MANKATO, MINN. – The first explosives charge at the bridge rang out like a starting gun, followed by the ratatat drumbeat of smaller explosions. The smoke cleared, revealing the concrete and steel beams of County Road 9 Bridge now resting in the river valley below.
The demolition work on Wednesday felled the middle 500 or so feet of the bridge, which was critically damaged in last year’s flooding at the Rapidan Dam, a few hundred feet downstream.
Engineers sought to demolish the bridge quickly before spring flooding, which could potentially further damage the bridge.
“We want to get everything that’s in the center channel of the river out as quickly as possible prior to any spring flood events,” Ryan Thilges, county engineer and public works director, said at the bridge site on Wednesday.
Water from the second-strongest flood ever recorded at the nearby Rapidan Dam last summer eroded the sandstone bedrock under the bridge.
The flooding made national headlines after causing the dam to partly fail. The west bank of the river flooded over the dam, with erosion pulling in a nearby house and destroying the Rapidan Dam Store, a longtime local business.
The bridge’s piers and outer spans are still intact, and the plan is to remove these parts of the structure without the use of explosives, Thilges said.
A contractor, Hosier Worldwide, began removing the deck of the bridge on Dec. 27, Thilges said. The demolition company, based in Deer River, Minn., built a causeway and plans to divert the flow of the Blue Earth River as they take down the bridge as part of a planned three-month demolition.
