Bay Bridge

Overview of East Span Replacement Project

The Bay Bridge opened to traffic on November 12, 1936.
© 1999 Barrie Rokeach (click image to enlarge)

After the Loma Prieta earthquake in October 1989 heavily damaged the eastern span of the San Francisco-Oakland Bay Bridge (a portion of the upper deck collapsed onto the lower deck, killing one person and knocking the entire bridge out of commission for a month), Caltrans launched an intensive analysis to determine whether the structure, built in 1936, could withstand the major earthquake anticipated to occur on the San Andreas or Hayward faults sometime in the next 30 years.

Caltrans engineers and world-renowned seismic experts concluded that the sturdy west-side suspension span between San Francisco and Yerba Buena Island could be strengthened to meet current seismic safety codes. But, after extensive studies, they determined in 1996 that the east-side span between Yerba Buena Island and Oakland is far more vulnerable to a major quake and in the long run, it would be safer and more cost effective to build a new span rather than retrofit the existing one.

At this juncture, MTC stepped in at the request of then-Senate President Bill Lockyer, creating the Bay Bridge Design Task Force in early 1997 to review policy and design issues and foster public involvement in decisions on a new eastern span. MTC also assembled an Engineering Design and Advisory Panel (EDAP) to provide technical expertise.

The opportunity to create a new gateway to the East Bay by replacing the eastern span of the Bay Bridge captured the public's imagination and sparked lively interest from the engineering and design community. Caltrans initially proposed several designs, ranging from a basic "skyway" to more ambitious and expensive cable-supported designs, and a dozen more concepts were submitted by firms and individuals. Through public testimony at some 23 Task Force and EDAP meetings, plus media editorials and thousands of letters, phone calls and e-mail sent to MTC, it became clear that the Bay Area wanted a landmark, signature bridge.

In June 1997, MTC adopted a series of recommendations to guide the design process. Key among these were directives to build the new span north of the existing bridge, and to develop two potential bridge design types--a cable-stayed and a self-anchored suspension design--for the main span across the deep-water shipping channel adjacent to Yerba Buena Island. Because of the geology of the eastern side of the Bay--shallow water underlaid by deep layers of mud--and the bridge's proximity to two earthquake faultlines, all of the designs considered for the main span, by necessity, link to twin viaducts that cross to the Oakland shore.

In late 1997, Caltrans selected the joint-venture team of T.Y. Lin International/Moffat & Nichol Engineers to develop the two main-span bridge types to the 30 percent stage in order to provide more information. Since both the cable-stayed and suspension designs could be built with single or double towers, there were actually four choices for design of the main span. Caltrans and MTC compared and evaluated vital issues of seismic safety, cost, construction materials and aesthetics for the four designs, as well as the possible location of a bicycle/pedestrian path on the span.

In July 1998, MTC, in its role as the Bay Area Toll Authority (BATA), voted for the single-tower suspension design for the main span and endorsed a 15.5-foot wide bicycle/pedestrian path on the south side of the eastbound deck. Significantly, the graceful suspension design complements the other suspension bridges on the Bay: the Golden Gate Bridge, the west span of the Bay Bridge and the new Carquinez Bridge.

East Span Funding
Pursuant to state Senate Bill 60 (Kopp), a $1 dollar surcharge was added to Bay Area bridge tolls in January of 1998, with eight years of proceeds required to pay the region's share of the entire toll bridge seismic retrofit program, including the replacement for the east span of the Bay Bridge. Under the Kopp bill, MTC had the option of extending that surcharge for two additional years to pay for an array of amenities that could go hand in hand with the new east span: a cable-supported structure for the Yerba Buena Island side of the east span, a bicycle/pedestrian path for the new east span, and rebuilding/relocating San Francisco's Transbay Transit Terminal.

In conjunction with selecting a design for the new east span in June 1998, MTC/BATA also approved extending the seismic retrofit toll surcharge by approximately 15 months to generate the estimated $141 million needed to pay for the amenities to the new east span -- $91 million, or 9.5 months of surcharge proceeds, for the incremental cost for including a self-anchored suspension component, and $50 million, or 5.2 months of surcharge proceeds, for the bicycle/pedestrian path. Estimated costs for the amenities were provided by Caltrans. Subsequent legislation has identified another possible use for the surcharge extension: providing bike access to the bridge's existing west span.

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