OLEM/OSRTI

Washington, DC 20460

NATIONAL PRIORITIES LIST (NPL) 

***Proposed Site*** April 2016 

BONITA PEAK MINING DISTRICT San Juan County, Colorado

San Juan County

 Site Location:

The Bonita Peak Mining District is located in southwest Colorado in unincorporated San Juan County, within the 

headwaters of the Animas River.

 Site History:

The Bonita Peak Mining District site consists of historic and ongoing releases from mining operations in three 

drainages, Mineral Creek, Cement Creek and Upper Animas, which converge into the Animas River near Silverton, 

Colorado. Mining began in the area in the 1870s. Forty eight mining related areas have been identified, each 

containing waste rock, tailings piles and/or discharging mine drainage. These areas are comprised of 35 mines, seven 

tunnels, four tailings impoundments and two study areas where additional information is needed to evaluate 

environmental concerns. The last producing mine ceased production in 1991. 

 Site Contamination/Contaminants:

Currently, the EPA has waste quantity information on 32 of the 48 identified source areas. For the 32 areas with 

known waste quantity information, there are approximately 248,000 cubic yards of waste rock and water discharging

out of mining adits at the cumulative rate of 3,740 gallons per minute (5.4 million gallons per day). Known 

contaminants associated with both waste rock and discharges from adits are aluminum, arsenic, cadmium, copper, 

manganese, and zinc. Samples collected from the waste rock piles, discharging adits, and from streams indicate the 

presence of these metals.

 Potential Impacts on Surrounding Community/Environment: 

Contaminants have been released into Mineral Creek, Cement Creek and the Animas River. Stretches of the Animas 

River and Mineral Creek support fisheries that that are harvested for human consumption. Additionally, Animas River, 

Cement Creek, and Mineral Creek have stretches of wetlands vulnerable to contaminants and the area is habitat known 

to be used by the Canada Lynx, a threatened species.

 Response Activities (to date):

The EPA’s Superfund Emergency Response Program has been active within the study area. In 2015, the EPA installed 

a bulkhead at the Red and Bonita mine in the Cement Creek drainage. In response to the Gold King Mine incident in 

August 2015, the EPA is currently treating adit drainage discharged from the Gold King Mine. Other parties, including 

the Bureau of Land Management, US Forest Service, State of Colorado’s Division of Reclamation, Mining and Safety, 

private parties, and a local stakeholder group have completed past response activities within the mining district 

including analytical sampling, rerouting of adit discharge, installing bulkheads, and waste pile consolidation. 

 Need for NPL Listing:

The documented ongoing releases of hazardous substances to surface water will require significant resources to 

investigate and clean up. Therefore, adding this site to the National Priorities List would be the most effective and 

comprehensive approach for investigating and cleaning up contamination. The Governor of Colorado has sent EPA a 

letter of support for listing the Bonita Mining District on the NPL. 

[The description of the site (release) is based on information available at the time the site was evaluated with the HRS. The description may 

change as additional information is gathered on the sources and extent of contamination. See 56 FR 5600, February 11, 1991, or subsequent 

FR notices.]

For more information about the hazardous substances identified in this narrative summary, including general information regarding the effects of exposure 

to these substances on human health, please see the Agency for Toxic Substances and Disease Registry (ATSDR) ToxFAQs. ATSDR ToxFAQs can be 

found on the Internet at http://www.atsdr.cdc.gov/toxfaqs/index.asp or by telephone at 1-888-42-ATSDR or 1-888-422-8737.