Formatted Title
Overview of State Approaches to Vapor Intrusion
Background/Objectives
Regulatory requirements for the evaluation of vapor intrusion (VI) continue to vary significantly among states. For site owners and responsible parties that have sites in different regulatory jurisdictions, one challenge is to know and understand how the requirements or expectations for VI differ from one jurisdiction to the next. Differing requirements make it difficult to manage sites in a consistent manner across multiple jurisdictions.
Approach/Activities
This paper updates the author’s previous overviews of state guidance for VI published in 2007, 2012, and 2018. Since the last update, over two dozen states have revised their guidance and some states that did not have VI-specific guidance have issued new guidance.
For each State, the review includes tabulations of the types of screening values included (e.g., groundwater, soil gas, indoor air) and the screening values for selected chemicals that commonly drive VI investigations (e.g., TCE, PCE, and benzene). Federal values are included for comparison. In addition, for each state, we summarize a number of key policy decisions that are important for the investigation of VI including: distance screening criteria, default subsurface to indoor air attenuation factors, policies for evaluation of petroleum VI, and policies for mitigation of VI.
Results/Lessons Learned
The details provide a useful technical and regulatory summary for practitioners and the regulated community nationwide. The specific screening values used for groundwater, shallow soil vapor, and indoor air were compiled for six compounds. Screening levels for indoor air varied by two to three orders of magnitude, whereas screening levels for groundwater varied by three to four orders of magnitude for these six compounds. The most variability was observed for shallow soil vapor, where values varied from four to five and one-half orders of magnitude. Therefore, there are significant differences from state to state as to what level of subsurface impacts will trigger further investigations.