Leaked groundwater containing tritium may have reached Mississippi River in Monticello

Electrical lines and towers frame a power plant
The Xcel Energy nuclear generating plant near Monticello, Minn., pictured on Match 24.
Ben Hovland | MPR News

Xcel Energy says groundwater containing radioactive tritium may have reached the edge of the Mississippi River in Monticello, but at very low levels that don’t pose a risk to human health or the environment.

Xcel has been pumping out contaminated groundwater since a broken pipe at its Monticello nuclear plant leaked water containing tritium last November.

So far, no tritium has been detected in the Mississippi, the Minneapolis-based utility said. But monitoring systems detected groundwater containing low levels in a sample about 30 feet from the river.

Xcel said it contained about 1,000 picocuries per liter, well below the federal standards for safe drinking water of 20,000 picocuries per liter.

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The Minnesota Pollution Control Agency and the state Department of Health released a joint statement saying the latest development does not present a threat to public health, and there are no immediate impacts to the safety of drinking water or private wells.

Health department testing of the river water just downstream of the plant this week did not find evidence of tritium, the statement read.

Tritium is a mildly radioactive form of hydrogen that occurs naturally in the environment, and also during nuclear power production.

Xcel says it's recovered about three-fourths of the leaked tritium. Most of the remaining contamination remains on the plant site.

Xcel temporarily shut down the plant in March to repair the leak. The company said it has increased the number of monitoring sites in the river, and is investigating further containment measures to prevent as much tritium as possible from reaching the river.

Xcel is seeking federal approval to continue operating the Monticello plant beyond its current license, which expires in 2030. It’s also requesting to store additional radioactive nuclear waste at the plant.