This site is one of the "Superfund" hazardous waste sites in Colorado. A site qualifies for the National Priorities List (NPL or Superfund list) when the U.S. Environmental Protection Agency (EPA) determines there is a release or threatened release of hazardous substances that may endanger public health, welfare or the environment. In Colorado, the lead agency for Superfund remediation may be either the EPA or the Colorado Department of Public Health and Environment.
This 1,400-acre site is located in Rio Grande County, approximately 18 miles southwest of Del Norte. The mine site is 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 Corp., 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 December 16, 1992. The site was placed on the National Priorities List of Superfund sites on May 31, 1994.
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 two 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 have not been of a level that affects the viability of local farm products or impacts the food chain.
Alamosa River Watershed Restoration Master Plan
In preparation for issuing the Solicitation for Project Proposals, the Federal and State Cooperative Trustee Council contracted with MWH Americas, Inc. to write the "Alamosa River Watershed Restoration Master Plan" (Master Plan) dated July 2005. The Trustee Council, authorized under the Comprehensive Environmental Response, Compensation and Liability Act (December 1980), is seeking to restore natural resources harmed in connection with impacts from the Summitville Mine, using natural resource damages (NRD) obtained in settlement from a responsible party. The Master Plan summarized current environmental conditions and developed restoration solutions to the identified problems in the Alamosa River basin, which will lead to a healthier watershed. The scope of the Master Plan includes the entire watershed, with the exception of the Summitville Mine Superfund Site. The focus of the Master Plan included:
Specific projects were identified and ranked and then combined into a watershed restoration strategy, with the intention of implementing the best combination of projects to obtain the watershed restoration vision.
The Trustee Council determined that it would allocate a total of $5 million in damages in two phases, in order to ensure the success of restoration projects in addressing the Council's goals, the effectiveness in using the available funds, and to maximize access to matching funds. Phase I would allocate up to $2.5 million, one half of which ($1.25 million) would come from the State account and one half ($1.25 million) from the Federal account.
Since 1992, EPA and the Colorado Department of Public Health and Environment 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 adits or underground mine entrances; and expanding the water runoff holding ponds, as well as operating a water treatment plant on-site.
The Colorado Department of Public Health and Environment led the largest interim measure to be implemented: Sitewide Reclamation and Revegetation. In addition, the Department 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 that remain on-going at the site, and determined what final construction projects or long-term measures must be added in order to wrap up the Summitville cleanup in the future. The study culminated with a site-wide Record of Decision (ROD) issued in the fall of 2001.
Along with ongoing operation and maintenance of the site, current activities include improvements to the Wightman Fork Diversion, Summitville Dam Impoundment dam and spillway channel, as well as an 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, the EPA and Colorado Department of Public Health and Environment plan to begin design of a new Water Treatment Plant, with construction estimated to start in 2010.
History 1992 to Present