In southern Minnesota, the Blue Earth River’s rushing waters have already left significant damage and debris at the edges of a dam that partially failed last week. Officials revealed on Tuesday that the structure most at risk might be the nearby County Road 9 Bridge.
The bridge, which is vital for local commuters, is in danger of collapsing. The risk escalated after heavy rain and flooding inundated the Midwest for days, causing the Blue Earth River’s water levels to rise significantly and stress the dam’s structural integrity. Although the dam has not collapsed, its stability remains uncertain.
Ryan Thilges, Blue Earth County’s public works director, expressed grave concerns about the bridge’s potential failure. “Unfortunately, we’re at the mercy of Mother Nature at this point,” he said. “We’re very concerned about the potential for partial or full failure of the bridge.”
Thilges was joined by Minnesota Governor Tim Walz and other officials on a hillside near the Rapidan Dam, close to Mankato, to assess flood conditions and recovery efforts.
The flooding has dramatically altered the area around the dam and the bridge, forging a new river channel and causing significant damage. The floodwaters have undermined the riverbank, toppling utility poles, damaging a substation, swallowing a home, and leading to the removal of a cherished local store. The hazardous conditions have prevented officials from conducting a thorough inspection of the bridge, though signs of damage are evident.
Large amounts of sediment have been washed away, destabilizing the bridge’s supporting piers, which are built on sandstone bedrock. While officials have managed to stabilize one pier, they have been unable to reach the others.
Adding to the complexity, a surge of dead trees, which were carried down the river on Sunday, collided with the bridge. The trees, casualties of recent droughts, have lodged against the bridge’s piers, and contractors have deemed it too dangerous to remove the debris.
Flooding has inflicted millions of dollars in damage to infrastructure across Minnesota, Iowa, Nebraska, and South Dakota. The Rapidan Dam, completed in 1910, has endured multiple flooding events over the decades. An April 2023 assessment by the National Inventory of Dams rated it in poor condition, prompting officials to consider removing it.
A federal disaster declaration for Blue Earth County has been approved, providing crucial resources for rebuilding. However, Thilges warned that the sensitive landscape could complicate relief efforts, potentially worsening the dam’s instability or causing additional erosion.
“We need Mother Nature to give us a break,” Thilges said, acknowledging the challenging situation.
