usepa region 2 vapor intrusion study

USEPA Region 2USEPA Region 2Vapor Intrusion StudyVapor Intrusion StudyCayuga Groundwater Contamination SiteMarch 4, 2009

Site BackgroundSite Background

2001 to Present – EPA Field Study

– Installed 23 Multi-level monitoring wells

– Seven Rounds of groundwater sampling (>500 groundwater samples)

– Quarterly water level measurement and geophysics support from USGS

– Surface water/sediment samples (Owasco Outlet, Crane Brook, Union Springs)

Site Background (cont’d)Site Background (cont’d)

Cayuga County DOH –1999-2008 - Multiple rounds of residential well sampling (>600 samples)

Remedial report and risk evaluations in progress

Monitoring WellsMonitoring Wells

Site OverviewSite Overview

Ongoing Field Study EffortsOngoing Field Study Efforts

Additional field work under NYSDEC/EPA:

– Additional monitoring wells

– Additional groundwater sampling

– Geophysical survey

– Hydraulic testing

Vapor Intrusion StudyVapor Intrusion Study

EPA field study indicates that chlorinated volatile organic compounds (CVOCs) are present in groundwater

CVOC-contaminated groundwater extends from West Genesee St. to Union Springs

CVOCs in groundwater can form vapors that migrate in the subsurface

Potential exists for vapors to enter buildings

Vapor sampling is being conducted to determine if vapors are present in buildings

Vapor Sampling LocationsVapor Sampling Locations

Selection of locations based on existing data:

– Location of CVOCs in groundwater

– Location of CVOCs in surface water

– Residential well data

– Human health risk evaluation

– Geologic/Hydrogeologic factors

Depth to contaminated groundwater (<100 feet) Degree of bedrock fracturing Presence of clean groundwater above

contaminated zones

Vapor Sampling Locations (cont’d)Vapor Sampling Locations (cont’d)

Three areas identified that meet initial criteria:

– South of West Genesee Street

– Pinckney Road/Overbrook Drive Area

– Union Springs

South of West Genesee StreetSouth of West Genesee Street

Insert Figure 1

Pinckney/Overbrook Area (east)Pinckney/Overbrook Area (east)

Insert Figure 2

Pinckney Road (West)Pinckney Road (West)

Union Springs Area (south)Union Springs Area (south)

Insert Figure 3

Union Springs Area (north)Union Springs Area (north)

Residential Vapor Intrusion Sampling Residential Vapor Intrusion Sampling ProceduresProcedures

Presented by:

Gary Newhart – EPA

Vapor Pathway into BuildingsVapor Pathway into Buildings

Vadose Zone

Groundwater Contamination

Interior space

Subslab soil gasSubslab soil gasintruding intointruding intointerior spaceinterior space

Ambient air Ambient air

VentilationVentilation

Key Questions for Vapor Intrusion Key Questions for Vapor Intrusion ImpactsImpacts

1. Does groundwater or soil contamination exist?- Yes, in this case, so we move to the next step

2. Does subsurface gas contamination exist above guidelines?- Answered through collection of subslab soil gas

3. If subsurface gas does exist above guidelines, is it entering the interior space?- Answered through collection of indoor air samples

4. If gas contamination exists in the residence, are the concentrations elevated and related to contamination- Answered by comparing results to health-based guidelines and conducting lifestyle and ambient investigation

Monitoring and Sampling StrategyMonitoring and Sampling Strategy

1. Initial Sampling- Subslab Location + Ambient (outdoor)

2. Subsequent SUMMA Canister Sampling- Subslab Location- Basement Location- First Floor Location

Indoor Air and Sub-Slab Soil Gas Indoor Air and Sub-Slab Soil Gas ActivitiesActivities

Drilling

Placement and Cementing of the Probe

Connection of the 3-Way Valve

Vapor Sampling ApparatusVapor Sampling Apparatus

Vapor Mitigation SystemVapor Mitigation System

What is a VI Matrix and how is it developed?

Chemical-specific

Considers potential health effects from long-term exposures for residents including children and adults

– Exposure Frequency of 24 hours/day and 350 days/year

– Exposure Duration is 30 years

Has comparison values for subslab soil gas and indoor air

Sub-slab Soil Gas

Concentration

Indoor Air Concentration (ug/m3)

(1) No Action (2) Investigate (3) Investigate

(4) Monitor(5)

Monitor or Pursue Remediation

(6) Investigate or Pursue Remediation

(7) Monitor or Pursue Remediation

(8) Pursue_ Remediation or Monitor

(9) Pursue Remediation

Vapor Intrusion Matrix for a Carcinogenic Chemical

Step 1. Does the subslab concentration exceed x ug/m3?No = Vapor intrusion investigation is over for this buildingYes = Consider indoor air sampling

Step 2. Evaluate subslab and indoor air concentrations.

Sub-slab Soil Gas

Concentration

Indoor Air Concentration (ug/m3)

(1) No Action (2) Investigate

(3) Monitor/ Remediate (4) Remediate

Vapor Intrusion Matrix for a Non-Carcinogenic Chemical

Step 1. Does the subslab concentration exceed x ug/m3?No = Vapor intrusion investigation is over for this buildingYes = Consider indoor air sampling

Step 2. Evaluate subslab and indoor air concentrations.

VI Decisions

VI Profile

– Subslab

– Indoor/Basement

– Indoor/First Floor Living Space

– Ambient Concentrations

Confounding Internal Sources

Confounding External Sources

Key Points in VI Decisions

Decision to remediate is not based on one piece of information

Complexity and uncertainty is associated with the fate and transport mechanism of vapors

Multiple lines of evidence are used in the decision making

Rely on “VI Team” to ensure consistency in decisions within EPA Region 2

Contact Information

USEPA Remedial Project Manager - Isabel Rodrigues – (212) 637-4248

USEPA Community Involvement Coordinator– Mike Basile - (716) 551-4410

New York State DOH – Krista Anders – (518) 402-7860

New York State DEC – Kevin Kelley – (315) 426-7421

Cayuga County DOH – Eileen O’Conner (315) 253-1405