Deschutes County road crews plan to replace an aging and structurally deficient bridge on Tetherow Road west of Redmond, tapping into more than $2 million in federal transportation funds for the project.
The 40-year-old bridge, about four miles north of Cline Falls State Park , crosses the Deschutes River and marks the spot where settlers arrived in Central Oregon from the Willamette Valley in the 1870s, according to The Bulletin’s archives.
But structural tests in recent years by county and state road officials found water erosion on concrete pads that support the bridge. Its design, low off the ground, has caused Deschutes River water to chip away at the support pads over time.
A recent Oregon Department of Transportation test on the Tetherow Road bridge gave it an engineering sufficiency rating of 32.3 out of a possible 100, a low-enough score to consider it structurally deficient, County Engineer George Kolb said.
While the bridge doesn’t pose an immediate threat to drivers, it needs to be able to support more than its current limit of 16 tons and possibly be widened beyond its current 20-foot width to accommodate truck traffic.
“Eventually, this bridge could deteriorate to the point where we would have to close the structure to all traffic,” George said.
Road department officials briefed county commissioners last week on a plan to remove the bridge and replace it with a new one. The department is working on a design for the new bridge and hopes to finalize the plan sometime next year.
Construction of the new bridge “could start in 2016,” Kolb said, “but these dates are subject to change.”
Commissioners signed off on the bridge replacement last week. The total project cost is $2.67 million, but the county is only on the hook for about $274,000, Kolb said. The rest comes from a federal fund called the Local Bridge Program, which helps cities and counties finance upgrades.
Older bridges around the state face similar structural issues, ODOT spokesman Peter Murphy said. Truck sizes have grown considerably in recent years, putting pressure on local governments to upgrade their infrastructure, he said.
The new Tetherow Road bridge is expected to be structurally sound for 75 years, according to Deschutes County Road Department documents.
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