The Standard Mine Site is located approximately 30 miles northwest of Gunnison and 10 miles west of Crested Butte in Gunnison County, Colorado, in the Ruby Range of the Gunnison National Forest, and encompasses approximately 10-acres of land that have been disturbed by past mining activities. The Standard Mine Site includes adits and shafts that access approximately 8,400 feet of open mine workings on six operating levels, waste rock and tailings piles, concrete footings and stem walls, a tailings pond, and various mine-related structures.

The Silverton Sites consist of the American Tunnel, the Mayflower Mill, the Mogul Mine, the Grand Mogul Mine, the Arrastra Gulch Dump, and the Sunnyside Mine, all mining-related sites in the Animas River and Cement Creek watersheds near Silverton, Colorado. The American Tunnel consists of an adit that accesses a vast complex of underground mine workings and an associated waste rock pile. The American Tunnel covers approximately two acres and is located primarily on public land under the administration of Interior. The Mayflower Mill consists of structures and tailings piles covering approximately 132 acres of mixed private land and public land under the administration of Interior. The Mogul Mine and Grand Mogul Mine consist of several adits and waste rock piles on a mixture of patented mining claims formerly leased by Standard Metals and public land under the administration of Interior. The Arrastra Gulch dump site consists of public land under the administration of Interior which was used for the unauthorized disposal of mining-related materials and substances. The Sunnyside Mine is located in the Animas River watershed northeast of Silverton, Colorado in San Juan County, Colorado. Injuries to aquatic and terrestrial natural resources have been identified at the Silverton Sites and in the Cement Creek and Animas River corridors.