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Proposed NPL Listing Based on Vapor Intrusion

The U.S. Environmental Protection Agency (EPA) recently proposed to add the Rockwell International Wheel & Trim Site (wheel cover & chrome-plating facility) in Grenada, Mississippi to the National Priorities List (NPL) based solely on the vapor intrusion pathway.  This is the first time EPA has ever proposed an NPL site based solely on vapor intrusion from subsurface contamination.

The Rockwell site is currently the location of a metal stamping operation.  Waste containing trichloroethylene (TCE) and dichloroethylene (DCE) were released to a wetland and to surface water via an outfall ditch.  The EPA determined that there was likely a complete pathway from the subsurface source of volatile organic compounds (VOCs) to the employees of the building.

The EPA scored the Rockwell site under the Hazard Ranking System (HRS).  The HRS score for the site was 50 based only on the subsurface intrusion.  While there are contaminants in other media, theses were not included.

The types of risks that have been quantified in the Superfund HRS are exposures to contaminated soil, surface water, groundwater, and ambient air.  Effective May 2017, the list of exposure was expanded by adding the risk of exposure to indoor air impacted by subsurface intrusion.