With the tenth anniversary of the 1989 Loma Prieta earthquake, we are again seeing pictures of the damaged San Francisco-Oakland Bay Bridge. The damage to the Bay Bridge was quickly repaired, and the entire eastern section is scheduled for replacement, but plans for making the region's bridges safer in earthquakes go well beyond the proposed new eastern span. Retrofits, replacements and new spans for the Golden Gate Bridge and five of the seven state-owned bridges in the Bay Area—the Benicia, Carquinez, Richmond-San Rafael, San Mateo and the western span of the Bay Bridge—are also scheduled or underway.
The western span of the Bay Bridge is well into its seismic retrofit, which includes three projects expected to take over six years to complete. The first project, strengthening the columns and footings where the bridge extends over Yerba Buena Island, is close to completion. The second project includes encasing piers in reinforced concrete and installing anchor bolts between the bridge towers and piers on the portion extending over the bay, and should be complete in mid-2000. The third project, which will be most visible to motorists using the bridge, will involve reinforcing the walls of the Yerba Buena tunnel portal and the entire superstructure of the western span. Steel plates will be installed on the towers and "shock absorbers" will be inserted between the roadway and the towers. The retrofit of the western approach to the bridge will be a complex process involving building temporary structures to handle traffic while the replacement structure is built. Ultimately, the bridge should be able to withstand a magnitude 8.0 temblor on the San Andreas fault.
Caltrans decided in February 1997 to pursue replacing the eastern span rather than retrofitting it. The goal was to create a bridge which would withstand a major earthquake on the Hayward Fault and still be usable—a "lifeline" span. The Metropolitan Transportation Commission (MTC) formed the Bay Bridge Design Task Force and its advisory panel to consider engineering and design of the replacement span, to allow public debate and to form a regional consensus.
While there has been much debate, some consensus has also been achieved during the months of task force and advisory panel meetings. As a result, MTC recommended in July 1997 that if additional funding were to be made available by the Legislature, it should go to three "amenities": using a cable-supported main span across the shipping channel, rather than a causeway; renovation or relocation of the Transbay Transit Terminal at the west end of the bridge; and building a bicycle/pedestrian path on the new span.
A preferred design incorporating these amenities was chosen by MTC in 1998. However, during the past year, new controversy has arisen over whether the new span should be built north or south of the existing bridge, and a study of rail service on the bridge was begun in response to action by voters in San Francisco, Oakland, Emeryville and Berkeley.
Meanwhile, in August 1997, legislation was passed and signed to fund the seismic program for the region's state-owned toll bridges through a $1 surcharge for eight years, beginning in January 1998. The surcharge was added to the basic $1 charge established by a 1988 regional ballot issue. The regional measure (RM 1) allocated income from the basic charge to operation and maintenance of the Bay Area toll bridges, traffic congestion measures, support of ferries and transit, bicycle and pedestrian improvements, and specific construction projects. These included construction of a new span of the Benicia-Martinez Bridge, replacement of the west span of the Carquinez Bridge, and widening the San Mateo Bridge.
The seismic surcharge is administered by Caltrans, which owns and operates the toll bridges. It may be extended for two more years if necessary to pay for the amenities on the eastern span of the Bay Bridge, or for a bicycle/pedestrian path on the western span. Any recommendation to extend the surcharge would come from the Bay Area Toll Authority (BATA), created by the same legislation which created the surcharge. In January 1998, BATA assumed administration of the basic $1 toll on the seven Bay Area bridges from the California Transportation Commission (CTC).
The Bay Area Toll Authority is staffed by MTC and MTC's commissioners serve as the BATA governing body. It is authorized to issue toll revenue bonds; the proceeds may be used to retire the pre-existing CTC bonds, and to finance the RM 1 bridge projects. Responsibilities include preparing a long-range plan for delivering the RM 1 bridge projects, developing a cooperative agreement with Caltrans describing the division of responsibilities between the two agencies, and submitting an annual financial report to the Legislature. BATA is also currently studying the appropriate action to be taken on the Transbay Transit Terminal, one of the MTC-approved uses for extra funding.
The RM 1 projects, like the retrofit of the Bay Bridge western span, are beginning to be evident to residents of the region. The preliminary steps for construction on both the Carquinez replacement span and the new Benicia span have already begun.
On the Golden Gate Bridge, the first phase of the retrofit, the north approach viaduct, should be complete in 2001. Two additional phases, first for the south viaduct and anchorage, and then for the remaining portions of the bridge, are planned to follow.
Early in the next century, hopefully before another devastating earthquake, newer and stronger bridges will serve the Bay Area.
Leslie Stewart
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