Cohasset wastewater spill estimate jumps fivefold; elevated sulfate, boron levels detected
Minnesota Power now estimates that 5.5 million gallons of coal ash wastewater spilled from a power plant in Cohasset, over five times the utility’s original projection of 1 million gallons.
The spill was first reported at the Boswell Energy Center on Tuesday morning, and officials with the Minnesota Pollution Control Agency and U.S. Environmental Protection Agency have been working to assess the extent of the contamination since then.
In an update Friday, Minnesota Power said the spill has contributed to elevated levels of sulfate and boron near where the wastewater entered Blackwater Creek but no mercury, arsenic or selenium was detected in initial sampling.
The MPCA on Friday said testing revealed sulfate levels in the surrounding waters were below the federal drinking water standard but above the state’s wild rice standard. That means sulfates tested at more than 10 parts per million but less than 250 parts per million.
There have been “no immediate impacts” to fish or aquatic plants, Minnesota Power said.
As previously reported, the Duluth-based utility said a loss of pressure in an underground plastic pipe on Tuesday morning alerted staffers that something was wrong. The pipeline transfers wastewater from an inactive coal ash pond to the plant for reuse.
Crews found that water was escaping through a crack in the pipe and into upland soil. Some of the wastewater made its way overland to nearby Blackwater Creek and into Blackwater Lake, right near the Mississippi River.
Mitigation efforts now involve excavating upland soils and evaluating how far the contaminants have spread.
The MPCA says it is consulting with the Leech Lake Band of Ojibwe on any cultural or tribal impacts excavation may have and that it is working with the Minnesota Department of Health to monitor drinking water safety downstream.
State officials have also hired environmental contracting firm Bay West to conduct independent monitoring and sampling.