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Rapidan Dam in MN Faces Imminent Failure Amid Severe Flooding

The Rapidan Dam in southern Minnesota is in a critical state following severe flooding from the Blue Earth River. Local authorities have issued warnings about the dam’s “imminent failure condition” as heavy rains and debris accumulation continue to strain the structure.

The Blue Earth County Sheriff’s Office first reported the precarious state of the 114-year-old dam on Monday. Since then, the situation has escalated with the river cutting around the dam’s west side, resulting in a partial failure of the west abutment. Despite these challenges, the dam remains intact as of the latest updates.

Authorities have been closely monitoring the situation since Sunday when reports of accumulated debris began pouring in. By Monday morning, the sheriff’s office announced that the dam had suffered a partial breach. This diversion of river flow around the west side has significantly increased erosion, placing nearby properties at risk, particularly a home directly on the riverbank, which is now in imminent danger of collapse.

Xcel Energy, which manages a substation at the dam, reported that their facility was washed away early Monday, leading to power outages for approximately 600 customers. Efforts are underway to deploy a mobile unit and restore power to affected areas.

As a precaution, the Blue Earth County Sheriff’s Office has activated the Rapidan Dam Emergency Action Plan. This plan involves notifying potentially affected residents, relevant regulatory agencies, and local authorities. However, there are currently no plans for mass evacuations. Residents in immediate danger have been directly notified.

Governor Tim Walz and state emergency officials are actively engaged in the response, emphasizing the safety of residents, protection of property, and public infrastructure. The governor highlighted the unprecedented rainfall—up to 18 inches over the past few weeks—that has saturated the ground, leading to uncontrollable water levels.

The flooding has prompted the Minnesota Department of Transportation (MnDOT) to announce road closures, including Highway 169 from north of Mankato to south of St. Peter, with traffic detoured to alternative routes. MnDOT crews are also installing a worm dike near Le Sueur to mitigate further flooding impacts.

In addition to road closures, the county is monitoring bridges on County Road 33 and County Road 90 for debris and potential structural impacts. Any necessary closures will be communicated promptly to ensure public safety.

The Rapidan Dam, constructed in 1910, has endured repeated flooding over the decades, causing significant structural damage. A 2021 assessment concluded that the dam either needs extensive repairs or complete replacement, both costly endeavors. Repairing the dam is estimated to take four years, while constructing a new dam could span a decade.

In light of the current situation, Blue Earth County had already begun the process of releasing its licensure exemption under the Federal Energy Regulatory Commission, potentially transferring control of the dam to the Minnesota Department of Natural Resources.

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