The ruins of the Rapidan Dam remain along the Blue Earth River months after a flood compromised the dam and the Highway 9 bridge in the background in 2024.
Jackson Forderer for MPR News

Blue Earth County took another step forward in its efforts to remove what’s left of the historic Rapidan Dam, which failed and was seriously damaged by severe flooding of the Blue Earth River in June of 2024.

An environmental assessment released by the Federal Energy Regulatory Commission, which had been overseeing the use of the dam because it previously had been a hydro-electric dam, found that “removal would have a long-term beneficial effect on environmental resources by removing a now-obsolete structure, restoring the project embankments and reestablishing the river channel.”

Raging flood waters breached the Rapidan Dam and carved a path around it on June 24, 2024 after days of torrential rain storms. The flooding also damaged the nearby County Road 9 bridge, which had been closed ever since and still needs to be replaced.

The waters of the Blue Earth River head downstream at a tremendous speed on Monday evening, southwest of Mankato in 2024.
Jackson Forderer for MPR News

The Rapidan Dam was built in 1910 to provide electricity to the region, which it did until 2019, but the dam was considered to be in poor condition long before it failed two summers ago.

Even though some area residents had hoped the dam would be rebuilt, the Blue Earth County Board voted to remove the historic dam later in the summer of 2024.

The environmental review process is moving forward, said Ryan Thilges, the public works director for Blue Earth Country. But he says it’s been a lengthy and complex process to navigate through, involving multiple federal and state agencies, including the Minnesota Department of Natural Resources, the Federal Emergency Management Agency and the Federal Energy Regulatory Commission, or FERC.

Thilges told MPR News that figuring out the scope of the dam removal project was the most challenging part.

“It’s taken us quite a bit of time just to understand what the roles of all these different agencies were and how they were involved in this, and how does the process flow and work because of all the crossover,” Thilges said. “Now we’re to the point where we can start developing those permits, finalizing the project plans. It’s a good feeling.”

This long-exposure drone photo provided by AW Aerial shows a home as it teeters before partially collapsing into the Blue Earth River at the Rapidan Dam in 2024.
Andrew Weinzierl | AW Aerial via AP

There were concerns about the impacts the dam removal project would have on water quality as well as wildlife habitats. But FERC found that Blue Earth County has mitigation plans for limiting stillwater and stormwater pollution, as well as working closely with the DNR to ensure that there’s minimal impacts to wildlife throughout the project.

“Project removal and restoration of the area would have an overall permanent beneficial effect on aquatic resources,” the report reads, “by returning the project reach to a free-flowing river which would allow unrestricted movement of aquatic resources through the project area.”

The Rapidan Dam removal project has faced several delays and obtaining relief funding from FEMA continues to be a challenge, Thilges said. The next steps for Blue Earth County will be applying for the federal and state environmental permits necessary to remove the dam and return the river channel to a free-flowing state.

“We’re going to be advancing project design plans from 60 percent complete to 100 percent complete, with the intent of hopefully being in an advantageous enough position to advertise and award a contract for the removal in early 2027,” Thilges said. “But again, that’s all so dependent on those federal regulatory agencies.”

The County Road 9 bridge was unsalvageable and Thilges said demolition work started in late 2024 and wrapped in early summer 2025.

He said there’s good progress on that ongoing project, as the county has now received bids for the construction work Thilges said the hope is that construction will begin later this fall, and he hopes the new bridge will open to the public sometime in fall or winter 2028.

A construction worker uses a large jackhammer to chip away at concrete and rebar on the Highway 9 bridge that spans the Blue Earth River near the Rapidan Dam in 2025.
Jackson Forderer for MPR News

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Federal report finds Rapidan Dam removal will have beneficial effects on Blue Earth River