Clark Fork River Superfund

Clark Fork River Superfund
Name	Clark Fork River Superfund
Location	Lake County; Missoula County; Deer Lodge County; Powell County; Granite County; Silver Bow County; Powell County, Montana
Coordinates	46°N 113°W
Designated	1989
Contaminants	Lead; Arsenic; Copper; Cadmium; Zinc; Mercury; Molybdenum; Selenium; Acid mine drainage
Responsible parties	Atlantic Richfield Company; Anaconda Copper Mining Company
Governing bodies	United States Environmental Protection Agency; Montana Department of Environmental Quality; U.S. Fish and Wildlife Service

Clark Fork River Superfund

The Clark Fork River Superfund refers to the comprehensive hazardous-waste remediation program addressing mining-derived pollution in the Clark Fork River watershed of western Montana. The effort centers on legacy impacts from large-scale copper mining and smelting operations associated with the Anaconda Company and its successor entities, with remediation directed by the United States Environmental Protection Agency and state partners. The site spans multiple counties and encompasses river corridors, floodplains, mines, smelter sites, and tailings that affected the Bitterroot Range and the Greater Yellowstone Ecosystem.

Background and contamination

The contamination originates from 19th- and 20th-century copper extraction and processing conducted by the Anaconda Copper Mining Company, linked to industrial expansion promoted by figures such as William A. Clark and Marcus Daly, and financed by interests tied to Amalgamated Copper Company and national capital markets. Smelting complexes at Anaconda, Montana and mining districts around Butte, Montana released particulate emissions, slag, and tailings onto floodplains and into the Clark Fork River, the Blackfoot River, and downstream to Flathead Lake and the Missouri River basin. Episodes like floods and dam operations at Milltown Dam and Noxon Rapids Dam redistributed contaminated sediments, creating widespread deposition of metals including lead, arsenic, copper, cadmium, and zinc.

Site designation and boundary

The Environmental Protection Agency placed the Clark Fork River corridor and associated source areas on the National Priorities List in 1989, following assessments influenced by reports from the U.S. Geological Survey and investigative work by the National Research Council. The Superfund boundary encompasses discrete operable units such as the Upper Clark Fork River, the Butte Priority Soils Operable Unit, the Silver Bow Creek/Butte Area, and the Milltown Reservoir Sediments Operable Unit, and interfaces with federal lands administered by the Bureau of Land Management and the National Park Service through watershed protections near Garnet Mountain. Jurisdictional coordination includes the United States Forest Service for headwaters in the Lolo National Forest.

Sources and contaminants

Principal sources include the Upper Clark Fork Mining District mines, the Washoe Smelter complex, the Anaconda Smelter Stack, tailings impoundments, and former mill sites tied to the Washoe Mine, Granite Mountain Mine, and numerous adits and shafts in the Highland Mountains. Contaminants of concern identified by the EPA and the Montana Department of Environmental Quality include heavy metals and metalloids—lead, arsenic, copper, cadmium, zinc, and mercury—plus acid mine drainage and processing-related waste such as slag, smelter flue dust, and cyanide residues from historical flotation practices. Chemical partitioning and bioavailability were evaluated using methods recommended by the United States Geological Survey and academic research from institutions like Montana State University and the University of Montana.

Remediation and cleanup efforts

Remediation strategies have combined source removal, dredging, repository construction, soil capping, water treatment plants, and engineered stream channel restoration. Major actions included removal of contaminated sediments behind Milltown Dam, demolition of the dam to restore fish passage, construction of the Milltown Reservoir Sediments Superfund cleanup, and the reclamation of the Butte Hill soils under the Butte Priority Soils project. Responsible party settlements with the Atlantic Richfield Company funded large-scale remedial design and implementation overseen by the EPA and monitored by the Montana Department of Natural Resources and Conservation. Treatment facilities employing lime neutralization, passive treatment wetlands, and active water treatment were installed at sites such as the Silver Bow Creek treatment system and the Berkeley Pit (as an associated but separate remediation effort). Restoration partners included the National Oceanic and Atmospheric Administration for aquatic resources and the U.S. Fish and Wildlife Service for riparian habitat rehabilitation.

Environmental and health impacts

Contaminant transport affected fish populations such as westslope cutthroat trout and bull trout, and deposited metals into riparian soils and floodplain ecosystems supporting species managed by the Montana Fish, Wildlife & Parks. Human exposure routes considered in risk assessments included ingestion of contaminated homegrown produce, dermal contact with contaminated soils, and consumption of affected fish, prompting public health advisories from the Centers for Disease Control and Prevention and the Montana Department of Public Health and Human Services. Epidemiological studies and ecological risk assessments referenced work by the National Institute of Environmental Health Sciences and academic collaborators at Harvard School of Public Health and Johns Hopkins Bloomberg School of Public Health assessing metal toxicity and community health outcomes in mining-affected towns like Butte, Anaconda, and Deer Lodge.

Stakeholder involvement and governance

Governance of cleanup involved litigation and agreements among parties including Atlantic Richfield Company, state agencies like the Montana Department of Environmental Quality, federal agencies such as the EPA, tribal governments including the Confederated Salish and Kootenai Tribes, and municipalities like Missoula and Helena. Citizen engagement occurred through forums with organizations like the Clark Fork Coalition, environmental NGOs including the National Wildlife Federation and Trout Unlimited, and academic advisory panels from Carnegie Mellon University and University of Colorado experts. Congressional attention involved hearings by committees such as the United States Senate Committee on Environment and Public Works and appropriations oversight by the United States House Committee on Appropriations.

Legacy and ongoing monitoring

Long-term monitoring programs employ geochemical sampling by the U.S. Geological Survey, biological monitoring by the U.S. Fish and Wildlife Service and Montana Fish, Wildlife & Parks, and compliance oversight by the EPA and the Montana Department of Environmental Quality. Remaining challenges include management of diffuse sources, climate change-driven hydrology shifts affecting contaminant mobilization, and continued habitat restoration in coordination with Bonneville Power Administration hydropower operations and regional conservation plans tied to the Lower Clark Fork Watershed Management Plan. Ongoing scholarship from institutions such as Stanford University and Oregon State University informs adaptive management, while community-led stewardship by groups like the Clark Fork Coalition and coordinated tribal initiatives ensure surveillance of human-health advisories and ecosystem recovery.

Category:Superfund sites in Montana Category:Clark Fork River watershed