Rapidan Dam in Minnesota is in 'imminent failure condition,' officials warn

The Rapidan Dam in Minnesota is in a precarious state after recent flooding of the Blue Earth River, prompting officials on Monday to warn that the structure is in "imminent failure condition."

The Blue Earth County Sheriff's Office said the river has cut around the sides of the dam and debris has been accumulating in the water. It announced the "imminent failure condition" status and notified those who may be impacted.

"We do not know if it will totally fail or if it will remain in place, however we determined it was necessary to issue this notification to advise downstream residents and the correct regulatory agencies and other local agencies," the sheriff's office said.

The dam is outside the city of Mankato, about 85 miles southwest of Minneapolis.

By Monday afternoon, the sheriff's office reported a "partial failure" of the dam on the west abutment.

"The dam in still intact and there are no current plans for a mass evacuation," the sheriff said on Facebook. "A portion of the river flow has diverted around the west side of the dam and water continues to flow."

An Xcel Energy substation at the dam, which supplies power to about 600 customers, was washed away early Monday. The utility company said its crews were working to replace the destroyed substation and restore power.

"The river level was already high from the large amounts of recent rainfall and moving fast when it diverted around the dam near the substation and flowed onto the bank," the company said in a statement.

Minnesota Gov. Tim Waltz at a news conference Monday morning noted that the state has received roughly 18 inches of rain over the last few weeks, saturating the ground and leaving the water nowhere else to go. There is potentially more rain coming, he added.

The Rapidan Dam is in a precarious state after recent flooding of the Blue Earth River. (KARE)
The Rapidan Dam is in a precarious state after recent flooding of the Blue Earth River. (KARE)
The river has cut around the sides of the dam (KARE)
The river has cut around the sides of the dam (KARE)

"With that being said, the resources that are being deployed are strategically out there," Waltz said. "We're making sure, first and foremost, people are safe, protecting property and protecting public infrastructure."

Flooding has impacted roughly 40 counties so far, with some declaring a state of emergency, Waltz said. The governor said he would move to request a presidential disaster declaration if the damage assessment reached a threshold that required federal assistance.

The Rapidan Dam was built in 1910 as an energy source and is managed by the county. Repeated flooding over more than a century has caused significant damage to the structure, according to the county's website.

A 2021 assessment concluded that the dam would have to be either repaired or replaced, both of which would be costly. The county says on its website, however, that to do nothing "would pose a public safety concern and a tremendous liability."

Repairing the dam would take four years, three of which would be the planning and design stage. But a completely new dam would take 10 years, including removal and river restoration, the county says.

The county said it was taking feedback from the community as it determines which course of action to take.

Last year, Blue Earth County said it began the process to release its licensure exemption under the federal Energy Regulatory Commission as the damage has inhibited the dam's ability to provide hydroelectricity. An approval would place the the dam under the control of the Minnesota Department of Natural Resources.

"No changes to the dam structure are being proposed at this time," the country said in an informational release. "Surrendering the exemption simply means that the FERC would no longer have regulatory authority over the dam."

Advertisement