Water is our most valuable shared resource and together we can keep it
that way for generations to come.
Milltown Dam

Built in 1907 at the confluence of the Clark Fork and Blackfoot Rivers, the Milltown Dam, just east of Missoula, now acts as a repository for sediment and mining wastes. Reports estimate that the Milltown Reservoir holds almost 6.6 million cubic yards of tailings washed downstream from abandoned mines and smelters. These wastes are considered to be highly toxic, contaminated with an estimated 2,100 tons of arsenic, 13,100 tons of copper, 1,700 tons of lead, 19,000 tons of zinc and 70 tons of cadmium, which have already impacted the Milltown drinking water supply.

Since 1983, the United States Environmental Protection Agency (USEPA) has been in the process of developing a program to protect the Missoula groundwater basin from these wastes. The Missoula community and local organizations, including the Mountain Water Company have been actively involved in the process from the beginning, insisting on the safe removal of the sediments from behind the dam to a depository that can keep the contaminants out of the river and groundwater.

In 2005 the USEPA issued a formal record of decision calling for removal of the dam and the most contaminated reservoir sediments and disposal of those sediments in tailings ponds 100 miles upstream in Opportunity. In early 2006, after considering public comments, a Federal District Court incorporated this decision into a legally binding consent decree. The consent decree legally binds the responsible parties to undertake the removal and disposal remedy that the USEPA recommended.

Prior to the actual work beginning for removal of the Milltown Dam and sediments, a monitoring plan for the surface water and groundwater was implemented by the USEPA and responsible parties along with input from Mountain Water Company and other interested agencies. Work on the dam removal and remediation project began in late winter of 2006 with a series of drawdowns completed before high water in the spring and will continue for five to seven years.

Throughout this process Mountain Water Company has been and remains vigilant in protecting and preserving the quality of water served to our customers. Above all, we are committed to protecting our pristine aquifer, Missoula’s priceless resource.

For more information on the EPA’s proposed sediment cleanup plan, you may access the USEPA’s Milltown report at www.epa.gov.

- The Missoula Aquifer
- Watershed
- Rattlesnake Lakes
- Backflow/Cross-Connection
- The Water Quality Report
- Water Quality Questions
- Bottled Water vs. Tap Water
- The Milltown Dam
- Private Wells vs. Regulated Water


The Milltown Dam removal and remediation project at the confulence of the Clark Fork and Blackfoot Rivers is under way. It is expected to be complete by 2013, or earlier.