Floods Cause Rapidan Dam to Break, Wreak Massive Damage

The recent flooding of the Blue Earth River has put the Rapidan Dam in southern Minnesota in an “imminent failure condition.” The dam was in a “state of disrepair,” according to an assessment done in 2021.

According to Blue Earth County, they were first informed of the accumulation of debris near the dam on June 23rd. The dam was reportedly under constant surveillance by officials from the sheriff’s office, Blue Earth County Public Works, and the emergency management organization, as stated in their Facebook post.

The warning follows devastating flooding that occurred over the weekend throughout the Midwest, killing one person in South Dakota and forcing rescue operations in other states.

Residents are told to keep an eye on developments and be ready to evacuate if necessary if they live in low-lying parts of the Minnesota River Valley.

The county owns the dam, which has been operational since 1910 and can produce 6 million watts of hydropower.

According to FEMA, overtopping caused by floods and structural collapse are two reasons dams might burst. Consistent floods and the impact of time have taken their toll on the dam, according to the 2021 Blue Earth County assessment. The options were to fix the dam or eliminate it. As the county pointed out, both solutions come with hefty price tags.

Officials were notified by dam operators at around 10 AM. According to Monday’s report from the National Weather Service, the river had thoroughly undermined the soil around the dam on the south side of Mankato.

Debris now includes bits of Xcel Energy and other county structures.

Xcel has been bolstering several downstream buildings with sandbags and barricades, according to the company, in case the dam collapses and water reaches the substations.

Last week, parts of the region experienced a month’s worth of rain in 48 hours, with Sioux Falls, South Dakota, receiving 6 inches of rain. The National Weather Service predicted the Minnesota River at Mankato would crest just below the major flood state on Tuesday morning.