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Upper Blackfoot Mining Complex CECRA Facility (UBMC)

Project Overview

The Upper Blackfoot Mining Complex (UBMC) is a state superfund facility located about 15 miles east of Lincoln.  Seeps from the tailings and waste rock dumps along with acid mine drainage from old adits have contaminated surface water, sediments, soils and groundwater.  Additional contamination exists due to the 1975 dam failure that washed metals-laden tailings down the Beartrap Creek drainage and into the upper Blackfoot River.

The Department of Environmental Quality (DEQ) will lead cleanup efforts in coordination with the United States Forest Service (USFS) and Montana Natural Resource Damage Program (NRDP) over the next few years.  The primary goal of the cleanup is to remove approximately 1 million cubic yards of tailings and mine waste for protection of human health and the environment.  This protection will be accomplished by minimizing direct contact with contaminants and limiting migration and mobility of contaminants within the environment.


The UBMC, also known as the Heddleston district, is an inactive mining district which was mined intermittently from 1889 to the 1950s and explored intermittently up to the present. The UBMC is located in the headwaters of the Blackfoot River in a fairly remote location on and near national forest land, which is used by hunters and other recreationists. The town of Lincoln is about 15 miles downstream.

The main workings at the UBMC are the Mike Horse, Anaconda, Carbonate, Edith, Mary P and Paymaster mines and a tailings impoundment on Beartrap Creek. Tailings are the materials created during the processing of the ore rock. They are generally fine-grained and contain metals at levels that are toxic to human health and the environment. The historic mining and exploration activities in this area have resulted in numerous tailings and waste rock dumps. Erosion from the tailings and waste rock dumps along with acidic seeps and mine drainage from old adits have contaminated surface water, sediments, soils and groundwater. Additional contamination exists due to the 1975 tailings impoundment failure that washed metal-laden tailings down the Beartrap Creek drainage and into the upper Blackfoot River.

Mike Horse Dam
Click map above for larger view of area descriptions.


The State of Montana and the USFS successfully reached a settlement with ARCO and Asarco for environmental damages at the UBMC. Claims and interest paid amounted to approximately $39 million.  More detail on the settlement can be found at the NRDP website. DEQ will lead cleanup efforts in coordination with the USFS and NRDP.

What's New?

Waste Repository Selected

After preparing a technical analysis and considering public comments, the USFS has selected Section 35 as the most protective waste repository location for mine waste removed from the UBMC, which includes the Mike Horse Dam.  In July 2012, the USFS issued an amendment to its 2007 Action Memorandum for wastes on National Forest Land.  This selection follows extensive analysis of alternative repository sites after investigations revealed concerns that substantially limited the possible use of the originally planned Paymaster repository.  Section 35 best meets the selection criteria under federal environmental law (the Comprehensive Environmental Response, Compensation, and Liability Act) for protectiveness, feasibility, and cost.

DEQ has concurred in the decision and will implement the site cleanup actions under a 2008 agreement between the USFS and state.  No other changes are being made to the 2007 Action Memorandum.

Section 35 is located east of Highway 279's crossing of the Blackfoot River, about 8.5 road miles from the Mike Horse Dam and approximately 13 road miles east of Lincoln.  In 2011, a repository study was prepared by Pioneer Technical Services, Inc. to review previous repository information, take a fresh look at potential sites, and make a recommendation for the most appropriate location.  The USFS released the study for public comment in September 2011.  The decision can be viewed at the Helena Forest website at

Section 35

What's Next?

Work to Do

In summer 2012, the agencies will be investigating the floodplain in the mining area to collect design-level information for cleanup and fine tuning waste quantities.  At the repository site, scientists will dig sample test pits and install additional monitoring wells to further ensure that a protective repository can be built on Section 35 and to determine the most protective location and design for a repository within Section 35.

DEQ's construction manager plans to meet with nearby residents to discuss the implementation of the project and how the residents' concerns will be addressed throughout the project. These meetings will begin the same week the decision is released.

The agencies will move into the design phase of the project this fall and winter. This includes conceptual design of the repository site and removal of the Mike Horse dam and tailings.

Our goal is to have a construction bid package for repository preparation by winter-spring 2012-2013 for bidders.  Design-level investigations are necessary before we can move to construction.  Construction (dam removal) should begin in summer 2014.  Hauling is expected to last 4 construction seasons (approximately 100 days between July and October).  With cleanup and restoration, the area should reap the benefits of a restored fishery and other amenities of the Blackfoot River headwaters as they were more than a century ago.

Information/Mailing List

DEQ, in coordination with NRDP and the USFS, puts out the Mike Horse Messenger. If you would like to receive notification of publications or any other mailings on the UBMC from DEQ, you have two choices. 1.) To receive the information electronically, please use this ListServ option to enter your email information, or 2.) use this link to enter your address information and the mailings will be put in the mail to you.

Upper Blackfoot Mining Complex

Project Contacts

Construction Activities

UBMC Virtual Tour


Water Treatment Plant

Image Gallery


Detailed Maps

Thank You

We appreciate the time and
energy that the community
and interested parties have
invested to provide input
and become engaged in the
process over the past several
years. The agencies value the
public's cooperation and
understanding that the repository
decision is based on the best
science available.  Having a
decision now allows us to move
forward toward our shared goal
of restoring the Blackfoot River.
We look forward to working with the Lincoln community and nearby residents throughout this important cleanup. 

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