Faced with lingering safety concerns over the San Francisco-Oakland Bay Bridge's new eastern span, California transportation officials say it will take more work — and up to $10 million — to get the bridge ready for its planned grand opening on Labor Day.
They discovered the problem after massive steel bolts were tightened to anchor part of the bridge's seismic safety system. Of the 96 that were tightened, 32 broke.
The broken bolts, which measure 3 inches in diameter, had "hydrogen embrittlement," the project's engineers say. When the bolts were produced in 2008, excess hydrogen was present, making them "susceptible due to the steel being harder on the outside than in the middle, or a lack of uniformity in the steel's microstructure," according to the California Department of Transportation.
Engineers say they won't rely on any of the 96 bolts from that batch. An additional 192 bolts made in 2010 are being tested but so far haven't shown problems, officials say. All of them were fabricated by Dyson Corp. of Ohio, which "has been making specialty forged products, such as giant bolts for bridges, for more than a century," Cleveland's Plain Dealer reported last month.
Because the bolts, with lengths between 9 and 17 feet, are embedded in concrete in confined spaces, engineers say replacing them is impossible. Instead, they said this week that they plan to install steel "saddles" over the bridge's seismic safety devices, along with more than 400 steel cables to hold them down.
The late fix could mean the holiday celebration meant to mark the bridge's opening for traffic may have to be put off.
"We believe the work can get done by Labor Day, but it will require extra shifts and perhaps a 24-hour-a-day operation, and that will cost more money," says the Metropolitan Transportation Commission's Steve Heminger, reports The Los Angeles Times.
The project has cost $6.4 billion, far exceeding early budget estimates. We've reported on the bridge before — most notably, on its being sheathed in an artist's installation of thousands of LED lights.