Metals loading adversely impacts the Animas River in the area around Silverton, San Juan County, Colorado. The metals of concern include iron, aluminum, cadmium, copper, lead, zinc, arsenic and nickel. The metals loading in the Animas River is due to acid rock drainage that is created when sulphide minerals are exposed to air and water to produce sulphuric acid. The acidic water can dissolve area minerals and then deposit metals in rivers like the Animas. Metals loading in the Animas River has limited aquatic life, including the trout fishery downstream from Silverton.
Sunnyside Gold Corp. (SGC) was formed and acquired the Sunnyside mine in 1985 and mined it from 1986 until
1991 under modern environmental regulations and using modern mining techniques. Since 1985, SGC has engaged in more than 30 years of reclamation and remediation in the Silverton Caldera. This article analyzes the geologic setting and historic mining that have caused the metals loading in the Animas River as well as the effect of SGC’s mining and extensive reclamation activities. It is also details how the remediation actions that SGC has taken have substantially reduced acid rock drainage and metals loading in the Animas River.
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