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Bridge repair could cost $10M

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POSTED May 8, 2013 9:11 p.m.


 

OAKLAND . (AP) — The planned repair for seismic safety rods that snapped on the new span of the San Francisco-Oakland Bay Bridge could cost between $5-to-$10 million, a state transportation official said Wednesday.

California Transportation Commission Executive Director Andre Boutros told a meeting of the Bay Area Toll Authority that the repair that officials plan to go ahead with for the 32 rods that failed involves installing steel saddles.

The saddles would be placed over the seismic shock absorber that was initially meant to be attached to the bridge by the broken rods. About 430 steel cables covered in concrete will tie down the saddles. Another repair option would have been more expensive.

Officials said they are taking no short cuts in order to get the bridge opened as currently scheduled on Labor Day, which is still a possibility.

"We're dealing here with not only engineering concerns but public confidence, and public confidence has taken a beating over the last few weeks, and we are mindful of that," said Steve Heminger, executive director of the Metropolitan Transportation Commission.

On that note, bridge officials Wednesday also sent a letter to the Federal Highway Administration requesting an independent review of the California Department of Transportation's investigation into the broken rods, and their chosen fix.

The rods connect steel earthquake safety devices called shear keys to the deck of the bridge and a large concrete cap. Shear keys would help control swaying during an earthquake.

The new bridge, which is replacing a span damaged during the 1989 Loma Prieta earthquake, is designed to withstand a major temblor. It is already years late in opening and billions of dollars over budget.

Documents released last month by the California Department of Transportation show its inspectors found structural integrity issues with some of the rods several years ago, before they were installed.

The documents were unclear about whether the problems were remedied before the rods were delivered and installed. The inspectors noted that they failed elongation tests for structural integrity and said they were concerned about the quality of work by the company that galvanized them to prevent corrosion.

The 32 rods that failed were among a group of 96 manufactured in 2008. Officials have blamed what's called hydrogen embrittlement — which could be have been introduced by moisture and water from the foggy environment enveloping the bridge — for their failure.

When hydrogen infects the steel, it makes it harder and thus more brittle and prone to cracking. Bridge officials said they still do not know how the hydrogen infected the steel on the failed rods.

According to a metallurgists' investigative report released Wednesday, the steel in the broken rods was "found to be less than ideal."

The report said the hydrogen problem could have been discovered earlier if Caltrans would have required tougher tests of the steel being used to make the rods.

"In hindsight, these are the type of requirements we should have had on the 2008 bolts," Heminger said. The agency is developing new requirements to be adopted for these kinds of bolts in the future that would require more testing of the steel.

Now, crews are busy completing tests on another batch of 192 bolts from 2010 that were installed in shear keys on other parts of the bridge. Tests of those bolts have shown no signs of weakness or hydrogen issues, Heminger said.

"We're starting to see more daylight between the 2008 bolts with the hydrogen embrittlement problem and the 2010 bolts, which do not seem to be developing this problem," he said.

In an abundance of caution, bridge crews are developing further "wet tests" to address concerns that the 2010 batch of bolts might corrode more quickly in the future.

The results of those tests will help determine if those also need to be replaced, which could push a delay in the bridge's opening.

"After the wet tests we'll know whether these bolts are OK or not, and those that are not we're going to rip them out and replace them," Marwan Nader, a bridge structural engineer working on the repairs, said.

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