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Projects > Alaskan Way Viaduct Replacement - SR99
Project Date: Active Project


BDHs was brought in early by Seattle Tunnel Partners on this world record setting project (Largest diameter). The J/V contractors were able to consult with our hyperbaric support managers to develop a first of its kind Saturation (SAT) Habitat specifically for tunnel work. By being on board early we are able to insure that the hyperbaric systems fulfill the needs of both the owners and the prime contractor while adhering to all applicable codes and standards. The SAT system will provide the capability of supporting up to 16 workers and their support crewing. BDHs schematic reviews, air consumption calculations, site assessments, hyperbaric operations manual and aid in acquiring variances have helped this ongoing project run very well from the outset.


Following the recent signing of a contract with Seattle Tunnel Partners (STP), Japan-based Hitachi Zosen Corporation will supply a TBM to bore the US$1.35 billion SR 99 tunnel project (Alaskan Way) in Seattle. Three other firms also vied for the contract, but Hitachi was chosen having satisfied technical requirements, support capabilities, price and schedule.

In July, Hitachi signed a letter of intent with STP – WSDOT’s design-build contractor for the project. This allowed the Japanese TBM-maker to begin its preliminary design soon after. WSDOT says it will pay STP approximately US$80 million for the machine, an amount included in the project’s US$1.35 billion contract.

Utility relocation and other preliminary tunnel work is about to take place, with excavation of the tunnel launch pit commencing next year, followed by tunnel boring in mid-2013. The tunnel is scheduled to open to drivers in late 2015.

More information on the Alaskan Way viaduct and seawall replacement programme at www.alaskanwayviaduct.org

Seattle Times / 158 Buildings  
WSDOT Animated Video of Project
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