Xcel Energy leak: ‘Fish kill’ caused by temperature change in Mississippi River

Xcel Energy announced a temperature-related "fish kill" in the Mississippi River caused by the temporary shutdown of its Monticello nuclear power plant to fix a radioactive water leak. 

On March 27, Xcel Energy notified the state duty officer with the Minnesota Pollution Control Agency (MPCA) that a change in water temperature led to the death of 230 fish near its Monticello nuclear power plant location.

"When a plant is running, it warms the water in the nearby river, keeping fish active," Xcel Energy explained in a statement about the occurrence. "When a plant is taken offline, the river cools down. Fish are affected by the change in water temperature. While we powered down the plant slowly to mitigate the impacts to fish in the river, 230 fish have died."

The affected fish types so far include bass, channel catfish, common carp, and one or more species of sucker fish, according to the announcement.

Xcel Energy says the tritium leak itself did not cause the fish to be killed.