State Highway 20 Feather River Bridge Project
The 2,673 foot-long Feather River Bridge of State Highway 20 (aka the 10th Street Bridge) connects the twin cities of Yuba City in Sutter County and Marysville in Yuba County. The structure, built in 1947, features steel plate girder continuous spans with a reinforced concrete deck sitting atop a total of 23 concrete piers.
Currently, this bridge is experiencing an emergency scour condition at two piers. High water flows have caused 19 feet of erosion under the footings of one the piers. Because of the shifting meander of the Feather River, another pier adjacent to the river is also considered at risk in a high-water event. Engineers have also ordered additional scour protection at three nearby piers.
An emergency contract has been issued to repair the bridge, strengthen these footings and install additional erosion protection. A time and material contract has been issued to Stewart Engineering Inc. of Redding, CA to make these repairs. Final plans and estimates for this work have not yet been completed but costs may exceed $10 million. Major items of work include:
• Construction of a temporary trestle to provide access to the piers
• A temporary coffer dam will be constructed to shield the work site from the river
• Additional piles will be driven and a new seal coarse will be placed to stabilize the mid-river pier.
• Rock Rip Rap will be placed for additional pile cap protection at three nearby piers
All work is scheduled to be completed by December.
An artist’s depiction shows what lies beneath the waters of State Route 20’s Feather River Bridge. In March, engineers with Caltrans Structures Maintenance and Investigation unit checked a mid-river pier of the bridge and discovered that increased scour from a meandering river had exposed 19 feet of the more than 80 steel piles that support the pier. To strengthen these piers, they will drive ten, four-foot diameter piles 160’ – 185’ feet. These piles will be fitted with steel cages, filled with concrete and then covered with a new seal course to protect these footings. Movement sensors have been placed on this bridge to detect any horizontal or vertical movement. These devices are checked every 10 minutes. If any substantial movement is detected, engineers will be dispatched to inspect the bridge immediately.
Plans depict a temporary trestle that will be constructed to provide workers to the bridge piers. When it is complete temporary coffer dams will be constructed and pile drivers will drill and place new plies to protect the two scour – critical piers in the Feather River.