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Seattle tunnelling machine salvage to restart

Work to reach a damaged tunnel boring machine (TBM) working on a road scheme in Seattle, US is set to resume this week after it was confirmed that the work was not causing severe ground movement.

The Hitachi Zosen TBM stopped work on the twin-deck 3.2km tunnel, which will replace the Alaskan Way Viaduct, in December 2013 after the cutterhead clogged and high temperature readings were recorded.

Design and build contractor Seattle Tunnel Partners (STP) announced in April this year that a shaft would be built to access the machine and carry out repairs but excavation was halted last week after structural damage was noted on buildings surrounding the site. Investigations in the last few days have concluded that the ground movement is within the range expected as a result of ground relaxation and STP has been given the go ahead to continue.

Repairs to the TBM are expected to be completed in March 2015 and will delay the tunnelling phase by up to 16 months.

In a statement client Washington State Department of Transport  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.”

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