On June 11, 2015, the United States Environmental Protection Agency released long-delayed final guidance for evaluating and mitigating risks at sites where vapor intrusion is an actual or potential concern. The final guidance applies broadly and will need to be considered at any site being evaluated by EPA under a CERCLA or RCRA corrective action, by EPA brownfield grantees, or by state agencies acting pursuant to a CERCLA or RCRA corrective action program.

Vapor intrusion refers to the migration of potentially hazardous vapors from subsurface vapor sources, such as contaminated soil or groundwater, through the soil and into an overlying building or structure. Vapor intrusion has been an area of increasing focus by EPA and state regulators since 2002, when EPA first issued draft guidance on the subject. EPA’s final guidance represents the culmination of a controversial, decade-long effort to establish national standards for the evaluation and mitigation of this exposure pathway.