The Blue Earth County Board of Supervisors voted Tuesday to demolish the Rapidan Dam and also demolish and replace the nearby bridge.

The project to demolish and replace the County Road 9 bridge could take several years, and detours have been in place since last month because of safety concerns caused by severe flood damage. County officials are also working with the U.S. Army Corps of Engineers to restore the Blue Earth River, while also seeking federal and state funding for the restoration.

The bridge has been closed since June. While this particular bridge does not see high traffic volumes, Commissioner Kip Bruender said during the meeting that it was still important to consider its importance to the region – including farm-to-market trips and the longer commute times for residents while the bridge is closed.

“From what I understand, this road is used a lot for field cultivation and transporting grain to market,” Bruender said. “I think that’s probably the bigger factor here.”

In late June, the Blue Earth River overflowed the Rapidan Dam, eroding and cutting a new riverbed around the western dam abutment. The partial failure of the Rapidan Dam released sediment pollution downstream that had accumulated over a century.

Blue Earth County explored the possibility of making temporary repairs to reopen the bridge, but given the damage to the piers and the washout of the riverbed that was causing further erosion of the river banks, the repairs were deemed financially unfeasible.

The county has access to about $19.5 million from the County State Aid Disaster Account Funds for bridge demolition and replacement. The remainder can then be paid back into the fund when federal funds come in.

The future of Rapidan Dam

During the flood, sediment that had accumulated over a century behind the Rapidan Dam entered the Blue Earth River downstream. Water quality experts and researchers were concerned about the potential environmental impacts of this pollution on the various ecosystems and wildlife.

The U.S. Army Corps of Engineers discussed its ecosystem restoration program and possible dam demolition and river restoration, attempting to restore and protect the Blue Earth River in its current state. At this time, the dam structure was still considered stable.

However, they are concerned about the safety and liability of the dam structure. County Engineer and Director of Public Works Ryan Thilges said it’s only a matter of time before someone is injured or possibly killed if the dam remains, and it will be difficult to keep people away from the dam.

The dam structure could also lead to an unfavourable flow of the river, which would require reinforcement to prevent or at least reduce further deterioration of the river banks. But even then, Thilges said, he is not convinced that these measures would be effective.

“I expect this will be a constant problem on this west dam,” he said. “Trying to protect it is a bottomless pit in the long run.”

Commissioners unanimously approved the dam removal, which includes restoring the river. They will work with the U.S. Army Corps of Engineers to restore the channel after the dam is removed. They mentioned that in the future they will bring together stakeholders to talk about the future of the Blue Earth River and creating recreational opportunities, including kayaking and biking around the Rapidan Dam.