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DEQ, USFS detail plans for cleaning up remaining UBMC contamination.

Blackfoot Valley Dispatch of Lincoln, Montana

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LINCOLN — With the removal of the Mike Horse dam and tailings impoundment on Bear Trap Creek complete, the Montana Department of Environmental Quality and the U.S. Forest Service are turning their attention to the remainder of the Upper Blackfoot Mining Complex.

Last month both agencies released their respective plans for dealing with contaminated areas outside the old impoundment area, which were discussed at a sparsely attended public meeting at the Lincoln Community Hall, Oct. 28.

Due to the mixed ownership of property in the UBMC, separate plans were needed to meet the requirements of the seperate state and federal environment cleanup laws.

"It's a legal issue," said David Bowers, the UBMC project officer for the state. "We have authority over private lands and the forest service manages those public lands. So we had to split up, go down parallel paths and come together again."

Since both plans are designed to integrate in a single clean up project, Bowers was able to address both.

Although some remediation work remains in the upper Mike Horse Creek drainage, the majority of the discussion last week centered on the area below the impoundment. A patchwork of federal land and privately owned patented mining claims. It's home to not only the contaminated headwaters valley, but to 73 mining features in the mountains and uplands of the UBMC, each with unique characteristics.

Bowers explained that remedial investigations of the UBMC in 2007, 2008 and 2011 looked at areas that had previously been cleaned up by ARCO and ASARCO in the 1990's and 2000's, as well as suspected areas of contamination and the extent of river and groundwater contamination.

They found some of the previously cleaned up areas were still contaminated, and identified old tailing piles and impoundments and other features from various mining operations throughout the area's 120 year history.

Bowers discussed the various methods they plan to use to address the different contaminated areas.

For soils and sediments, removal will likely be the most noticeable action. Plans call for the soil and sediment of the valley floor between the old Mike Horse dam and the upper marsh to be removed and taken to the UBMC repository on Section 35. Old mine tailings and waste piles in the valley, adjacent gulches and hillsides are expected to be taken out along the way.

The floodplain will then be restored and reconfigured using clean material. "Everything's coming out of there, so everything has to be rebuilt," Bowers said.

In some areas where removal isn't feasible, contaminated material will be contained in place, covered with soil or rocks and engineered to reduce exposure and limit migration and water infiltration. Some contaminated material may also be neutralized using lime. Barriers such as fencing, gates or plugs are planned for features that can't be removed, such as old adits or other physical safety hazards

Bowers said the upper marsh, formed where the Blackfoot River is joined by Pass and Paymaster Creeks, is an area of particular concern. "The upper marsh is full of sensitive areas that are unique to Montana," Bowers said. One particularly unique feature are iron bogs, which formed in the course of a thousand years as iron rich peat accumulated in the marsh.

"The biologist who found these are really excited because they are unique to Montana. You do not find them in very many places in Montana at all," said Bowers.

Unique plant species have also begun appearing where lodge pole pine stands survive in areas being taken over by the marsh.

The upper marsh also holds a significant amount of mine tailings washed out of the Mike Horse impoundment during the 1975 breach. Ironically, the Anaconda Company's mineral exploration in the upper marsh in the late 1960's is believed to have actually helped limit the extent of the contamination. A road Anaconda put in to access an exploratory drill rig bisected the area, creating a division between the eastern and western upper marsh. A second road accessed the rig from the east. Both roads are now underwater, but they are believed to have slowed the surge of water in 1975 and acted as a dike, which caused much of the contaminated tailings to settle in the eastern side of the upper marsh.

"We've got our deepest (deposit) of mine tailings — just like the tailing that came out of the Mike Horse repository — right in this area," Bowers said.

Plans also call for the use of monitored natural recovery, or MNR, for areas outside the main contamination area.

MNR reduces contamination in sediments over time as the clean sediments are washed downstream and mingle with the contaminated sediments.

As similar process, called Monitored natural attenuation is part of the plan for recovery of the ground and surface water in the UBMC. Since water will no longer leach minerals from the surroundings it should begin to dilute the contamination in the groundwater.

Additional measures for dealing with contaminated surface and groundwater includes diversion of clean water around waste removal areas, retention ponds and filters, inundation of old mine workings to raise water levels inside to reduce acidic drainage, some chemical treatment, and continued use of the water treatment facility to take care of any remaining contaminated water.

Legal controls, such as deed restrictions, easements and covenants are a final piece of the plan aimed at limiting possible future contamination and to protect special areas with the UBMC, such as the iron bogs.

Bowers, who has worked on the UBMC project for 13 years, is looking forward to seeing the results of the cleanup

"Pretty soon, by monitoring, we're gonna be able to come to the public and say 'you know what? The Blackfoot River is healthy again,'" he said.

The total cost of the remaining clean up is projected to be approximately $21 million. Current estimates are that the final price tag of the entire UBMC cleanup project will fall within the $39 million budget funded by the setdement with ASARCO in 2008.

The DEQ's proposed plan is available online at

The Forest Service Technical Memorandum can also be found online at

The comment period for the DEQ plan ends Nov. 9, while the comment period for the Forest Service technical memorandum closes Nov. 23.

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Original Publication Date: November 5, 2015

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