Flushing of water from mill tailings at the Homestake Grants reclamation project

Dewatering of uranium tailings at Homestake Mining Company’s Grants uranium mill site has proven to be more difficult than initially predicted. The removal of in-situ water in the tailings pile is important in controlling the potential for long-term impacts to the local ground water system. The use of fresh water injection to drive the water to adjacent collection/recovery wells was initially evaluated in 2000. A complete flushing program for the tailings pile was initiated in 2002 with an average total injection rate of 302 gpm into 152 wells. Production from the tailings dewatering wells has increased to above 100 gpm after declining to below 35 gpm prior to the initiation of the injection/flushing program. Testing to date has indicated that the injection/flushing program is successful in reducing uranium, molybdenum and selenium concentrations in the tailings pile to levels that minimize potential for impact to the local alluvial ground water system.