State Highway 20 Feather River Bridge Project Update
Despite ever-rising waters due to increased releases from Oroville Dam, Prime Contractor Stewart Engineering has made significant progress on Caltrans’ project to strengthen State Highway 20’s 10th Street Bridge over the Feather River.
Since “in water work” began June 1, a trestle, which serves as a work platform, is nearly complete. A coffer dam has also been constructed alongside one of the bridge’s two piers that are situated in the Feather River.
Next week, workers expect that the first 48” diameter pile will be delivered. Ultimately, ten of these piles will be driven down 160-185’ into the river bed to strengthen the two “in-water” piers. This first pile will be driven with a vibratory hammer attached to one of the two 165 – ton cranes stationed at the work site.
Biologists from both Caltrans and Gallaway Consulting of Chico California are on site to ensure that avoidance and minimization measures that prevent the project from impacting state and federal listed species are in place. Affected species include the Central Valley steelhead, Central Valley spring-run Chinook salmon, and green sturgeon. Caltrans is also monitoring best management practices such as the placement and number of sediment fences to prevent soil from the construction site entering the river. The placement and number of “in water” silt screens which prevent turbid water, associated with sediment disturbance from work, from flowing down river are also being monitored.
An emergency contract for time and materials was awarded April 29 to Stewart Engineering Inc. of Redding, CA to repair the bridge, strengthen its footings and install additional erosion protection. Final plans and estimates for this work have not yet been completed but costs may exceed $10 million. All work is scheduled for completion by December.
Caltrans engineers, utilizing automatic sensors, continue to monitor the bridge’s piers for any horizontal or vertical movement. So far, no significant movement has been detected. In the unlikely event that substantial movement is detected, engineers will be dispatched immediately to inspect the structure and the bridge could be subject to immediate closure.