Duluth-based Minnesota Power says it is working closely with state and federal agencies after an estimated 1 million gallons of coal ash wastewater leaked from a pipeline at Boswell Energy Center, a large coal-fired power plant in Cohasset with much of it flowing into a nearby lake.
The utility said the leak occurred from an underground pipeline that transfers the wastewater from an inactive coal combustion residual pond to the plant for process water.
The leak has been contained. Staff from the Minnesota Pollution Control Agency and U.S. Environmental Protection Agency were notified, and the utility is monitoring potential impacts to water and wildlife.
Because the water had been in contact with residual material left behind from the burning of coal, it could contain sulfate or heavy metals, said Josh Skelton, chief operating officer of Minnesota Power.
“And that’s the component analysis that we’ve been doing in our sampling, and that we continue to work with the EPA and MPCA on, to make sure we’re understanding the impacts to the external world,” Skelton said.
While there don’t appear to be impacts to be concerned about, Skelton said the utility is “committed here to remediate any further impacts, and restore it as best we can to original condition as a result of the spill.”
The MPCA said the company reported the incident at 11:30 a.m. Tuesday. The spill was discovered at 11:15 a.m. Officials said it did not affect local sewers or drinking water.
The ash wastewater leak occurred on land and flowed about 300 to 400 yards through tall grass and trees into Blackwater Lake, said Skelton. According to the Minnesota Department of Natural Resources, the lake is a 674-acre impoundment on the Mississippi River.
Skelton said the utility estimated that one million gallons of the wastewater could have made it into the lake. Crews built berms and installed booms and fencing to control the leak.
“We’ve ceased the operation of that return line while we investigate the root cause, and come up with a plan and sampling and monitoring and ultimately remediation,” Skelton said.
Minnesota Power draws water from the lake to help cool the Boswell plant. The utility plans to cease coal operations at the power plant’s Unit 3 by 2030, and at Unit 4 by 2035, to comply with the state’s requirement for 100 percent carbon free electricity by 2040.
The pond where the water originated was used to store particulates that were scrubbed out of the coal plant with pollution control devices. The pond was used from 1980, when Boswell 4 was built, until 2015, when advanced pollution controls were installed, Skelton said.
The particulate matter settles out at the bottom of the pond. The utility pipes the water from the pond back to the plant to help control the temperature, and for dust control. Skelton said the pond gets continually replenished from rain and snow storms.
At least one environmental group that has pressured Minnesota Power to shut down its coal fired generators at the Boswell power plant says the accident should push the utility to retire its coal units sooner.
“Minnesota Power must take steps to ensure something like this doesn’t happen again, starting with a commitment to retire all of its coal generation burning units by 2030 at the latest. There is no safe way to burn fossil fuels,” said Jenna Yeakle, central region campaign manager with the Sierra Club in Duluth.
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