Photo courtesy of Caltrans
The new five-span box girder bridge will be more than 600 ft. (183 m) longer than the current Antlers Bridge.
The California Department of Transportation (Caltrans), along with the Federal Highway Administration has awarded a contract for the Antlers Bridge Replacement Project to Tutor Perini of Sylmar, Calif., for $125 million, 43 percent below the engineer’s estimate. Construction on the 6 year project began mid-October 2009. The project is financed with federal and state transportation dollars through the State Highway Operation and Protection Program.
This project replaces Antlers Bridge on Interstate 5 in Shasta County over the Sacramento River arm of Shasta Lake near the community of Lakehead. The new structure is a 1,942-ft. (592 m) long, 104-ft. (31.7 m) wide, five-span cast in place reinforced concrete segmental box girder bridge. It is being constructed on a new parallel alignment slightly east of the existing bridge. In addition, a 0.4 mi. (.6 km) long section of highway south of the bridge is undergoing a realignment and the existing 1,330-ft. (405 m) long structure will be demolished and removed.
Shasta Dam was built over a 10-year period, from 1935 to 1945 and its outflow provides electricity and irrigation to areas of California below the dam. It also serves as flood control for the Sacramento River during the rainy season. Shasta Lake was formed in 1948 and is presently a popular spot for fishing, water skiing and houseboating. It is currently the largest man-made reservoir in California.
The existing bridge is a spandrel braced cantilever deck truss bridge built in 1941 and rehabilitated in 1967. Under FHWA National Bridge Inventory Standards, the bridge is presently designated “fracture critical” and operationally non-compliant.
“This is a main route for travel between the West Coast ports, from Portland, Ore., down to Los Angeles,” said Eric Akana, project manager of Caltrans. “Nearly 30 percent of the traffic is truck traffic and the ADT has been steadily increasing,” he added.
Tutor Perini Corporation, who is self-performing the substructure and superstructure work on Antlers Bridge, has worked on a number of high profile projects in California. Among these are the Alameda Corridor, the San Francisco Bay Bridge and the Los Angeles International Airport runway and taxiway improvements.
Tutor has enlisted the help of several subcontractors, including Force Drilling, a division of Shaft Drilling of West Virginia for foundation work, and Schwager Davis Construction, based in San Jose, Calif., for post-tension and prestressing. Harris-Salinas Rebar of Livermore, Calif., is supplying the iron and rebar, as well as performing the installations. Cleveland Wrecking Company, headquartered in Covina, Calif., will demolish the existing bridge when the new bridge is complete and open to traffic.
Working around Shasta Lake has posed a unique set of challenges to the contractors; most notably, the fluctuating lake levels. With the water vacillating 80 to 100 feet annually, crews have had to find alternatives for typical in-water tasks, like pile driving. Caltrans presented a site specific contractor outreach presentation and tour prior to bidding so contractors could view and better understand the challenges. Comprehensive pre-bid foundation drilling investigations and information sharing efforts also proved beneficial in planning the project.
The bridge requires 38,000 cu. yds. (29,055 cu m) of concrete and 6,550 tons (5,941 t) of steel. Crews have balanced approximately 261,590 cu. yds. (200,000 cu m) of earth on the job.
During the construction period, there has been some inconvenience to traffic and recreational activities, such as freeway traffic detours and restrictions to certain areas near the construction zone. However, Antlers Boat Ramp will remain open and lake access through the construction zone will be maintained.
The project is situated within a National Forest Boundary with a significant amount of archaeological resources and biological resources including bald eagles, ospreys, fisheries, parks, camping and recreation. Significant stakeholders include interregional traffic and trucking, the National Forest Service, Bureau of Reclamation, Army Corps, Fish and Game, Water Quality Control Board and Marina Operators.
In order to protect the wildlife in and around Shasta Lake, crews are complying with noise and building restrictions during certain months for nesting periods.
Despite the challenges, Caltrans anticipates that the project will be complete by the contract date of 2015.
For more information, visit www.dot.ca.gov/dist2/projects/antlers.htm.