A bridge near a Minnesota dam may collapse. Officials say they can do little to stop it

MINNEAPOLIS — 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 failed last week, but on Tuesday officials admitted that the bridge looming nearby is most at risk.

The County Road 9 Bridge is in danger of collapsing and officials said they have little recourse. The threat to the bridge increased after an attack by heavy rain and flooding ravaged the Midwest for days. Water levels in the Blue Earth River rose dramatically and tested the structural integrity of the damThe dam held, but the danger of collapse has not gone away.

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’re at the mercy of Mother Nature at this point,” said Ryan Thilges, public works director for Blue Earth County. “We’re very concerned about the potential for 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 whether the bridge will be structurally damaged and need to be replaced?” Walz said.

The floodwaters have created a new riverbed around the dam that has cut deep into a steep riverbank, toppling electricity poles, destroying a power plant, swallowing a house and removal of a beloved storeConditions make it too dangerous for officials to get close enough to thoroughly inspect the bridge, but they have already identified worrying 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 life to push those trees through the trees,” Thilges said.

Flooding has caused millions of dollars in damage to bridges, homes and roads across Minnesota, Iowa, Nebraska, and South DakotaThe 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 extra 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.”