Steamboat Springs Motorists headed to Clark and Steamboat Lake State Park on Routt County Road 129 this summer will have to endure delays for a period of six weeks or more. Traffic on a short section of the road will be reduced to one lane while repairs are made to a bridge over Mad Creek.
County Road and Bridge Supervisor Paul Draper said the bridge, about 8 miles northwest of Steamboat Springs, is not in imminent danger of collapse. However, he is concerned enough that he has posted a weight restriction on the bridge. It requires operators of heavily loaded trucks to get a permit from the county to use the bridge.
"From a public-safety standpoint, I had to do something in there," Draper said.
The road sees an average of 2,200 daily vehicle trips.
The affected portion of the road will be reduced to one-way traffic around the clock while repairs are underway. There is an alternative route via Routt County Roads 44 and 52E. However, those unpaved roads will not be signed as a detour because they were not designed to sustain heavy traffic, Draper said.
Repair work will begin sometime after July 4, when stream levels in the creek have reached seasonal lows, Draper said. He intends to use a system of automated stop-and-go lights on a timing system to alternate between north- and southbound traffic through a single lane on the bridge.
The damage to the bridge is confined to one of seven concrete-encased box girders that support the bridge. The damaged girder is on the upstream side of the bridge. That means the traffic lane on the downstream side will be unaffected while repairs are made.
Drivers of trucks with loads of 21 tons or more are being asked to contact Draper's office for a permit.
Those trucks can still use the bridge until repairs are made, but drivers are being directed to cross the bridge on the downstream side at no more than 10 mph. The low speed limit ensures the load won't bounce excessively, the impact of which can damage the bridge, Draper said.
A trucking firm hauling charred logs out of the area of last year's forest fires is under permit, Draper said. The arrangement has worked well because the trucks are only loaded while southbound and naturally driving on the downstream side of the bridge.
The girders were installed in the 1970s, Draper said. The concrete itself is only there to protect tensioned steel cables that form the structural part of the girder. Some of the concrete has cracked and fallen away from a single girder, exposing the cables to minor corrosion.
"All of the other girders are fine," Draper said.
He tentatively expects the complicated repair to cost about $100,000. The county has issued a request for proposals from engineering firms to design the repair. It is complex, because the seven girders are interconnected by tie rods.
Draper said he wants to retain an engineering firm with experience on similar repairs to ensure removal and replacement of the single girder won't have implications for the rest of the bridge.
A state-contracted bridge inspection firm recommended the county simply narrow the roadway on the bridge to avoid driving over the damaged girder. Draper said he ruled that option out because of safety concerns related to Routt County's extreme winter weather and snow-removal operations.