EPA Superfund Site

ELLSWORTH AIR FORCE BASE

SD | EPA ID SD2571924644

About this site’s exposure pathways: As of September 2025, the Ellsworth Air Force Base Superfund site is considered Human Exposure Not Under Control (HENC) because of a newly identified exposure pathway and contaminant. Per- and polyfluoro alkyl substances (PFAS) have been found in drinking water off-base, and the extent of the contamination has not been fully defined. PFAS are a group of thousands of man-made chemicals that includes Perfluorooctanoic acid (PFOA), Perfluorooctane sulfonate (PFOS), GenX PFAS chemicals, and many other chemicals. Historic uses of aqueous firefighting foams are the primary source of PFAS at the base. Well survey data for off-site domestic water indicate PFAS migration in ground water and surface water extends at least 30 miles off-base to the south and east. Off base drinking water and private wells (used for agriculture) are impacted by PFAS.
Currently, the planned activities to address this pathway include several ongoing removal actions and an ongoing off-base Remedial Investigation (RI) of Operable Unit (OU) 13. The first phase of the on-base RI was completed in 2025. Since October 2018, several removal actions have been taken to provide alternative water supplies, including bottled water, water filtration systems, larger treatment systems, or connecting to existing water lines. Removal actions to provide alternate water supplies and point of use treatment systems to affected residents. Some residents have refused access to the Air Force for sampling as part of the RI.
If you are impacted by risks inherent at this site, it is recommended to drink filtered water. Please coordinate with Rita Krebs ([email protected]) for additional information. The HENC status does not necessarily mean that unacceptable exposures are occurring. Human exposure could come under control as soon as the extent of the plume is identified, alternate sources of drinking water are supplied, and ICs are implemented. Ellsworth Air Force Base currently anticipates that there will be sufficient data for human exposure to come under control by September 2033.
The Air Force has an on-going informational program including a newsletter and direct outreach to impacted residents which advise not to drink the water. Annual Town Halls are also conducted to update the communities on ongoing remedial investigation and removal actions, the most recent Town Hall was held on March 25, 2025.