SAN FRANCISCO'S Metropolitan Transportation Commission this week approved the £1.15bn asymmetric suspension bridge and causeway to replace the earthquake-vulnerable Oakland Bay eastern crossing.
Work is expected to start in mid-2000 following a detailed environmental impact assessment of the area. Caltrans, California's transportation authority, expects that work to dismantle the existing structure and erect the replacement should be complete by 2004.
Lead designer on the project is international consultant TY Lin which so far has its plan about 30% complete. The £850M main bridge in the 3.5km crossing - a single-towered self-anchored suspension bridge - was chosen for its looks, despite costing £30M more than a cable stayed alternative.
Vulnerability of the existing crossing to earthquakes has forced Caltrans to carry out a £35M retrofitting programme to strengthen the 1936 structure before it is pulled down. In 1989 the bridge, vital to San Francisco's transport network, had to be closed for one month after a span was lost in an earthquake.
Other earthquake protection retrofitting on the west crossing - a high level suspension bridge to the city - will bring Caltrans' total spend by 2004 to £1.6bn. This will be covered by existing bridge toll revenue and new bond issues.