In 2017, EPA finalized a rule that updated its Hazard Ranking System (HRS), used to determine when to add contaminated sites to the National Priorities List (NPL), to allow ranking of sites based on subsurface intrusion, including both vapor and water seepage from underground contamination. EPA has now added the first two sites to the NPL based on vapor intrusion alone—on September 11, EPA finalized listing of the Rockwell International Wheel & Trim site in Grenada, Mississippi, and the Delfasco Forge site in Grand Prairie, Texas on the NPL. The Rockwell site was listed because of vapors of trichloroethylene (TCE) passing into the main building on the site which is occupied by 217 workers. The Delfasco Forge site was listed because of volatile organic compound (VOC) vapor intrusion into residential properties adjacent to the site.
Although these listings could be the beginning of a flood of vapor intrusion sites being added to the NPL, it is thought that most sites that include vapor intrusion also rank under the HRS for other exposure pathways. For more information on the effects of vapor intrusion from contaminated sites, contact Steve O’Day or Phillip Hoover.