BART is looking to retrofit its underwater Transbay Tube to withstand a major earthquake.
The BART Board of Directors is set to vote on the potential $267 million earthquake retrofit at its regular meeting Thursday.
The transit agency put out bids for the Transbay Tube Internal Retrofit as part of the BART Earthquake Safety Program. The program includes a host of already completed retrofits, from El Cerrito Plaza Station to San Francisco’s Church Street Station, from 2009 through today.
Yet-to-be completed earthquake retrofits, according to BART, include the Coliseum and Fruitvale BART stations in the East Bay, as well as the Transbay Tube itself, which sees more than 27,300 riders pass through it in each morning commute.
Deep in a 133-foot trench, the 3.6 mile long tunnel is composed of 57 binocular-shaped steel segments that was lowered into the San Francisco Bay by a barge, and opened for service in 1974. Only 15 years later, the tube withstood the magnitude-7.1 Loma Prieta earthquake.
But the tube as it stands now must be retrofitted “in anticipation of a future major earthquake in the San Francisco Bay Area,” according to a BART staff report, which includes installation of “internal lining” along portions of the tube and a new pumping system.
“Although the tube is structurally sound, in a very large, very rare earthquake event (greater than every 500 years), the outer shell and concrete liner are predicted to crack, causing leakage,” BART spokesperson James Allison wrote in an email to the San Francisco Examiner.
The inner steel liner BART is proposing to build “is designed to prevent or slow leakage,” he wrote.
The funding mostly comes from general obligation bonds issued by BART, according to the staff report, which were approved by San Francisco, Contra Costa and Alameda county voters in 2004.
The agency classified this as a “Security Sensitive Information Contract,” wherein BART restricts access of certain information regarding the contract to identified people among the prospective bidders.
BART sent notices to 94 prospective bidders, and advertised the bid to retrofit the tube in January, according to the staff report. Engineers estimated a base bid for the project at $229 million.
The top three bids selected by BART district staff are from Shimmick/CEC Joint Venture of Oakland for $267 million, Granite/American Bridge a Joint Venture from Rancho Cordova at $293 million, and Barnard Construction Company Incorporated from Bozeman, MT at $440 million.