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Upper Blackfoot – Mike Horse

2008 Settlement – Mike Horse Dam

In April 2008, state and federal officials announced a $37 million settlement of litigation with Atlantic Richfield Co. and ASARCO LLC to remove the aging Mike Horse Dam and the contaminated tailings behind it, and to clean up and restore the Upper Blackfoot River and Mining Complex.  This MT Department of Environmental Quality website provides an overview of the project and status updates.

Under the terms of the settlement (PDF), ASARCO and Arco paid the state $8 million. The state also received a $19.77 million allowed claim in the ASARCO bankruptcy, and the U.S. Forest Service will receive $1 million to oversee the state’s implementation of the project and a $230,000 allowed claim for past costs.

The dam sits in a floodplain at the headwaters of the Blackfoot River, and the tailings behind it will be moved to a repository on higher ground on ASARCO property. The project will also include cleanup of tailings along the Upper Blackfoot River, Beartrap Creek and Mike Horse Creek and the state will restore those streams to eventually bring back westslope cutthroat and bull trout.

Under terms of a second settlement, ASARCO paid an additional $10 million into a custodial trust for perpetual water treatment of contaminated adit discharges from the abandoned mines located at the site. Use of this $10 million will be directed by the State in consultation with the U.S. Forest Service.

Mike Horse Background

Mining of the Mike Horse Mine began in 1898 and was expanded into a larger operation in 1919. In 1938, the Mike Horse Mining and Milling Company leased the mine and built a 150 tons-per-day flotation mill. In 1941, the Mike Horse Dam was built across Beartrap Creek to contain the tailings generated from the flotation mill.  In 1975, heavy rains caused a partial failure of the dam and high creek waters eroded contaminated tailings into Beartrap Creek and the Upper Blackfoot.

In 2005, a U.S. Forest Service Dam Safety Report determined that the dam was unsafe, and recommended that it be removed from service. In July 2007, USFS released an action memorandum (PDF) calling for the remMoval and disposal of the dam, mine tailings and wastes.

In 2008 the State of Montana and the U. S. Forest Service successfully reached a settlement with Asarco and Arco for environmental damages at the Mike Horse site. An agreement with the Montana Department of Environmental Quality (MDEQ), the Natural Resource Damage Program and the USFS, was reached soon after the settlement to coordinate cleanup activities at the site. MDEQ is the lead agency coordinating the cleanup.   In 2013 a repository was constructed to hold approximately 1 million cubic yards of mine wastes that will be hauled to the repository location over the next four years.  Information about the UBMC, including maps and fact sheets, can be found at DEQ’s website at http://deq.mt.gov/StateSuperfund/UBMC/default.mcpx

Draft Conceptual Restoration Plan

The State of Montana, Department of Justice, Natural Resource Damage Program (NRDP) completed a Draft Conceptual Restoration Plan for the Upper Blackfoot Mining Complex; Restoration of the Stream and Floodplain Ecosystem, a draft conceptual restoration plan for the Upper Blackfoot River and Mining Complex (UBMC) project area located in headwaters of the Blackfoot River about 15 miles east of Lincoln. The Montana Department of Environmental Quality (DEQ) is the lead agency in addressing the contamination at the UBMC site and is coordinating these remedial activities with the NRDP and the United States Forest Service. Currently, remedial actions related to removal of the Mike Horse Dam and impoundments, and removal of mining tailings associated with the UBMC, are in the planning stages. The Draft Conceptual Restoration Plan proposes general approaches to integrating restoration and remediation activities in an efficient and compatible manner in order to maximize benefits to the ecosystem and native fish habitat given the available funding resources. Through a 2008 settlement with ASARCO and Arco, the state obtained about $40 million for remediation and restoration of the UBMC site.

The timeframe for remediation and restoration actions at the UBMC is slated to occur over the next decade. As summarized in the Conceptual Restoration Plan, specific elements of the restoration vision include restoring stream channel and floodplain function, creating riparian conditions that exchange nutrients and other materials with the aquatic environment, and providing high quality habitat for westslope cutthroat trout and other aquatic and terrestrial organisms. Throughout the life of this project, continued coordination among the various state and federal agencies involved with remediation and restoration activities at the UBMC will be critical to achieving restoration goals at the site. This draft plan serves as a working document, and the first of several documents, that will culminate in a final restoration plan for the UBMC project area.

The State of Montana’s Natural Resource Damage Program is currently seeking comments on the Upper Blackfoot Mining Complex 50% Preliminary Restoration Design. This document outlines proposed restoration activities to be coordinated with Montana Department of Environmental Quality (DEQ) remedial actions related to removal of Mike Horse Dam and mine tailings at the Upper Blackfoot Mining Complex (UBMC) located in Lewis and Clark County, Montana, approximately 15 miles east of Lincoln, Montana.  This action is funded by a settlement that the State of Montana and the United States Forest Service (USFS) successfully reached with Asarco and Arco in 2008 for environmental damages at the UBMC.

DEQ is leading the cleanup efforts in coordination with the Natural Resource Damage Program and the USFS.  Cleanup actions at the site are expected to occur mainly over the next four years with removal of about one million cubic yards of mine waste materials that are present throughout the floodplain of the upper Blackfoot River.  The purpose of preparing this preliminary restoration design is to define the restoration vision for the site, which will be closely coordinated with DEQ cleanup activities.

Information about the UBMC can be found on DEQ’s webpage: Upper Blackfoot Mining Complex.

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