On September 13, 2018, the United States Environmental Protection Agency (“EPA”) took the final, unprecedented step of adding a contaminated site to the Superfund National Priorities List (“NPL”) based solely on the risk to human health posed by indoor air vapor intrusion at the site. The newly designated site, which consists of the former Rockwell International Wheel & Trim facility and its surrounding 76 acres (the “Site”), is located in Grenada, Mississippi. The Site has an extensive history. Beginning in 1966, the Rockwell facility operated as a wheel cover manufacturing and chrome plating plant. After chrome plating operations ceased in 2001, the facility was used for metal stamping until approximately 2007. According to EPA, the Site’s historic operations resulted in multiple releases of trichloroethene, toluene, and hexavalent chromium into the surrounding soil and adjacent wetland. However, EPA’s primary concern—and reason for listing the site—is the potential for airborne volatile organic compounds (“VOCs”) to enter the facility through cracks, joints, and other openings, resulting in contaminated indoor air. The potential for indoor air contamination appears to be of particular concern to EPA, given that nearly 400 individuals currently work within the facility.

The Site will now join a list of approximately 160 contaminated sites that have been federally designated as NPL sites. The NPL includes the nation’s most contaminated and/or dangerous hazardous waste sites. A contaminated site must be added to the NPL to become eligible for federal funding for permanent cleanup under the Comprehensive Environmental Response, Compensation, and Liability Act. While EPA’s decision to list the Site based on risks from indoor air contamination is unprecedented, the move is not all together surprising, given EPA’s recent rulemaking actions. In May 2017, EPA passed a final rule expanding the list of factors the agency is allowed to consider when designating NPL sites to specifically include risks to human health from impacted indoor air. In the preamble to the rule, EPA noted that it needed the authority to list sites on the basis of significant risk to human health from vapor intrusion contamination.

In contrast to EPA’s position, environmental consultants operating at the Site have strongly opposed the NPL designation. Several of the firms submitted comments on the final listing, asserting that EPA’s risk evaluation failed to take into account the Sub Slab Depressurization System (“SSDS”) installed at the facility in 2017, which subsequently reduced levels of VOCs in the indoor air to safe levels. However, EPA rejected these arguments, noting that even though the SSDS may protect workers from immediate threats, “it is not intended to address possible long-term remedial goals such as addressing the sources of the contamination below the building.”

EPA’s designation of the Site should alert potentially responsible parties that vapor intrusion issues may result in an increased chance of a site becoming listed on the NPL. In addition, parties relying on engineering controls to maintain compliant indoor air vapor levels should note the potential for EPA to deem such actions insufficient as long-term site remedies.