Rapidan Dam not at risk of failure; future still uncertain

Tim Krohn, The Free Press, Mankato, Minn.
·2 min read

Jan. 8—The Rapidan Dam, which still faces an uncertain future between removal or ongoing repairs, at least isn't about to fall down on its own.

A recent study updated by an independent consultant found no potential for failure of the dam, built in the early 1900s.

"That's good news," Blue Earth County Public Works Director Ryan Thilges said while updating County Commissioners last week.

But the study also found that the dam is no longer suitable to be operated as a hydropower facility.

The hydro facility of the county-owned dam was heavily damaged by flooding in 2019 and hasn't generated power since.

The report "found no indication or evidence with respect to the potential failure modes that the project structures require immediate remedial action."

But the tainter gates are damaged and inoperable.

The county board has long been weighing whether to repair the dam, at a cost of about $15 million, as well as ongoing maintenance costs, or to remove it, which would cost some $82 million and take a decade to deconstruct.

The removal process would also involve re-establishing the river and replacing the County Road 9 bridge south of the dam.

Dam removal would not require continued ongoing maintenance costs to the county and would open the stretch of river up to potential for additional recreational activities in the area.

One of the big costs of removal would be to remove and properly dispose of more than a century of silt that has settled behind the dam.

The latest report said that if any silt is removed upstream of the dam in the future, the county would need to do it in a way that would ensure the dam's stability.

The repair study included what would need to be done to return hydropower as well as do robust repairs for the downstream apron and other issues.

A survey of the public commissioned by the county was released last year.

Overall, 69% of responses were in favor of repairing the dam. Eighteen percent were in favor of removing the dam and 14% said they would support either decision.