An international group of bridge experts says the new $6.4-billion San Francisco-Oakland Bay Bridge has major structural and rust problems that must be addressed immediately.
A yearlong study by the International Cable Supported Bridge Operators Association concluded the bridge’s main cable is rusting, but because of the bridge’s design inspecting the damage and treating it are not easy.
The cable is thousands of steel strands that loop over the top of the tower, travel beneath the bridge and then over the tower again. It is protected from water intrusion using conventional methods employed in bridges around the world.
Apparently it doesn’t work.
“Cracks in wires and wire breaks have been found within the cables of a significant number of suspension bridges,” the San Francisco Chronicle reported the group said in a presentation this week to the Toll Bridge Oversight Committee. “It would appear that there is now serious doubt on whether the traditional method of painting to provide protection to the main cables of these bridges is sufficient to provide a service life similar to the full design service life of the bridge.”
The group would like to have recommended smearing the cable wire strands with corrosion-fighting oil, but the bridge’s design discourages that. So, they recommended dehumidifiers.
They are apparently used around the world to blow dry air along cables at low pressure, and are now employed under the Bay Bridge roadway to prevent leaking. But the California Department of Transportation (Caltrans) rejected a proposal years ago that they be installed along the main cable because they were considered untested.
The bridge experts said there was no doubt dehumidifiers would work and should be installed immediately unless someone has a good reason not to. They didn’t mention the cost, but it is expected to run into the tens of millions of dollars. The Bay Bridge can use money from a $68-million maintenance fund, but that money is also used by seven other toll bridges.
One of the reasons there might not be a big rush to tap the maintenance fund is that the main cable rust issue is just the latest in a string of problems Bay Bridge operators are wrestling with. Cracks in tower rods, related to water intrusion, have been identified. Giant support rods have been replaced, leaks have been plugged and weld defects have been fixed.
The oversight committee did not indicate whether they would be making the changes recommended by the bridge experts. “We asked for advice. We don’t have to take every bit of advice we get,” committee chairman and BATA Executive Director Steve Heminger told the Chronicle.