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Abandoned Mine Land Reclamation Project Cleans the Most Polluted Stream Entering Yellowstone

Cooke City, MT, USA
The Atlas Community Team

Government Champion

Department of Environmental Quality


21.9 Million USD

Project Status

Operational since 2014

At a Glance

Abandoned mine reclamation work by Montana’s Department of Environmental Quality transformed Soda Butte Creek from the most polluted stream entering Yellowstone National Park to become Montana’s first water body delisted from the Clean Water Act.

Problem Addressed

Soda Butte Creek is a mountain stream located in the Absaroka and Beartooth Mountains of Montana and Wyoming. Along its 20-mile length, the stream traverses high mountains and flows past the northeast entrance to Yellowstone National Park. In the 1870s, the land around where the creek meets the entrance to Yellowstone was discovered to have held large deposits of gold, silver, lead, zinc, and copper. Because the land held such coveted resources, the area surrounding the stream was transformed into the McLaren Mill and Tailings mining site and worked for over 70 years until mining in the area concluded in the 1950s.

Although mining of the land had been at a standstill for decades, the legacy it had left behind was still very much reflected by mine tailings that leached heavy metal pollution into the creek and contributed to its red color. A five-mile segment of the stream that entered Yellowstone was determined to be an impaired water body under the Clean Water Act, and Soda Butte Creek was labeled the most polluted stream entering Yellowstone National Park.

With portions of the stream being categorized as an impaired water body under the Clean Water Act, The Montana Department of Environmental Quality was faced with finding a way to remove the waste and pollution from the creek and restore it to its previous state.

Montana Dept. of Envi. Quality used/is using abandoned mine reclamation strategies to address this/these challenge(s).

Solution(s) Used

In 2010, after years of targeting the MacLaren Mill and Tailings mine for reclamation, the Montana Department of Environmental Quality (MTDEQ) undertook a 4-year project to clean up the stream through several different projects including the removal of the tailings impoundment, the relocation of contaminated floodplain sediments, the improvement of water quality, and restoration of the creek’s health. The project was funded through grants from the Department of the Interior Office of Surface Mining Reclamation and Enforcement and from the Montana Department of Natural Resources and Conservation Reclamation and Development Grants Program.

The scope of the cleanup was immense as the tailing impoundment amounted to nearly 500,000 tons and covered an area of approximately 10 acres. The long-term leaching of heavy metal toxicity into the water had led there to be approximately one million gallons of contaminated groundwater that required treatment.

To prevent further contamination from the tailings, groundwater around the perimeter of the tailings impoundment was captured and sent to be treated using calcium hydroxide to increase the pH and precipitate dissolved metals. The tailings themselves were mixed with calcium oxide to neutralize acidity and dry them for compaction.

As part of the reclamation, the MTDEQ reconstructed areas of Soda Butte Creek and a neighboring creek in locations where they had been disrupted by mining activity. The 110 million gallons of contaminated water that had been treated was discharged to Soda Butte Creek to undergo regular quality testing. To further restore the creek’s health, the disrupted areas were covered with soil and seeded to allow for new growth.

After the project was concluded, water quality tests the next year confirmed that heavy metal levels were far below the maximum allowed by state and federal standards.


  1. Abandoned mine reclamation project removed 0.5M tons of mine tailings, treated 110M gallons of contaminated water, and restored 1,500+ feet of the Soda Butte Creek stream channel.
  2. In 2018, Soda Butte Creek became the first Montana water body delisted from the Clean Water Act 303(d).
  3. Post-project water quality sampling confirmed that copper, lead, and manganese levels in the creek were well below the maximum allowed by state and federal standards.
  4. The restoration of the creek meant the return of recreational opportunities for residents unavailable in previous years.

Something Unique

The project earned a National Recognition Award from the American Council of Engineering Companies in 2015.

Who Should Consider?

Cities and states looking to address abandoned mine reclamation, and restore bodies of water whose pollution as a result of mining or other industrial work is an environmental concern.

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