Superfund Information Systems: Site Profile

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The Basin Mining Area site is located in and around the unincorporated town of Basin in Jefferson County, Montana. The site encompasses approximately 77 square miles and includes the town of Basin and approximately 300 individual abandoned mine sites in the surrounding watersheds of Basin Creek, Cataract Creek and part of the upper Boulder River. Hard rock mining in the Basin Watershed began in the 1870s and continued intermittently into the late 1960s. Releases of hazardous substances such as arsenic, cadmium, lead, zinc, silver and copper pose a risk to human health and the environment.

A 1989 Screening Site Investigation indicated elevated contamination in soil, sediment, and surface water samples collected throughout the Basin Mining Area. In addition, arsenic contamination was indicated in a sample taken in the Basin Elementary School yard.

Following a 1991 Expanded Site Inspection of the Town of Basin that found elevated levels of lead and arsenic in several residential yards, Montana Department of Environmental Quality (MDEQ), asked EPA's Removal Branch to consider the site for a removal action. In 1998, EPA began a removal action at the south end of Valley Street in the Town of Basin.

EPA listed the Basin Mining Area to the Superfund National Priorities List in October 1999. The EPA, in cooperation with the United States Forest Services and the MDEQ, conducts and oversees cleanup of the site.

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What Has Been Done to Clean Up the Site?

EPA prioritized the town of Basin due to human health concerns. The long-term remedy, selected in 2001, and detailed in the Record of Decision (123 pp, 65 MB, About PDF) included excavation, transportation and disposal of contaminated residential soil and mine waste from the town of Basin to the Luttrell Repository. Cleanup also included backfilling and revegetation of affected areas and implementation of institutional controls.

Site cleanup also included removal actions, or short-term cleanups, to address immediate threats to human health and the environment. In the summer of 1998, EPA removed some of the mining waste sources near residential properties in the town of Basin. EPA conducted removal actions at the Buckeye/Enterprise, Crystal, and Bullion mines. The removal actions were completed in 2002. Wastes were disposed of in the joint EPA/Forest Service Luttrell Repository.

EPA has conducted two five-year reviews at the site. The Second Five-Year Review Report (138 pp, 11.8 MB, About PDF) concluded that the remedy continues to be protective of human health and the environment.

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What Is the Current Site Status?

The site consists of six areas, referred to by EPA as operable units (OUs).

  • OU1 addresses the town of Basin. The residential component of the remedy began in September 2002 and finished in November 2004.
  • OU2 addresses the Basin Watershed. Through a Remedial Investigation (RI) report (368 pp, 202.9 MB, About PDF) and Feasibility Study (FS) report (487 pp, 139.2 MB, About PDF) completed for the Basin Watershed in 2005, EPA decided to first address the two mine sites in the watershed that contribute the most to water quality degradation; the Crystal (OU5) and the Bullion (OU6) mine sites.

Within the Basin Watershed there are four additional OUs:

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Sampling and Monitoring

Water quality monitoring at the Bullion Mine site is ongoing.

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Emergency Response and Removal

EPA excavated and disposed of approximately 5,000 cubic yards of contaminated soil/tailings in the Town of Basin. The Removal Action was completed in October 1999.

Working in partnership with the U.S. Forest Service (USFS), EPA conducted Time Critical Removal Actions at the Buckeye/Enterprise, Crystal, and Bullion mines located in the Basin and Cataract Creek watersheds. These actions were completed in 2002. Wastes were transported to the Luttrell Repository, a local jointly-owned and managed waste disposal facility by the EPA, USFS and the Montana Department of Environmental Quality.

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