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. 

	A Terex 160-ton crane (at left) is used to wield the D-100 hammer capable of delivering 22,000 lbs of force when driving piles. Photo courtesy of D-3 Graphic Services. James Ta (left), an Associate Materials and Research engineer with the Department of Engineering Services Geotechnical Services and Gary Pelfrey (right) the project’s Structures Representative look on as technicians ready their equipment for a two-million pound load test on two of the bridges 20 new piles.  One of those piles yielded and technicians were unable to verify the compression capacity of the pile.  That pile will be driven deeper with a new hydraulic hammer – capable of driving a pile with 30,000 lbs of force. Photo courtesy of D-3 Graphic Services. Chris Hallstrom, a welder Golden State Bridge, grinds a splicing joint on a bridge pile. Photo courtesy of D-3 Graphic Services. Laser beams are used to detect any pile movement for the two-million pound load test. Photo courtesy of D-3 Graphic Services. A set of four powerful hydraulic jacks will be used to exert pressure on the new bridge piles for an upcoming two million-pound load test. Photo courtesy of D-3 Graphic Services.
Bob Bond, an engineering technician with Caltrans’ Foundation Testing Branch, hooks an electrical lead from displacement meters used to administer a two-million pound load test.  “This test is the best tool we have to measure the capacity of the new piles,” explained the project’s Structure Representative Gary Pelfrey.  Photo courtesy of D-3 Graphic Services.

 

 

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