Bullion Mine was the largest and most productive mine in the Basin Mining District. The 40-acre Site and associated claims is within the Basin Creek drainage on the northwest slope of Jack Mountain. The Site is located north of the Town of Basin in Jefferson County, Montana.
This removal action will install a relief well designed to prevent a potential blowout of 2.5 million gallons of acid mine drainage (AMD) trapped in the mine. The acidic mine pool (pH of 2.5) will be treated, the treated water will be discharged though an existing limestone channel to Jill Creek, and then the plug removed and sent for disposal
Bullion Mine was worked periodically from 1897 to 1974. The mine produced approximately 30,000 tons of gold, silver, copper, lead and zinc ore between 1905 and 1955. The Bullion Mine Site is now a significant source of AMD that is impacting water quality in Jill Creek, Jack Creek, and Basin Creek. AMD leaving the Site is laden with arsenic and heavy metals, particularly aluminum, cadmium, copper, lead, manganese and zinc.
The Montana Department of Environmental Quality classifies Jack Creek (and Jill Creek as its tributary) as a B-1water (sufficient to support recreational activities such as bathing and swimming; growing and propagation of salmonid fish and associated aquatic life and other wildlife; agricultural and industrial water supply; and drinking and culinary purposes). Water from Jack Creek eventually recharges Basin Creek and shallow alluvial aquifers which are a source of drinking water for Basin residents and is a primary human exposure pathway.
Due to the high snow pack and existing 2.5 million gallons of AMD pooled behind a debris plug, there is a high potential of a catastrophic failure that could release a significant volume of AMD, containing toxic metals and potentially release into Jill Creek and then into Jack Creek (both tributaries of Basin Creek), and contaminate properties owned by the USFS and other private owners. This would result in the exposure of residents, recreational visitors and environmental receptors to high concentrations of harmful metals including arsenic, cadmium and lead.
