The Milltown Reservoir Sediments Superfund Site is a major

Superfund Superfund is a United States federal environmental remediation program established by the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA). The program is administered by the United States Environmental Pro ...

site in

Missoula County Missoula County is located in the State of Montana. As of the 2020 census, the population was 117,922, making it Montana's third-most populous county. Its county seat and largest city is Missoula. The county was founded in 1860. Missoula Coun ...

Montana Montana () is a state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota to the east, Wyoming to the south, and the Canadian provinces of Alberta, British Columbi ...

, seven miles east of

Missoula Missoula ( ; fla, label=Salish language, Séliš, Nłʔay, lit=Place of the Small Bull Trout, script=Latn; kut, Tuhuⱡnana, script=Latn) is a city in the U.S. state of Montana; it is the county seat of Missoula County, Montana, Missoula Cou ...

. It was added to the

National Priorities List The National Priorities List (NPL) is the priority list of hazardous waste sites in the United States eligible for long-term remedial investigation and remedial action (cleanup) financed under the federal Superfund program. Environmental Protec ...

in 1983 when arsenic groundwater contamination was found in the Milltown area. The contamination resulted from a massive flood three years after its construction in 1905, which washed millions of tons of mine waste into the Clark Fork River, ultimately ending up behind the Milltown Dam. Since 1992, the site has been a part of the

Clark Fork River The Clark Fork, or the Clark Fork of the Columbia River, is a river in the U.S. states of Montana and Idaho, approximately long. The largest river by volume in Montana, it drains an extensive region of the Rocky Mountains in western Montana and ...

Superfund Complex, consisting of three major sites (the other two in

Anaconda Anacondas or water boas are a group of large snakes of the genus ''Eunectes''. They are found in tropical South America. Four species are currently recognized. Description Although the name applies to a group of snakes, it is often used to re ...

and

Butte __NOTOC__ In geomorphology, a butte () is an isolated hill with steep, often vertical sides and a small, relatively flat top; buttes are smaller landforms than mesas, plateaus, and tablelands. The word ''butte'' comes from a French word mea ...

) along a 120-mile stretch of the Clark Fork River. The Complex is the largest and most expensive Superfund site in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

.EPA Milltown Reservoir Sediments page
epa.gov; accessed May 9, 2015.

Overview

The Milltown Dam () was an earth-fill gravity-type

hydroelectric Hydroelectricity, or hydroelectric power, is electricity generated from hydropower (water power). Hydropower supplies one sixth of the world's electricity, almost 4500 TWh in 2020, which is more than all other renewable sources combined and ...

dam A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use, a ...

on the Clark Fork river in

, in the western part of

. The dam was located about seven miles east of

Missoula, Montana Missoula ( ; fla, label=Salish language, Séliš, Nłʔay, lit=Place of the Small Bull Trout, script=Latn; kut, Tuhuⱡnana, script=Latn) is a city in the U.S. state of Montana; it is the county seat of Missoula County, Montana, Missoula Cou ...

, at the confluence of the Blackfoot River with the Clark Fork. Built in 1908 by copper mining tycoon

William A. Clark William Andrews Clark Sr. (January 8, 1839March 2, 1925) was an American politician and entrepreneur, involved with mining, banking, and railroads. Biography Clark was born in Connellsville, Pennsylvania. He moved with his family to Iowa in 1 ...

, it was meant to supply hydroelectricity to his sawmills in nearby Bonner, Montana. Clark's sawmills supplied the giant timbers used to shore up the walls of the mine shafts in Butte. Since the 1870s, the

and

areas had been mined as one of the richest deposits of

copper sulfide Copper sulfides describe a family of chemical compounds and minerals with the formula CuxSy. Both minerals and synthetic materials comprise these compounds. Some copper sulfides are economically important ores. Prominent copper sulfide minerals ...

ever found in North America. With the dam just months old, however, a record flood on the Clark Fork washed tons of toxic mining sediment downstream, where it settled at the base of the dam to remain until remediation began, with a cumulative total of around 6.6 million cubic yards of sediment contaminated with arsenic, lead, zinc, copper, and other metals in the former reservoir bed.

Superfund designation and study

In 1981, through a routine Missoula County water quality study, four wells in Bonner that served 35 households, were found to be contaminated with heavy metals. The

Environmental Protection Agency A biophysical environment is a biotic and abiotic surrounding of an organism or population, and consequently includes the factors that have an influence in their survival, development, and evolution. A biophysical environment can vary in scale f ...

and the Montana Department of Environmental Quality closed the wells and began to look into the cause of the contamination of Milltown area groundwater. Two years later, in September 1983, it was determined that the contamination was the result of a buildup of heavy metal laden sediment from years of intensive mining upstream by the

Anaconda Copper Mining Company The Anaconda Copper Mining Company, known as the Amalgamated Copper Company between 1899 to 1915, was an American mining company headquartered in Butte, Montana. It was one of the largest trusts of the early 20th century and one of the largest min ...

. That finding resulted in the addition of the Milltown Dam Site to the initial

. Review began immediately by the EPA to determine the Potentially Responsible Party (PRP) and to develop a plan to fix the groundwater contamination problem. In 1977 Anaconda Copper was purchased by the Atlantic Richfield Corporation (

ARCO ARCO ( ) is a brand of gasoline stations currently owned by Marathon Petroleum after BP sold its rights. BP commercializes the brand in Northern California, Oregon and Washington, while Marathon has rights for the rest of the United States an ...

), which assumed liability for the damages. In 2000, ARCO was purchased by British Petroleum. In 1992, through the action of committed citizens in the Deer Lodge Valley, the EPA designated the

upstream from the Milltown Dam to the Warm Springs Ponds part of the Superfund Site.Milltown Reservoir Sediments Superfund Site
epa.gov; accessed May 9, 2015. In 1995, the study of the extent of site contamination was completed by the EPA and ARCO. A subsequent feasibility study attempted to determine how to restore the Milltown groundwater. That study was halted, however, as the unusually wet winter of 1996 sent a large ice jam down the Blackfoot River and into the Milltown Reservoir, causing a severe scouring of the contaminated sediment in the reservoir bed and caused a fish kill downstream. Fearful of a major uncontrolled release of water (and sediment), officials quickly drew down the level of the reservoir, stranding the ice pack before it could cause any more damage.Milltown Reservoir Sediments Superfund Site
nytimes.com; accessed 9 May 2015. The EPA immediately began to examine the extent of the damage, and after a contentious public discussion, it became clear that the threats of continued releases of contaminated sediments into the downstream fishery must be addressed in the final remediation plan. Over 10,000 residents of Western Montana sent public comments in support of complete dam removal and full cleanup. In 2003 the State of Montana, through its Natural Resource Damage Program, drafted a conceptual plan for the restoration of the Milltown Dam site.
NRDP Restoration Road Map In December 2004, the final remediation plan was released by the EPA, calling for the removal of more than two million cubic yards of contaminated sediment and the removal of the Milltown Dam. In August 2005, a consent decree was signed by the parties, allowing the project to move out of the planning phase and onto the ground. After over 20 years of study and litigation, work began on the Milltown Site on June 1, 2006 with a drawdown of the Milltown Reservoir. Contaminated reservoir sediments were hauled to an upstream repository near the town of Opportunity, a move opposed by some local residents.

Three Rs of the Superfund project

Remediation

Remediation is defined as the cleanup of hazardous substances to protect human health and the environment. The remediation on the Milltown/Clark Fork River Site is being led by the EPA and its chief contractor, Envirocon. The remediation phase includes the removal of three million tons of contaminated sediment and the Milltown Dam itself. Remediation goals include the restoration of the Milltown Aquifer and the downriver water quality as well as the trout fishery through the confluence area. Work on the ground began in the summer of 2006 and the remediation phase should come to a close by December 2009, with the project leadership shifting over to the

State of Montana Montana () is a state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota to the east, Wyoming to the south, and the Canadian provinces of Alberta, British Columbia ...

for the restoration of the area.

Restoration

Restoration in the context of Milltown is the creation of a natural river and floodplain following dam and sediment removal. With funds gained through a Natural Resource Damage Program lawsuit against

, the State of Montana is leading the restoration of the confluence area to a natural state. Restoration work began in summer 2008 and ramped up as the sediment removal drew to a close. The restoration work includes the sculpting of a new river channel, the creation of fluvial wetlands, bank reinforcement, and reestablishment of natural vegetation cover.State of Montana Natural Resource Damage Program Restoration Road Map
/ref> Restoration work was scheduled to be finished by 2012.

Redevelopment

Redevelopment is the effort to return former hazardous waste sites to productive use. The plan for the redevelopment of the Milltown area includes the creation of a state park with a trail system connecting the surrounding communities. In 2007, a conceptual design for the park was created in cooperation by the Milltown Superfund Redevelopment Working Group and the Montana Department of Fish, Wildlife, and Parks, the National Park Service Rivers and Trails Program, the Idaho-Montana Chapter of the American Society of Landscape Architects. In 2009, a grant proposal for the initial park development was submitted to the Natural Resource Damage Program. Milltown State Park opened in 2018.

References

External links

Clark Fork River Technical Assistance CommitteeClark Fork CoalitionTwo Rivers HistoryEPA Region 8 Milltown Reservoir Sediments
* * *
Milltown Oral History Project
(University of Montana Archives) {{Missoula, Montana Dams in Montana Energy infrastructure completed in 1908 Buildings and structures in Deer Lodge County, Montana Buildings and structures in Granite County, Montana Hydroelectric power plants in Montana Buildings and structures in Missoula County, Montana Buildings and structures in Powell County, Montana Buildings and structures in Silver Bow County, Montana Superfund sites in Montana 1983 establishments in Montana Historic American Engineering Record in Montana 1908 establishments in Montana