Holes in the new $6.5 billion San Francisco-Oakland Bay Bridge – first detected by California Department of Transportation employees last winter – have continued to leak water inside the structure during recent storms.
Andrew Fremier, deputy executive director of the Bay Area Toll Authority, said in an interview Friday that efforts to caulk about 900 bolt holes for guard rails had been only partly successful. Water is again collecting inside the splay chambers – supposedly sealed rooms where the main bridge cable is secured to the new span.
“You obviously don’t want water in the splay chambers,” Fremier said.
Those chambers are meant to be bone dry to prevent corrosion of the main cable and the anchor rods that attach it to the span, Fremier said.
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Fremier didn’t know how many holes are still leaking, or how much water was pooling inside the chambers. But dehumidifiers have kept the air moisture to a safe level, he said. Experts say that humidity below 40 percent prevents corrosion. Caltrans has measured humidity at 38 percent despite the presence of water, Fremier said.
The chambers were drenched between December 2011 and December 2012 during construction, according to Bill Casey, a top Caltrans engineer for the new span. Last winter, the bolt-hole leaks caused splay-chamber humidity to spike as puddles of water formed inside during storms. At that time, the dehumidification system was not fully operational.
The episode raised concerns among independent engineering experts about the prospect of corrosion damage. In April, a Sacramento Bee investigation examined conditions inside a splay chamber. Laboratory tests of corrosion residue collected by The Bee, along with photographic evidence, found two types of corrosion: white rust from a protective layer of zinc, and reddish-brown rust from the underlying steel.
Using a scanning electron microscope, which detects the elements in sample particles of residue, rust was found both on the strands of the main cable and the anchor rods.
The tests also showed that the rods and strands were coated with salt from the marine environment. Salt accelerates corrosion.
Experts told The Bee that rust can make the rods and the cable strands vulnerable to cracking over time. This could be a particular risk for the strands, because large trucks passing overhead cause them to vibrate thousands of times every day.
In April, a bridge spokesman denied that corrosion was occurring inside the chambers, and said it was not a concern.
Officials had hoped to seal all the leaks before this year’s rainy season. Fremier said he learned from Caltrans engineer Ken Brown, who heads maintenance for the new span, that the effort fell short.
Brown declined to comment.
Fremier blamed the leaks on a design error. He said Caltrans would pay for all repairs as a maintenance issue, rather than trying to get compensation from the bridge designers, a joint venture of TY Lin International and Moffatt & Nichol.
“I do think that most of the water (leaking into roadway sections) outside the splay chambers is more of a nuisance than anything else,” Fremier said.
Earlier this week, Caltrans spokeswoman Leah Robinson-Leach said information on possible leaks was still being collected.
“There will always be some type of water presence after storms like those,” she said. “(The bridge) never was and never will be waterproof.”
Call The Bee’s Charles Piller, (916) 321-1113. Follow him on Twitter @cpiller.