Environmental group calls for tighter water permit for coal plant that spilled next to rice beds

A northern Minnesota power plant that was the site of a massive ash-water spill last summer has for years legally pumped wastewater with even higher concentrations of sulfate than was detected in a nearby stream after the accident.

The July spill from Boswell Energy Center in Cohasset sent sulfate-tainted water from a broken pipe into a nearby creek, threatening the wild rice that grows downstream. But the plant has been discharging wastewater with levels of sulfate that are 48 times higher than the water-quality standard to protect wild rice.

An environmental group called attention to this fact as the Minnesota Pollution Control Agency moves to renew Boswell’s long-expired wastewater permit. Hudson Kingston, legal director at the environmental group CURE, discovered in permit documents that Boswell was emitting sulfate at concentrations of 481 parts per million from its outfall pipe.

In lakes and streams where wild rice grows, the concentration of sulfate cannot exceed 10 parts per million.

“You would think some of the pollutants would concentrate” in wastewater, as much of the water in the plant evaporates out of cooling towers, Kingston said. “But you would also think they wouldn’t then discharge that directly to the Mississippi River.”

The MPCA says Boswell’s new permit will protect wild rice in Blackwater Lake, the section of the Mississippi River where the plant discharges wastewater. The water that comes out of its outfall is immediately diluted.

Minnesota Power, the utility that owns and operates Boswell, also said it has always adhered to permit limits, and that rice downstream of the site has thrived.

The Boswell permit is the first time the state is applying the wild rice sulfate standard to the power plant. The rule was created in the 1970s but never enforced until the EPA demanded it in 2022.

Blackwater Lake is a popular ricing spot for many Minnesotans, including the nearby Leech Lake Band of Ojibwe.

In an email, a spokesperson for MPCA wrote that many factors go into determining the pollution that’s permitted at the end of an industrial facility’s pipe, including the sulfate already in the river, the flow of the river and the volume of water from the pipe.

“These new limits are more stringent than the previous permit and were developed using the 10 [ppm] water quality standard,” agency spokeswoman Becky Lentz wrote. The new permit slashed the amount of sulfate that Boswell may release by 57%, but the plant won’t have to make changes because it is already releasing less than that amount.

Kurt Anderson, director of environmental and land management for Minnesota Power, said the sulfate in the plant’s wastewater is coming from sulfuric acid. The acid is used to reduce mineral buildup in the plant and control the pH of wastewater. He added that the plant has always met the standards in its permits, and that “there’s a very long history of very healthy downstream stands of wild rice from our facility.”

But Kingston questioned whether the state’s calculations factored in all the data they should — including all the sulfate that spilled this summer. Lentz wrote that this data would be incorporated the next time Boswell’s permit came up for renewal.

Sulfate has also leached into the groundwater under Boswell’s coal ash holding ponds, which CURE argues should be remediated. The coal plant is required to clean out its ponds under a new federal rule, and Lentz said the cleanup will prevent more sulfate from infiltrating into groundwater.

But, Kingston said, “We have to have some accountability for this legacy pollution. We can’t just pretend like it didn’t happen and hope that, you know, things get better as time goes on.”

This spring, state officials warned Minnesota Power to be more careful after logging 11 smaller spills at Boswell between 2021 and 2023. Then, in July, an underground pipe that siphoned water off the top of a coal ash pond burst, allowing 5 million gallons to escape into a creek that feeds Blackwater Lake.

Since then, Anderson said the utility has excavated about 2,000 cubic yards of tainted soil, pumped up 20 million gallons of water from the creek, and installed a dam that cuts off the creek from Blackwater Lake. The extent of sulfate pollution in the lake itself was not immediately clear — MPCA said the data was not public because of an ongoing investigation of the spill.