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California drops Oakland megaspan

A CONCRETE viaduct could replace the controversial 'signature' single tower selfanchored suspension span (SAS) on California's Oakland Bay Bridge project, officials announced last week.

California transport secretary Sunne Wright McPeak declared the viaduct the preferred option on Friday. The state legislature must now approve the decision in the New Year.

The concrete viaduct, an extension of the giant twin, five lane Skyway section of the crossing already under construction, was chosen from six options considered by California's Department of Transportation (Caltrans).

Four involving concrete towered versions of the original SAS design or different concrete cable stay options were rejected because of the delays involved in redesign and the need for beefed up foundations.

But Caltrans was unable to decide between a rebid and 'de-federalised' version of the original design using foreign steel, and the extended Skyway.

Selecting the original design would allow work to start sooner, as most design work is done and all permissions and environmental assessments are in place.

Construction costs would be lower and more predictable with the extended Skyway option, but there could be considerable delays in getting new planning permissions.

There is also a significant risk that the US Coastguard will oppose this option because of the restrictions its much shorter spans would impose on shipping.

There are also concerns that choosing this option would turn current Skyway contractor KFM into a monopoly supplier, as it already has a mammoth precast yard in operation capable of handling deck segments up to 800t in weight.

Locally there is anger over the loss of a landmark structure and the fact that Caltrans would have to write off £105M it has already invested in the SAS project.

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