Ellsworth Air Force Base covers 4,858 acres near Rapid City, South Dakota. Military activities over the past 50 years left soil, sediment, surface water, and groundwater contaminated with hazardous chemicals, both on the base and on nearby private land. The site was added to the Superfund National Priorities List on August 30, 1990, and cleanup work began in 1992. Above-ground areas were partially deleted from the list in December 2006, with additional above-ground portions removed in May 2012. Groundwater cleanup is still active, and the site has not yet achieved full deletion from the list.
EPA has identified more than 60 contaminants of concern. The most widespread is trichloroethene, a solvent found in groundwater at eight different areas and in soil at the Fire Training Area. Other contaminants include tetrachloroethene, benzene, toluene, xylene, chlorinated compounds, pesticides such as aldrin and heptachlor, and heavy metals including arsenic, lead, and cadmium. PFAS, which stands for per- and polyfluoroalkyl substances, comes from firefighting foams and was first detected in groundwater in 2011, then in local private drinking water wells starting in 2016. The PFAS plume stretches about 25 miles.
The Air Force handles all cleanup work, with oversight from the EPA and the South Dakota Department of Agriculture and Natural Resources. The site is divided into fourteen operable units. Most completed their cleanup actions between 1996 and 1999. Groundwater treatment has continued longer, with newer pump-and-treat systems replacing original ones since 2007. For PFAS, the Air Force supplies bottled water to three off-base properties, operates 21 residential treatment systems, and is building a new community water line for some affected areas. A formal cleanup decision for the PFAS unit is estimated between September and November 2027.
The most recent five-year review, completed September 23, 2025, found that much of the site is protective, but groundwater was rated only short-term protective. Human exposure is not yet under control, and contaminated groundwater continues to migrate beyond its original area. Cleanup goals have not been fully met across the entire property.
Community members can stay informed through newsletters, announcements, and presentations provided by the base. Residents can sign up for an EPA email list to receive updates about upcoming meetings. The Restoration Advisory Board website posts slides from past meetings. The Agency for Toxic Substances and Disease Registry also maintains a website with PFAS information for both residents and health care providers.
