The Summitville Mine site is located 25 miles south of Del Norte, Colorado at an elevation of 11,500 feet above sea level in the San Juan Mountains of southwestern Colorado. The mine site is situated south of Wightman Fork, a tributary of the Alamosa River, about two miles east of the Continental Divide. Mountain peaks surrounding the mine site range between 12,300 and 12,700 feet elevation. The historic town of Summitville is just to the north of the mine site on the other side of Wightman Fork. The area is traditionally subject to severe winters with heavy snowfall accumulating on steep slopes. Snow may often remain on the ground until late spring or early summer, providing water in quantities sufficient to keep streams, including Wightman Fork, flowing year-round, and acting as a continual source of water entering the soil.
Gold and silver mining began at Summitville around 1870. Large-scale, open-pit mining began at the site in 1984. The mine operator, Summitville Consolidated Mining Corp., Inc. (SCMCI), used cyanide heap leaching to extract precious metals from the ore. In this process, ore excavated from the mountain was crushed and placed onto the clay and synthetic-lined heap leach pad (HLP). A sodium cyanide solution was then applied to leach out gold and silver.
Almost immediately after its construction in 1986, a leak was detected in the HLP. SCMCI abandoned the site and announced it was filing for bankruptcy in December 1992. EPA immediately assumed responsibility of the site as an emergency response. On May 31, 1994 Summitville was placed on the National Priorities List (NPL) of Superfund sites.
Source: US EPA Region 8, Superfund.