The Rapidan Dam in Minnesota is in a precarious state after recent flooding of the Blue Earth River, prompting officials to warn Monday that it is in “imminent failure condition.”
The Blue Earth County Sheriff’s Office said that the river has cut around the sides of the dam and that debris has been accumulating in the water. It announced the “imminent failure condition” status and notified those who may be affected.
“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 on Facebook.
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,” it said. “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,” it said in a statement.
Minnesota Gov. Tim Waltz noted at a news conference Monday morning that the state has received roughly 18 inches of rain over the last few weeks, saturating the ground and leaving the water nowhere to go. More rain could be coming, he added.
“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 affected roughly 40 counties so far, some of which declared states of emergency, Waltz said. He said he would move to request a presidential disaster declaration if the damage assessment reached a threshold that required federal assistance.
The Rapidan Dam, which was built in 1910 as an energy source, 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 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. 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 had begun 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. Approval would place the dam under the control of the state 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.”