MINNEAPOLIS (AP) — The rushing waters of the Blue Earth River have already left a trail of debris and destruction along the edges of a dam in southern Minnesota that partially breached last week. But officials acknowledged Tuesday that the structure most at risk is the bridge looming nearby.
The County Road 9 Bridge is in danger of crumbling, and officials said they have little recourse. The threat to the bridge increased after a period of heavy rains and flooding battered the Midwest for days. Water levels in the Blue Earth River rose dramatically, testing the dam’s structural integrity. The dam held, but the specter of collapse has not abated.
The approximately 40-year-old bridge that locals use to travel from the countryside to nearby towns over the dam could collapse if the weather does not cooperate.
“Unfortunately, we are at the mercy of Mother Nature at this point,” said Ryan Thilges, public works director for Blue Earth County. “We are very concerned about the possibility of partial or complete collapse of the bridge.”
Thilges stood on a hill on the east side of the Rapidan Dam near the city of Mankato, Minnesota. He was flanked by Minnesota Gov. Tim Walz and other officials who were headed to the dam to get an update on flood conditions and recovery efforts.
Officials are keeping a close eye on both the dam and the bridge, and they see that the still-raging river has drastically changed the area.
“I think the concern is, will the bridge be structurally damaged by this and will it need to be replaced?” Walz said.
The floodwaters have created a new riverbed around the dam, which has cut deep into a steep riverbank, toppling power poles, destroying a substation, swallowing a home and removing a beloved store. Conditions have made it too dangerous for officials to get close enough to thoroughly inspect the bridge, but they have already identified troubling signs of damage.
The river is washing away large amounts of sediment, causing instability at the bridge’s support piers, which are built on sandstone bedrock. Officials have been able to stabilize at least one pier, but said they have not been able to reach the others.
Complicating matters further was “a huge log that came down the river Sunday,” Thilges said. The dead trees, a product of the past few years’ drought, crashed into the bridge and some are hanging from the piers. The county has been unable to find contractors who feel safe enough to remove the debris.
“Nobody was willing to send their operator out there and risk their operator’s life to try to push those trees through the trees,” Thilges said.
Flooding has caused millions of dollars in damage to bridges, homes and roads in Minnesota, Iowa, Nebraska and South Dakota. The dam drew attention after officials initially said there was an “imminent threat” of collapse.
The Rapidan Dam is more than a century old, having been completed in 1910. Although the dam was built to generate electricity, it has been damaged by several floods in recent decades. An April 2023 assessment by the National Inventory of Dams found Rapidan to be in poor condition, and officials have been exploring the possibility of removing the dam.
A federal disaster declaration has been approved for Blue Earth County, and local officials said the additional funds will be crucial for rebuilding. But those projects could be complicated by a sensitive landscape where emergency aid can sometimes exacerbate deterioration, Thilges said.
“I’ll be honest, every solution we came up with had almost as bad or worse negative consequences that could have further compromised the stability of the dam, or it could have caused damage to the bridge or additional erosion,” he added. “We need Mother Nature to give us a break.”
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