a conservative benchmark for this pathway. No recent samples exceed this screening level, and pre-remediation samples only slightly exceeded the screening level. Therefore, this pathway was not identified as a potential current or future exposure pathway. Volatilization to indoor air. The soil protection of groundwater screening level based on protection of residential indoor air (Table 7) was used to evaluate potential exposure for above-ground receptors, including residents and workers. Soil above the water table on the ABP property exceeds this screening level only for TCE. The SVE system currently operating on the property, and the presence of concrete and asphalt surfaces, mitigates this pathway for above-ground workers, and this pathway is not currently complete. This pathway is considered a potential future exposure pathway that would need to be addressed in the FS.

TCE has not been detected above the screening level in soil above the water table off of the ABP property. Therefore, this pathway is not considered a current or potential future exposure pathway for soil off of the ABP property.

Volatilization to outdoor air. A soil screening level protective of outdoor air for residents and above-ground workers was not developed. It is assumed that vapor intrusion from relatively high concentrations of TCE in soil above the water table at the facility (up to 12 mg/kg) is a potential exposure pathway if current controls were removed9. TCE concentrations in vadose-zone soil and groundwater in the Water Table Interval off the property are much lower or not detected; therefore, off the ABP property

9 The PSC Risk Assessment (PSC 2001) estimated vapor intrusion to yield outdoor air concentrations approximately 100 times lower than indoor air concentrations. The maximum detected concentration exceeds the soil-to-groundwater-to-indoor air screening level by more than 100 times.

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vapor intrusion to outdoor air is not considered a potential current or future exposure pathway because of the much greater dilution.

The soil protection of groundwater screening level based on protection of residential indoor air was used to evaluate potential exposure for below-ground workers. Soil above the water table on the ABP property exceeds this screening level for TCE. Company policy prohibits subsurface work; in the event that subsurface work is required, the company would assume air within trenches or excavations is potentially contaminated and would implement mitigation methods to prevent unacceptable exposures.

Because vadose zone soil on the ABP property exceeds screening levels for TCE, the volatilization to outdoor air pathway is a potential future exposure pathway that would need to be addressed in the FS.

TCE has not been detected above the screening level in soil above the water table off of the ABP Property. Therefore, this pathway is not considered a current or potential future exposure pathway for soil off of the ABP property.

Leaching to groundwater. To evaluate this pathway, the soil protection of groundwater screening level developed for the most stringent of either protection of residential indoor air or surface water (Table 7) was used. Soil above the water table on the ABP property exceeds this screening level for TCE. A separate soil screening level for protection of surface water was not developed, but it is assumed that concentrations on the ABP property would exceed one if developed. As discussed in Sections 9.2.3 and 9.2.4 below, potential exposure pathways for the air and surface water pathways are either incomplete based on existing data or are being mitigated; however, these pathways represent potential future exposure pathways that would need to be addressed in the FS.

TCE has not been detected above the screening level in soil above the water table off of the ABP property. Therefore, this pathway is not considered a current or potential future exposure pathway for soil off of the ABP property.

9.2.2 Groundwater Potential exposure pathways for VOCs in groundwater include direct contact and transport to air and surface water. The direct contact and transport to air pathways are evaluated for groundwater in the Water Table Interval (to a depth of 20 feet10). The transport to surface water pathway is evaluated for groundwater from the water table to the maximum depth of contamination.

Direct human exposure via dermal contact. As discussed in Section 5, this is considered a potential exposure pathway only for below-ground workers because of the unlikelihood of residents or above-ground workers from coming into contact with groundwater. A risk-based screening level specific to this pathway was not developed for the RI. To evaluate this pathway, the residential groundwater to indoor air screening level was used11. Groundwater in the Water Table Interval exceeds the screening level for TCE 10 The standard point of compliance for direct contact for soil is 15 feet. Groundwater was evaluated to a depth of 20 feet for convenience, since this depth comprises the Water Table interval. 11 Although this is a conservative evaluation, it is likely that actions that will be considered in the FS to address the groundwater-to-air pathway will also address the groundwater direct contact pathway, or be easily amended to (e.g., through controls).

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on and off the ABP property as shown on Figure 54. No current projects involving excavation to groundwater are known in the area of affected groundwater, and utilities in the area are located above the water table, minimizing the potential for utility workers to encounter contaminated groundwater. To further mitigate this pathway, ABP has notified agencies or companies with utilities in the area immediately downgradient of the ABP property (including: Century Link, SPU, and PSE) of the presence of contaminated groundwater. This pathway is not considered a current pathway, but represents a potential future exposure pathway that would need to be addressed in the FS.

Volatilization to indoor air. The groundwater protection of residential indoor air screening level (Table 8) was used to evaluate this pathway. Groundwater in the Water Table Interval exceeds the screening level for TCE on and off the ABP property as shown on Figure 53. Buildings within this area have been further evaluated and, if appropriate, mitigation measures have been implemented (see Appendix E). This area represents a potential future exposure pathway that would need to be addressed in the FS.

Volatilization to outdoor air. Groundwater contamination is assumed to not contribute to outdoor air contamination for above-ground receptors12. For below-ground workers, the groundwater protection of residential indoor air screening level (Table 8) was used to evaluate this pathway. Groundwater in the Water Table Interval exceeds the screening level for TCE on and off the ABP property as shown on Figure 53. To mitigate this pathway, ABP has notified agencies or companies with utilities (including: Century Link, SPU, and PSE) in the area immediately downgradient of the ABP property of the presence of contaminated groundwater. This area represents a potential future exposure pathway that would need to be addressed in the FS.

Discharge to surface water. To evaluate this pathway, the groundwater protection of surface water screening level (Table 8) was used. Groundwater on and off the ABP property exceeds this screening level for TCE, cis-DCE, and vinyl chloride. The area of TCE exceedances is shown on Figure 53. The area of vinyl chloride exceedances is comingled with other area plumes as described in Section 7.3.1. As discussed in Section 9.2.4 below, potential exposure pathways for the surface water pathways are incomplete based on existing data. However, these pathways represent potential future exposure pathways that would need to be addressed in the FS.

9.2.3 Air Potential exposure pathways for VOCs in air include inhalation of vapors in indoor and outdoor air resulting from vapor intrusion from contaminated soil and groundwater13.

Inhalation of vapors in indoor air. Contaminated soil above the water table or groundwater at the water table can be a source of chlorinated COC vapors to indoor air. To evaluate this pathway, soil data above the water table was compared to the soil screening level protective of groundwater quality to residential indoor air screening level

12 Although a specific screening level was not developed, the PSC Risk Assessment (PSC 2001) estimated vapor intrusion resulted in VOC concentrations approximately 100 times less in outdoor air than in indoor air. None of the existing data at the Water Table Interval is more than 100 times the groundwater screening level based on protection of residential indoor air. 13 As discussed in Section 5, it is assumed that the SVE system, which discharges soil gas that has been treated, is monitored and maintained to prevent unacceptable exposures to area residents and workers.

ASPECT CONSULTING


(Table 7), and groundwater in the Water Table Interval was compared to the groundwater protection of residential indoor air screening level (Table 8). The extent of the area exceeding these screening levels is shown on Figure 54. As described in Section 6.1, there are multiple structures potentially within the footprint of the ABP plume in the Water Table Interval. At all of these structures, either a monitoring program or active vapor mitigation system has been implemented to ensure protectiveness of the indoor air pathway. Therefore, this exposure pathway is not currently complete.

Inhalation of VOCs entering indoor air through vapor intrusion on and off the ABP property is a potentially complete pathway that is currently being monitored and mitigated, where potentially needed, by SVE or subslab depressurization systems. However, these pathways represent potential future exposure pathways that would need to be addressed in the FS.

Inhalation of vapors in outdoor air. Screening levels for soil and groundwater specific to outdoor air was not developed. As discussed above, soil vapors entering outdoor air are significantly more dilute than those entering indoor air, and it is assumed that outdoor air off the ABP Property is not significantly impacted for above- ground residents and workers. To evaluate this pathway for below-ground workers, soil data were compared to the soil-to-groundwater-to-residential indoor air screening level, and groundwater data were compared to the groundwater-to-residential air screening level.

On the ABP property, TCE concentrations in soil above the water table exceed the soil-to-groundwater-to-residential indoor air screening level. Because the maximum soil concentrations exceed the indoor air screening level by more than 100 times, it is assumed that inhalation of vapors in outdoor air is a potential exposure pathway. Outdoor inhalation of VOCs by above-ground workers is currently mitigated by the existing SVE system and the presence of concrete and asphalt caps. Company policy prohibits subsurface work; in the event that subsurface work is required, the company would assume air within trenches or excavations is potentially contaminated and would implement mitigation methods to prevent unacceptable exposures. Therefore, on the ABP this pathway is currently incomplete, but is identified as a potential future exposure pathway that would need to be addressed in the FS.

Off the ABP property, inhalation of VOCs in air is a potentially complete pathway for off-property below-ground workers. To mitigate this pathway, ABP has notified agencies or companies with utilities (including: Century Link, SPU, and PSE) in the area immediately downgradient of the ABP property of the presence of contaminated soil and groundwater.

Because of ongoing mitigation efforts, potential indoor and above-ground outdoor air exposure pathways are currently considered incomplete, but are identified as potential future exposure pathways that would need to be addressed in the FS.

9.2.4 Sediment/Surface Water Potential exposure pathways for VOCs in sediment/surface water include direct contact by humans and organisms, ingestion by organisms, and ingestion of organisms by humans and organisms. These pathways are evaluated in sediment porewater at a depth of 10 cm below mudline (see Section 5).

ASPECT CONSULTING


A discussion of potential exposure pathways for organisms and human ingestion of organisms is provided in Appendix J. Based on current data, concentrations of ABP COCs in contaminated groundwater discharging to contaminated surface water are below ecological screening levels.

Currently, recreational uses in the area of potential contaminated groundwater discharge are limited due to the industrial nature of this area of the Waterway. Subsistence shellfish harvesting activities are limited due to limited available populations, and when considering potential site-specific consumption rates (see Appendix J), potential exposures are below acceptable levels. Therefore, these pathways are currently considered incomplete, but are identified as potential future exposure pathways in the event conditions change.

10 Conclusions and Recommendations

1. This RI confirms the release of TCE and specific plating metals to the environment from historical operations at the ABP Facility. Use of TCE as a degreasing solvent has been discontinued and all current plating activities are conducted in areas with secondary containment. Investigation data yielded no evidence of DNAPL beneath the Facility.

2. A source control AS/SVE system has been installed as an interim measure and operated at the Facility since September 2008. Chlorinated solvent concentrations in groundwater have improved significantly as a result. Performance monitoring demonstrates concentration reductions of 90 to 99 percent in the vicinity of the Facility. In addition, quarterly monitoring shows statistically significant declines at a distance up to 1,000 feet downgradient. The AS system was temporarily shut down in December 2011 to evaluate potential for rebound. The SVE system continues operating at present. As mass removal rates from the AS/SVE system decline and groundwater quality at the Facility improves, it is appropriate to continue evaluating potential operational adjustments that lead to the eventual shut-down of the system.

3. Investigation and monitoring data have been used to map the lateral and vertical extent of contaminant releases from the Facility. The chlorinated solvent plume exceeding screening levels extends from the Facility to the Waterway, a distance of about 2,200 feet. Plating metals exceed groundwater screening levels, but are much less mobile in groundwater. The metals have not migrated as far from the source area as the chlorinated solvent plume and do not reach the Waterway.

4. Ecology has identified PSC, Capital, and Blaser as three nearby industrial facilities where releases of chlorinated solvents and other constituents have been confirmed. The location of each has bearing on the potential for co-mingling with releases from the ABP Facility:

a) PSC is located east and upgradient of ABP and serves as an on-going source of low-to-moderate chlorinated and 1,4-dioxane screening level

ASPECT CONSULTING


exceedances migrating into the ABP Study Area via groundwater flow. Monitoring confirms that ABP does not contribute to the 1,4-dioxane release, but that CVOCs originating from Art Brass and PSC do become co-mingled.

b) Blaser and Capital are located to the south and cross gradient from ABP. Groundwater elevation and chemical data define a clear boundary that separates the ABP TCE plume from the releases originating at Blaser and Capital.

c) Vinyl chloride in the Shallow and Intermediate intervals appears co-mingled from degraded TCE releases originating from PSC, ABP, Capital, and Blaser.

5. Investigation data indicates a relatively consistent 200 to 250 foot width to the ABP TCE plume between the Facility and the Waterway.

6. Groundwater in the area is not suitable for potable use, so screening levels used for comparison with chemical data are established to be protective of vapor migration to indoor air and discharge to surface water.

7. Based on existing data, most potential exposure pathways are not complete. Potentially complete exposure pathways are currently mitigated as follows:

a) Vapor migration from groundwater to indoor air is mitigated by monitoring and/or subslab depressurization/SVE systems within areas of vadose-zone soil and water table groundwater contamination. Downgradient property owners have been cooperative in providing access for vapor intrusion monitoring and mitigation.

b) Impermeable covers (asphalt and concrete) prevent contact with contaminated soil.

c) To mitigate potential exposure to underground workers, utility companies have been contacted to inform them of areas of shallow groundwater contamination.

8. Using reasonably conservative fate and transport model input parameters, model-predicted groundwater concentrations near the Waterway are generally similar to what has been recently observed in wells. This indicates that there is a reasonable likelihood that concentrations in groundwater approaching the Waterway will not increase over time. However, given the uncertainty in model inputs, it is also conceivable that concentrations could increase over time, and neither potential future outcome can be rejected. Continued monitoring is warranted to empirically evaluate trends.

9. Recommended actions are as follows:

a) Continue operating the AS/SVE system, monitor performance, and continue to test a sequence of operational modifications to optimize efficiency and mass removal.

ASPECT CONSULTING


b) Continue to implement the Vapor Intrusion Mitigation Program as an interim measure until a final cleanup action is selected. Installed mitigation systems will be evaluated per program requirements and proposed for shutdown once the Ecology-approved criteria are met. Refer to Appendix E for a detailed listing of recommended actions.

c) Conduct routine groundwater monitoring at select wells to support interim action performance monitoring, vapor intrusion assessment, and plume stability evaluation. Ecology has already approved the 2012 Groundwater Monitoring Plan that outlines specific wells for semi-annual monitoring and concurred with the separate request to monitor wells MW-16-40, MW-17-40, MW-17-60, MW-22-30, and MW-24-30 on a quarterly basis to assess plume stability. The approved plan includes metals analyses for empirical evaluation of plating metals plume extent and mobility. ABP will submit a proposal for the 2013 groundwater monitoring plan that will include a reduced program focusing on semi-annual monitoring. The reduced program will support interim action performance monitoring, vapor intrusion assessment, and plume stability evaluation.

d) Negotiate an amendment to the existing Agreed Order No. DE 5296 for the preparation of a Feasibility Study consistent with MTCA Chapter 173-340-350(8). In previous correspondence, Ecology has indicated a preference for the W4 Group to prepare a joint FS rather than having separate FS documents for the ABP, BDC, and CI facilities and for the portion of the PSC plume extending west of Fourth Avenue South. However, several characteristics of the ABP facility releases are unique to the area and would be more efficiently dealt with in their own FS. In particular:

A narrow, well-defined TCE plume that is not comingled with TCE plumes from other facilities.

The ABP chlorinated solvent plume extends to the Waterway shoreline. This potential exposure pathway will warrant specific remedial action objectives not being considered by the other facilities.

The presence of plating metals above screening levels at the Facility, which are not COCs at the other facilities. The presence of these COCs will affect the selection and evaluation of potential remedial technologies.

The presence of geochemical conditions that are distinct within the ABP Study Area, including low pH at the Facility and less reductive dechlorination than observed downgradient of other facilities. Because of the distinct conditions many potential remedial technologies will likely be evaluated differently for the ABP study area than for other areas.

ASPECT CONSULTING


The timing to complete an FS may depend on multiple factors, including the progress of interim measures and potential exposure pathways. A joint FS would meet the lowest common denominator for schedule, and could result in unnecessary delays to implementing a cleanup action.

Coordination with the W4 group will be necessary prior to amending the Agreed Order to redefine an appropriate Study Area. Ongoing coordination during FS work will be needed, as with the RI, to ensure data is shared and analyses (e.g., fate and transport modeling) are consistent.

ASPECT CONSULTING


References

Aronson, D. and Howard, P., 1997, Anaerobic Biodegradation of Organic Chemicals in Groundwater: A Summary of Field and Laboratory Studies, Environmental Science Center, Syracuse Research Corporation, November 12, 1997.

Arrow et al., 2007, Interim Vapor Intrusion Plan, West of 4th Avenue South Investigation Area, Seattle, Washington, Arrow Environmental, LLC (for PSC), Aspect (for ABP), Farallon Consulting, LLC (for Capital Industries), and Pacific Groundwater Group (for Blaser Die Casting), July 20, 2007.

Aspect, 2005a, Preliminary site investigation results, Art Brass Plating, Inc., July 19, 2005, Seattle, Washington.

Aspect, 2005b, Follow-up site investigation results, Art Brass Plating, Inc., December 1, 2005, Seattle, Washington.

Aspect, 2006a, Results of data gaps investigation, Art Brass Plating, Inc., November 6, 2006, Seattle, Washington.

Aspect, 2006b, Tier 3 Sampling Report, Resampling at 215/217 South Findlay Street, January 27, 2006.

Aspect, 2007, Interim Cleanup Action Plan, Draft, Art Brass Plating, Inc., April 5, 2007, Seattle, Washington.

Aspect, 2008, Remedial Investigation Work Plan, Art Brass Plating, September 25, 2008.

Aspect, 2010a, Tier 3 Assessment Report for December 2009 Air Sampling Event, 214 South Findlay Street, Seattle (Location 19), 218-1/2 South Findlay Street, Seattle (Location 10), 222 South Orcas Street, Seattle (Location 17), January 25, 2010.

Aspect, 2010b, Tier 3 Assessment Report for Supplemental Air Quality Monitoring, 222 South Orcas Street, Seattle (Location 17), May 25, 2010.

Aspect, 2011a, Duwamish Waterway Sediment Porewater Sampling Work Plan, Art Brass Plating, Agreed Order No. DE 5296, January 28, 2011.

Aspect, 2011b, Phase One Spatial Variability in Groundwater Discharge, Duwamish Waterway Sediment Porewater Sampling Program, Art Brass Plating, Agreed Order No. DE 5296, March 7, 2011.

Booth and Herman, 1998, Duwamish Basin Groundwater Pathways Conceptual Model Report, Duwamish Industrial Area Hydrogeologic Pathways Project, Prepared for City of Seattle Office of Economic Development and King County Office of Budget and Strategic Planning, University of Washington and Hart Crowser, Seattle, Washington.

ASPECT CONSULTING


Ecology, 1994, Natural Background Soil Metals Concentrations in Washington State, Toxics Cleanup Program, Department of Ecology, October 1994, Publication #94-115.

Geomatrix, 2006, Revised Technical Memorandum No.1: Modeling, Cleanup Levels, Constituents of Concern, Conditional Points of Compliance, and Corrective Action Schedule for Site Wide Feasibility Study, PSC Georgetown Facility. Prepared for PSC, June 2006.

Geomatrix, 2010, Draft Cleanup Action Plan, PSC Georgetown Facility, Seattle, Washington, Prepared for Philip Services Corporation, 2010.

Newell, Charles J., Hanadi S. Rifai, John T. Wilson, John A. Connor, Julia A. Aziz, Monica P. Suarez, 2002, Calculation and Use of First-Order Rate Constants for Monitored Natural Attenuation Studies, United States Environmental Protection Agency, November 2002, EPA/540/S-02/500.

Parkhurst, D.L. and Appelo, C.A.J., 1999, User's guide to PHREEQC (version 2)--A computer program for speciation, batch-reaction, one-dimensional transport, and inverse geochemical calculations: U.S. Geological Survey Water-Resources Investigations Report 99-4259, 312 p.

Philip Services Corporation (PSC), 2001, Draft Comprehensive RFI Report, Part II Draft Human and Ecological Risk Assessment, Philip Services Corporation (PSC), August 10, 2001.

PSC, 2002, Revised Inhalation Pathway Interim Measures Work Plan, Philip Services Corporation, August 12, 2002 and Errata Document, September 17, 2002.

PSC, 2003, Final Comprehensive Remedial Investigation Report For Philip Services Corporation’s Georgetown Facility, Philip Services Corporation, November 14, 2003.

PSI, 1999, Soil and Groundwater Sampling and Analysis Results, Art Brass Plating, Inc., Facility, PSI, April 16, 1999.

Windward, 2004, Lower Duwamish Waterway Remedial Investigation, Data Report: Survey and Sampling of Lower Duwamish Waterway Seeps, Final. Prepared for Lower Duwamish Waterway Group, Windward Environmental LLC, Seattle, WA, November 18, 2004.

Xu, M. and Y. Eckstein, 1995, Use of Weighted Least-Squares Method in Evaluation of the Relationship Between Dispersivity and Scale, J. Ground Water, 33(6): 905-908.

ASPECT CONSULTING


Limitations

Work for this project was performed and this report prepared in accordance with generally accepted professional practices for the nature and conditions of work completed in the same or similar localities, at the time the work was performed. It is intended for the exclusive use of Art Brass Plating, Inc. for specific application to the referenced property. This report does not represent a legal opinion. No other warranty, expressed or implied, is made.

Table 1 - Aquifer Hydraulic Conductivity Estimates from Slug Tests*Art Brass Plating 050067

DRAFT

Well ID

cm/sec ft/day

Water Table Interval

MW‐81

1.7E‐03 4.7

MW‐101

9.4E‐04 2.7

MW‐11 3.7E‐03 11

MW‐13 2.4E‐03 6.7

PSC‐138‐WT 1.7E‐02 49

PSC‐142‐WT 3.0E‐03 8.5

Shallow Interval

MW‐6‐30 1.8E‐02 51

MW‐8‐30 6.9E‐03 20

MW‐11‐301 1.6E‐02 44.9

MW‐16‐40 1.8E‐01 51

MW‐22‐30 3.3E‐02 94

MW‐24‐301 4.0E‐02 113

PSC‐138‐40 2.4E‐01 68

PSC‐142‐40 1.3E‐02 37

Intermediate Interval

MW‐8‐70 5.0E‐04 1.4

MW‐16‐75 1.6E‐04 0.4

MW‐21‐501 1.6E‐02 46.3

MW‐21‐75 2.1E‐03 5.8

MW‐22‐50 2.3E‐04 0.7

MW‐24‐501 1.0E‐02 29.4

PSC‐138‐70 3.8E‐03 11

AB‐142‐70 9.6E‐03 27

Notes:

*‐ Refer to Appendix D for detailed summary of slug tests.

1 ‐ Hydraulic conductivity shown represents geomeatric mean of two measurements

Hydraulic Conductivity

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Table 1Page 1 of 1

Table 2 - Well Completion SummaryArt Brass Plating 050067

DRAFT

Well IDTop of Casing

Elevation*

Ground Surface

Elevation*

Date of Well Installation

Easting Northing Top Bottom Top Bottom

AB-CG-140-70 15.33 15.82 12-Mar-10 1269427.14 204279.89 60 70 -44.18 -54.18AB-CG-142-70 16.53 17.05 18-Nov-08 1269481.43 204976.69 60 70 -42.95 -52.95

MW-1 16.22 16.71 05-Oct-05 1270672.26 205260.88 3.75 13.75 12.96 2.96MW-2 16.34 16.66 05-Oct-05 1270751.19 205272.54 4 14 12.66 2.66MW-3 14.89 15.30 05-Oct-05 1270644.08 205240.04 4.2 14.2 11.1 1.1

MW-3-30 14.83 1270640.00 205243.00 20 30MW-3-50 14.76 1270640.00 205250.00 40 50

MW-4 14.36 15.03 05-Oct-05 1270729.15 205216.40 3.8 13.8 11.23 1.23MW-5 14.89 15.52 24-Jun-06 1270644.38 205279.84 4 14 11.52 1.52MW-6 17.04 17.73 24-Jun-06 1270852.94 205325.12 4 14 13.73 3.73

MW-6-30 17.25 17.92 24-Jun-06 1270855.03 205327.14 19.5 29.5 -1.58 -11.58MW-7 13.92 15.21 18-Mar-08 1270604.79 205279.58 4 14 11.21 1.21MW-8 14.99 15.39 08-May-07 1270545.87 205203.62 5 15 10.39 0.39

MW-8-30 14.72 15.27 12-Mar-08 1270548.65 205203.49 19.5 29.5 -4.23 -14.23MW-8-70 14.96 15.24 17-Nov-08 1270541.66 205203.62 60 70 -44.76 -54.76

MW-9 15.94 16.26 18-Mar-08 1270526.33 205268.56 4 14 12.26 2.26MW-10 16.51 16.91 09-May-07 1270238.60 204965.16 5 15 11.91 1.91MW-11 16.94 17.24 09-May-07 1270598.85 204952.09 5 15 12.24 2.24

MW-11-30 16.74 17.25 11-Mar-08 1270599.11 204953.12 19.5 29.5 -2.25 -12.25MW-12 14.88 15.29 17-Mar-08 1270749.50 205330.92 4 14 11.29 1.29MW-13 15.51 15.89 18-Mar-08 1270517.08 205329.10 4 14 11.89 1.89MW-14 15.48 15.81 17-Mar-08 1270766.41 205188.47 4 14 11.81 1.81MW-15 14.75 15.20 03-Dec-08 1270418.72 205227.61 4 14 11.2 1.2MW-16 16.90 17.34 18-Mar-09 1270238.94 205159.84 5 15 12.34 2.34

MW-16-40 16.58 17.06 16-Mar-09 1270236.00 205051.00 30 40 -12.94 -22.94MW-16-75 16.52 17.01 16-Mar-09 1270235.96 205046.82 65 75 -47.99 -57.99MW-17-40 16.71 17.04 21-Mar-09 1269860.52 204780.17 30 40 -12.96 -22.96MW-17-60 16.53 16.97 21-Mar-09 1269862.95 204777.53 50 60 -33.03 -43.03MW-18-50 14.74 15.26 17-Mar-09 1269895.80 205079.84 40 50 -24.74 -34.74MW-18-70 14.92 15.32 17-Mar-09 1269894.15 205082.10 60 70 -44.68 -54.68MW-19-40 14.79 15.35 18-Mar-09 1270002.66 204781.96 30 40 -14.65 -24.65MW-19-60 14.80 15.23 18-Mar-09 1270006.92 204778.72 50 60 -34.77 -44.77MW-20-40 16.25 1269872.00 204656.00 30 40MW-20-60 16.17 1269875.00 204658.00 50 60MW-21-50 16.27 16.62 08-Mar-10 1269496.09 204578.53 40 50 -23.38 -33.38MW-21-75 16.30 16.59 08-Mar-10 1269497.58 204574.39 65 75 -48.41 -58.41MW-22-30 11.97 12.31 09-Mar-10 1268818.53 204011.44 20 30 -7.69 -17.69MW-22-50 11.72 12.34 09-Mar-10 1268819.56 204008.55 40 50 -27.66 -37.66MW-23-30 13.40 13.72 10-Mar-10 1268860.46 203896.17 20 30 -6.28 -16.28MW-23-50 13.48 13.79 09-Mar-10 1268861.59 203893.06 40 50 -26.21 -36.21

MW-24 12.32 12.63 13-Mar-10 1268903.72 204206.13 5 15 7.63 -2.37MW-24-30 12.72 13.01 13-Mar-10 1268998.87 204216.07 20 30 -6.99 -16.99MW-24-50 12.56 13.00 13-Mar-10 1269002.05 204216.00 40 50 -27 -37MW-25-50 15.66 1269702.00 204648.00 40 50MW-25-75 15.76 1269708.00 204649.00 65 75MW-26-40 16.05 1269515.00 204514.00 30 40MW-26-55 15.93 1269516.00 204509.00 45 55

MW-27 14.81 1270604.00 205136.00 4 14PMW-1 16.38 16.74 24-Jun-06 1270698.68 205270.81 4 14 12.74 2.74

PSC-CG-135-40 17.31 17.79 25-Mar-02 1270999.93 205373.49 30 40 -12.21 -22.21PSC-CG-135-50 17.34 17.82 25-Mar-02 1270999.83 205376.59 40 50 -22.18 -32.18PSC-CG-138-40 16.66 16.98 07-Mar-02 1270243.33 205260.19 29.92 39.92 -12.94 -22.94PSC-CG-138-70 16.65 17.00 07-Mar-02 1270243.43 205265.49 60 70 -43 -53PSC-CG-138-WT 16.62 16.94 07-Mar-02 1270243.13 205255.19 4.5 14.5 12.44 2.44PSC-CG-139-40 16.68 16.99 11-Mar-02 1270294.23 205777.89 30 40 -13.01 -23.01PSC-CG-140-30 15.23 15.68 1269422.70 204273.90 20 30 -4.32 -14.32PSC-CG-140-40 15.20 15.65 12-Mar-02 1269427.63 204274.99 30 40 -14.35 -24.35PSC-CG-142-40 16.63 17.16 13-Mar-02 1269446.93 204977.19 30 40 -12.84 -22.84PSC-CG-142-WT 16.73 17.23 13-Mar-02 1269451.43 204976.69 4.5 14.5 12.73 2.73PSC-CG-143-40 15.60 16.08 06-Mar-02 1269332.63 205522.79 30 40 -13.92 -23.92PSC-CG-143-WT 15.80 16.13 06-Mar-02 1269339.23 205522.29 4.5 14.5 11.63 1.63PSC-CG-144-35 15.55 15.89 08-May-02 1268831.31 204984.00 25 35 -9.11 -19.11PSC-CG-145-35 15.49 15.83 08-May-02 1268842.81 205130.70 25 35 -9.17 -19.17PSC-CG-151-25 11.65 12.02 25-Jul-03 1268749.60 204170.40 15 25 -2.98 -12.98

PZ-1 14.64 15.21 17-Mar-09 1269894.15 205082.10 5 15 10.21 0.21

Well Coordinates(WA SPN NAD83 ft)

Depth of Screen Interval in Feet

Screen Interval Elevation in Feet

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Table 2Page 1 of 1

Table 3 - Summary of Monitoring Objectives for Individual WellsArt Brass Plating 050067

DRAFT

Water Level Interim ActionVapor

IntrusionCVOC Plume

Centerline

CVOC Select Plume

BoundaryWaterway

Wells Metals Extent

Water Table IntervalMW-1 X X XMW-2 X X XMW-3 X X XMW-4 X X XMW-5 X X XMW-6 X X X XMW-7 X X XMW-8 X X X X XMW-9 X X XMW-10 X X XMW-11 X X XMW-12 X X XMW-13 X X X XMW-14 X X X XMW-15 X X XMW-16 X X XMW-24 X XMW-27 X XPMW-1 X XPSC-CG-138-WT X XPSC-CG-142-WT XPSC-CG-143-WT X

Shallow IntervalMW-3-30 X XMW-6-30 X XMW-8-30 X X X XMW-11-30 X XMW-16-40 X X XMW-17-40 X XMW-19-40 X XMW-20-40 X XMW-22-30 X X XMW-23-30 X XMW-24-30 X X XMW-26-40 X XPSC-CG-135-40 XPSC-CG-138-40 XPSC-CG-139-40 XPSC-CG-140-30 X XPSC-CG-142-40 XPSC-CG-143-40 XPSC-CG-144-35 XPSC-CG-145-35 XPSC-CG-151-25 X X

Well #

Monitoring Objectives

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Table 3Page 1 of 2

Table 3 - Summary of Monitoring Objectives for Individual WellsArt Brass Plating 050067

DRAFT

Water Level Interim ActionVapor

IntrusionCVOC Plume

Centerline

CVOC Select Plume

BoundaryWaterway

Wells Metals ExtentWell #

Monitoring Objectives

Intermediate Interval MW-3-50 X XMW-8-70 X XMW-16-75 X XMW-17-60 X XMW-18-50 XMW-18-70 X XMW-19-60 XMW-20-60 X XMW-21-50 X XMW-21-75 X XMW-22-50 X X XMW-23-50 X XMW-24-50 X X XMW-25-50 X XMW-25-75 X XMW-26-55 X XPSC-CG-135-50 XPSC-CG-138-70 XAB-CG-140-70 XAB-CG-142-70 X

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Table 3Page 2 of 2

Table 4 - Summary of Chemical Analyses Completed to Date for Groundwater MonitoringArt Brass Plating 050067

DRAFT

RI GW: June 2009 RI GW: December 2009

Chlorinated

Solvents

Total Iron &

Manganese

Natural

Attenuation

Parameters

Chlorinated

Solvents

Dissolved

Chromium,

Copper,

Nickel, Zinc

1,4‐DioxaneChlorinated

Solvents

Dissolved

Copper,

Nickel, Zinc

Total Iron &

Manganese

Total Arsenic &

Barium

Select

Plating

Analytes1

Natural

Attenuation

Parameters2Chlorinated Solvents

Chlorinated

Solvents

Total Iron &

Manganese

Total Arsenic

& Barium

Natural

Attenuation


Water TableMW‐01 X X X X X X X X X X X X X X X X

MW‐02 X X X X X X X X X X X

MW‐03 X X X X X X X X X X X X X X X X X

MW‐04 X X X X X X X X X X

MW‐05 X X X X X X X X X X

MW‐06 X X X X X X X X X X X X X X X X

MW‐07 X X X X X X X

MW‐08 X X X X X X X X X X X X X X

MW‐09 X X X X X X X

MW‐10 X X X X X X X X X

MW‐11 X X X X X X X X X

MW‐12 X X X X X X

MW‐13 X X X X X X

MW‐14 X X X X X X

MW‐15 X X X X X

MW‐16 X X X X X X X X

MW‐24

MW‐27

PMW‐01 X X X X X X

PSC‐CG‐138‐WT X X X X X X X X

PSC‐CG‐142‐WT X X X X X

PSC‐CG‐143‐WT X

ShallowMW‐03‐30

MW‐06‐30 X X X X X X X X X X X X X

MW‐08‐30 X X X X X X X X X X X X X X

MW‐11‐30 X X X X X X X X X

MW‐16‐40 X X X X X X X X

MW‐17‐40 X X X X X X X X

MW‐19‐40 X X X X

MW‐20‐40

MW‐22‐30

MW‐23‐30

MW‐24‐30

MW‐26‐40

PSC‐CG‐138‐40 X X X X X X X X

PSC‐CG‐140‐30

PSC‐CG‐140‐40

PSC‐CG‐142‐40 X X X X X

PSC‐CG‐144‐35

PSC‐CG‐151‐25

IntermediateAB‐CG‐140‐70

AB‐CG‐142‐70 X X X X X X

MW‐03‐50

MW‐08‐70 X X X X X X X X X X X



MW‐18‐50 X X X X

MW‐18‐70 X X X X

MW‐19‐60 X X X X

MW‐20‐60

MW‐21‐50

MW‐21‐75

MW‐22‐50

MW‐23‐50

MW‐24‐50

MW‐25‐50

MW‐25‐75

MW‐26‐55

PSC‐CG‐135‐50 X X X X X X X X X

PSC‐CG‐138‐70 X X X X X X X X X X

PSC‐CG‐141‐50

Interim Action Baseline Monitoring RI GW: March 2009 RI GW: September 2009RI GW: December 2008

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Table 4Page 1 of 3


DRAFT

Water TableMW‐01

MW‐02

MW‐03

MW‐04

MW‐05

MW‐06

MW‐07

MW‐08

MW‐09

MW‐10

MW‐11

MW‐12

MW‐13

MW‐14

MW‐15

MW‐16

MW‐24

MW‐27

PMW‐01

PSC‐CG‐138‐WT

PSC‐CG‐142‐WT

PSC‐CG‐143‐WT

ShallowMW‐03‐30

MW‐06‐30

MW‐08‐30

MW‐11‐30

MW‐16‐40

MW‐17‐40

MW‐19‐40

MW‐20‐40

MW‐22‐30

MW‐23‐30

MW‐24‐30

MW‐26‐40

PSC‐CG‐138‐40

PSC‐CG‐140‐30

PSC‐CG‐140‐40

PSC‐CG‐142‐40

PSC‐CG‐144‐35

PSC‐CG‐151‐25


AB‐CG‐142‐70

MW‐03‐50

MW‐08‐70

MW‐16‐75

MW‐17‐60

MW‐18‐50

MW‐18‐70

MW‐19‐60

MW‐20‐60

MW‐21‐50

MW‐21‐75

MW‐22‐50

MW‐23‐50

MW‐24‐50

MW‐25‐50

MW‐25‐75

MW‐26‐55

PSC‐CG‐135‐50

PSC‐CG‐138‐70

PSC‐CG‐141‐50

RI GW: June 2010 RI GW: December 2010 RI GW June 2011

Chlorinated

Solvents

Total Iron &

Manganese

Total Arsenic

& Barium

Dissolved

Copper,

Nickel, Zinc

Chlorinated SolventsChlorinated

Solvents

Dissolved

Copper,

Nickel, Zinc

Total Iron &

Manganese

Total Arsenic &

Barium1,4‐Dioxane

Natural

Attenuation


Chlorinated

Solvents

Dissolved

Chromium,

Copper,

Nickel, Zinc

Chlorinated SolventsChlorinated

Solvents

Dissolved

Copper,

Nickel, Zinc

Total Arsenic

& Barium

Select Plating

Analytes11,4‐Dioxane

X X X X X X X X X X X X X X





X X X X X X X X X X X X


X X X X X X X X X X X X X


X X X X X X X X X X

X X X X X X X X X X




X X X X X X X

X X X X X X

X X X X X X X X

X X X X

X X X X X X X X X X

X X

X

X X X X X X X X X X




X X X X X X X

X X X X X

X X X X X X X X X

X X X X X X X

X X X X X X X X X

X X X X X X X

X X X X X X

X

X X X

X

X X X X X X X X

X X X X X

X X X X

X X X X X X X


X X X X X X X X

X X X

X X X X

X X X

X X X X X X X

X X X X X X X

X X X X X X X

X X X X X X X

X X X X X X X

X X X X X

X X X

X

RI GW: September, 2010 RI GW: March 2011 RI GW September 2011RI GW: March 2010


Table 4Page 2 of 3


DRAFT

Water TableMW‐01

MW‐02

MW‐03

MW‐04

MW‐05

MW‐06

MW‐07

MW‐08

MW‐09

MW‐10

MW‐11

MW‐12

MW‐13

MW‐14

MW‐15

MW‐16

MW‐24

MW‐27

PMW‐01

PSC‐CG‐138‐WT

PSC‐CG‐142‐WT

PSC‐CG‐143‐WT

ShallowMW‐03‐30

MW‐06‐30

MW‐08‐30

MW‐11‐30

MW‐16‐40

MW‐17‐40

MW‐19‐40

MW‐20‐40

MW‐22‐30

MW‐23‐30

MW‐24‐30

MW‐26‐40

PSC‐CG‐138‐40

PSC‐CG‐140‐30

PSC‐CG‐140‐40

PSC‐CG‐142‐40

PSC‐CG‐144‐35

PSC‐CG‐151‐25


AB‐CG‐142‐70

MW‐03‐50

MW‐08‐70

MW‐16‐75

MW‐17‐60

MW‐18‐50

MW‐18‐70

MW‐19‐60

MW‐20‐60

MW‐21‐50

MW‐21‐75

MW‐22‐50

MW‐23‐50

MW‐24‐50

MW‐25‐50

MW‐25‐75

MW‐26‐55

PSC‐CG‐135‐50

PSC‐CG‐138‐70

PSC‐CG‐141‐50

Chlorinated

Solvents

Dissolved

Copper,

Nickel, Zinc

Chlorinated

Solvents

Dissolved

Copper,

Nickel, Zinc

Total Iron &

Manganese

Total Arsenic &

Barium

Select

Plating

Analytes1

Natural

Attenuation

Parameters2

Chlorinated

Solvents

Dissolved

Copper,

Nickel, Zinc

X X X X X X

X X X X X X

X X X X X X X X

X X X X X X Notes:X X X X X X

X X X X

X X X X

X X X X X X

X X X X

X

X

X X X X

X X

X X

X

X X X X X

X

X X X

X X X

X

X

X X X X

X X X X

X X X X

X

X X X X X

X X X X X

X

X X

X X X

X

X X X

X X

X

X

X

X

X

X X X X

X X X

X X X X X

X X X X X

X

X

X

X X

X

X

X

X

X

X X

X X

X X

X

X

1 ‐ Select Plating Analytes include total mercury, cadmium,

and silver, dissolved lead, and cyanide.

2 ‐ Natural Attenuation Parameters include alkalinity,

chloride, nitrate, nitrite, sulfate, methane, ethane, ethene,

and total organic carbon, with one exception. During the

interim action baseline monitoring, chloride and total organic

carbon were not included.

RI GW December 2011 RI GW April 2012 RI GW June 2012


Table 4Page 3 of 3

Table 5 - Data Gaps Identified in Ecology's Comments on the Draft RIArt Brass Plating 050067

DRAFT

Media

Groundwater

Sampling Interval

(if Media=GW)1 Parameter General Location

Explanation of why the data gap will not be filled prior to completing

the FS

GW

Water Table,

Intermediate TCE, VC

North/northwest of South Findlay Street between

1st and 2nd Avenues (north/northwest of SPO‐14)

Concentrations are to be interpolated based on data from well

clusters MW‐18 and PSC‐138 and boring SPO‐14.

GW

Water Table,

Shallow,

Intermediate TCE

South of South Findlay Street, between 3rd and 2nd

Avenues (Southwest of SPO‐4)

Concentrations are to be interpolated from well clusters MW‐8 and

MW‐16. Additional data is also available from the Water Table Interval

from borings SPO‐4, SPO‐37, SPO‐38, and SPO‐52.

GW

Shallow,

Intermediate TCE, DCE, VC

North/northeast of intersection of Findlay Street

and 2nd Ave (north of MW‐15)

Extent of contamination to be estimated based on data from the

Water Table Interval at MW‐15 and well cluster PSC‐138.

GW

Shallow ,

Intermediate DCE, VC

West of 1st Avenue, between Orcas and Mead

Streets, until reaching East Marginal Way (i.e., west‐

northwest of SPO‐18 and northwest of W4‐2)

Extent of contamination to be estimated based on data from well

clusters MW‐17, MW‐25, and PSC‐142 and borings SPO‐18, SPO‐39,

SPO‐40, SPO‐47, and SPO‐48,

GW Intermediate VC

North/Northwest/Northeast of the mib‐block of 1st

Avenue between Findlay and Orcas Streets (i.e., in

the area of well cluster MW‐18)

Extent of contamination to be estimated based on extrapolation and

interpolation of existing data from MW‐17‐70, MW‐18‐70, PSC‐CG‐

138‐70, and AB‐CG‐142‐70.

GW Intermediate VC

South of the mid‐block between 1st and 2nd

Avenues on Orcas Street until well cluster MW‐19

Extent of contamination to be estimated based on existing data from

well cluster MW‐19‐ and the Capital Industries data set.

GW Intermediate VC

Vertical bounding at intersection of Orcas Street

and 1st Avenue (W4‐1, SPO‐10)

Extent of contamination to be estimated based on existing data from

well clusters MW‐17 and MW‐18 and borings SPO‐17.

GW

Shallow,

Intermediate TCE

West/Southwest of East Marginal Way, between

Mead and Fidalgo Streets (i.e., St Gobain property

and RR ROW on west side of East Marginal Way)

This area is not accessible due to plant facilities. ABP has installed a

new well cluster upgradient of the plant facilities (MW‐26‐40/‐55).

Concentrations beneath the facilities may be inferred from this new

data and previously collected data (GP‐8, STG‐VAS‐3, STG‐VAS‐1).

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Table 5Page 1 of 2

Table 5 - Data Gaps Identified in Ecology's Comments on the Draft RIArt Brass Plating 050067

DRAFT

Media

Groundwater

Sampling Interval

(if Media=GW)1 Parameter General Location

Explanation of why the data gap will not be filled prior to completing

the FS

GW

Water Table,

Shallow VC North of Fidalgo and west of East Marginal Way

This area is not accessible due to plant facilities. Extent of

contamination to be estimated based on existing data.

GW

Water Table,

Shallow,

Intermediate VC

South of Fidalgo and west of East Marginal Way

(i.e., Longview Fiber and RR ROW on west side of

East Marginal Way)

Some of this area is not accessible due to plant facilities (Longview

Fiber) and railroad ROW.

GW

Shallow,

Intermediate Dioxane

Southwest of ABP Facility (well clusters PSC‐135 and

MW‐6)

Downgradient extent of dioxane has been bounded. Data from wells

PSC‐135 and MW‐6 sufficient to complete the RI and FS.

GW Intermediate As, Mn

Vertical bounding at well clusters MW‐17, PSC‐138‐

70, and MW‐8.

The vertical extent of arsenic and manganese to be estimated based

on data from well clusters MW‐17, PSC‐138, and MW‐8.

GW Water Table Mn Upgradient of ABP Facility Existing data is sufficient for completing the RI.

Soil Saturated zone Ni Downgradient of boring SP‐32 Existing structures limit accessibility.

Notes

1 ‐ Groundwater sampling intervals defined in Section 3.4 and Figure 7.

GW = groundwater

TCE = Trichloroethene

DCE = cis‐dichloroethene

VC = vinyl chloride

As = arsenic

Mn = manganese

Ni = nickel

Zn = zinc

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Table 5Page 2 of 2

Table 6 - Summary of Potential Exposure Pathways Considered for Identifying Screening LevelsArt Brass 050067

DRAFT

Medium Pathway Potential Receptor Current Use

Potential Future

Use Current Use

Potential Future

Use

Soil Direct Contact Above‐Ground Workers X X X X

Below‐Ground Workers X X X X

Residents ‐‐ X X X

Dust Inhalation Above‐Ground Workers X X X X

Below‐Ground Workers X X X X

Residents ‐‐ X X X

Volatilization to Air See Air X X X X

Leaching to Groundwater See Groundwater X X X X

Groundwater Direct Contact Below‐Ground Workers X X X X

Volatilization to Air See Air X X X X

Discharge to Surface Water See Surface Water/Sediments ‐‐ ‐‐ X X

Surface Water/Sediments Direct Contact Recreational River Users ‐‐ ‐‐ X X

Recreational Fishers ‐‐ ‐‐ X X

Subsistence Fishers ‐‐ ‐‐ X X

Aquatic Organisms ‐‐ ‐‐ X X

Ingestion Aquatic or Terrestrial Organisms ‐‐ ‐‐ X X

Ingestion of Aquatic Organisms Recreational Fishers ‐‐ ‐‐ X X

Subsistence Fishers ‐‐ ‐‐ X X

Aquatic Organisms ‐‐ ‐‐ X X

Air VOC Inhalation Above‐Ground Workers ‐ Indoor X X X X

Above‐Ground Workers ‐ Outdoor X X X X

Below‐Ground Workers (Outdoor) X X X X

Residents ‐ Indoor ‐‐ X X X

Residents ‐ Outdoor ‐‐ X X X

Key:

X = Potential Exposure Route Considered For Identifying Screening Levels

‐‐ Potential Exposure Route Not Applicable

Off‐PropertyOn‐Property

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Table 6Page 1 of 1

Table 7 - Soil Screening LevelsArt Brass Plating 050067

DRAFT

Analyte

Metals

Arsenic 7 0.67 24 0.023 88 1,100 5

Barium -- NR 16,000 3.3 NR 700,000 12,400

Cadmium 1 NR R-ND 0.035 NR R-ND 2 (food) 0.1

Copper 36 NR 3,200 1.4 NR 140,000 6,910 0.6

Iron 42,100 NR 56,000 -- NR 2,500,000 -- 6

Manganese 11 NR 11,000 -- NR 490,000 -- 1

Nickel 38 NR 1,600 11 NR 70,000 3,730 1

Zinc 86 NR 24,000 101 NR 1,100,000 56,000 5

Volatile Organic Compounds

1,1-Dichloroethene -- R-ND 4,000 0.027 R-ND 180,000 0.0175 0.0009

cis-1,2-Dichloroethene -- NR 160 3.4 NR 7,000 0.00993 0.0009

Tertrachloroethene (PCE) -- 500 480 0.053 65,600 21,000 0.0019 0.0009

trans-1,2-Dichloroethene -- NR 1,600 0.35 NR 70,000 0.0000969 0.0009

Trichloroethene (TCE) -- 11.5 40 0.058 2,830 1,800 0.00006 0.0009

Vinyl chloride -- 0.67 240 0.0087 88 11,000 0.00012 0.0009

Other Parameters

1,4-Dioxane -- 10 2,400 -- -- -- --

Notes

NR Not Reported

R‐ND Resesarched‐No Data

a MTCA Method B values are values for direct contact presented in Ecology's CLARC database.

b Values are calculated as per WAC 173‐340‐747 using the groundwater screening levels listed in Table 8 and default input parameters, with one exception. The foc (fraction of organic carbon)

used in the equation was 0.002 gram per gram based on Study Area data.

Washington State Background

Concentrations for Metals (mg/kg)

Method Detection Limit (mg/kg)

Method C, Industrial (mg/kg) from PSC CAP,

2010

Method B, Direct Contact,

Carcinogenic (mg/kg) aMethod C, Direct Contact,

Non-Carcinogenic (mg/kg) a

Soil, Method B, Groundwater Protection

(mg/kg) b

Method B, Direct Contact,

Non-Carcinogenic (mg/kg) aMethod C, Direct Contact,

Carcinogenic (mg/kg) a

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Table 7Page 1 of 1

Table 8 - Groundwater and Surface Water Screening Levels a

Art Brass Plating 050067

DRAFT

sVOCsTetrachloroethene Trichloroethene 1,1-Dichloroethene Cis-Dichloroethene Trans-Dichloroethene Vinyl Chloride 1,4-Dioxane

Groundwater, Method B, Carcinogenic, Residential, Groundwater to Indoor Air (MTCA Eq. 750-2) (µg/L) 104 6.8 -- -- -- 1.3

Groundwater, Method B, Non-Carcinogenic, Residential, Groundwater to Indoor Air (MTCA Eq. 750-1) (µg/L) 210 17 53 -- 56 21

Groundwater, Method B, Carcinogenic, Commercial, Groundwater to Indoor Air (MTCA Eq. 750-2) (µg/L) 250 16 -- -- -- 3

Groundwater, Method B, Non-Carcinogenic, Commercial, Groundwater to Indoor Air (MTCA Eq. 750-1) (µg/L) 50 40 230 -- 238 88

Surface Water, Method B, Carcinogenic, Human Health, Fish Consumption - API Fisher (MTCA Eq. 730-2) (µg/L) 45 5 -- -- -- 1.7 69

Surface Water, Method B, Non-Carcinogenic, Human Health, Fish Consumption - API Fisher (MTCA Eq. 730-1) (µg/L) 535 130 2,500 3,000 3,500 710 20,700

Surface Water, Ecological Risk Assessment (µg/L) 98 (b) 47 (b) 25 (b) 590 (c) 12,000 (d) 12,000 (d)

Surface Water, ARAR (e) (µg/L) 3.3 30 3.2 -- 10,000 2.4

Water Table Interval, Most Stringent (µg/L) 3.3 6.8 3.2 590 56 1.3 69Shallow Interval, Most Stringent (µg/L) 3.3 30 3.2 590 3,500 2.4 69Intermediate Interval, Most Stringent (µg/L) 3.3 30 3.2 590 3,500 2.4 69

Arsenic Barium Cadmium Copper Iron Manganese Nickel Zinc

Surface Water, Method B, Carcinogenic, Human Health, Fish Consumption - API Fisher (MTCA Eq. 730-2) (µg/L) 0.04 -- -- -- -- -- --

Surface Water, Method B, Non-Carcinogenic, Human Health, Fish Consumption - API Fisher (MTCA Eq. 730-1) (µg/L) 12 19 114 -- 1,600 47 705

Surface Water, Ecological Risk Assessment (µg/L) 36 (f) 4 (b) 9.3 (f) 3.1 (f) -- 120 (c) 8.2 (f) 81 (f)

Surface Water, ARAR (µg/L) 0.14 (e) -- 0.25 (g) 3.1 (h) 1000 (h) 100 (e) 8.2 (h) 81 (h)

Water Table Interval, Most Stringent (µg/L) 0.04 4 0.25 3.1 1000 100 8.2 81Shallow Interval, Most Stringent (µg/L) 0.04 4 0.25 3.1 1,000 100 8.2 81Intermediate Interval, Most Stringent (µg/L) 0.04 4 0.25 3.1 1,000 100 8.2 81

Notesa Screening levels are based on those established by the PSC Georgetown Facility in their Site Wide Feasibility Study (Geomatrix, 2006). Updated cleanup levels are provided in PSC’s east-of-4th Cleanup Action Plan (Geomatrix, 2010). Some values may differ from those listed in the CAP due to changes (or anticipated changes) to the CLARC database since 2010.b Oak Ridge Nation Laboratory Toxicological Benchmarks for Screening Potential Contaminants of Concern for Effects on Aquatic Biota (Geomatrix, 2010)c NOAA Screening Quick Reference Tables, NOAA OR&R Report 08-1, Seattle WA, Office of Response and Restoration Division, National Oceanic and Atmospheric Administration.d United States Geological Survey - Selection Procedure and Salient Information for Volatile Organic Compounds Emphasized in National Water Quality (Geomatrix 2010).e Federal Ambient Water Quality Criteria (AWQC, Section 304 of Clean Water Act), Human Health, Consumption of Organisms Only.f WAC 173-201A, Water Quality Standards for Surface Waters of the State of Washington (Geomatrix, 2010)g Federal AWQC Freshwater CCC. Note that this is hardness dependent. The value listed is based on a default hardness of 100 mg/L.h Federal AWQC Saltwater CCC (Geomatrix, 2010).

Shaded cell indicates most stringent screening level

VOCs

Metals

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Table 8Page 1 of 1

Table 9 - Indoor Air and Groundwater IPIMALs for Residential and Commercial Scenarios1,2

Art Brass Plating 050067

DRAFT

COC Cancer Noncancer Cancer Noncancer Cancer Noncancer Cancer Noncancer

1,1-Dichloroethene — 9.1 — 39 — 53 — 230

cis-1,2 Dichloroethene — 1.6 — 6.8 — 73 — 310

Tetrachloroethene 8.8 1.8 21 4.2 104 21 250 50

Trichloroethene 0.37 0.09 0.87 0.22 6.8 1.7 16 4

Vinyl Chloride 0.28 4.6 0.66 19 1.3 21 3 88

Notes:

— = No toxicity value was available. Therefore, an IPIMAL could not be calculated.COC = Constituent of concern IPIMAL = Inhalation pathway interim measure action levelµg/L = Micrograms per literµg/m3 = Micrograms per cubic meter

2.) The United States Environmental Protection Agency (EPA) published updated toxicity information for tetrchloroethene (PCE) and trichloroethylene (TCE). The new information was published in EPA’s Integrated Risk Information System (IRIS) on-line database on September 28, 2011. Indoor air and groundwater IPIMALs have been adjusted accordingly.

1.) The IPIMALs presented in this table are based on the Preliminary Remedial Action Levels (PRALs) presented in Philip Services Corporation's Human Health and Ecological Risk Assessment (PSC, 2001), and include action level adjustments resulting from a Washington State Department of Ecology memo dated October 20, 2008.

Indoor Air IPIMALs (µg/m3) Groundwater IPIMALs (µg/L)

Residential Commercial Residential Commercial

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Table 9Page 1 of 1

Table 10 - Summary of Literature on Biodegradation Rate Half LivesArt Brass Plating 050067

DRAFT

Parameter Value Units Source of value

Advection

Hydraulic Conductivity 9.9E-03 cm/secGeometric mean of slug tests at wells completed in the Shallow Interval at the Art Brass Plating, Blaser, and Capital Industries sites

Hydraulic Gradient 0.002 unitless Average gradient for the Shallow IntervalEffective Porosity 0.25 unitless Typical value for sand aquiferSeepage Velocity 82 feet/year Calculated

DispersivityLongitudinal (x) 28.6 Feet Xu and Ekstein equaiton, with 1,400 foot flow path.

Transverse (y) 2.86 Feet One-tenth of longitudinal

Vertical (z) 0 Feet Assumed no vertical dispersionAdsorption

Soil bulk density 1.51 L/Kg Default value in MTCASoil fraction organic carbon 0.0025 unitless Average of analyses of 12 soil samplesKoc-TCE 94 Kg/L Default value in MTCA

Koc-DCE 35.5 Kg/L Default value in MTCA

Koc-VC 18.6 Kg/L Default value in MTCABiodegradation Half Lives

TCE 1.8 Years 25th percentile values from Newell, et al. (2002)DCE 1.6 Years 25th percentile values from Newell, et al. (2002)VC 1.7 Years 25th percentile values from Newell, et al. (2002)

Model and Source Area DefinitionModel Length 1,400 Feet Distance from MW-17 cluster to Duwamish WaterwaySimulation Time 50 YearsSource Area Width 200 Feet Estimated plume width near well MW-17-40Source Area Depth 25 Feet Vertical delineation of the plume near well MW-17-40TCE Concentration 2,350 g/L June 2012 sample from well MW-17-40DCE Concentration 168 g/L June 2012 sample from well MW-17-40VC Concentration 12.4 g/L June 2012 sample from well MW-17-40

Notes:Koc - octanol-carbon partitioning coefficient

TCE - TrichloretheneDCE - cis -1,2-dichloretheneVC - Vinyl chlorideMTCA - Model Toxics Control Act

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Table 10Page 1 of 1

Table 11 - Summary of Literature on Biodegradation Rate Half LivesArt Brass Plating 050067

DRAFT

Literature Source and Reported Half Lives in Years

Constituent

Aronson and Howard

Average Value1

Aronson and HowardAverage Value - Fe

and SO4 Reducing1

Newell, et al. 25th Percentile

Value2

Newell, et al.

Minimum Value2

PSC Area-Wide

FS Value3

BIOCHLOR Recommended

Range4

Selected Initial

Model Value5

Trichloroethene 0.76 0.62 1.8 1.9 3 0.29 to 3.21 1.8cis-1,2-Dichloroethene not reported not reported 1.64 16.4 0.7 0.31 to 6.93 1.6Vinyl Chloride 0.11 0.55 1.74 1.9 0.8 0.14 to 1.73 1.7

Notes:1 From Aronson, D. and Howard, P., 1997. Values are the mean of all reported field and in situ values and the mean of field values under iron and sulfate reducing conditions, respectively.2 From Figure 5 of Newell, C. et al, 2002.3 From Geomatrix, 2006.4 From Aziz, et al., 2000.5 Selected as the Newell, et al. 25th percentile values.


Table 11Page 1 of 1

Table 12 - Summary of BIOCHLOR Model ResultsArt Brass Plating 050067

DRAFT

Model Run and Modeled Concentration near the Waterway Near Shore Well ID and Concentration

Constituent Base Case Groundwater Velocity x2

Groundwater Velocity x2, Modify

Biodegradation Rates MW-22-301 MW-24-301

TCE 4.8 78 259 234 106DCE 13.8 145 176 268 73Vinyl Chloride 27.2 163 69 15 25

Model Run and Modeled Concentration near the Waterway Near Shore Well ID and Concentration

Constituent

Groundwater Velocity x2, Modify

Biodegradation Rates, Increase Source Area

Concentration

Increase Groundwater Velocity x10, Modify

Biodegradation Rates MW-22-301 MW-24-301

TCE 396 1,169 234 106DCE 266 342 268 73Vinyl Chloride 103 73 15 25

Notes:All concentrations are in g/L1- Concentrations at wells MW-22-30 and MW-22-40 are average concentrations from quarterly sampling events between 3/2010 and 6/2012.TCE - trichloroetheneDCE - cis -1,2-dichloroethene


Table 12Page 1 of 1

Table 13 - Evaluation of Potential Exposure PathwaysArt Brass Plating 050067

DRAFT

Medium Pathway Potential Receptor Current Use

Potential Future

Use Current Use

Potential Future

Use

Screening Level Used to Evaluate Whether Pathway May Be

Potentially Complete Location Screening Level Applied

Soil Direct Contact Above‐Ground Workers M X I I Residential Direct Contact

Below‐Ground Workers M X I I Residential Direct Contact

Residents ‐‐ X I I Residential Direct Contact

Dust Inhalation Above‐Ground Workers I I I I Residential Direct Contact

Below‐Ground Workers I I I I Residential Direct Contact

Residents ‐‐ I I I Residential Direct Contact

Volatilization to Air See Air M X M X Protection of Groundwater (Residential Air)

Leaching to Groundwater See Groundwater M X M X Protection of Groundwater (Residential Air and Surface Water)

Groundwater Direct Contact Below‐Ground Workers M X I X Residential Protection of Indoor Air

Volatilization to Air See Air M X M X Residential Protection of Indoor Air

Discharge to Surface Water See Surface Water/Sediments ‐‐ ‐‐ I X Minimum Surface Water Water Table to Max. Depth of

Contamination

Surface Water/Sediments Direct Contact Recreational River Users ‐‐ ‐‐ I X

Recreational Fishers ‐‐ ‐‐ I X

Subsistence Fishers ‐‐ ‐‐ I X

Aquatic Organisms ‐‐ ‐‐ I X

Ingestion Aquatic or Terrestrial Organisms ‐‐ ‐‐ I X

Ingestion of Aquatic Organisms Recreational Fishers ‐‐ ‐‐ I X

Subsistence Fishers ‐‐ ‐‐ I X

Aquatic Organisms ‐‐ ‐‐ I X

Air

VOC Inhalation Above‐Ground Workers ‐ Indoor M X M X

Above‐Ground Workers ‐ Outdoor M X I I

Below‐Ground Workers (Outdoor) M X M X

Residents ‐ Indoor ‐‐ X M X

Residents ‐ Outdoor ‐‐ X I I

Notes:

X = Potential Exposure Route

M = Potential Exposure Route, Currently Mitigated to Prevent Exposure Above Acceptable Levels

I = Incomplete Pathway Based on Available Data

‐‐ Potential Exposure Route Not Applicable

Surface Water to Depth of 10 cm Below

Mudline

Soil from Ground Surface to Water Table;

Groundwater from Water Table to Depth

of 20 Feet

Soil Protection of Groundwater (Residential Air) and Groundwater

Protection of Residential Air

Minimum Surface Water

On‐Property Off‐Property

Ground Surface to Water Table

Water Table to Depth of 20 Feet

Aspect Consulting9/27/2012V:\050067 Art Brass Plating\RI Report\Sept 27 Agency Review Draft\Tables\T6, T13_Exposure Pathway Tables

Table 13Page 1 of 1

APPENDIX A

Boring Logs

APPENDIX B

Data Tables

APPENDIX C

Facility Background

APPENDIX D

Hydraulic Studies

APPENDIX E

Vapor Intrusion Assessment

APPENDIX F

Interim Measures Evaluation

APPENDIX G

Mann-Kendall Trend Tests and Plots

APPENDIX H

BIOCHLOR Modeling Results

APPENDIX I

Geochemical Modeling Results

APPENDIX J

Duwamish Waterway Porewater Risk Assessment – Anchor QEA

APPENDIX K

Data Usability with Lab and Data Validation Reports on CD

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