Minnesota Pollution Control Agency warns Minnesota Power to prevent leaks at Boswell coal-fired power plant before massive coal ash spill into sewage

State pollution regulators told Minnesota Power it should take action to prevent wastewater leaks from its massive coal-fired power plant in Cohasset, Minnesota, about three months before 5.5 million gallons of wastewater containing coal ash spilled from a burst pipe.

Duluth-based Minnesota Power reported 11 spills — all much smaller — between October 2021 and August 2023, including three sewage ash spills.

Those incidents occurred at other plant functions and were unrelated to the July discharge, said Kurt Anderson, director of environmental and land management for Minnesota Power. Until the larger spill, the utility “didn’t have a problem with that system,” Anderson said.

Asked if the leaks were related, the Minnesota Pollution Control Agency (MPCA) said it was still investigating to determine the cause of the July leak.

In an April 2 letter, the MPCA also said the utility failed to immediately notify the state after six spills, which was one reason the agency sent a warning letter for alleged violations of a key water permit.

The MPCA said Minnesota Power should “submit and execute a plan to prevent future unauthorized water discharges” and asked the company to provide evidence, including photos, that it had done so. KSTP-TV first reported the letter last week.

Smaller leaks ranged from 50 gallons of wash water from a truck bay to 1,000 gallons of wastewater from an ash silo, a byproduct of spraying coal to prevent dust. The causes were attributed mostly to equipment failures, but one leak was caused by a power outage and another by employee error.

The MPCA said that overall the coal-fired power plant “appears to be well maintained and in good working order.”