Bay Bridge Rising

Sketch drawing of the proposed San Francisco-Oakland Bay Bridge (1913) from Overland Monthly, April 1913.

The Bay Bridge will be closed from September 3rd at 8:00 p.m. until the 8th at 5:00 a.m. During these 105 hours, Caltrans will perform an "essential and unprecedented construction feat."

It turns out there was a lot I didn't know about the Bay Bridge. Its official name, for example is not the Bay Bridge. It's "The James 'Sunny Jim' Rolph Bridge," after the California Governor who died in 1934, two years before the bridge opened (The Golden Gate Bridge opened 6 months later). Around 280,000 vehicles traverse the bridge every day—nearly $7 in bridge tolls per second; The Yerba Buena Tunnel that connects the eastern and western segments is the world's largest diameter bore tunnel; Much of the eastern span is supported by old growth Douglas Firs, driven into firm mud.

As construction grows increasingly noticeable, the new eastern section rising out of the bay, more people are wondering: How will it attach? What happens to the old bridge? What's with the retrofit of the western suspension? And what is this unprecedented feat of construction happening over Labor Day weekend?

The construction website, baybridge360, just received a Webby award in the Government category, and is worth a visit. Videos and slide shows are overlaid on a satellite image of the bay and provide answers to these and other engineering questions. There's a bit of Troy McClure style narration, epic synthesizer for the construction scenes, and techno pop for the fast-forward time lapse photography. At one point, the “Governator” dons a pair of terminator sunglasses for a ceremonial blowtorching.


The new site may be sleek, but some of the most interesting information is buried in the old stalwart: The western span's retrofitting, completed in 2004, added some 17 million pounds of structural steel, and included new rollers between the roadway and the bridge supports. The new eastern segment (slated for rebuilding since a section collapsed in the 1989 Loma-Prieta earthquake) will include the world's longest Self-Anchored Suspension (SAS) bridge, connected to a pier-supported "Skyway" (elevated roadway over a mile of mudflats), sloping down to the "Oakland Touchdown."

The 2,047-foot asymmetric SAS will be supported by a single steel tower, embedded in rock, rising 525 feet above sea level. While most suspension bridges use a pair of cables, the new SAS employs a single cable, anchored on the east side, wrapped over and around the tower, and down to the west. The Skyway is supported by a set of steel pipes, driven 300 feet into deep bay mud by a massive hydraulic hammer.

Amidst the construction clamor, considerable attention is afforded to local wildlife. Dense columns of air bubbles helped dissipate shockwaves from the hammering to ease construction-related stress on local fish. For the birds, platforms under the new east span provide cormorant nesting habitat, and the crew is building a 500 square-foot island for the pleasure of the snowy egret and ruddy turnstone. And at the Oakland touchdown, a turbidity-controlling curtain was installed to protect eelgrass, which in turn serves as a filter, improving water quality.

So consider all this next time you lament the $4 bridge toll. The original 1936 toll, collected in both directions, works out to over $20 in 2009 dollars. The bridge is scheduled for completion in late 2013.

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