Breaking news! Bay Bridge at risk! Possibility of major structural breakdown!
Sounds familiar, doesn’t it? Amazingly, this one has nothing to do with bolts.
I know not everyone is as fascinated as I am by the ongoing soap opera that is the Bay Bridge, so I try to limit the updates to one a month at most. Sometimes, though, I just can’t hold off. This is one of those times.
On Sunday the fourth, our go-to guy for all that is the BBBB, Jaxon Van Derbeken, reported that the lead designer of the firm that designed the bridge, Marwan Nader, warned Caltrans that leaks in the guardrail system are allowing water to drip onto the bridge’s main cable. Yes, lest we forget, the Bay Bridge is a suspension bridge. The main cable is what holds the bridge up.
According to Jaxon, Nader delivered the warning Caltrans in July, although minutes of the meeting were only released recently. He specifically called out the “splay boxes” where the cable strands spread out and attach to the roadbed. The splay boxes are supposed to be sealed to prevent water from getting to the cable, but holes that are part of the system that anchors the guardrail are allowing rain to drip into the splay boxes. These are, by the way, the same supposedly-sealed boxes that were left open to the elements for most of 2012, during construction. A senior bridge engineer warned Caltrans that water was pooling in the boxes in May of 2012, but they weren’t sealed until December.
There is a dehumidification system in place, which Caltrans says is sufficient. Nader disagrees. As usual, there’s no independent third-party opinion available. And, as usual, the situation is even more complicated. Brian Maroney, the bridge’s chief engineer said in March that he had “recently learned” that “a key element” of the bridge’s drainage system had been eliminated, which adds to the amount of water leaking through the guardrail system.
So, once again, we have a design change that the chief engineer wasn’t aware of, a problem that’s been known in one form or another for several years, and–as far as I can tell from Jaxon’s article–no plan to do anything about it.
Just over a week later, Jaxon revealed that it’s not only the ends of the cable that are at risk.
According to a panel of independent maintenance experts, the entire cable is endangered.
The group, which includes bridge officials from New York, Hong Kong, and Scotland, completed a yearlong review of the Bay Bridge. Their report notes that suspension bridge cables are vulnerable to corrosion, but because the Bay Bridge’s cable is wrapped in a protective steel jacket, it’s impossible to inspect the cable for rust. They recommend an immediate retrofit–at a cost of tens of millions of dollars–to make it possible for inspectors to get to the cable and to install a dehumidification system for the entire length of the cable.
The critique gets better (or worse, depending on how you feel about watching disasters in the making). The panel also called out several other areas where inspection of important bridge components is difficult or impossible, including the supporting cables, which cross over the bridge roadway, and the steel “tendons” that hold the skyway together. Similar tendons on London’s Hammersmith flyover were exposed to salt water, causing corrosion which was only discovered when an acoustic monitoring system was installed.
We’ve been talking about design decisions that make some parts of the bridge impossible to repair since the very first Bay Bridge Bolt Botch revelations. Now we’ve got critical elements that can’t be inspected to see if they need replacing. Delightful.
As usual, let me point out that none of these problems pose any immediate danger to the bridge or the people driving across it. There is time to implement protective measures.
All Caltrans has to do is spend some money–something they haven’t had any trouble with in the past. Oh, but first they need to admit there’s a problem. That’s been rather harder for them.