San Francisco Market Report

The massive San Francisco-Oakland Bay Bridge project is the largest undertaking in California history, and consists of three distinct phases: the West Approach, the Skyway and the Self-Anchored Suspension Span.

By David Silva

When trying to describe the $6.6 billion San Francisco-Oakland Bay Bridge seismic retrofit projects, big just doesn’t cut it.

The massive effort – considered the largest in state history -- will not only greatly improve the 3.7-mi bridge’s safety, but will fundamentally alter one of America’s most-traveled pieces of infrastructure in function and appearance.

The Bay Bridge is actually a series of bridges and transition complexes. A 1-mi portion of Interstate 80 called the West Approach leads to twin double-deck suspension spans (the West Span), reaching 9,260 ft from San Francisco to Yerba Buena Island in the middle of San Francisco Bay.

The Yerba Buena Island Transitions, a short viaduct-and-tunnel complex on the island, connects to a double-deck cantilever span and smaller truss bridges – collectively called the East Span – that reach 10,176 ft to the entrance and exit ways known as the Oakland Approach.

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Along with a complete facelift and seismic retrofitting of the West Approach, West Span, YBIT and the Oakland Approach, plans call for the eastern stretch to be demolished and replaced with a 1,263-ft-long Self-Anchored Suspension Span connecting to a 1.2-mi Skyway.

Both the SAS and Skyway will consist of parallel east- and westbound decks, each five lanes wide and featuring a 15-ft-wide, cantilevered bicycle and pedestrian path on the eastbound side.

Caltrans awarded the $1.4 billion SAS construction contract to a joint venture of American Bridge Inc. of Coroapolis, Pa., and Fluor Enterprises of Aliso Viejo, Calif. 

“Most bridge projects we’re involved in are such that the biggest pieces weigh 100 to 150 metric tons,” says Michael Flowers, American Bridge executive vice president. “On this project, we have many pieces over 1,000 metric tons. It takes a special piece of equipment to handle that.”

The required piece of equipment was so special, in fact, that American Bridge had it custom-built and shipped in from China. The massive crane, featuring a 328-ft-long boom and capable of lifting 1,700 metric tons, recently arrived at the project site via a barge – itself custom-built – the length and width of a football field.

The transformation of the Bay Bridge has, in a sense, been underway since Oct. 17, 1989, when the 7.1-magnitude Loma Prieta Earthquake caused a 50-ft section of the structure to collapse, killing one person. While the damage was quickly repaired, state officials realized major renovations were needed to ensure the bridge could withstand another major temblor.

Several of the renovation projects have already been completed, including the seismic retrofitting of the West Span in 2004. The span, consisting of twin double-deck suspension bridges, was reinforced with new steel plates and braces, and its original rivets were replaced with twice as many high-strength bolts. Massive rollers were installed under the bridges and 96 “viscous dampers” were installed to help absorb the force of seismic events. 

Contractor Tutor-Saliba Corp. of Sylmar in June completed the seismic retrofit of the network bridge entrance and exit points known as the West Approach. The $429 million project, which began in 2003, was “one of the most difficult in the history of Caltrans,” says Caltrans spokesman Bart Ney.

“It required the department to demolish 1 mi of freeway and seven on- and  off-ramps and completely replace them in the footprint of the original structures, all while working within inches of existing  structures, businesses and homes and while keeping the bridge open to  traffic,” Ney says. 

Workers completed the Skyway in January after more than six years of steady labor. Built by the joint venture Kiewit-FCI-Manson of Oakland and designed by T.Y Lin of San Francisco and Moffat & Nichol of Long Beach, the $1.2 billion Skyway comprises 452 precast concrete segments fabricated in Stockton.

T.Y. Lin project manager Sajid Abbas says about half the cost of the project went into the Skyway’s unique marine foundation, which included 160 hollow steel-pipe piles battered at an angle 300 ft into the mud by massive hydraulic hammers. The system provides the Skyway with greater stability in the event of an earthquake, a  critical need given the bridge’s close proximity to two major faults.

T.Y. Lin also designed the East Tie-In, a massive temporary structure that will help connect the Yerba Buena Island Transitions to the SAS roadways. To keep the Bay Bridge open to traffic during construction, Caltrans called for the new East Span to be built directly to the north of the existing structure.

When the SAS reaches Yerba Buena, workers will shut down traffic in both directions and, over a single long weekend, push the old bridge out of the way and push the new one into position.

“We built 150-ft-tall, false-work towers underneath one of the four trusses that hold up the bridge segments,” Abbas says. “On top of the towers, we put skid beams holding jacks that engage the bottoms of the truss. The jacks will basically push the truss upward, and then horizontal jacks will push them sideways and set them down on skid beams, which, again, are 150 ft in the air.

“As soon as the old truss is out of the way, the new truss is pushed in until it reaches its proper position. Everything has to go right. We cannot afford to make mistakes, because all these operations happen over one long weekend.”

Abbas says Caltrans has not yet set a date for the bypass other than it wants it to happen this year.