US Steels Minntac's Watershed Moment: Eco-Friendly Strides

MinnatecImage Source: NPR News


U.S. Steel's Minntac Mine has invested approximately $8 million in a major water return project aimed at improving the water quality in its tailings basin. The project replaces water with high sulfate levels from Mountain Iron Pit with an internal water return system, resulting in long-term water quality improvement.


United States Steel Corp’s Minntac Mine has taken a notable environmental step by voluntarily investing $8 million in a water return project. This initiative aims to replace the existing high-sulfate make-up water from Mountain Iron Pit with an internal water return system.

Previously, water from Mountain Iron Pit was used to supplement the water pumped from the tailings basin to an on-site reservoir and then to the processing plants. This water had high levels of sulfate, which contributed to lesser water quality in the tailings basin.

The newly installed internal water return system is designed to bring significant long-term improvement to the water quality. The idea for this project was conceived back in December 2018 when Minntac received a new tailings basin water permit that had various goals and requirements.

To solve the water return problem, Minntac Mine collaborated with Barr Engineering to develop a computer model that would allow for a greater volume of water to be pumped from the tailings basin to the reservoir feeding the plant. This led to the installation of two new three-mile long pipes, 24 inches in diameter.

The project has been deemed a success. Robert Wilmunen, U.S. Steel Minntac Mine engineering manager, stated that these new pipes could deliver an additional 11,500 gallons of water per minute back to the plants. This alleviates the need to use high-sulfate water from the Mountain Iron Pit, thereby reducing the sulfate load in the tailings basin by 18,000 pounds per day.

The decision to invest in this water return project was not mandated by any permits but was a voluntary act aimed at improving environmental conditions. While immediate effects are not visible due to the large volume of water in the tailings basin, the project is considered a significant step toward long-term environmental benefits.


The $8 million water return project at Minntac Mine represents a commendable effort toward sustainable and responsible mining. Although the immediate impact on water quality may not be easily quantifiable, the project sets a precedent for voluntary environmental stewardship in the mining industry.

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