Superfund Information Systems: Site Profile

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The 1,400-acre Summitville Mine site is a former gold mine in Rio Grande County, Colorado. Gold mining started in the late 1800s. By 1984, the Summitville Consolidated Mining Corporation Inc. began open pit mining for gold, copper and silver. Mining processes, waste disposal practices, and the discharge of large amounts of copper and other metals to Wightman Fork and the Alamosa River contaminated soil, surface water and groundwater with heavy metals. Following cleanup, operation and maintenance activities are ongoing.

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What Has Been Done to Clean Up the Site?

The site is being addressed through state and federal actions.

EPA has conducted several five-year reviews of the site’s remedy. These reviews ensure that the remedies put in place protect public health and the environment, and function as intended by site decision documents. The most recent review concluded that response actions at the site are in accordance with the remedy selected by EPA and that the remedy continues to be protective of human health and the environment in the short term. Continued protectiveness of the remedy requires completion of the SDI seepage capture system and refinement of water management practices in the Cropsy basin; commissioning of the new water treatment plant; completion of the SDI spillway raise; completion of the seepage diversion downstream of the A3-Ditch Turnout; revision of the site water balance; and implementation of a Mine Pool Management Program.

Institutional control options are currently being developed to ensure the long-term protectiveness of the remedy. These controls will be documented in a modification to the site’s Record of Decision (ROD).

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What Is the Current Site Status?

Since 1992, EPA and the Colorado Department of Public Health and Environment (CDPHE) have started several interim projects to slow the amount of acid mine drainage coming from the site. These projects have included detoxifying, capping and revegetating the heap leach pad (HLP); removing waste rock piles and filling the mine pits; plugging adits and underground mine entrances; expanding water runoff holding ponds; and operating a water treatment plant on site.

The site’s long-term remedy included construction of a new water treatment plant; possible breach and removal of the existing Summitville Dam Impoundment; construction of a sludge disposal repository; upgrade of the Wightman Fork Diversion and select site ditches; and construction of groundwater interceptor trenches. Additional remedial components included construction of a highwall ditch; rehabilitation of the Reynolds Adit; management of mine pool water; continued site maintenance; and geotechnical, groundwater, surface water, sediment and aquatic life monitoring. Remedy construction took place between 1995 and 2013. Site monitoring is ongoing.

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Green Remediation

In 2008, EPA and the state made significant progress toward the installation of a hydroelectric power system at the site, completing construction of the inlet structure. In 2010, EPA and the state built the powerhouse and installed the 35-kilowatt turbine. The plant became operational in 2011. Energy produced by the plant feeds back into the grid, offsetting the costs of operating the site remedy. In 2009, the site received $17 million in American Reinvestment and Recovery Act (ARRA) funds to construct the Summitville water treatment plant. Completed in 2011, the water treatment plant removes high metals concentrations from acid mine drainage originating at the site. Plant construction provided more than 100 construction jobs in this area, and the cleanup significantly contributed to improving the water quality and restoring fish and aquatic life to the Alamosa River and Terrace Reservoir.

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