Summitville Mine is a 1,400-acre former gold and copper mine in Rio Grande County, Colorado. Mining that began in 1984 released heavy metals into soil, surface water, and groundwater, contaminating Wightman Fork and the Alamosa River downstream. The site was added to the Superfund National Priorities List (NPL) on May 31, 1994, and cleanup has been organized into five operable units targeting the heap leach pad, a mud dump, mine reclamation and revegetation zones, an adit drainage area, and site-wide water treatment.
EPA has identified 18 contaminants of concern at the site. These include arsenic, cadmium, chromium(VI), copper, lead, mercury, nickel, silver, zinc, aluminum, iron, manganese, and cyanide, among others. Contamination is found in groundwater, surface water, soil, sediment, leachate, and solid waste across multiple areas of the mine property.
Cleanup work has involved contouring, capping, and revegetating mine waste piles, filling and capping open pits, sealing mine entrances, and detoxifying the cyanide that was held in the heap leach pad. A water treatment plant completed in 2011 captures acid mine drainage and removes high metal concentrations before water leaves the site. It can handle up to 2,100 gallons per minute and typically runs from April through October. Physical construction across all five operable units was completed in September 2013, and the site is now in the operation and maintenance phase.
EPA's most recent five-year review, completed in September 2025, found that cleanup actions protect human health and the environment in the short term. Human exposure is currently under control, and contaminated groundwater is stabilized with no unacceptable discharge to surface water. However, full long-term protectiveness depends on finishing a seepage capture system, a spillway raise, and a Mine Pool Management Program. Institutional controls are still being developed and will be recorded in a modification to the site's Record of Decision. The site is estimated to be ready for anticipated reuse between September and November 2028 and has not yet been deleted from the NPL. Colorado leads long-term operation and maintenance and has subscribed to community solar gardens in the San Luis Valley to offset the electricity costs of running the water treatment plant.
Community members can review site documents at the Del Norte Public Library in Del Norte, Colorado, the Colorado Department of Public Health and Environment (CDPHE) Records Center in Denver, or the EPA Superfund Records Center in Denver. For questions, contact the EPA Remedial Project Manager or Community Involvement Coordinator. CDPHE is also available.
