Milltown Dam

A view of the Milltown Reservoir Sediments and Milltown Water Supply Operable Units, part of the greater Milltown/Clark Fork River Superfund site. Much of the site has been reclaimed since 2004, and all mine waste at the site has been moved to the BP-ARCO Waste Repository near Opportunity, or stored in a much smaller on-site repository. Restoration and redevelopment in the area is ongoing. Map from the EPA Five Year Review Report for the site (2011).

A view of the Milltown Reservoir Sediments and Milltown Water Supply Operable Units, part of the greater Milltown/Clark Fork River Superfund site. Much of the site has been reclaimed since 2004, and all mine waste at the site has been moved to the BP-ARCO Waste Repository near Opportunity, or stored in a much smaller on-site repository. Restoration and redevelopment in the area is ongoing. Map from the EPA Five Year Review Report for the site (2011).

Large volumes of mine waste from Butte and Anaconda washed down the Clark Fork River and were deposited in the Milltown Reservoir near Missoula, at the confluence of the Clark Fork and Blackfoot Rivers. More specifically, considerable volumes of mine tailings were washed to the dam in a historic 1908 flood. In the 1990s, it was discovered that arsenic from the mine waste in the reservoir had spread to the drinking water supply of nearby Milltown and Bonner. Cleanup of the site began shortly after, including removal of the dam and mine waste.

Final waste removal was completed in 2009, and remediation and restoration activities at the site were completed in September 2012. Redevelopment and reuse projects, including developing a state park at the site, are now underway.

A historic 1908 flood washed large volumes of mine waste from Butte and Anaconda downstream to the Milltown Dam.

A historic 1908 flood washed large volumes of mine waste from Butte and Anaconda downstream to the Milltown Dam.

In 2011, EPA issued the First Five Year Review Report for Milltown/Clark Fork River sites. An Executive Summary of the Five Year Review is also available from EPA.

 

Background

In early 2008, the Milltown Dam was breached, allowing the Clark Fork River to flow freely past for the first time in a century. The diversion was needed to allow access to mine waste below the old Milltown Reservoir. Since that time, most mine waste has been moved to the BP-ARCO Waste Repository near the town of Opportunity. A smaller volume of waste is buried under clean soil on-site and regularly monitored.

In early 2008, the Milltown Dam was breached, allowing the Clark Fork River to flow freely past for the first time in a century. The diversion was needed to allow access to mine waste below the old Milltown Reservoir. Since that time, most mine waste has been moved to the BP-ARCO Waste Repository near the town of Opportunity. A smaller volume of waste is buried under clean soil on-site and regularly monitored.

In December 2004, EPA, with the Montana Department of Environmental Quality (DEQ), issued the Milltown Reservoir Sediments Record of Decision (ROD). The ROD contains four parts:

You can also download a much shorter EPA Fact Sheet on the Milltown Record of Decision (2004). The U.S. Department of Interior/Fish and Wildlife Service and the Confederated Salish and Kootenai Tribes also concurred with the Milltown ROD. There is no public comment on the Record of Decision. It is a final document.

Consent Decree negotiations, which determine who pays for and performs the work, as well as specific cleanup details, were completed in the summer of 2005 for the Milltown site, although negotiations are ongoing in other parts of the greater western Montana Superfund complex, most notably in the Butte area. An EPA Milltown Consent Decree Fact Sheet (2005) is also available.

The confluence of the Clark Fork and Blackfoot Rivers above the Milltown Dam, several months after the dam was breached in 2008.

The confluence of the Clark Fork and Blackfoot Rivers above the Milltown Dam, several months after the dam was breached in 2008.

The Milltown Reservoir Sediments cleanup (remediation) has been carefully planned and coordinated with the State of Montana’s Natural Resource Damages Program, integrating remediation (EPA’s responsibility) and restoration (the responsibility of DEQ and the Montana Natural Resource Damages Program, or NRDP) activities. Similar coordination has been successful on the Streamside Tailings Operable Unit of Silver Bow Creek.

In coming years, the site will be fully restored and redeveloped, with the addition of recreational amenities and a possible interpretive center.

 

Further Exploration

The former Milltown Reservoir in 2009, as crews completed the removal of historic mine waste. Most waste was transported to the BP-ARCO Waste Repository 100 miles upstream near the town of Opportunity.

The former Milltown Reservoir in 2009, as crews completed the removal of historic mine waste. Most waste was transported to the BP-ARCO Waste Repository 100 miles upstream near the town of Opportunity.

 

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