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WAITING TO EXHALE – OR HOW TO MANUEVER THROUGH THE INDOOR AIR MAZE. Vapor Intrusion Pathway. By: Lisa Campe, MPH, LSP Woodard & Curran, Inc. Can be a Public Health “Problem” Vapor Intrusion can be a key exposure pathway from both soil and/or groundwater sources - PowerPoint PPT Presentation
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COMMITMENT & INTEGRITY DRIVE RESULTS
WAITING TO EXHALE – OR HOW TO
MANUEVER THROUGH THE INDOOR AIR
MAZE Vapor Intrusion Pathway
By: Lisa Campe, MPH, LSPWoodard & Curran, Inc.
COMMITMENT & INTEGRITY DRIVE RESULTS
HOW DOES VAPOR INTRUSION FIT IN?
2
Can be a Public Health “Problem”
•Vapor Intrusion can be a key exposure pathway from both soil and/or groundwater sources
•Indoor Air can become impacted by volatile subsurface chemicals
•Inhalation of indoor air contaminants can pose a health risk
COMMITMENT & INTEGRITY DRIVE RESULTS
HOW DOES VAPOR INTRUSION FIT IN?
3
Regulatory Framework requires it•Risk Assessment Components in Georgia Voluntary Remediation Program Act (VRP) and Hazardous Site Response Act (HSRA)•VRP Performance Standard to reduce exposure to “safe levels”•HSRA
– Type 1 (residential) and 3 (comm./ind.) Standards - risk assessment “built in”
– Type 2 (res.) and Type 4 (c./i.) – can use site-specific risk assessment
– Type 5 – consider engineering controls/restrictive covenants/pathway elimination
COMMITMENT & INTEGRITY DRIVE RESULTS 4
Soil Vapor
Groundwater
Ambient Air
Chemical Source
COMMITMENT & INTEGRITY DRIVE RESULTS
Indoor Air Pathway
• Groundwater-to-indoor air pathway now a widely recognized exposure pathway
• Exposure assessment is in one sense simple – breathing of indoor air
• Difficulty introduced by uncertainty in pathway completeness & significance
• Significant number of sites have volatile organic contaminants (VOCs)
5
COMMITMENT & INTEGRITY DRIVE RESULTS
Vapor Intrusion - Why We Need to Pay Attention
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• Can’t find “alternate” source of air - health concerns
• Assessment and mitigation can be costly and complex
• Liability if impact tenants/owners of subject or nearby properties
• Property value diminution
• Federal and State regulatory focus on pathway
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• Concentrations predicted in the point of entry room
• Vapors enter through the crack around the perimeter of the foundation
• Default mode based on a “tight” residential structure
• Steady-state conditions apply• Source of vapors can be
groundwater, soil, soil-gas, or NAPL• Significant preferential flow
pathways (e.g., sumps and drains) are not considered
• Basic models do not account for source depletion
Johnson & Ettinger ModelsConceptual Model (from U.S. EPA guidance)
COMMITMENT & INTEGRITY DRIVE RESULTS
Vapor Pathway Lines of Evidence
8
• VOC concentrations near/under building in:– Groundwater– Soil– Soil vapor– Ambient air
• VOC concentrations in indoor air• Results from screening of preferential
pathways (e.g., sumps, cracks)
COMMITMENT & INTEGRITY DRIVE RESULTS 9
• How do you deal with background …(multiple sources)?
• How do you evaluate significance of the impacts?
• How do you evaluate future vs. present use?• Reconciling measurements in multiple media
and/or modeling can be difficult• If do site-specific modeling, verify key
assumptions
Indoor Air Pathway Challenges
COMMITMENT & INTEGRITY DRIVE RESULTS
Data Collection to Evaluate VI
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• Indoor air sampling is the most direct approach, but not always preferable
• Background levels exist for many contaminants• Groundwater data should focus on water table
screening; “clean lens” can be present• Soil data can be relevant and difficult to deal with• Soil-gas data should be considered/collected • Preferential pathways (e.g., sumps) can be
significant• Sampling should assist in source id/delineation
COMMITMENT & INTEGRITY DRIVE RESULTS
Background sources of VOCs
• Consumer products (cleaners, paints etc.)• Off-gassing from building materials,
clothing, furnishings• Occupant activities (solvent use, hobbies,
smoking)• Indoor emissions (e.g., heating systems)• Ambient/outdoor sources
COMMITMENT & INTEGRITY DRIVE RESULTS
EPA OSWER 2011 Background Indoor Air Study
Background Indoor Air Concentrations of Volatile Organic Compounds in North American Residences (1990–2005): A
Compilation of Statistics for Assessing Vapor Intrusion . EPA 530-R-10-001
http://www.epa.gov/oswer/vaporintrusion/documents/oswer-vapor-intrusion-background-Report-062411.pdf
•Objective: “to illustrate the range and variability in VOC concentrations in indoor air resulting from sources OTHER THAN vapor intrusion.”•Full statistical distribution of background indoor air concentrations in 15 studies post-1990
COMMITMENT & INTEGRITY DRIVE RESULTS
EPA 2011 Methods
• Mostly SUMMA 24 hour samples• GC/MS, TO-14 and TO-15 analyses• 25th, 50th, 75th, 90th and 95th percentile
ranges based on individual study results (not all percentiles reported in each study)
• Number of studies included in survey varied by compound (for TCE – 14 and for PCE – 13)
Source: EPA 2011
Range of percentiles: TCE/PCECompound Number
of Samples
Total Percent detection
50th Percentile range
95th Percentile range
Trichloroethylene (TCE)
2,503 42.6% <RL(0.02-2.7) – 1.1 µg/m3
0.56 – 3.3 µg/m3
Tetrachloroethylene (PCE)
2,312 62.5% <RL(0.03-3.4) – 2.2µg/m3
4.1 – 9.5 µg/m3
RL = reporting limit (not detected)
COMMITMENT & INTEGRITY DRIVE RESULTS
Key Changes/Concerns about NewPolicies and Enforcement Actions
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• Variable/unclear performance standards for closure across states and EPA regions
• Sites closed out years ago have been reopened by EPA and numerous state agencies
• Stringent and shifting policies impede investment and development
COMMITMENT & INTEGRITY DRIVE RESULTS
Case Study #1 - NJ Vapor Intrusion (VI) Site
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• Former Dry Cleaner source – highest concentrations near floor drain/equipment area
• PCE in groundwater, soil vapor and indoor air in/beneath cleaner and adjacent spaces
• Although concentrations in all media > NJ screening levels, soil vapor highest
000000.00 17
COMMITMENT & INTEGRITY DRIVE RESULTS
Remedial Strategy for VI
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• Goal – Reduce indoor air to < screening levels (IASL) and soil vapor to < 10* SVSL (no ongoing monitoring) & close out
• Focused on addressing sub-slab source versus (previous consultant) low level groundwater contamination for under half the cost (100k vs. 250k)
• Three Prongs:– Soil Vapor Extraction “Pilot Study”– Soil excavation of floor drain area– Passive Sub Slab Depressurization System (SSDS)
COMMITMENT & INTEGRITY DRIVE RESULTS 19
Medium Screening Level Pre-Remediation Post-Remediation
Groundwater 1 ug/L ND-51 ND-18
Soil Vapor 360 ug/m3 9,500-220,000 52-161
Indoor Air 3 ug/m3 ND-5 ND-0.95
Before and After..
COMMITMENT & INTEGRITY DRIVE RESULTS
The Light at the End of the Tunnel
20
• Successfully demonstrated NFA for vapor intrusion (VI) pathway to NJDEP
• Groundwater being addressed via Monitored Natural Attenuation (MNA)
• Client is in process of obtaining reimbursement for VI work from Brownfields Reimbursement Fund
COMMITMENT & INTEGRITY DRIVE RESULTS
Case Study #2: Human HealthRedevelopment at Vapor Intrusion Site
• Chlorinated solvents in soil and groundwater
• Two buildings planned, one in a more contaminated area than the other
• Modeled from GW – Significant Risk• Collected soil vapor from proposed
footprints and modeled using soil vapor – Significant Risk
COMMITMENT & INTEGRITY DRIVE RESULTS
Case Study 2 Cont.
• Performed soil remediation of potential source areas as part of footprint excavation / construction
• Integrated liquid boot and SSD systems into construction of slabs
• SVE for a few months to get the mass down in the “bad” area, then turned off
COMMITMENT & INTEGRITY DRIVE RESULTS
Case Study 2 Cont.
• Collected two rounds of indoor air in the winter
• Demonstrated that chlorinated COPCs were not getting in / posing risk
• Prepared pre-occupancy letters / certification prior to tenant occupation
• Class A-3 RAO with AUL filed- AUL includes maintenance of SSDS and Slab
Post Remediation Site Data (key constituents)
Constituent
Groundwater EPC
(ug/L)Soil Vapor EPC
(ug/m3)Indoor Air EPC
(ug/m3)
Site-wide Building 1 Building 2 Building 1 Building 2
Tetrachloroethene 0.835 2.34 2.89 ND 1.88
Trichloroethene 30.5 3.00 4.27 ND 1.2
Vinyl chloride 272 ND ND ND ND
cis-1,2-dichloroethene 467 ND ND ND 0.792
COMMITMENT & INTEGRITY DRIVE RESULTS
Installation of liquid boot and overlying membrane
COMMITMENT & INTEGRITY DRIVE RESULTS
Risk Management
• Focus on data collection for risk assessment
• Proactively evaluate risk and response actions prior to development
• Consider changing climate of vapor intrusion policies as you proceed
COMMITMENT & INTEGRITY DRIVE RESULTS
Useful Links and Resources
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ITRC -http://www.itrcweb.org/guidancedocument.asp?tid=49
MassDEP -http://www.mass.gov/dep/cleanup/laws/vifin.pdf
USEPA -http://www.epa.gov/wastes/hazard/correctiveaction/eis/vapor.htm
NYDOH -http://www.health.ny.gov/environmental/investigations/soil_gas/svi_guidance/