Seismic equipment on new Bay Bridge forgotten
by Robert Freehling and Rick Feher
In a startling admission, the chair of the panel of experts guiding the engineering and design of a proposed new eastern span of the San Francisco-Oakland Bay Bridge said that earthquake monitoring instrumentation was inadvertently omitted from the bridge design. Joseph Nicoletti, chair of the Engineering and Design Advisory Panel (EDAP), made the admission to the Metropolitan Transportation Commission's (MTC's) Bay Bridge Task Force on July 14, 1999 in Oakland.
California law requires seismic detection and recording equipment to be installed on all new and retrofitted bridges. Such equipment is analogous to the "black boxes" on airplanes, which are used to analyze causes of failure or damage. On a bridge, the instruments would measure and record stresses in elements of the bridge, movement between elements, and motions in the ground, via a network of sensors and recording devices.
Continuous monitoring is critical for ensuring the long-term integrity of a bridge such as the Bay Bridge, the most heavily travelled bridge in the world. Monitoring also provides invaluable data to designers of future bridges. "There is actually no measurement at all of the response of a major bridge during a great earthquake," according to James Roberts, director of the Engineering Services Division of the State Department of Transportation (Caltrans) and currently acting Deputy Director. Roberts's statement underscores the importance of incorporating technology for continuous bridge monitoring in the design of the new east span. Its omission in a widely publicized seismic safety project is strange, to say little about why it might have happened. Perhaps significant is the fact that the stability of the proposed design has been called into question by experts outside of EDAP. The panel considered and rejected a dozen proposals in early 1997; among them was at least one in which rigorous monitoring of structural integrity was integral to the design.
According to Caltrans officials, funds for monitoring equipment were to be taken out of MTC's "amenities" budget. "Amenities" is legally defined for this project as including, among other things, a bicycle/pedestrian path, a self-anchored partial span supported by cables suspended from a single tower, and improvements to the Transbay Terminal in San Francisco. Funds for for these items, legally considered as options added to a basic bridge, are being raised by a $1 toll surcharge enacted two years ago. The July 14 meeting was an opportunity for MTC's Bay Bridge Task Force to accept the recommendations of EDAP. The recommendations favor placing aesthetic illumination below the deck, which would be visible only from afar, and adding white concrete cladding on the outer few inches of the suspension tower and the sides of the bridge deck. These amenities are expected to cost between 30 and $50 million. The Task Force, Caltrans and MTC staff disputed whether seismic monitoring would be an amenity, in which case it would be paid for out of the toll-surcharge funds, or whether it should be considered part of the baseline cost of the bridge. Task Force Chair Mary King recommended the amenities, but rejected the idea of MTC paying for seismic monitoring. According to MTC Executive Director Lawrence Dahms, no allocation has yet been made for the Transbay Terminal, the seismic renovation of which is expected to be costly. The terminal plus other recommended add-ons now exceed the approved budget for amenities. Accordingly, the MTC must either choose among the amenities or find additional funding. The Task Force postponed decisions until a future meeting in September.
At the July 14 meeting, Mary King admonished the U.S. Navy for irresponsibly delaying this important seismic safety project. But the project already has a long history of delay. It took seven years before the idea of a complete retrofit was abandoned, and by Spring of 1997, work had still barely begun on an interim retrofit. Then, in April of 1997, the Engineering and Design Advisory Panel was formed to select the basic design and route of the bridge; MTC anticipated ending public input in four weeks, with EDAP making its final recommendaton two weeks later. Dissension among members of the engineering panel over which of two designs to recommendboth designs proposed by firms connected to some members of the paneldelayed the type selection for more than a year. In the spring of 1998, as MTC was about to accept EDAP's final recommendation, opposition erupted among critics in the East Bay who claimed their concerns were scarcely heard and that the selected proposal was a "freeway on stilts." This past February the U.S. Navy joined a Congressional delegation and the City of San Francisco in dissatisfaction over the bridge's proposed route, which runs north of the existing bridge. The Navy has blocked the bridge with "infinite" refusal to allow it, or any northerly bridge, to land on Yerba Buena Island. The northern-alignment design under contention was proposed by firms which were represented on EDAP. The panel rejected two straight southern bridge designsa viaduct proposed by state engineers, and a complete suspension bridge.
A portion of the original eastern span of the Bay Bridge, completed in 1936, collapsed during the 1989 Loma Prieta quake. The replacement span was declared by state law to be "safer, stronger, longer-lasting and more cost-efficient to maintain" than a retrofit (repair and strengthening) of the existing east span.
A five-man "independent" seismic safety peer-review panel, appointed by Caltrans for this project, wrote to Gray Davis in March, assuring the governor that the bridge design was carefully thought out for seismic safety. That panel is also chaired by Joseph Nicoletti, and all five are also members of the Engineering and Design Advisory Panel.
"Please be assured that the design of the replacement bridge is being developed by experienced engineers with careful attention to engineering principles and with diligent regard for seismic safety," the engineers wrote. Their letter to the governor arrived after findings of U.C. Berkeley engineering professor Dr. Abolhassan Astaneh were widely publicized. Dr. Astaneh's analysis confirmed dangerous instability and weakness in the proposed partial suspension span of the new bridge, a conclusion which was also evident in the designers' own report.
The partial suspension span is a functionally unnecessary part of the bridge and is, lengthwise, only a small fraction of the entire structure. It is, however, the largest single "amenity" by cost. It was recommended by EDAP as an aesthetic improvement over a shore-to-shore viaduct originally proposed by Caltrans. The simple viaduct would have cost at least $200 million lessand may have rendered the $1 toll surcharge unnecessary.
Selection of a simpler bridge would also not have made it easy for private engineering firms to have a stake in the project, since Caltrans's design for a viaduct, which the department considered a functionally adequate replacement, was already substantially developed. A fourteen-year legal dispute over "contracting out" to private firms for engineering and design services was settled last year. In the settlement, the state was ordered to bring 1,200 additional engineers to its own staff to reduce the need for private consultants. And Caltrans was to terminate all contracts in the seismic retrofit program. The Bay Bridge project was specifically exempted in the settlement, however, and private firms have continued to bill the state throughout the delays and during the current impasse with the Navy.
Private firms which have historically contracted with the state for engineering services were well-represented on EDAP. Two proposals for single-masted cable-supported enhancements were proposed by firms with representatives on the Engineering and Design Advisory Panel who also judged and approved the designs, while denying conflict-of-interest allegations. Design fees billed to the state are expected to total more than $70 million.
A lengthy popularity contest between two competing cable-supported structures was presided over by MTC. Due to confusing and misleading reportage, the cable spansamenities bothwere often perceived as whole bridges. Caltrans officials long maintained that the simple viaduct was the most reliable, cost-effective option. But the self-anchored suspension bridge amenity was recommended by the Engineering and Design Advisory Panel and approved by the MTC in June of 1998. More than a year later, MTC's Task Force is again worried about amenities, while discovering that the design team, forgetting the new bridge's status as a seismic safety project, neglected to wire it for the 21st century.