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New schedule released for SR 99 tunnel project

Seattle Tunnel Partners (STP) has submitted an updated tunnelling schedule for the Alaskan Way Viaduct Replacement Programme.

Tunnelling work on the project has been delayed since December 2013 when the tunnel boring machine (TBM), named Bertha, stalled after overheating.

The contractor started installing the machine’s redesigned seal system in June and last week began installing a new main bearing.

Machine repairs are anticipated to be complete in autumn 2015, according to the revised schedule STP submitted to the Washington State Department of Transportation (WSDOT).

STP and manufacturer Hitachi Zosen will then perform an extended series of tests to ensure the machine is ready to complete the tunnel drive.

Tunnelling is scheduled to resume in late November, with the machine emerging at the north end of downtown approximately one year later.

At the start of work in 2013, STP had originally planned to complete the tunnelling work by the end of 2015 which was ahead of WSDOT’s expectations of November 2016.

The SR 99 tunnel is now expected to open in spring 2018.

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