Ash Wastewater Spill at Cohasset Coal Plant Now Estimated at 5.5 Million Gallons

After reporting an coal ash wastewater spill from their Boswell Energy Center in Cohasset last week, Minnesota Power now says the volume of wastewater released is much higher than originally estimated.

The spill was discovered last Tuesday, where Minnesota Power originally estimated that 1 million gallons of wastewater were released. On Friday, the company revised its estimate and now says up to 5.5 million gallons were released.

The spill originated from a pipeline carrying wastewater from an onsite storage pond to the Boswell Energy Center and first entered upland soils, with a portion subsequently flowing overland to Blackwater Creek. In a press release, the company adds that the updated spill volume does not change spill mitigation and response activities underway at the site, and that it has been reported to regulators.

According to the release, monitoring and sampling results indicate increased levels of sulfate and boron in the immediate area where the wastewater entered Blackwater Creek. Sulfate levels are said to be below the federal drinking water standard, but above Minnesota’s wild rice-based standard.

Initial sampling results from the most impacted area of Blackwater Creek did not detect any mercury, arsenic, or selenium, says Minnesota Power. In addition, no immediate impacts to fish or aquatic plants have been seen.

The company says mitigation efforts will continue, and that they are coordinating with the Minnesota Pollution Control Agency, the Leech Lake Band of Ojibwe, and the federal Environmental Protection Agency to remove contaminants by excavating affected upland soils near the spill site.