Minnesotas Rapidan Dam at risk of failure as floods hit Midwest

August 21, 2024

Rising waters on the Blue Earth River in Minnesota washed out a portion of the Rapidan Dam near the town of Mankato, 50 miles southwest of Minneapolis, as floods inundated parts of the Midwest.

“The water cut away some land at the west side and is now free flowing,” Jeremy Brennan, chief deputy at Blue Earth County Sheriff’s Office, told The Washington Post. Downstream residents had been notified of the possibility of dam failure, but evacuation orders were not needed, officials said.

The situation was the latest brought on by days of torrential rains last week, triggering flooding that killed at least two people. In addition to a death South Dakota Gov. Kristi L. Noem (R) confirmed but did not provide details about, authorities in Clay County, Iowa, said they recovered the body of a man Monday whose truck had been swept away in floodwaters, the Des Moines Register reported.

Flooding that spread across parts of Iowa, South Dakota and Minnesota this past weekend is forecast to worsen in some areas Tuesday as rivers continue to rise, and meteorologists warned that any additional rain from possible thunderstorms could extend or heighten the risks of inundation.

In Minnesota, authorities said emergency services teams were on the ground and monitoring the situation closely.

“There’s a serious situation in and around Mankato with the Rapidan Dam potentially failing,” Sen. Amy Klobuchar (D) said in a post on social media. Minnesota’s Star Tribune newspaper reported that the dam was in “imminent failure condition,” citing Blue Earth County officials.

Video from the scene showed a lone house on the bank, close to fast-moving water carrying tree branches and structural debris.

“Nobody has dealt with such a situation before. Managing the people who are coming out to view the dam and keeping them safe is a big challenge,” Brennan said.

The National Weather Service’s flash flood warning for the Blue Earth River was in place until Tuesday morning local time, the agency said.

Officials from the city of North Mankato said they built a 34.6-foot earth wall levee as a precautionary measure. “Currently the river level is at 28.92 ft and predicted to crest at 29.6 ft on Tuesday,” the city said in a statement posted on social media.

“If the Rapidan Dam does fail, engineers on-site predict an increase in the river levels of 6 inches to 2 ft, depending on location downstream,” it said at 6:19 p.m. local time Monday.

The Rapidan Dam is more than 100 years old. Damage from regular flooding over the years has prompted questions over its future, according to the Blue Earth County website.

“The structural integrity of the dam has been in question for a long time,” Minnesota Gov. Tim Walz (D) said Monday.

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