Ellsworth Air Force Base (EAFB) is located six miles east of Rapid City, South Dakota, next to the town of Box Elder. 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.