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A southern Minnesota dam and a nearby bridge that nearly collapsed last month after heavy rains prompted the declaration of a federal emergency will be demolished, officials said Tuesday.
The Blue Earth County Board of Commissioners has voted to demolish the Rapidan Dam near the city of Mankato, about 80 miles south of Minneapolis, and replace the County Road 9 Bridge because both were in danger of collapsing. Officials have begun a reconstruction process that will likely take years because the structural integrity of the dam and bridge remains uncertain.
The Blue Earth River’s water levels rose dramatically in late June and early July after days of heavy rains lashed the Midwest. The structures eventually held, but the floodwaters carved a new riverbed around the dam and cut deep into a steep river bank. Power poles fell, a substation was destroyed, a home was swallowed up, and a popular business had to be demolished.
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With fear of a future bridge collapse still in the minds of concerned local residents, officials said they must act in the name of public safety. However, they are concerned about the impact of the bridge closure on local farmers, one of the rural area’s main economic drivers.
“We know this is a rural community and they use (the bridge) to get their goods from farm to market. We also know the fall harvest is coming up and it’s going to be inconvenient,” said Jessica Anderson, a Blue Earth County spokeswoman. “But safety has been our priority from the beginning. And we can’t afford to put it at risk.”
Floodwaters carve a channel around the Rapidan Dam near Mankato, Minnesota, on June 27, 2024.
(AP Photo/Mark Vancleave, File)
Blue Earth County Commissioner Vance Stuehrenberg said farmers may have to drive more than 45 minutes around the bridge to reach their fields.
The river water has washed away large amounts of sediment and made the bridge’s support pillars, which are built on sandstone cliffs, unstable. The timeline for reconstruction is unclear, but Anderson said it will take “years, not months.”
How much reconstruction will cost was also unclear Tuesday. Studies commissioned by the county in 2021 found that repairing the dam would cost $15 million and demolishing it would cost $82 million. But Anderson said environmental conditions have changed since then.
The next step will be securing funding for the repairs, which could come from both state and federal sources. The county is currently working with federal agencies such as the Federal Emergency Management Agency and the Federal Energy Regulatory Commission to develop a plan, Anderson said.
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A federal disaster has been declared for Blue Earth County, and local officials said the additional funds are critical to rebuilding efforts. But those projects could be complicated by the sensitive landscape, where relief efforts can sometimes make deterioration worse, officials warned.
Stuehrenberg is also concerned about the impact the closure will have on recreational opportunities near the dam, which is a popular area for bicyclists. Minnesota Governor and Democratic vice presidential candidate Tim Walz, who visited the dam in July, is one of those who used to ride his bike on a nearby trail.
The Rapidan Dam is over a century old, having been completed in 1910. Although it was built to generate electricity, it has been damaged by several floods in recent decades. The dam has not generated electricity since previous floods dried up this small source of income.
There are about 90,000 major dams in the United States. At least 4,000 of them are in poor or unsatisfactory condition and could cause loss of life and environmental damage if they fail, according to data from the U.S. Army Corps of Engineers. They need to be inspected, upgraded and even emergency repaired.
