The Rio Algom mines and mill (the Site) are located in the Ambrosia Lake subdistrict of the Grants Mineral Belt. The current Site owner is Rio Algom Mining LLC, a wholly owned subsidiary of BHP Billiton. The Site includes underground workings and associated facilities at nine mines and the Quivira mill facility. Uranium ore was extracted from underground mine workings and milled at the Site from 1957 through 1985. During this time, approximately 33 million tons of ore were processed at the mill.