Caltrans preparing new Bay Bridge ahead of storm

(KGO)
November 27, 2012 6:23:32 PM PST
Extra precautions are being taken to make sure the heavy equipment working on the new span of the Bay Bridge does not topple during the windy storm headed towards the Bay Area.

What most people refer to as "the new Bay Bridge" is actually a few distinct structures that will all be linked together. They all react differently to high winds. For instance, the model of the signature self-anchored suspension span with a tower survived wind tunnel wind speeds of up to 150 mph. The real thing is expected to move only a maximum of six inches in any given direction in high winds.

Next to that, the concrete skyway is expected only to vibrate in high winds. Beyond that, the Oakland touchdown is so low to the ground, in fact, on the ground, officials are less worried about wind as they are rain.

Tidal water is already a problem on the eastern end of the bridge. With a possible deluge expected Tuesday night, Caltrans contractors are getting ready. "We are expecting some pretty heavy rains over the next five days so we don't want weather to impact the construction schedule, so we do as much as we can during the dry weather so when the rain comes, we're ready for it and work can go on according to plan," Caltrans spokesperson Jordana Jackson said.

Even in dry weather, hoses pump tidal waters off the excavation site one section at a time for concrete pourers. Engineers are worried rain and bay water could undermine the cement wall so on Tuesday, more hoses and a special self-starting pump were brought in.

Caltrans wants to keep the construction site and materials in good shape, but it's also worried about controlling polluted runoff. "We have a storm water pollution prevention plan which we call our sweet pea plan. Basically, it maps out how we plan to deal with heavy rainfall whenever it comes," Jordana said. Special felt-like fabric lines the drains to catch sediment and let water pass through. Those were tested and replaced if necessary.

On the suspension span, high winds are a threat to workers who will have to come down and out of heavy equipment when wind speeds reach above 20 mph. Rain is also a threat. Water is the corrosive enemy of the critical single main cable. Much of it has already been wrapped in layers of zinc paste and interlocking S-wire. The rest is now wrapped in plastic.

The bridge is built to last. A little wind and rain shouldn't be a problem. "The bridge is designed to withstand the biggest earthquake that will happen in a 1,500 year period," Jordana said. "It has a 150-year design life so this bridge is expected to last 150 years."

Just a little retrofitting should bring it up to code for the year 2163. The new Bay Bridge is on schedule to open on Labor Day weekend next year.


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