Metropolitan Transportation Commission officials said Wednesday that they're troubled by the discovery of problems with 32 large bolts on the new eastern span of the Bay Bridge but they're still hopeful the bridge will open on schedule in September.
Referring to other problems that have affected the lengthy construction process for building the new $6.4 billion span, MTC Executive Director Steve Heminger said, "We have surmounted far greater engineering challenges than this one and we're confident that we'll get through this one as well."
Heminger said the MTC's initial assessment is that there is hydrogen in the metal in the bolts, which has made them brittle, and if that proves to be correct then "there clearly was a quality control failure" by the firm that manufactured the bolts.
He said “a failure rate of one-third is very high" and that if Caltrans has to order more bolts, it will do a more thorough job of inspecting them this time.
MTC spokesman John Goodwin said that 32 bolts have popped out of place by a couple of inches since they were tightened. In all there are 288 anchoring bolts that tie the road decks down to a supporting pier below.
“I don’t characterize this as a small problem, but on a project of his size everything gets magnified,” Goodwin told KTVU. “Keep in mind these are bolts. This is the kind of thing that we all deal with every day, but they are 17-feet-long. Everything on the Bay Bridge gets magnified.”
The bolts, ranging from 9 to 17 feet in length, are located near where the new span's self-anchored suspension span meets its skyway.
“This anchoring system is there to resist the seismic forces so in order to achieve seismic safety on the bridge a resolution to this problem is going to have to be found and installed,” he said.
"It's not common, but it does happen," Goodwin added, noting that the fault may have occurred during the manufacturing or galvanizing process in Ohio, where the bolts were made.
Over the course of the past month, the batch of bolts, which were manufactured in 2008, have failed to tighten properly due to excessive hydrogen in the steel, which causes embrittlement.
Based on preliminary estimates, the error may cost an extra $1 million to $5 million to correct because the giant bolts will need to be remanufactured specifically for the project, Goodwin said.
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