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.
Blue Earth County bridge demolished after damage from flooding of nearby Rapidan Dam
It may be years before the County Road 9 bridge gets replaced.
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.
The Blue Earth County Board voted in August to replace the bridge. Funding for the $1.16 million demolition comes from a Federal Highway Administration emergency grant.
It could be years before the new bridge is completed, Thilges said.
The nearby Rapidan Dam is also being removed. In August, the County Board voted to remove the dam rather than fix or replace it. They argued it would cost far more to keep the dam than remove it. Removal of the Rapidan Dam could cost from $59 million to $75 million, according to an estimate by Barr Engineering in August.
Engineers plan to start removal of the Rapidan Dam in 2027, in a process that would continue through 2028, according to a preliminary schedule from Barr Engineering.
It may be years before the County Road 9 bridge gets replaced.