Coal ash wastewater leak prompts questions on groundwater impact

COHASSET — One week after a large spill of coal ash wastewater at Minnesota Power’s Boswell Energy Center in Cohasset, nearby residents aren’t sure what to expect about the quality of their water.

When Tom Swalboski’s son first sent him an article about the wastewater spill, he was confused.

Swalboski lives a quarter-mile down the Mississippi River from the coal power plant and said there weren’t any noticeable differences in the water. Without visible impacts, he said he trusts Minnesota Power has everything handled. But he’s still got some questions.

“My biggest thing is how’s that going to affect the groundwater, I mean, I have a well here, is there going to be any effect with the groundwater," Swalboski asked. "And where did it go? That’s a lot of water, where did it all go?”

The leak is thought to have occurred in an underground pipe, with an unknown amount of wastewater reaching the surface and flowing to Blackwater Creek, which flows into Blackwater Lake, part of the Mississippi River and Pokegama Reservoir system.

The state said preliminary tests show increased levels of sulfate and boron where the wastewater entered the creek.

Jennie Harkness is a research hydrologist with the U.S. Geological Survey California Water Science Center. She’s researched coal ash contamination in the South and Wisconsin.

She explained that coal ash is the solids left behind after coal is burned, the same way there’s solid ash left when you use a charcoal stove. Because the ash is so fine, power plants often mix it with water to keep it from blowing away.

The ash contains higher concentrations of things like sulfur or boron because the organic parts of the coal were burned.

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“The water’s interacting with the sulfur compounds coming from the coal ash, it can make the water more acidic, which can impact the plants and animals that are living or using the water or it could cause damage in other ways,” she said.

In a leak like this, Harkness said the solids in the wastewater could be contained, but the water would just move with the creek or river.

“But as it moves into larger bodies of waters, it is getting diluted, so whether or not it will have an overall impact is hard to say without knowing the actual volume that’s mixed in.”

Harkness said the bigger concern would be pollutants getting trapped in the soil, but excavation can address that issue. Minnesota Power plans soil removal as part of its cleanup effort.

Funding for this environmental story was provided by the Minnesota Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources (LCCMR).