Mike Horse Repository Study - Decision and Amendment to 2007 Action Memorandum

HELENA, MONT., July 9, 2012—Based on a technical analysis and the consideration of public comments received during the comment period, the Forest Service has amended its 2007 Action Memorandum for the removal of the Mike Horse dam and impounded tailings. The amendment identifies the alternative known as Section 35 as a suitable repository site for the mine wastes from the Upper Blackfoot Mining Complex east of Lincoln. Section 35 lies north of Highway 279 and east of the Blackfoot River.

“Now that a repository location has been selected we will begin site-specific data collection and investigation to develop the proper design of the repository,” Helena Forest Supervisor Kevin Riordan said. “This site-specific analysis is necessary to help ensure that the construction of the repository is both cost effective and fully protective for the long term.”

“This decision was based on the best science available, and DEQ is pleased that we now have a suitable and safe place to isolate the Mike Horse waste,” said Richard Opper, Director of the Montana Department of Environmental Quality (DEQ). “I appreciate the time and energy the community has invested and look forward to working with our public and agency partners towards our shared goal, which is to clean up the headwaters of Montana’s historic Blackfoot River.”

DEQ has concurred in the decision and will implement the site cleanup actions under a 2008 agreement between the Forest Service and the state. The agencies will coordinate closely throughout the implementation of the cleanup.

The Upper Blackfoot Mining Complex, of which the Mike Horse dam is part, is an historic, inactive mining district. In 1975, the Mike Horse dam, holding a large tailings (mine waste) impoundment, breached and released metals-contaminated tailings into the Blackfoot River causing fish kills and environmental damage for miles downstream. In a settlement with Asarco, LLC about $39 million was obtained to address the cleanup actions by the U.S. Forest Service, DEQ and Montana Department of Justice’s Natural Resource Damages Program (NRDP).

In September 2011, members of the public were invited to submit comments on the repository sites that were considered in the Repository Siting Study for the Upper Blackfoot Mining Complex, which was prepared by Pioneer Technical Services, Inc., an independent engineering firm. Pioneer was contracted to research, analyze and recommend the most suitable and cost-effective repository site for the mine waste.

The 2007 Action Memorandum originally stated that the Paymaster site would be a suitable repository site; however, design-level investigation identified concerns that substantially limited use of that location. The agencies conducted a new evaluation to determine if other areas would be more suitable for use as a repository site.

The amended decision is issued under the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA). A copy of the amendment to the 2007 Action Memorandum is available at the following locations: www.deq.mt.gov, www.fs.usda.gov/helena, Lincoln Ranger District office at 1569 Highway 200 and Lincoln Library at 102 9th Street, and in Helena at the Lewis & Clark Library at 120 South Last Chance Gulch, Helena National Forest office at 2880 Skyway Drive, and the Montana DEQ office at 1100 North Last Chance Gulch.

For more information contact the Helena National Forest Supervisors’ office at 406-449-5201.