RAPIDAN TOWNSHIP, Minn. – County and state officials gathered at the Rapidan Dam near Mankato on Tuesday to assess a still-closed bridge next to the dam that may be at risk of “partial or full failure” as a result of the dam’s worst flooding in nearly 60 years.
The assessment came during a visit by Gov. Tim Walz to tour the dam, which county officials said last week was at risk of “imminent failure” but remains standing.
Erosion caused by the now-receding floodwaters is threatening the stability of County Road 9 bridge, which is just upstream of the dam, Walz and county officials said. The Blue Earth River last week swelled to the second-strongest flood ever recorded at the dam as the area received some 10 inches of rain in a week.
“The concern is that [the bridge] is going to be structurally damaged here and it will need to be replaced,” Walz said.
The bridge was constructed on top of erodible sandstone bedrock, said Ryan Thilges, county engineer and public works director for Blue Earth County.
“As the river level continues to decrease and cut the riverbed elevation down, we’re very concerned about the potential for partial or full failure of the bridge,” Thilges said at a news conference.
The county launched an emergency operation last week to stabilize one of the bridge’s supports, but because of safety concerns officials were not able to stabilize a second support, he added.
The county closed the bridge eight days ago and is monitoring it, he said.
