Officials with the Missouri Department of Transportation are hopeful approximately $1.3 million in repairs could be complete by mid to late summer for a damaged section of Highway T near Wappapello Dam.
Several hundred feet of road was ripped away by water topping the secondary spillway following flooding that started May 1.
When the overflow stopped this week, pavement, dirt and large concrete pipes had been moved downstream by the force of the water.
"We're going to build back the same design and accelerate construction," said David Wyman, area engineer for the southeast district.
The project is expected to go out for bid by early summer, through an emergency bidding process, Wyman said.
Traffic is being routed along County Road 514 (Butler County) and County Road 517 (Wayne County) until the work is done. The road is also known as old Iron Bridge road. MoDOT has brought in extra gravel to help make the dirt road easier to travel, at the request of the U.S. Army Corps of Engineers.
The decision to use the existing design is based on the limitations of how a bridge structure could be used in coordination with the function of the secondary spillway, according to officials.
A bridge span cannot be placed in front of the 740-foot concrete auxiliary spillway, because it could hamper the operation of the dam, according to the Corps.
Placement of a small bridge in the spillway could impede the ability of water to pass through the secondary spillway, said John Osterhage, levee safety program manager for the St. Louis district.
It could impact the amount of water passing through the outlet area, and make the flow of water and function of the spillway less predictable, he said.
While a typical bridge with multiple spans might cost about $2.2 million, Wyman said, crossing that distance without a center span could raise expenses as high as $40 million.
"It really comes down to cost, the expense of building a bridge in that location is very high," Wyman said.
Actual costs to replace the existing design may be less expensive than current estimates, Wyman added. It will depend, in part, on how far the damage extends.
In addition to the mission section, the remaining road has been undermined. Dirt was cut away leaving behind several feet of pavement with no base support.
Barriers have been placed to prevent the public from accessing areas that could be dangerous, said project manager Cindy Jackson.
The road began breaking up around 7:30 p.m. May 1, less than 12 hours after water began topping the secondary spillway. Flow was less than 11,000 cubic per second. It reached nearly 22,000 cubic feet per second at the height of the overflow.