The Anderson-Calhoun Mine & Mill Site is a former lead and zinc mine and mill. Mineral exploration, mining, and milling activities were conducted between 1910 and the early 1980s. Historic mining-related features at the Site include two small open pits used to mine zinc ores, the remains of a flotation mill used to process zinc and barite ores, a tailings impoundment used to contain the residues from the processing of zinc and barite ores, and associated mining and milling infrastructure. The mill has generally been abandoned since the barite processing ended in the early 1980s.
EPA first identified the Site in 2001 as part of the Preliminary Assessment and Site Inspection (PA/SI) for Upper Columbia River Mines and Mills in Stevens County. The PA/SI inventory of the Site identified numerous 55-gallon drums, oil-filled transformers and other electrical equipment, a fuel storage tank, and other structures and equipment associated with mining and milling activities. The PA/SI also documented evidence of elevated concentrations of metals in the tailings pile and in soils near the former mill.
In 2002, EPA conducted a removal evaluation and determined that the release or threat of release of hazardous substances at the Site presented an imminent and substantial endangerment to public health and the environment.
To mitigate imminent human health and ecological threats from the release or threatened release of hazardous substances, EPA implemented a time-critical removal action at the Site between October 27 and November 3, 2002. The time-critical removal action involved the removal and disposal of containers and drums containing hazardous and non-hazardous substances, and the removal and disposal of transformers and other electrical equipment containing polychlorinated biphenols (PCBs). EPA completed a Removal Action Report in March 2003 that identified potentially responsible parties (Combustion Engineering, Goldfield Corporation, and Blue Tee Corporation) at the Site and concluded that further assessment was necessary to determine if the Site warranted additional response action.
In August 2004, EPA entered into an agreement with the potentially responsible parties to prepare an Engineering Evaluation and Cost Analysis (EE/CA) and to reimburse EPA’s EE/CA oversight costs. The final EE/CA report, completed in 2007, concluded that the lead-zinc and barite tailings at the Site presented unacceptable human health and ecological risks. The constituents of concern identified at the Site included barium, cadmium, copper, lead, selenium and zinc. In an Action Memorandum dated October 11, 2007, EPA selected a non-time critical removal action to address the threats to human health and the environment identified in the EE/CA. The proposed non-time critical removal action calls for the excavation of tailings located next to the mill building, as well as a small amount of oil-stained and other contaminated soils, and the consolidation and capping of these materials, along with other cleanup actions.
EPA entered into a settlement agreement with Combustion Engineering, Inc. and Goldfield Corporation in April 2009. EPA also entered into a settlement agreement with Blue Tee Corporation in February 2010 for payment of response costs for implementation of the selected cleanup action. EPA mobilized to the site on 5 July 2010, and the cleanup action was completed on 21 September 2010.
