State Highway 20 Feather River Bridge Project Update
Pile driving continues on Caltrans’ ongoing project to strengthen State Highway 20’s 10th Street Bridge over the Feather River.
In the past several weeks, bridge workers and welders have driven and welded 20 of the 48” diameter piles which will be used to strengthen the bridge’s two piers that are situated in the Feather River.
These piles have been driven as deep as 180 feet into the river bed by a specialized hammer that delivers approximately 22,000 lbs. of force. Despite that considerable pounding, bridge workers have encountered one site with considerable resistance. The solution was a bigger hammer, one capable of 30,000 lbs. of force which is now in use. Pile driving and welding operations will continue for the next few months.
An important project milestone is also approaching. It’s a 2,000,000 lb. load test, which along with a dynamic pile analysis will be used to verify the foundation design. The pile load test will permit time for any adjustment to the design or construction schedule. “This test is the best tool we have to measure the capacity of the new piles,” explained the project’s Resident Engineer Gary Pelfrey. This test will be performed again in late September.
Project biologists continue to monitoring the site on a weekly basis to ensure that the recommended avoidance and minimization measures are being followed to prevent the project from impacting sensitive species. They also continue to monitor the best management practices such as the sediment fences which prevent soil from the construction site entering the river and the “in-water” silt screens which prevent turbid water from flowing downriver.
This work continues as part of an emergency contract awarded April 29 to Stewart Engineering Inc. of Redding, CA to repair the bridge, strengthen its footings and install additional erosion protection. 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.