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Vapor Intrusion Guidance Proposed Updates VAP CP Coffee April 13, 2015 Audrey Rush 614-644-2286 audrey.rush@epa.ohio.gov 1

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Vapor Intrusion is The migration of volatile chemicals from the subsurface into overlying buildings. 2 Dissolved contamination LTLT Diffusion Vadose zone Building zone of influence Wind effects Enclosed space Cracks Q soil Air streamlines Convection Top of capillary zone Water Table Stack effects Mixing in indoor air and inhalation Advection/ Convection Diffusion Phase partitioning C gw to C soil gas

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VI isnt. Ambient (background) On-site processes Indoor air sources 3

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History of VI Guidance Johnson and Ettinger (1991): Heuristic Model for Predicting the Intrusion Rate of Contaminant Vapors into Buildings - not updated since 2004; 1-D 2002 - OSWER Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway from Groundwater and Soils (Still Draft!) 2005 3D VI model by Abreu and Johnson 2005 - DERR TDC Methodology for Vapor Intrusion Assessment 2007 - ITRC Guidance 4

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History of VI Guidance 2010 - Ohio EPA Guidance May 2010 - a bit of OSWER 2002, ITRC, and CAL EPA, plus Ohio EPA specific experience 2011 - Background Indoor Air Concentrations of Volatile Organic Compounds in North American Residences (1990 2005): A Compilation of Statistics for Assessing Vapor Intrusion. 2012 - EPA's Vapor Intrusion Database: Evaluation and Characterization of Attenuation Factors for Chlorinated Volatile Organic Compounds and Residential Buildings. 2012 VISL calculator and users guide 5

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More. 2012 - Conceptual Model Scenarios for the Vapor Intrusion Pathway Indoor Air Vapor Intrusion Mitigation Approaches, FAQs, etc. April 2013 - US EPA Office of Underground Storage Tanks Draft Petroleum Vapor Intrusion Guidance April 2013 - U.S. EPA VI guidance (super secret document available from Inside EPA for a limited time only!) expected update .????? October, 2014 ITRC Petroleum Vapor Intrusion Fundamentals of Screening, Investigation, and Management 6

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US EPA VISL calculator: Uses the RSL construct for indoor air values Applies attenuation factors to calculate screening values for soil gas and ground water (based on the 2012 US EPA VI Database) Adjust for exposure scenario (C/I vs residential) 7

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What is an attenuation factor? AF ( ) unitless ratio of the indoor air concentration (C indoor ) to the subsurface contaminant concentration VISL and OSWER: GW = C IA /(C GW *H*1000L/m 3 ) =.001 (vapor at source) soil gas = C IA /C SG =.1 crawl space = C IA /C SG = 1 However soil gas =.03 (SG = 33 X IA) According to US EPA draft comment 8

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Vapor Attenuation slab contaminated soil or groundwater subslab vapors Ratio of Vapor Flux to Indoor Air Exchange Indoor Air Exchange Rate (L/minute) Vapor Flux Rate (L/minute) Subslab AF = Vapor Flux Rate IAER

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Example: PCE (IA standard res = 42 g/m 3 12 Method C SG ( g/m 3 ) VISL ( SG = 0.1) 420 VISL ( SG =0.03) 1,400 J&E screen ( SG =0.00013) 32,000 Vapor Flux Rate* (4.5 L/min) IAER (1,016 L/min) ( SG =0.0045) 9,333 * Estimated for Ohio, Brewer, et.al.

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Proposed Changes Include RCRA Clarify use of OSHA PELs COC List Current (2010) Ohio EPA guidance: US EPA 2002 tables plus a few Proposed: VISL calculator list plus H 2 S; special consideration for cis-1,2 DCE Major change: Must have reliable inhalation toxicity factors (no extrapolation) The source vapor concentration < toxicity 14

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Proposed Changes Use VISL as front line screening for further evaluation More robust mitigation/remedy alternatives section Sampling for remedy verification Frequency Site specific Update sampling SOPs and forms 15

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Special Consideration for Petroleum Releases 16

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Challenges Direct user to stepwise empirical data collection How much data are necessary to make a decision for evaluation and remedy? Use VISL calculator only? Allow J&E? If so, defaults only? When are building parameters engineering controls? Some other AF calculation? 17