Glen Martin writes in this morning’s San Francisco Chronicle about the new San Francisco-Oakland Bay Bridge. To be precise, it’s the old eastern “cantilever section” of the bridge that’s being replaced.
The existing east span rests on 60- to 70-foot-long wood pilings that are essentially suspended in the deep strata of mud and silt that constitutes the bay’s bottom. The pilings aren’t anchored to bedrock, which is why the current structure would be unlikely to fare well in a huge quake.
The skyway portion of the new bridge, by contrast, will sit on 300-foot- long steel pilings driven into the rock underlying the sediment strata.