Overview of State Approaches to Vapor Intrusion: 2023 Update

Site owners, regulators, and consultants now have decades of experience with vapor intrusion (VI), but guidance for the evaluation of VI continues to vary significantly among states. For those with sites in different regulatory jurisdictions, one challenge is addressing how the requirements or expectations for VI investigation and mitigation differ from one jurisdiction to the next. The overall lack of consensus can make it difficult to manage sites in a consistent manner between jurisdictions. This paper takes into account VI guidance, petroleum hydrocarbon-specific VI guidance, and/or media-specific volatilization criteria found in broader regulatory programs. This is an update of the author's previous reviews published in 2007, 2012, and 2018. Since our most recent update, 30 states have revised their guidance, issued new guidance or updated criteria or other VI-related information. For each State and the District of Columbia, the review includes tabulations of the available types of screening values (e.g., soil, groundwater, soil gas, and indoor air), the screening values for selected chemicals that commonly drive VI investigations (e.g., trichloroethylene [TCE], tetrachloroethylene [PCE], benzene, and other selected volatile organic compounds [VOCs]), and the basis of risk levels used for cancer and non-cancer risk. Federal values are also included for comparison. In addition, we summarize available key policy criteria for each state including: trigger distances, default subsurface to indoor air attenuation factors, policies for evaluation of petroleum VI, strategies for preferential pathways, and policies for mitigation of VI. The details presented in this paper provide a useful technical reference and regulatory summary for practitioners and the regulated community nationwide. Review of vapor intrusion guidance across the United States shows areas of consensus and areas where approaches differ.image