Environmental Due Diligence—EPA Adds Subsurface Intrusion to Superfund Hazard Ranking System

Last week, EPA finalized a rule that will allow it to consider subsurface intrusion (most commonly found as “vapor intrusion”) when deciding whether to add a site to the CERCLA National Priorities List (“NPL”).  The addition will enable EPA, using its “Hazard Ranking System,” to directly consider the human exposure to contaminants that enter building structures through the subsurface environment.  The move is designed to allow EPA to evaluate the relative potential risk posed by the uncontrolled release of hazardous substances through the subsurface pathway.  According to EPA, “the addition will enable EPA to identify risks posed by subsurface intrusion of hazardous substances into regularly occupied structures for all populations who live and work in areas where the subsurface environment may create exposures.”

While vapor intrusion has been an important topic in environmental due diligence over the past few years, and is now included in the scope of EPA’s All Appropriate Inquiries regulation and the ASTM 1527-13, the rule issued last week serves to underscore that EPA considers vapor intrusion to be a serious CERCLA concern, and makes clear that vapor intrusion will now be considered in the process of scoring and ranking sites for the NPL.  As a result, two additional types of sites will now be eligible for the NPL—(1) those that have only subsurface intrusion issues and (2) those with subsurface intrusion issues that are coincident with a groundwater or soil contamination problem.  That is, as a result of the new rule, subsurface intrusion, either alone or in combination with other issues, will now factor into the calculus EPA uses to determine whether to include a site on the NPL.

Inclusion of a site on the NPL often results in additional EPA investigation and can subject a site to the full panoply of EPA’s remedial powers under CERCLA. While inclusion on the NPL does not, in and of itself, result in liability, the NPL serves as EPA’s basis for prioritizing CERCLA enforcement actions.  More practically, once a site is listed on the NPL, it can become very difficult, if not impossible, to transfer in a real estate transaction.

While subsurface and vapor intrusion are already a part of most environmental due diligence processes, this new rule raises the stakes of transactions where subsurface intrusion is present and serves as a reminder that EPA is focusing significant attention on the issue.


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