file under: Environment, Federal Government, North America

Transforming the Upper Tenmile Creek Mining Area

Master planning and management tools for smart decision-making


The Upper Tenmile Creek Mining Area Superfund site bares numerous abandoned and inactive gold, lead, zinc and copper mine sites from the late 1800s and early 1900s, which now adversely affect recreational fisheries and public health. The 53-square-mile watershed area also encompasses the upper Tenmile Creek and its tributary basins, whose surface waters provide 50 percent of the water supply for the city of Helena.


CDM Smith supported the U.S. Environmental Protection Agency (EPA) by evaluating the nature and extent of contamination to help them best allocate resources for an integrated, watershed-wide approach. Our work included remedial investigation/feasibility studies, remedial design and remdial action, including disposing of contaminated wastes, reclaiming and re-vegetating remediated property, upgrading and operating the onsite leachate water treatment and land application disposal system, and operational monitoring.

A spreadsheet-based ranking and prioritization system cost-effectively evaluated the relative risks among the 150 abandoned mine sites, allowing EPA to prioritize sites for remediation in the Record of Decision. The prioritization system also included the development of a master planning tool that determined the most efficient multi-year schedule as well as produced the information required by EPA’s priority panel team to determine the funding requirements for the multi-faceted remedy.


CDM Smith worked closely with multiple federal and state environmental regulatory agencies and the county public works and health departments to implement these remedial actions across the large, complex watershed during times of government funding uncertainty. Successfully scheduling, procuring and managing remediation efforts and collaborating with the watershed’s numerous stakeholders allowed EPA to achieve a cleanup that was expedient, efficient and long-lasting.

Related Solutions

U.S. Environmental Protection Agency