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Ellsworth Air Force Base (EAFB) is a U.S. Air Force Air Combat Command base located six miles east of Rapid City, South Dakota, next to the town of Box Elder. EAFB began operating in July 1942 as the Rapid City Army Air Base, a training facility for B-17 bomber crews. In 1948, as part of the 28th Strategic Reconnaissance Wing, it became a permanent facility.

Historically, EAFB has been operations headquarters for a variety of aircraft, as well as the Titan I intercontinental ballistic missile system and the Minuteman missile system. Presently, the 28th Bomb Wing (B-1B bombers) is the host unit of EAFB.

EAFB covers about 4,858 acres in Meade and Pennington counties. The base includes runways, airfield operations, industrial areas, housing and recreation facilities. A half-century of military activities contaminated soil, sediment, surface water and groundwater with hazardous chemicals on the base and on private land beyond its boundaries. Following cleanup, operation and maintenance activities and groundwater monitoring are ongoing.

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What Has Been Done to Clean Up the Site?

The Air Force performs all cleanup activities. EPA and the state of South Dakota provide regulatory oversight.

The Air Force has conducted five-year reviews at the site. These reviews evaluate whether the remedies put in place protect public health and the environment, and function as intended by site decision documents. The most recent review concluded that groundwater remedies are in place and operating, and that they protect human health and the environment because contaminated groundwater is contained at the base boundary, high concentration source areas have been identified and are being treated, and land use controls and alternate water supplies prevent contaminated groundwater use.

New areas under remedial investigation and site inspection do not yet have identified remedies in place. They were discussed but not evaluated in the last five-year review. If remedies are required, they will be evaluated in the next five-year review.

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What Is the Current Site Status?

The site consists of 12 areas, referred to by EPA as operable units (OUs). These areas include landfills, a fire protection training area, spill sites, industrial areas and an explosive-ordnance disposal area. EPA and the Air Force have selected and implemented remedies at all OUs. The 2015 draft five-year review identified four areas that need further investigation to determine whether they belong in a new or existing OU. These include: munitions on base, vapor intrusion on base, PFCs from multiple potential sources on base, and buried concrete monoliths near OU-2 that may need removal.

The long-term remedies included groundwater pump-and-treat systems, bio-dechlorination, landfill covers, soil treatment systems, excavation activities, natural attenuation and institutional controls. The systems are functioning properly. Beginning in 2007, in-place reductive treatment (IRT) systems replaced the pump-and-treat systems for groundwater cleanup. Operation and maintenance activities and groundwater monitoring are ongoing.

Additional cleanup measures included abandonment of base water supply wells and extension of a water supply line off base. EAFB supplied water to east off-base residents until 2007, when a license for operation and maintenance of the water supply line by the City of Box Elder became active. EAFB still provides water to southwest off-base residents.

Groundwater is currently identified as the only remaining portion of the site requiring further cleanup. All surface areas of the site were proposed for deletion from the Superfund Program’s National Priorities List (NPL) in the Federal Register in March 2012. No comments were received. The final notice of partial deletion was published in the Federal Register in May 2012. Routine monitoring and maintenance activities will continue for deleted portions of the site.

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