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As remarkable feats of construction go, the San Francisco-Oakland Bay Bridge - to give its full title - or Bay Bridge as it is more often known, takes some beating. Consisting of 3 separate bridges, and a huge tunnel, the Bay Bridge stretches some 4 1/2 miles connecting the city of San Francisco to its East Bay neighbours of Oakland and Berkeley. As little as 9 years before construction started in 1933 the concept of a bridge from San Francisco to Oakland was deemed impossible due to the largely mud-based bed of the Bay, and because of concerns over earthquakes. In the event the bridge did withstand the only real test it has faced - the Loma Prieta Earthquake of 1989 - relatively unscathed.
The first section of the bridge was constructed in around 3 years and consists of 2 linked suspension bridges each of around 1 mile in length. These are anchored in the centre of the Bay on a man-made 'island' that sinks 220 feet (67m) down through the water and then mud of the Bay and rises 288 feet (88m) above the water. This construction alone used more concrete than the Empire State Building in New York! The next component is a tunnel, 2950 feet (900m) long, through Yerba Buena Island. From Yerba Buena Island to Oakland a third bridge, this time featuring a cantilever section of 1400 feet (427m) completes the connection. This third bridge is also in the region of 2 miles in total length.
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The structure is further complicated by the fact that all of the bridges, and the tunnel are actually double-decked. Originally there were 3 vehicle lanes on the lower deck along side 2 rail lines, with 5 lanes for vehicles on the upper deck. The train lines were removed in the 1950's and today's configuration was implemented, with the upper deck being used to bring traffic into the city, and the lower deck taking traffic from San Francisco to Oakland. The views from the San Francisco-bound upper deck, particularly on the suspension sections after the tunnel are stunning, frequently offering drivers a view of Alcatraz and when it's not too foggy the Golden Gate Bridge as well. Tolls are paid to cross the bridge - but on the West-bound span only. The toll-plaza is also configured with 'metering lights' used to ease the flow of traffic onto the bridge during peak hours. The resulting lines that develop when the metering lights are on can stretch some way back along the four major freeways that connect to the Eastern end of the bridge.
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The cantilevered Eastern span of the Oakland Bay Bridge. Within a few short years this will cease to exist as a new eastern section is constructed to the North of the current route. The new bridge will follow a dramatically different design, featuring a single-tower suspension bridge at the Yerba Buena Island end which will then be connected to a 'skyway' to link it to the current toll-area in Oakland. The need for a replacement to the eastern cantilever section was identified following its partial collapse in the 1989 earthquake. The link between San Francisco and Oakland is deemed a vital 'lifeline' connection and as such must be able to withstand the largest imagined earthquake and remain open, and the damage suffered in 1989 showed that the current bridge simply could not fulfil that requirement.
The new design is not without its critics who feel that the design (particularly of the skyway section) is ugly. Perhaps more worryingly there appear to be seismic survey reports and studies that indicate that the new design will be particularly prone to damage from earthquakes because of the way the suspension section and skyway sections are joined and anchored to the bay floor. Anyway, with the project signed and sealed, you'll be able to see the new bridge for yourself soon. Construction started in January 2003 but won't be completed until 2010 or later!
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Other Images of Oakland Bay Bridge....
(Just click on the image for a full-size version) |
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