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Vapor Intrusion Vapor Intrusion Assessment ToolsAssessment Tools

Derek W. TomlinsonDerek W. Tomlinson, M.A.Sc., P.Eng., M.A.Sc., P.Eng.Environmental Resources ManagementEnvironmental Resources Management

Exton, Pennsylvania, USAExton, Pennsylvania, USA28 October 200828 October 2008


SLIDE 2

Overview

• What is Vapor Intrusion?• Guidance Documents• Investigative Tools• Management Options• Questions


SLIDE 3

Photo: Dave Webb, Ill. DPH

Vapor Intrusion is Real(sometimes visible)


SLIDE 4

Vapor Intrusion Definition

Vapor Intrusion (VI), the migration of a compound of concern (COC) vapor from a subsurface soil or groundwater source into the indoor air environment of an existing or planned structure. (ASTM 2008)


SLIDE 5

Vapor Intrusion

IndoorAir

Vadose Zone Soil

Gas

Soil and Groundwater

Contamination

Commercial/Industrial Worker

Working over Plume Without BasementResident Living over Plume

Basement or Crawl Space

(USEPA 2002, ITRC 2007)

Migration of volatile chemicals from the subsurface into overlying buildings


SLIDE 6

Regulatory Vapor Intrusion Guidance

USEPA 2002Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway from Groundwater and Soilshttp://epa.gov/osw/hazard/correctiveaction/eis/vapor.htm

ITRC 2007 Vapor Intrusion Pathway: A Practical Guidehttp://www.itrcweb.org/teampublic_Vapor.asp

ASTM 2008Standard Practice for Assessment of Vapor Intrusion into Structures on Property Involved in Real Estate Transactions (ASTM E2600)http://www.astm.org/Standards/E2600.htm


SLIDE 7

General Regulatory Process

• Federal and many State Guidance use multiple lines of evidence approach

• Typically three Tiers evaluating• Groundwater (Soil)

• Soil Gas

• Indoor Air

• Spatial relationship of indoor air contamination to subsurface contamination

• Modeling can also be used to assess


SLIDE 8

Typical Screening Distances

Petroleum VOCs = 10 m (30 feet)

Other VOCs = 30 m (100 feet)

LNAPL = 30 m (100 feet) Petroleum VOCs = 10 m (30 feet)

Other VOCs = 30 m (100 feet)

-30m


SLIDE 9

Multiple Lines of EvidenceApproach

1. Groundwater2. Soil gas3. Sub-slab soil gas4. Indoor air


SLIDE 10

PetroChlorinated VOCs Freshwater Lens

Depth

Groundwater


SLIDE 11

Groundwater Assessment Tools

• Direct-push tools• Membrane Interface Probe (MIP)

• Waterloo Profiler

• Passive diffusion bag samplers• Low-flow purging and sampling• Volume-averaged purge and sample


SLIDE 12

Groundwater – Membrane Interface Probe (MIPs)

(Photo courtesy Geoprobe)

(image courtesy Geoprobe)


SLIDE 13(Images courtesy R. Joseph Fiacco, Jr, ERM)


SLIDE 14

Groundwater –Waterloo Profiler™

(Photo courtesy Geoprobe)


SLIDE 15(Images courtesy R. Joseph Fiacco, Jr, ERM)


SLIDE 16

(Image courtesy R. Joseph Fiacco, Jr, ERM)

Example Profiling Data


SLIDE 17

Groundwater – Passive Diffusion Bag Samplers

• Use in monitoring wells

• Limited to VOCs• Diffusion of VOCs

through membrane• 2 week

implacement


SLIDE 18

Groundwater – Traditional Methods

• Low-Flow Purging and Sampling• Samples collected at a low flow 100 to 250 mL/min

• Parameters (DO, ORP, Eh, pH) monitored until stable and sample collected

• Able to target shallow water

• Volume-averaged Purge and Sampling• Not recommended for new data related to vapor

intrusion as concentration averaged


SLIDE 19

In Well Transport

• Wells that are screened over a large distance may sample deeper water

• Key for VI assessment is shallow water

Silty Sand

Sand

Clay


SLIDE 20

LNAPL - Laser Induced Florescence (LIF)

(courtesy Dakota Technologies)


SLIDE 21

Soil Gas Assessment Methods

• Active sampling• Direct push temporary and permanent points

• Permanent wells

• Passive sampling• Passive diffusion samplers (e.g., Gore Sorbers)


SLIDE 22

Soil Gas Sample Locations

Building Exterior> 3 m (10 ft) from slab

Sub-SlabSamples collected

beneath the slab

Near Slab< 3 m (10 ft) from slab


SLIDE 23

Soil Gas Sample Locations

• Soil gas profile may be affected by building

• More significant for biodegradable compounds

(Johnson & Abreu, 2006)


SLIDE 24

Soil Gas Sampling Wells


SLIDE 25

Temporary Rod Used for Sampling

(Photo courtesy B. Hartman, H&P Mobile Geochemistry)


SLIDE 26

Temporary Soil Vapor Implants

(Photo courtesy B. Hartman, H&P Mobile Geochemistry)


SLIDE 27

Installing Sub-slab soil point


SLIDE 28

Permanent Temporary


SLIDE 29

Typical fittings – Permanent Point


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Soil Gas Point Tightness Testing• Add helium (He) to shroud• Sample directly with helium

detector from the soil gas point

• Collect Tedlar and screen air within Tedlar

• Laboratory screening

• <5% He in extracted air point passes test

• Fails re-seal and re-test

He

He

HeHe He


SLIDE 31

Purging Permanent Subslab Soil Gas Point


SLIDE 32

Subslab Sample Collection- Permanent Point


SLIDE 33

Sub-Slab Sample CollectionSubslab Sample Collection – Temporary Point


SLIDE 34

Near Slab Sample Collection– Permanent Point


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Soil Gas – Passive• GORE-TEX® Membrane

• Chemically inert, waterproof, vapor permeable

• Designed for vapor diffusion• Hydrophobic, engineered sorbents

• VOCs, SVOCs, PAHs

Sampler insertion

Hammer drill

Slam barHammer drill Module insertion

(photos & image courtesy J. HodnyW. L. Gore & Associates, Inc.)


SLIDE 36

Passive SamplerExample Results- TCE

(Image courtesy Dr. J. Hodny, W. L. Gore & Associates, Inc.)


SLIDE 37

Indoor Air Assessment Methods

• Active sampling• Summa Canisters

• Sorbent Tubes

• Passive sampling• Passive diffusion samplers (e.g., Gore Sorbers)


SLIDE 38

Indoor Air Sampling - Summa Canisters

• Summa Canister used for indoor air sampling

• 30 day hold times• 6 L stainless steel canister with flow

controller, moisture trap, and pressure gauge

• Regulated to collect either:• 8 hr sample – Commercial

• 24 hr sample – Residential

• Analyzed via either TO-14a or TO-15


SLIDE 39

Sample Volumes


SLIDE 40


SLIDE 41

Indoor AirSampling

• Typically, co-located with sub-slab location

• Sample breathing zone



SLIDE 42

Indoor Air Sampling – Sorbent Tubes

• Based on VOC or SVOC, tubes are different and flow rates/sample rate/ times vary

• Must be shipped at 4°C• Limited hold times• Analyzed via TO-17


SLIDE 43


SLIDE 44

Passive Air Sampling

• AirCrawlspace airIndoor air

(photos & image courtesy J. HodnyW. L. Gore & Associates, Inc.)


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Assessing Lines of EvidenceAssemble as many lines as necessary

Chemistry of Air Samples:Breakdown productsIn-building sourcesOutdoor air qualityFresh vs weathered petroBasement vs upper floors

ModelingJohnson & EttingerSite-specific inputs

Totality of Evidence For VI

Totality of Evidence Against VI

Conceptual Site Model


SLIDE 46

Management Options

1. Remediation2. Institutional Controls3. Mitigation


SLIDE 47

Mitigation Methods

• Passive Systems• Vapor Barriers• Passive Venting

• Active Systems• Sub-Slab Depressurization• Sub-Membrane Depressurization• Sub-Slab Pressurization• Building Pressurization• Indoor Air Treatment

(ITRC, 2007)

(Courtesy Liquid Boot)


SLIDE 48

Questions?

Derek W. Tomlinson, M.A.Sc., [email protected]

Environmental Resources Managementwww.erm.com