Minnesota Power said more than 1 million gallons of coal ash wastewater spilled at its large coal plant in Cohasset, Minn., pouring out over land with at least some reaching nearby Blackwater Lake.
In a news release Tuesday, the Duluth-based electric utility said a pipeline leaked at the Boswell Energy Center that transfers wastewater from a pond containing the byproducts of coal combustion to the plant where it is used as process water.
Minnesota Power said the leak has been contained and the company is monitoring for potential impacts to water and wildlife, and also notified the Minnesota Pollution Control Agency and the Environmental Protection Agency.
Coal ash contains pollutants including mercury, cadmium and arsenic, which can pollute water and air if not properly managed, according to the EPA.
The 674-acre Blackwater Lake is a reservoir on the Mississippi River, according to the state Department of Natural Resources. Lake levels are controlled by the Pokegama Dam operated by the U.S. Army Corps of Engineers.
Minnesota Power draws water from the lake to cool its plant and releases heated water. The DNR describes the lake as “essentially a flooded river channel.” A bay where the DNR said the coal plant discharges heated water attracts fish and is popular with anglers, according to the agency.
The Boswell plant is Minnesota Power’s largest electricity source. Its two operating coal-fired units are capable of producing 932 megawatts of electricity. One unit at the plant is scheduled to retire in 2030, and the second is slated to close in 2035 as the utility transitions to carbon-free power to meet its climate goals and state regulations for a carbon-free grid by 2040.
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