The lead front page story in The San Francisco Chronicle this morning is "S-curve crash shows why changes needed". Reading this block type, you'd probably figure they were suggesting that the new S-curve structure on the East side of the Treasure Island splice of the two-part San Francisco Bay Bridge ought to be redesigned, and reconstructed, but you'd have been wrong. Caltrans' "changes" include lowering the speed limit, putting in radar speed-displays, and perhaps road-bumps to alert drivers to the approaching hazard.
The history of the Bay Bridge isn't complicated. It was constructed in the 1930's, to replace ferries (which was how people once got from Oakland-Berkeley to San Francisco and back). It was a sound structure, given the state of engineering in its time, and it admirably served its purpose. The lower deck originally was built for the old yellow "F Train" track, the rail system we had in place before the Teamsters Union persuaded Bay counties to scrap it in favor of upper and lower vehicle service. (We had to wait 20 years later for the idea to be resuscitated as the BART system!)
After the Loma Prieta Earthquake in '89, engineers told us we had to rebuild or retrofit the old bridge, lest a catastrophic failure occur in a really big quake (of the '06 proportions). Engineers and geologists in California have been conducting a little cottage industry of chicken little warnings for the last half century here, all doom and gloom about the dire consequences of not investing millions upon millions of dollars in structural retrofits and disaster planning. No one ever questions how effective or thrifty all this expenditure may be, or why the construction trades industry and engineering professions might have a vested interest in stirring up all this fuss. If another earthquake occurs, there is little doubt that structures built out of unreinforced brick, or sited atop (or near) known faults, will likely suffer considerable damage. But the fact is that the greatest damage from large earthquakes, here, is likely to result from fires and explosions in and around gas-mainlines. Installing a little triangular bracing on traditional foundation platforms in housing and business structures is comparatively cheap, but any earthquake strong enough to cause houses to shiver off their foundations would make such "mitigations" pretty irrelevant in the event.
It may indeed sound presumptuous for a non-professional to question the advisability of building a completely new bridge to replace one that was constructed 70 years ago, but there has been preciously little debate about the issue, at least in the press.
The Bay Bridge "retrofit"--which turned out to be a completely new span on the Eastern section, has been plagued by design reviews, disagreements, delays, and construction snafus from the beginning. Now we learn, to our dismay, that the ultimate design includes a preposterous re-routing of traffic exiting the island tunnel on the East side away from the old eastern span hook-up, radically left to the new span, about 500 feet to the left (North), in the form of a violent "S-curve" immediately upon exiting the tunnel entrance. Experts have predicted significant delays of as much as 30% for all traffic flowing in both directions, as a result of this crazy design feature. In addition, the curves are so sharp, and unexpected, that they've already caused a number of serious accidents in the very short time since it was opened.
How could a professional team of designers and engineers make such a stupid mistake? Couldn't they see that building the new span 500 feet to the North of the old one would require a redesign of the connection between the North side of the island tunnel, and Western edge of the new span? This is a problem even a 5-year old could have foreseen in a nanosecond.
Caltrans has made blunders in the past. The connection between I-80 South to the Nimitz/580 split was botched 10 years ago, and has never been fixed: Drivers, especially those unfamiliar with that split, are forced to negotiate a rapid eccentric turn to the left. Scrapes and impact scars by the dozens along the concrete barriers are testament to this poorly conceived "solution."
There is little doubt that the new "S-curve" will have eventually to be rebuilt, somehow. The sooner this is initiated, the better off we'll be, in the long run. Resigning ourselves to another dangerous, confusing and inconvenient structural anomaly for another half-century doesn't make sense.
California drivers deserve better. We pay billions for our highways and bridges, supposedly designed to facilitate our advanced transportation system, upon which our economy and convenience depends. Why don't we get first-rate design and engineering? It's a mystery, and a disgrace.
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