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The U.S. EPA's Review of the Draft 2002 Subsurface Vapor Intrusion Guidance

By James A. Vroman

On August 30, 2010, the U.S. EPA's Office of Solid Waste and Emergency Response ("OSWER") published its "Review of the Draft 2002 Subsurface Vapor Intrusion Guidance."  OSWER's Review of the Draft 2002 Guidance suggests that when OSWER finalizes the Draft 2002 Guidance, which it has promised will be done by November of 2012, the final version of the Guidance will present a more rigorous and comprehensive, and, thus, a more expensive, Soil Vapor Intrusion ("SVI") assessment process than the one presented in the Draft 2002 Guidance.  For example, the Review advised that the EPA plans to include in the final version of the SVI Guidance, in addition to the list of chemicals that will trigger a SVI assessment, "chemical-specific characteristics" that will be used to identify chemicals of concern that may generate vapors.  The EPA will also update the toxicity values of a number of the chemicals listed in Table 1 of the Draft 2002 Guidance.  In addition to these changes to the Draft Guidance, OSWER noted that the SVI assessment process that will be presented in the final version of the SVI Guidance will recommend that the assessment evaluate multiple lines of evidence rather than a single line of external evidence such as soil-gas samples or externally collected groundwater samples.  Consistent with this recommendation, the Review also noted that the final version of the Guidance will provide that the SVI assessment should expand its evaluation of SVI risks beyond single-family residential buildings to include other types of buildings such as non-residential and mixed-use buildings. 

OSWER published this Review in response to the EPA's Office of the Inspector General 2009 evaluation report "Lack of Final Guidance on Vapor Intrusion Impedes efforts to Address Indoor Air Risks (Report No. 10-P-042; U.S. EPA,2009a).  In this evaluation report, the Inspector General encouraged OSWER to identify those portions of the Draft 2002 Guidance "that remain valid and the portions that should be updated."  The Draft 2002 Guidance is available at http://www.epa.gov/osw/hazard/correctiveaction/eis/vapor/complete.pdf.