County officials next month will close a highly used path for pedestrians and bicycles between Oregon City and Gladstone in order to construct seismic retrofits on the 82nd Drive bridge.
Last week Clackamas County commissioners approved a $2.68 million contract with Stellar J Corporation to build new structural supports designed to increase the bridge's load capacity. County officials say that the seismic upgrades will make the bridge able to withstand a magnitude 9.0 earthquake, which means the bridge would be able to serve as a "vital path for emergency vehicles" to cross the river in such an emergency.
After the construction of Interstate 205 in the mid-1970s, the bridge was converted for use by pedestrians and bicyclists. This bridge now supports 12- and 20-inch-diameter sewer lines, a gas line and a link of the Clackamas Broadband Express fiber-optic communications system.
"The north approach to the bridge is supported by wooden timbers that are no longer structurally sound," wrote Greg Geist, director of the county's Water Environment Services department to commissioners. "The 82nd Drive Pipe-Pedestrian Bridge is owned by WES and is a vital piece of infrastructure that supports multiple sanitary sewer force mains across the Clackamas River."
Signs are being posted closing the bridge in both directions and directing pedestrians and bicyclists to a detour route. The closure is expected through February 2020, during which time the detour will add approximately 2 miles to trips for people, compared to walking and biking across the Clackamas River bridge. The detour to McLoughlin Boulevard will force pedestrians and bicyclists across the narrow sidewalks of the Highway 99E bridge and along Oregon City's Main Street and Gladstone's Arlington Street.
Built in the early 1920s, the bridge was purchased by WES in 1998 to hold the two lines that carry sewage to the Oregon City treatment plant from the sewage plant in Milwaukie that had been overwhelmed by population growth in the Happy Valley area. In 2012, during the construction of the second sewage line, resistograph testing found the bridge's north-approach timber supports to be in unsafe condition.
In 2012, the bridge was closed to pedestrian traffic until a timber reinforcement design was completed. County officials say that the design constructed seven years ago was only designed as a temporary fix for the timber supports with a five-year life expectancy.
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