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Seattle tunnelling to restart in March 2015

Repairs to the tunnel boring machine (TBM) being used on the Alaskan Way Viaduct in Seattle, US will take until next March to complete according to an announcement by design and build contractor Seattle Tunnel Partners (STP).

The Hitachi Zosen TBM stopped work on the twin-deck 3.2km tunnel, which will replace the Alaskan Way Viaduct, in December after the cutterhead clogged and high temperature readings were recorded.

Hyperbaric inspections in January revealed that there were no major obstructions in front of or within the cutterhead and the contractor has since been working on a solution to the problem.

STP announced this week that it will construct and access shaft to access the TBM in order to repair damage to the seal system and main bearing. The contractor has said that it hopes to start testing the repaired machine in February next year with tunnelling activity resuming in late March 2015.

Washington State Department of Transport (WSDOT) has said that the repair work will delay the tunnelling timeline by up to 16 months. In a statement WSDOT said: “STP hopes to recover as much as four months of schedule to meet the November 2016 tunnel opening date we established in our 2010 request for proposals. STP had proposed opening the tunnel in late 2015, 11 months earlier than our original requirement.

“STP has informed us that crews will replace the machine’s main bearing and install a more robust seal system, which could include strengthening the seals, installing redundant systems, and adding monitoring equipment. Additional details will be included in a plan to be submitted to us for review by 16 June.

“The repair schedule will include additional time to accommodate potential improvements to the machine that STP or Hitachi might choose to make after the cutterhead is removed and crews are able to perform a full inspection. We will work with our strategic technical advisory team, made up of international and national tunnelling experts, as well as consultants, to review the plan.”

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