EPA works in cooperation with the Montana Department of Environmental Quality , the U.S. Forest Service, and other state and federal agencies for cleanup work at the site.

The site consists of three areas, referred to by EPA as operable units (OUs) and defined in Site Status. Cleanup at this site uses two approaches:

1. Removal actions are used to expedite cleanup of the most immediate threats to human health and the environment. The cleanup approach using removal authority is documented in Action Memoranda:
   • Action Memorandum: Time-Critical Removal Action at the Carpenter Snow Creek Site (PDF) (25 pp, 1.5 MB, About PDF)
   • Action Memorandum: Request for approval of Time-Critical Removal Action and Exemption from the 12 month statutory limits (PDF) (17 pp, 2.8 MB, About PDF)
   • Action Memorandum: Amendment regarding request for Ceiling Increase and Change in Scope (PDF) (47 pp, 97 MB, About PDF)
2. A longer term remedial program is being implemented to assist in determining the nature and extent of contamination and selecting cleanup alternatives.
   • For OU1, a Record of Decision (PDF) (274 pp, 39.5 MB, About PDF) was issued in 2009.
   • For OU2, a remedial investigation (RI) is ongoing that will determine the nature and extent of contamination. A final OU2 RI report is expected in 2017.
   • For OU3, draft reports for a site-wide RI and a feasibility study are currently being evaluated and final drafts of both reports are expected in the spring 2018.

The 9,000-acre Carpenter Snow Creek Mining District site is located in the Little Belt Mountains of southern Cascade County, Montana. The site includes mine tailings, waste rock and mine-influenced waters due to many inactive and abandoned mines. EPA has identified about 96 abandoned mines at the site; at least 21 of these are probable sources of contamination. Historic mining operations contaminated soil, groundwater, surface water and sediment with metals and other hazardous chemicals. Investigation and cleanup activities are ongoing.

Mining began in the area in the 1880s when silver deposits were discovered near the future Neihart town site. Mines yielded primarily silver, lead and zinc ores. During the 1920s, lead and zinc were produced in large quantities. The mining district has been largely inactive since the 1940s, although some mines have reported mine development work and some sporadic production.