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Demolition of Milltown Dam Powerhouse near Missoula, Mont., begins today


Demolition of the historic Milltown Powerhouse begins today, marking a major milestone in the cleanup and restoration of the Milltown Reservoir near Missoula, Mont. The demolition will begin with the north wall and the 100-year old structure will be taken down in sections. Removal of the Powerhouse walls and roof will take approximately three weeks to complete. During this time, workers from Envirocon will be constructing a coffer dam just upstream of the Powerhouse to completely divert the water through the radial gate and allow for removal of the Powerhouse foundation. This coffer dam will be breached and the river lowered 12-14 feet in late March 2008. Immediately prior to breaching, the Clark Fork River will be diverted into the bypass channel. After being blocked by the Milltown Dam for more than a century, the removal of the powerhouse begins the process of restoring the Clark Fork River and Blackfoot Rivers to a more natural and free-flowing state.

The Milltown Redevelopment Working Group has worked closely with NorthWestern Energy to save many of the historic items from the Powerhouse, including a generator, control panels, windows, signs, and bricks. Plans are to publicly display these items and celebrate the rich history of the Bonner-Milltown area, located at the confluence of the Clark Fork and Blackfoot Rivers.

The dam was built in 1906-1907 to supply power to the local lumber mill, which in turn, supplied lumber for the mining operations upstream in Butte. In 1908 an enormous flood washed mine waste downstream from the Butte Mining District, depositing the wastes behind the newly constructed Milltown Dam. Over time, the arsenic in the reservoir sediments made its way into the Milltown aquifer, polluting the local drinking water supply. Copper in the sediments would periodically scour from the reservoir and kill fish downstream of the dam. Due to the public health risks, the site was listed as a federal Superfund Site in 1983.

In 2004, EPA and the Montana Department of Environmental Quality announced the decision to remove the Milltown Dam and contaminated sediments. Since then, EPA, DEQ and the site trustees have been working with Atlantic Richfield Company, NorthWestern Energy, and Envirocon to carry out the cleanup plan.

The Milltown Reservoir Sediments Site is an Operable Unit within a larger Superfund Site, the Milltown Reservoir Sediments/Clark Fork River Superfund Site. This Site includes approximately 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, in western Montana.

For safety reasons, the project area is closed to the public. This includes the area around the Dam, Powerhouse and portions of the Clark Fork and Blackfoot Rivers near the Superfund Site. Non-authorized personnel are not allowed on site. For more information about viewing site activities, please contact Diana Hammer, EPA, (406) 457-5040.

For more information, please visit:

EPA’s Milltown Reservoir Sediments Superfund Site website:

Clark Fork River Technical Assistance Committee’s Milltown website:

Clark Fork Coalition Milltown Project web cam:


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