A technical review of the San Francisco-Oakland Bay Bridge, released Thursday by a panel of engineers formed by the state Legislative Analyst’s Office, provided a mixed review of problems facing the new span – praising some actions by the California Department of Transportation and questioning others.
The report, based solely on unverified documents and comments from Caltrans and its contractors, concluded that the department had conducted adequate testing of the tower foundation to ensure good performance in a major quake, even if flaws might remain in the concrete.
It found that Caltrans also had correctly repaired the section of the bridge affected when anchor rods snapped last year, and suggested a risk assessment and monitoring program of all high-strength fasteners similar to the ones that broke.
But the many problems on the project suggest “a lack of a robust construction quality assurance,” the report noted. It suggested “having independent third parties responsible for construction quality assurance services so that there are no real or perceived conflicts of interest.”
The panel also urged Caltrans to use independent peer review experts to “add significant value to the process and alleviate any concerns of conflict of interest.”
In a written statement, Caltrans Director Malcolm Dougherty said he was pleased that the LAO panel validated the department’s positions on soundness of the tower foundation and anchor rod retrofit. “Caltrans will continue to evaluate the (LAO panel) recommendations included and build on lessons learned going forward to improve management practices on megaprojects,” he said.
The Sacramento Bee reported last year that members of Caltrans’ Seismic Safety Peer Review Panel were burdened by financial and professional conflicts of interest with the project and Caltrans. Likewise, The Bee found that some members of the LAO panel, including its chair, Georgia Tech University engineering professor Reginald DesRoches, have had financial and professional ties to Caltrans, the Bay Bridge and its contractors. Ethics experts say that conflicts of that kind can bias expert assessments.
The panel also addressed a problem reported by The Bee in April, that the main cable of the new bridge had rusted. Caltrans plans to dehumidify the chambers where the cable is exposed to reduce the chance that corrosion can advance. The LAO panel warned that the dehumidification system, if improperly designed, might increase the risk of localized corrosion that could make cable strands brittle – and recommended study and monitoring.
The panel also suggested further review of internal steel tendons that support the skyway portion on the bridge, which a separate Bee investigation found had corroded from exposure to water during a breakdown in construction procedures.
“This review should include an assessment of their risk of developing stress-corrosion over the life of the bridge and the possible consequences,” the panel wrote. It recommended the development of a monitoring system to detect if tendons break.
Caltrans has so far called concerns about corrosion of the skyway tendons and main cable unfounded.
The panel said that some of the lapses were the product of the suspension span’s unique and highly complex “self-anchored” designed. Rather than using a cable anchored to bedrock, it anchors to the bridge itself.
“In an engineering system, the greater the complexity of the system, the greater the potential for problems and deficiencies,” the panel wrote. “… The (self-anchored design) was chosen on the basis of aesthetics and broader community input without a full appreciation of the complexity of the undertaking and the potential for problems and cost overruns.”
The LAO formed the expert panel in 2012 at the request of Sen. Mark DeSaulnier, D-Concord, chairman of the Senate Transportation and Housing Committee, to review possible flaws in the concrete foundation for the new suspension span tower described in The Bee investigation. The panel later expended its work to include other concerns about the new span.