WAITING TO EXHALE – OR HOW TO MANUEVER THROUGH THE INDOOR AIR MAZE

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.


HOW DOES VAPOR INTRUSION FIT IN?

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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


HOW DOES VAPOR INTRUSION FIT IN?

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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


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)

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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)


Vapor Pathway Lines of Evidence

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• 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)


• 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


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


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


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




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)


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


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


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)


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..


The Light at the End of the Tunnel

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• 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


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


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


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


Installation of liquid boot and overlying membrane


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


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/

Documents

WAITING TO EXHALE – OR HOW TO MANUEVER THROUGH THE INDOOR AIR MAZE