Costs rise for Seattle floating bridge

Published: November 21, 2008

Latest estimates for a new floating bridge to carry the SR 520 highway in the western USA have put the cost at US$1.728 billion. The costs cover the pontoon construction site, primary and supporting pontoons and the floating bridge's deck.

Washingston State Department of Transportation has released the revised cost estimates for its project to improve SR 520 highway corridor. Costs range between $4.562 billion and $6.672 billion, depending on which design option is chosen for the western side of the scheme. Estimates in September 2006 had been in the range of US$2.79 to US$4.38 billion.

It cites five key factors that have increased the costs:

increases in construction material costs;

updated geotechnical information resulting in a complex design for the pontoon construction site.

increases in quantities of materials as a result of additional design information;

new regulations affecting wetland mitigation and stormwater treatment;

provision for future high capacity transit.

Revised costs have also been released for a range of surface, elevated and below ground options for the Seattle's Alaskan Way Viaduct project, putting the cost at between US$800 million and US$3.5 billion.

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