Superfund Site Profile

EPA recently completed the second five-year review for the Milltown Reservoir / Clark Fork River Superfund site. Five-year reviews are conducted to determine how the remedy is working and if the remedy remains protective of human health and the environment.

Second Five-Year Review Report for the Milltown Reservoir / Clark Fork River Superfund Site (PDF) (223 pp; 26.8 MB, About PDF)


The Milltown Reservoir Sediments site is located in Milltown, Montana. The site is part of a larger Superfund site, known as the Milltown Reservoir Sediments/Clark Fork River site. The site includes about 120 miles of the Clark Fork River upstream of the Milltown Dam and Reservoir. The Milltown Dam and Reservoir are located at the confluence of the Clark Fork and Blackfoot Rivers, a few miles upstream of Missoula. From the 1860s until well into the twentieth century, mineral- and arsenic-laden waste from mining activities in the region flowed into the headwaters of the Clark Fork River. As contaminated sediments and mine-mill wastes moved downstream, about 6.6 million cubic yards of these sediments accumulated behind the Milltown Dam over time. These mining activities and the downstream transport of mining-related wastes contaminated sediment, surface water and groundwater with heavy metals. Much of the site has been cleaned up, and remedy construction is underway to address remaining contamination.