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Summitville Mine


This is a National Priorities List (NPL), or Superfund, hazardous waste site. While we’re the lead agency for remediation of the site, the U.S Environmental Protection Agency (EPA) Superfund program provides technical support and input on all remediation-related activities to ensure the objectives of the Superfund program are met.

Site updates

Site summary


  • This 1,400-acre site is about 18 miles southwest of Del Norte in Rio Grande County.
  • In the San Juan Mountains at an elevation of 11,500 feet, surrounded by the Rio Grande National Forest.
  • The Alamosa River and its tributaries flow from the site through forest and agricultural land in Rio Grande and Conejos counties and past the San Luis Valley towns of Capulin and La Jara.
  • The Terrace Reservoir, used for irrigation, is on the Alamosa River 18 miles downstream from the site.


Gold and silver mining began at Summitville around 1870. The latest mining operator, Summitville Consolidated Mining Corporation Inc. (SCMCI), mined the site from July 1986 through October 1991 and abandoned the site in December 1992. The company opened a pit heap leach gold mining operation, using cyanide to extract the gold. The EPA Emergency Response Branch assumed responsibility of the site on Dec. 16, 1992. The site was placed on the National Priorities List of Superfund sites on May 31, 1994.

Environmental concerns


The chemicals of concern are heavy metals (copper, cadmium, manganese, zinc, lead, nickel, aluminum, iron) on site and in the acid mine drainage.


  • Mining operations deforested and denuded the area, removing topsoil and vegetation on most of the land area at Summitville,which led to large-scale erosion. Because of the highly mineralized character of the site, almost all exposed earthen materials are capable of acid generation. This acid mobilizes the variety of metals that contaminate the Alamosa River system below the site. Surface water quality downstream of the mine has been substantially degraded by low pH (acidic water),elevated dissolved solids and heavy metals (especially copper).
  • Human exposure to these contaminants is limited, since no one lives within 2 miles of the site nor uses the immediately surrounding groundwater for drinking. Drinking water wells for San Luis Valley residents living more than 20 miles downstream of Summitville have been sampled on numerous occasions and have never shown elevated metals concentrations associated with the site. In 1997, the Agency for Toxic Substances and Disease Registry (ATSDR) released a Public Health Assessment that classified the Summitville site as no apparent public health hazard.
  • Ecological impacts from site contaminants are considerable, as the Alamosa River system below Summitville cannot currently support aquatic life. Studies have found potential adverse effects to agriculture and livestock from regular use of Alamosa River water. Preliminary results have indicated some uptake of metals in livestock and some agricultural soil degradation from irrigation. However, in both cases the effects haven\'t been of a level that affects the viability of local farm products or impacts the food chain.

Site remediation

Since 1992, we and EPA have initiated several interim projects designed to slow the amount of acid mine drainage coming from the site. These interim projects have included:
  • Detoxifying, capping and revegetating the heap leach pad.
  • Removing waste rock piles and filling the mine pits.
  • Plugging the underground mine entrances.
  • Expanding the water runoff holding ponds.
  • Operating a water treatment plant on site.
  • We led the largest interim measure to be implemented: sitewide reclamation and revegetation.
  • In addition, we led the Remedial Investigation and Feasibility Study (RI/FS) for the site, which began in 1998.
  • The study evaluated the effectiveness of the interim measures that have been completed or remain ongoing at the site, and determined what final construction projects or long-term measures must be added to finish the Summitville cleanup in the future.
  • The study culminated with a sitewide Record of Decision (ROD) issued in fall 2001.

Current activities

  • Ongoing operation and maintenance.
  • Improvements to the Wightman Fork Diversion, Summitville Dam Impoundment dam and spillway channel.
  • Installation of Micro-Hydro-Power to reduce the site's dependence on line energy power.
    • With the 2007 changes to the Alamosa River underlying aluminum standards, we and EPA plan to begin design of a new water treatment plant, with construction estimated to start in 2010.

History 1992 to present

  • 1992-1994: EPA and Colorado Department of Public Health and Environment emergency response at abandoned Summitville Mine.
  • 1994: Interim Record of Decision:
    • 1: Water treatment plant.
    • 2: Cropsy Waste Pile, Beaver Mud Dump, Summitville Dam Impoundment and mine pits.
    • 3. Heap Leach Pad.
    • 4. Reclamation.
  • 1994-1995: Heap Leach Pad detoxification.
  • 1994: Reynolds Adit bulkhead.
  • 1996: Cropsy Waste Pile, Beaver Mud Dump, Summitville Dam Impoundment and mine pit closure.
  • 1996-2000: Modification to the existing water treatment plant.
  • 1994-1998: Cropsy Valley restoration and revegetation.
  • 1998: Heap Leach Pad cap complete.
  • 1998: Completion of Heap Leach Pad, North Waste Dump.
  • 1998-2001: Sitewide Remedial Investigation and Feasibility Study.
  • 2001: Sitewide Record of Decision (ROD).
  • 2002: Complete sitewide reclamation.
  • 2004: Complete water treatment plant design.
  • 2004-2005: Complete contaminant source collection structures.
  • 2005: We assume lead role for wastewater treatment plant and site operation and maintenance.
  • 2006: Rule change before the Water Quality Control Commission for the Alamosa River.
  • 2008-2009: Wightman Fork and Summitville Dam Impoundment improvement, installation of micro-hydro-power.
  • 2010: Begin construction of new water treatment plant.
  • 2011:Completed construction of new water treatment plant
  • 2013: Completed reconstruction of the Wightman Fork rundown structure, Summitville Mine site achieved the site-wide construction completion milestone



Additional resources