San Francisco-Oakland Bay Bridge East Span Project, CA, USA

The San Francisco Metropolitan Transportation Authority (acting as the Bay Area Toll Authority) has approved a single-tower, self-anchored suspension design for the main span of the new east half of the San Francisco-Oakland Bay Bridge in 1998. However, the project has been considerably delayed, leaving the earthquake-vulnerable bridge in situ.

INTERVENTION OF FEDERAL AGENCIES

In October 2000 the project was reinvigorated by the intervention of two federal agencies, and the American Department of Transportation decided to transfer land to the State of California from the US Navy. The uncertainty over the right of way on this land had held the project back by several months. The Army Corps of Engineers further bolstered the project by coming down in favour of a new, rather than a retrofitted bridge, as being less vulnerable to earthquake damage.

EARTHQUAKE PROOF BRIDGE

The project was prompted by studies carried out after serious earthquakes in 1989. These concluded that the eastern span of the San Francisco-Oakland Bay Bridge, unlike the western, could not be expected to withstand the scale of earthquakes that were likely to affect it. In March 1997, a design team was set up to tackle the problem. Recommendations went forward from this ground in June 1997.

T.Y. Lin International/Moffat & Nichol Engineers won the contract for further work in late 1997. The present scheme was only decisively adopted in July 1998 and finally broke ground in March 2002. The east span of the San Francisco-Oakland Bay Bridge will see a series of seismic advances, from steel piles deep in the ground to the 600ft shock absorber and main tower. The tower's strength comes from its four legs, linked by a network of steel beams, which would take the brunt of most quakes. These links can be replaced while the bridge is operational. The roadway will consist of 5 lanes in each direction and is estimated to take five years for full completion.

COST AND FUNDING

The project is being paid for from extra toll money levelled on San Francisco's toll bridge. The extra toll is a dollar and is expected to be levied over eight years. In conjunction with selecting a design for the new east span, MTC/BATA approved extending the seismic retrofit toll surcharge by approximately 15 months to generate an estimated $141 million to pay for the amenities to the new east span - $91 million, or nine and a half months of surcharge proceeds, for the incremental cost for including a self-anchored suspension component, and $50 million, or five months of surcharge proceeds for the bicycle/pedestrian path.

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