Region 8
Serving Colorado, Montana, North Dakota, South Dakota, Utah, Wyoming and 27 Tribal Nations
Milltown Reservoir Sediments
National Information
Regional Information
Site Information
National Priorities List (NPL) History
Proposed Date
12/30/1982
Final Date
9/8/1983
View of the project area at the confluence of the BlackFoot and Clark Fork Rivers
Read EPA's bi-weekly Cleanup Updates.
These cleanup updates are intended to provide you with the latest information aboutremediation, restoration, and redevelopment of the Milltown Reservoir Sediments Superfund Site.
Site Status & Updates
September 24, 2009 - The last trainload of contaminated sediments leaves the Milltown Site
This important project milestone comes nearly two years after the first trainload left the Site (October 2, 2007). Since that time, almost every day a trainload of 45 cars – each carrying approximately 100 tons of sediment – has carried the sediments some 90 miles to the Anaconda Smelter Superfund Site for disposal. At that Site, the material can be used in establishing vegetation for site reclamation. EPA had estimated it would take between 200 and 2000 years to naturally deplete this source of arsenic in the sediments. Once the source of arsenic is removed, EPA estimates the local drinking water supply will be safe to drink within a decade. Read the September 24, 2009 press release.
The 2004 Milltown Record of Decision called for removing the Milltown Dam and 2.2 million cubic yards (over 3 million tons) of contaminated reservoir sediments. The dam is now gone and so are the sediments. Removing these contaminants removes the source of pollution – arsenic – that polluted the local drinking water wells years ago. Removing these sediments also means that copper from the sediments can no longer periodically scour from the reservoir and kill or chronically impair the fishery below the former Milltown Dam. Completing this removal is a necessary step to permanently address the public health and ecological risks posed by the reservoir sediments.
As significant as this milestone is, much work remains to be done. This project integrates the “3Rs” – Remediation, Restoration, and Redevelopment. The focus of this project is now shifting from Remediation to Restoration and Redevelopment.
The State of Montana’s Restoration program – led by the Montana Natural Resource Damages Program - is well underway to return the Clark Fork and Blackfoot Rivers to naturally-functioning systems. More information is found on the Milltown Dam Restoration Program Web site.
The objectives of the Milltown Restoration Plan are to:
- restore the river channels at the confluence to be naturally functioning and self-maintaining
- maintain water quality
- provide high quality habitat for fish and wildlife
- improve aesthetic values in the area by creating a diverse, natural setting
- provide functional wetland and riparian communities
- provide safe recreational opportunities such as river boating, fishing and trail access for hiking and bicycling
Redevelopment efforts are led by the Milltown Redevelopment Working Group. The working group is working closely with EPA, the State of Montana – particularly the Department of Fish, Wildlife and Parks, Missoula County, and the community to turn the Superfund Site into a State Park.
Conceptual Vision of a possible Milltown/Two Rivers Park at the site of the current Superfund Site
What's happening with the 3Rs: Remediation, Restoration, and Redevelopment at the Milltown Site?
Recent milestones:
- March 27, 2009: Breached the Spilway Coffer Dam; Began Stage 3 of the Cleanup
- February 2009: Reached the 2,000,000 ton mark of sediments excavated, loaded and hauled off-site for disposal.
- Sediment excavation and removal is about 3/4 complete!
- January 2009: Removed the Milltown Dam spillway.
- October 2008: 1 year anniversary of contaminated sediment excavation, loading and hauling off-site
- November 2008: State of Montana removed 5,000 logs from the Blackfoot River
- November 2008: State of Montana completed the Highway 200 Bridge over the Blackfoot River
- November 2008: Missoula County completed the new pedestrian bridge over the Blackfoot River
- November 2008: Missoula County completed additional recreational trails along Highway 210 E
- July 2008: The Milltown Redevelopment Working Group revised its Conceptual Redevelopment Plan for the project area.
Clark Fork Coalition hosts the "Dam Cam", Live Milltown Reservoir WebCam
March 27, 2009 -The Milltown Spillway Coffer Dam is Breached – Stage 3 begins!
The Spillway Coffer Dam (located just upstream of the former Milltown Dam spillway) was successfully breached on Friday, March 27, 2009. This event was "more historic and less dramatic" than last year's breach of the Milltown Dam. "More historic" in that the river was re-directed closer to the base of the Milltown bluff --- thought to be the original river channel; "less dramatic" because the river elevation l only dropped about two feet below the project area. Initially, only about 20% of the combined Blackfoot and Clark Fork River flows were captured by the new channel but by the following Monday, about 70% of the flow was in the new channel at the base of the Milltown bluff. Crews are hoping to divert the entire flow into the new channel so soil stockpiled between the two channels (old and new Clark Fork River channels) can be recovered for later use in site restoration.
The Spillway Coffer Dam (located just upstream of the former Milltown Dam spillway) was successfully breached on Friday, March 27, 2009. This event was "more historic and less dramatic" than last year's breach of the Milltown Dam. "More historic" in that the river was re-directed closer to the base of the Milltown bluff --- thought to be the original river channel; "less dramatic" because the river elevation l only dropped about two feet below the project area. Initially, only about 20% of the combined Blackfoot and Clark Fork River flows were captured by the new channel but by the following Monday, about 70% of the flow was in the new channel at the base of the Milltown bluff. Crews are hoping to divert the entire flow into the new channel so soil stockpiled between the two channels (old and new Clark Fork River channels) can be recovered for later use in site restoration.
To see before and after pictures of the breach of the spillway coffer dam, see the photo/video gallery section of this page.
Clark Fork Coalition hosts the "Dam Cam", Live Milltown Reservoir WebCam 
Conceptual Vision of a possible Milltown/Two Rivers Park at the site of the current Superfund Site
View pictures and videos of the Milltown Dam removal and Clark Fork River diversion
March 28, 2008 --- The Milltown Dam is breached!
The Milltown Dam was completed in 1908 and around noon on Friday, March 28, 2008, a century later, the Milltown Dam was officially breached. This was an historical moment in both the cleanup of the Milltown Reservoir Sediments Superfund Site and in the rich cultural and natural history of the Milltown-Bonner area.
Approximately 1000 people, including Montana Governor Schweitzer, Senators Baucus and Tester, local legislators, city council members, tribal, state, federal, and local officials, community groups, and members of the public, gathered on the bluff overlooking the reservoir and near the dam. Everyone anxiously watched and waited as an excavator scooped out the last bit of soil and the dam was officially breached. Water trickled through slowly at first, gathering speed as more and more of the river flows were captured. The chasm deepened as more and more of the coffer dam eroded away. Then, just before dark Friday night, the Blackfoot River flows had been completely captured. Now the Clark Fork and Blackfoot Rivers are flowing freely downstream for the first time in over a century.
While much as been accomplished, more remains to be done. For the next year and a half, work crews will continue to excavate and load contaminated sediments onto rail cars (45 cars/day) en route to the Anaconda Smelter Superfund Site nearly 100 miles away. Later this summer, when river flows drop, workers will begin removing the rest of the Milltown Dam (divider block, radial gate and spillway). As the cleanup (remediation) continues, restoration and redevelopment of the site are beginning. The remediation should be done in 2010 and restoration should be completed by 2012. Redevelopment is ongoing. Hopefully, this Superfund site will one day become a state park.
Cleanup Progress
This innovative cleanup integrates remediation, restoration, and redevelopment and plans to:
- Remove the Milltown Dam and Powerhouse
- Excavate approximately 2.2 million cubic yards of the most highly contaminated sediments in the Milltown Reservoir
- Restore the Milltown drinking water supply in as little as a decade
- Allow unrestricted fish passage, and
- Return the Clark Fork and Blackfoot Rivers to a more natural and free-flowing state.
Cleanup is underway!
Artist's rendition of the restored confluence of the Clark Fork and Blackfoot Rivers (PDF, 205 K; about PDF files)
Public Involvement the Cleanup Design
EPA has convened a Design Review Team to to work on the remedial design. The Design Review Team has been meeting periodically since the fall of 2005. Along with EPA, the State of Montana, the US Fish and Wildlife Service, and the Confederated Salish and Kootenai Tribes, Missoula County and the Clark Fork River Technical Assistance Committee are representing the public in design discussions. The Design Review Team continues to meet regularly to review and discuss site cleanup plans.
A number of new design documents and other site-related documents are available to the public. You can download the documents from the Clark Fork River Technical Assistance Committee.
Background and Cleanup Goals
In December 2004, EPA, with the concurrence of the Montana Department of Environmental Quality, issued the Milltown Reservoir Sediments Record of Decision (ROD). ROD Summary fact sheet
The ROD contains 3 parts: Part One: The Declaration (8 page legal summary which EPA and DEQ signed); Part Two: Decision Summary (fully describes the selected remedy, including information leading to this decision); and Part Three: Responsiveness Summary (public comments and responses to those comments). The US Department of Interior/Fish and Wildlife Service and the Confederated Salish and Kootenai Tribes also concur with the Milltown Reservoir Record of Decision. There is no public comment on the Record of Decision. It is a final document.
Consent Decree negotiations (to determine who pays for and performs the work) were completed in the summer of 2005. Consent Decree fact sheet.
The 3 Rs: Remediation. Restoration. Redevelopment. The Milltown Reservoir Sediments cleanup (remediation) is being carefully planned and coordinated with the State of Montana's Natural Resource Damages Program, integrating remediation and restoration activities.
Redevelopment: Envisioning the Future
The Superfund cleanup (remediation) portion should be complete in 2009. The restoration work should be completed about 2 years later (2011). What will the area look like once the remediation and restoration are complete? What do we want to see in 5, 10, 20, or 50 years?
This is the question the commuity-based Milltown Redevelopment Working Group seeks to answer. This group of citizens was appointed by the Missoula County Commissioners in 2003 to work with their neighbors and other community members to examine possible land re-use and redevelopment options for the Milltown Superfund Site. In early 2005, after many meetings, public outreach and public comment, the Milltown Redevelopment Working Group presented a Conceptual Redevelopment Plan to the Missoula County Commissioners for consideration. The redevelopment plan (PDF, 58 pp, 8 MB) was adopted by the County in March 2005. Highlights of this plan include walking, biking, and equestrian trails in the Bonner-Milltown area, upgrading the Bonner pedestrian bridge over the Blackfoot River, and looking at ways to tell the stories of the area's rich history through historic preservation activities.
There are currently 3 Workgroup subcommittees:
- Recreation and Trails (chaired by Sue Furey, Piltzville). Current focus: Planning for a possible public park
- History and Culture (chaired by Judy Matson, West Riverside). Current focus: Preserving local historic photos and items from the Powerhouse.
- Outreach (chaired by Gary Matson, West Riverside). Current focus: Outreach about planning for a possible public park.
Over the past couple of years, the Redevelopment Working Group has been raising funds to implement parts of the Conceptual Plan. The Working Group currently has about $4 million for various redevelopment projects. Recent examples include:
- Safety trail for school children and other pedestrians along Highway 210 East from the Bonner School to the Piltzville Fire Station (EPA funded).
- New pedestrian "hybrid" bridge over the Blackfoot River in Bonner (funding from EPA, Montana Natural Resources Damage Program, and the federal highway bill for alternative transportation projects).
During the summer of 2007, the Working Group made presenatations to various area groups and neighbors about the Conceptual Plan and gathered some ideas about how to refine the "concepts" and move more towards designing what may one day become a state park or other state-managed property (e.g., fishing access site or wildlife management area). In September 2007, the Working Group hosted a "Design Workshop" where 30 participants (community members, experts from agencies, and volunteer landscape architects) spent 2 days talking and dreaming and ultimately coming up with designs for 3 potential park areas::
- Milltown Gateway: low intensity design ; higher intensity design
- Confluence Area (Clark Fork and Blackfoot Rivers) lower intensity design
- Former Milltown Resevoir Area: larger area: more detailed design; bluff overlook
As currently envisioned, the lands owned by NorthWestern Energy Corporation in the area in and around the Milltown Reservoir Sediments Superfund Site would be converted to a publicly-owned park with trails, river access sites, bridges, interpretative signage, viewing area on the bluff overlooking the confluence of the Clark Fork and Blackfoot Rivers, and possibly an interpretative center. Ideally, a trail system would link the Milltown Gateway, Confluence and former Reservoir areas along the Blackfoot and Clark Fork Rivers as well as connecting to Missoula's Riverfront Trail system, extending the Kim Williams Trail along the Clark Fork River.
An interpretative center/signage is also envisioned, describing the history of the area from Glacial Lake Missoula to the Native Americans' road to the buffalo, Lewis and Clark's voyage of discovery, the mining and logging history, the construction of the Milltown Dam and Powerhouse, area poets and artists, to the present-day Superfund cleanup, river restoration and area redevelopment.
The Redevelopment Group meets the 4th Tuesday of each month at Our Saviour's Lutheran Church in Bonner. Meetings run from 6:30-9:00 pm, are free and open to the public. For more information, please contact Peter Nielsen, Missoula City-County Health Department, at (406) 258-4968 or Diana Hammer, EPA, at (406) 457-5040. Read the Redevelopment Working Group newsletter (PDF, 6 pp, 1.9 MB).
Community Involvement
EPA strives to keep the community involved and informed about site activities through on-going community outreach and education efforts.
- Cleanup Updates about the cleanup progress - EPA publishes short (2-page) regular (every 2 weeks) updates describing cleanup progress, upcoming events, and other site-related issues. Click here to subscribe.
- Informational kiosks - these provide an overview of the cleanup (remediation), restoration, and redevelopment activities, including the weekly updates. Kiosks are located at: the Milltown Community Office, start of the Kim Williams Trail along the Clark Fork River, the Missoula Public Library, the Missoula County Court House, the Weigh Station River Access on the Blackfoot River and one will soon be located in the parking lot for the bluff overlook.
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Bluff Overlook - the best place from which to view the on-going cleanup of the Milltown Resevoir is from the bluff overlooking the site. Through the generous donation of land from the Plum Creek Timber Company (donated), NorthWestern Energy (in progress) and a private landowner (in progress) and the public service spirit of the Carpernters' Union Local #28, the bluff overlook should remain a public asset for years to come! The bluff is open to the public -- please respect posted signs and neighboring private property. Directions to the overlook.
In the near future: EPA is partnering with others to design and build a handicap-accessible trail leading to a fenced area on the bluff. There will be a small parking lot and interpretataive signage on the bluff and at the parking lot. EPA is currently working with the State of Montana and Burlington Northern Railroad to (hopefully!) aquire additional land on the bluff and along the south side of the Clark Fork River.
- Tours can be arranged by calling Diana Hammer, EPA, (406) 457-5040.
- EPA allows hosts periodic public meetings, publishes site fact sheets, and makes presentations to area organizations and community groups.
We welcome your ideas and comments!
Site Description
The Milltown Reservoir Sediments Site (Milltown 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.
Behind the Dam are approximately 6.6 million cubic yards of contaminated sediments. Arsenic in the sediments has polluted the local drinking water aquifer and release of copper in the sediments threatens downstream fish and other aquatic life. These sediments were deposited over the past century, the result of historical mining operations upstream in Butte.
There are Superfund cleanup activities on-going throughout the Clark Fork Basin. EPA issued a Record of Decision in December 2004, calling for removal of the Milltown Dam and the most highly contaminated sediments. There was broad public support for this cleanup plan some 98% of the nearly 5,000 comments received during the public comment periods supported EPA's proposed plans.
The Milltown Site is located adjacent to the unincorporated communities of Milltown and Bonner. Other nearby unincorporated communities in the "Two Rivers Area" are Piltzville, West Riverside, Pine Grove, and East Missoula. Missoula, the county seat is 6 miles west of the Site. There are approximately 60,000 people in Missoula and 95,000 people in Missoula County.
Site Risk
Immediate risks to public health from a contaminated drinking water supply have been temporarily addressed .With the implementation of the Milltown Reservoir Sediments Record of Decision, EPA expects the Milltown drinking water supply to be cleaned up permanently. The groundwater should be clean within a decade following removal of the source of pollution (reservoir sediments contaminated with arsenic) and the Milltown Dam (which provides hydraulic pressure, driving the pollution into the Milltown groundwater).
| Media Affected | Contaminants | Source of Contamination |
| Groundwater, reservoir sediments | arsenic, copper | historic mining activity |
Site Documents
To keep the public up to date about cleanup activities at the Milltown Reservoir Superfund Site, EPA produces weekly updates and maintains a site photo gallery.
cleanup activities. To plan and carryout the cleanup, EPA produces a number of technical documents such as the Record of Decision (ROD), monitoring plans, design work plans, etc.
Click on the links below to access the Milltown Reservoir site documents:
- Milltown Reservoir cleanup updates
- Milltown Reservoir fact sheets
- Milltown Reservoir technical documents
Note: many of the documents below are Adobe PDF files (about PDF files)
Arsenic levels drop in Milltown water
It's been 16 years since residents of Milltown received official notice their arsenic-contaminated aquifer might be purified someday. Now well water test results indicate that process may have finally begun. Read more.
Milltown Reservoir/Clark Fork River Contacts
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