A bridge near a dam in Minnesota is on the verge of collapsing into the Blue Earth River due to heavy rains and flooding.
The nearly 40-year-old County Road 9 bridge near Mankato, Minnesota, is at risk of collapse if the weather doesn’t improve enough to allow for proper structural reinforcement work.
Heavy rains and flooding have battered the Midwest for days, causing water levels to rise sharply on the Blue Earth River and putting the structural integrity of Rapidan Dam to the test.
Minnesota dam partially fails, part of house falls into raging water, video shows
On the left is the County Road 9 bridge, and on the right is the Rapidan Dam. Officials say the bridge is in danger of collapsing. (Michael Goldberg/AP)
The dam has already partially failed, causing homes along the Blue Earth River near the dam to fall into the river and destroying a nearby dam warehouse. Rapidan Dam is located about 14 miles south of Mankato in southern Minnesota.
“Unfortunately, at this point we’re at the mercy of nature,” Blue Earth County Public Works Director Ryan Silges told reporters Tuesday, as he was joined by Minnesota Gov. Tim Walz and other officials who visited the dam to hear updates on the flood situation and recovery efforts.
Tilges said the piers were built on piles of sediment and set on sandstone bedrock, not driven into the bedrock, and that gushing water could wash away some of the sediment, putting the stability of the bridge at risk.
“All of the lateral stability of the piles was achieved by the sediments that were stored in the river basin during the life of the dam,” Tilges said.
“The river’s headwaters have been dramatically reduced, causing river levels to fall and losing stability as large volumes of sediment are washed away.”
He said the water was flowing too fast to measure sediment in the river or on the jetty, which local residents use to commute from their rural properties across the dam to nearby towns.
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Floodwaters flow around Rapidan Dam near Mankato, Minnesota, on June 27, 2024. (Mark VanCleave/The Associated Press)
“We currently believe approximately 50 percent of the bridge is exposed, and as the river levels continue to fall and the riverbed level drops, we are very concerned that the bridge could collapse partially or completely,” Tilges said. “With that being said, the bridge has been closed since the dam began overtopping Monday morning and will remain closed in the interest of public safety.”
Officials say they began reinforcing the west pier of the County Road 9 bridge with riprap last week as an emergency mitigation measure to prevent further exposure of the pier’s base. The riprap remains in place and the bridge remains closed as officials continue to monitor its stability.
Waltz said he was concerned the bridge would collapse and have to be replaced, but he assured locals that if the worst were to happen, the bridge would be replaced.
“One thing Minnesotans should be reassured about is that we can rebuild. The costs will be shared among all of us,” Walz said, “so the burden won’t fall on the shoulders of county commissioners.”
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Minnesota Governor Tim Walz (left) speaks with Blue Earth County Public Works Director Ryan Silges. (Michael Goldberg/AP)
Last week, the Governor’s Office announced that the Federal Emergency Management Agency (FEMA) has approved a federal disaster declaration for 22 Minnesota counties affected by flooding. State funds provided by the Minnesota Legislature will also be made available to assist communities. Fox 9 reports.
of The dam partially collapsed After heavy rains last week, water did not flow through the dam’s gates but instead flowed around the west side of the structure.
Construction of Rapidan Dam was completed in 1910. It was built to generate electricity, but has been damaged by several floods in recent decades. An assessment conducted by the National Dam Inventory in April 2023 found Rapidan Dam to be in poor condition, leading officials to consider possible removal.
The Associated Press contributed to this report.
