As many as 600 massive steel bolts on the San Francisco-Oakland Bay Bridge, reinforcing the new eastern span against earthquakes, may need to be replaced in the first year it’s open, according to the Metropolitan Transportation Commission.
The bolts girding a 2.2-mile section are subject to long-term corrosion, unlike 32 bolts that snapped in March after they became brittle due to processing, Executive Director Steve Heminger said yesterday at a hearing in Oakland.
The $6.3 billion Bay Bridge is the most expensive public works project in California history. Opening of the new section in September has been delayed, potentially costing the prime contractors performance incentives, while 270,000 drivers a day must depend on a bridge finished in 1936 and damaged in the 1989 Loma Prieta earthquake.
“When you buy a new bridge, you don’t expect to replace 600 bolts in the first year,” said Heminger, whose agency will be responsible for maintaining the span. “That is probably what we are going to have to do.”
He didn’t estimate the cost. Bridge planners have come up with two steel “saddles” as a work-around for the rods that failed. Those bolts, which can’t be replaced because they’re embedded in concrete, are each about the diameter of a baseball and as much as 17 feet (5 meters) long. That work is estimated at about $20 million, Heminger said.
The commission is seeking at least partial reimbursement from the project’s prime contractors and engineers, Heminger said. A joint venture of American Bridge Co. and Fluor Corp. is the contractor, while a joint venture of San Francisco-based T.Y. Lin International Group and Moffatt & Nichol is the engineer of record. Heminger said the commission has opened discussions with them about sharing the costs and plans to file a claim against the engineers’ insurance company.
Keith Stephens, a spokesman for Fluor and American Bridge, said it would be premature to comment on the issue. Tracy Russell, a spokeswoman for Moffatt & Nichol, declined to comment. Maribel Castillo, a spokeswoman for T.Y. Lin, didn’t respond to requests for comment.
The suspension bridge is designed to move slightly during an earthquake, rather than break, through a combination of bearings and seismic control devices known as shear keys, according to a report by the Toll Bridge Program Oversight Committee. The 600 bolts that may need to be replaced anchor the devices.
When 32 other bolts, manufactured by Dyson Corp. in Painesville, Ohio, were tightened in March, according to the report, “Rods began failing after three days of tensioning.”
Engineers made the rods susceptible to breaking by specifying the wrong anti-corrosion treatment, according to the report.
“The specifications, the grades of material they ordered, were the grades we provided,” said Brian Rawson, the president of closely held Dyson, the low bidder. The company, which makes bolts, screws and fasteners, supplied components of the original Bay Bridge, on which construction began in 1933. “They should have specified a higher-grade material.”
The state Transportation Department, known as Caltrans, shares responsibility for the failure with project contractors and engineers, according to the oversight report.
The engineers approved dipping the 32 rods in molten zinc at 850 degrees Fahrenheit (450 Celsius) to protect against corrosion. The technique can cause hydrogen embrittlement, in which hydrogen atoms spiderweb through the metal and weaken it, Thomas Devine, a professor of materials science and engineering at the University of California, Berkeley, said by e-mail.
The 600 other rods, also made by Dyson, are vulnerable to stress corrosion, which is a long-term problem unlike hydrogen embrittlement, Heminger said. The cause is linked to the high stress the parts are subjected to on the bridge, and exposure to the elements, particularly saltwater, he said.
Fluor, based in Irving, Texas, rose 0.47 percent yesterday to $59.29 in New York, after falling July 8 to $57.75, the lowest in two months. Coraopolis, Pennsylvania-based American Bridge, T.Y. Lin and Moffatt & Nichol are closely held.
Tax-exempt Bay Area Toll Authority revenue bonds maturing in April 2028 traded July 8 for the first time since May at an average yield of 3.84 percent, the highest since the debt was sold in September, data compiled by Bloomberg show. The penalty relative to AAA rated munis was 1.26 percentage points, close to the highest since issuance, the data show.