EPA will soon publish a notice of opportunity for public input on whether to include a vapor intrusion component in the CERCLA Hazard Ranking System (HRS). The HRS is the principle mechanism EPA uses to place sites on the CERCLA National Priorities List (NPL). According to EPA, “The potential addition would allow the HRS to directly consider human exposure to contaminants that enter building structures through the subsurface environment.”  

Specifically, EPA seeks comments on the following topics: (i) “The level and extent of vapor intrusion contamination that would warrant evaluation for placement on the NPL”; (ii) “Methods for incorporating vapor intrusion into the HRS while, to the extent possible, maintaining the structure of the other pathways in the current HRS”; (iii) “Consideration of the importance of evaluating the potential threat to populations not demonstrated to be exposed to contaminant intrusion”; (iv) “The identification of sampling procedures available and practical to detect the presence of contamination due to vapor intrusion”; (v) “The availability of screening sampling strategies that can adequately compensate for the variability in vapor intrusion rates under different climatic and seasonal conditions”; (vi) “Identification of analytical methods that are sufficiently precise and accurate to demonstrate a significant increase in contaminant levels from vapor intrusion”; (vii) “The importance of the threat posed by exposure to contaminant vapor intrusion via inhalation, dermal contact” and ingestion; (viii) “The identification of what environmental factors . . . and structural and lifestyle factors . . . should be considered in determining whether a site warrants sampling for contaminant vapor intrusion”; (ix) “In addition to residences, schools and other occupied structures, the identification of structures in which contaminant vapor intrusion could result in a significant threat to human health”; and (x) “The possible need to consider not only contaminant vapor intrusion, but also intrusion of contaminants in solid (i.e., particulates) and liquid forms.”

EPA will conduct three public listening sessions on these topics before making a decision about whether to issue a proposed rulemaking to add a vapor intrusion component to the HRS. EPA will accept comments on the issues raised for 75 days after publication in the Federal Register.