Last summer's fish kill near Lewiston likely caused by rainfall runoff, MPCA says

LEWISTON, Minn. — Rainfall-driven runoff is the likely culprit behind last summer's significant fish kill in Rush Creek near Lewiston.

On Thursday, the Minnesota Pollution Control Agency announced the results of a multi-agency investigation into the fish kill, which was discovered on July 26, 2022 , along Rush Creek between Winona County Roads 29 and 90. Approximately 2,500 fish, mostly brown trout, died.

After the agencies tested water samples, took field measurements and spoke with upstream landowners, the MPCA said it could not pinpoint an exact cause of the kill. The report notes, however, that the fish kill did not occur naturally, and investigators concluded that "recent upstream applications of manure and pesticides combined with low-flow conditions in the creek prior to rainfall on July 23 may have led to the fish kill."

While they didn't directly cause the fish kill, two facilities in Lewiston were issued violation notices during the MPCA's investigation. According to the agency, those facilities — which are not named in the report — received notices for incorrect record keeping and violating manure application setback requirements around sinkholes and special protection areas.

In September, a group of Winona County residents and Land Stewardship Project members sent a letter to Gov. Tim Walz urging action on preventing fish kills in the area.

On the topic of prevention, the MPCA said state agencies will start a communication campaign to inform farmers, residents, businesses and more about how to consider weather conditions ahead of fertilizer and pesticide application.

“We share the public’s frustration around events like this that impact hundreds of fish and oftentimes don’t point to any one cause,” said Dana Vanderbosch, MPCA assistant commissioner for water policy and agriculture. “We have had numerous meetings with members of the community to explain challenges around these investigations, and we will continue to work with residents, businesses, and landowners on strategies to reduce the risk of future fish kills.”

Winona County, the Minnesota Department of Natural Resources and the Minnesota Department of Agriculture assisted with the investigation.