Bay Bridge officials weigh plans to protect span

- Officials are getting down to the fine points of how to make sure the new Bay Bridge span will last 150 years and survive the largest expected quake in 1,500 years.

If you listen between the lines, this bridge may be way stronger than it needs to be.
The Bridge Oversight Committee is pondering what to do about making sure that some, but not all, of the rod bolts in the base of the tower are not bathing in bay water.

It is a long term problem that might be remedied by replacing the poorly installed grout with new grout or some other water proof material. Whatever is decided, the problem should be eliminated within a year because the rod bolts are performing as designed under full seismic stress.

"406 out of 407 rods passed with full seismic loads," said Caltrans Chief Bridge Engineer Brian Maroney.
Another concern: the massive white cable that holds the bridge deck up. The part of the cable that's exposed is well-protected already.

Each and every one of the 14,000 individual steel strands that make up the main cable are individual galvanized against rust, and all of that coated with a heavy, thick layer of highly rust-resistant zinc paste.

That's all tightly wrapped with a band of interlocking rust resistant steel topped by several thick layers of primer and paint. This formidable barrier to water getting on the cable gives it expected life span of 150 years.

Nonetheless, bridge officials asked an international maintenance engineers to inspect and suggest what else might be done to better protect the cable.
The vast hollow spaces where the cable is hidden and anchored inside the bridge deck as well as the area where the cable passes over the tower are already dehumidified by machines.

"The fact that we actually implemented a dehumidification system speaks to the fact that we were conscious of maintenance, from the very, very beginning," said Bay Bridge Project Chief Spokeswoman Leah Robinson-Leach.

Nonetheless, the Committee recommends that Caltrans pump dry, dehumidified air through the entire length of the cable as one more additional protection.

"It is now a valid idea or a valid point of how to go about maintaining a cable, especially for one that you want to maintain for 150 years," said Caltrans Structural Maintenance Chief Kenneth Brown.

But, for the ten to twenty million dollars needed to install that system, bridge officials will have to think hard and long if that adds any meaningful protection that simply making sure the bridge coatings don't already supply.

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