Seattle Tunnel Partners has begun reconnecting the two largest pieces of the SR 99 tunnelling machine’s front end.
Tunnel boring machine Bertha has been stalled since December 2013, delaying progress on the Alaskan Way Viaduct replacement programme.
Mammoet crane crews have lifted the TBM’s bearing block into place on top of the cutterhead and drive unit.
The newly reconnected front end of the machine will remain at the surface while manufacturer Hitachi Zosen installs the motors. When installation of the motors is complete, Mammoet will lower the 2,000t piece back into the pit.
Watch the video below to see the repair sequence in detail:
Once Bertha is in the pit, crews will begin reconnecting wires, hoses and other parts to the section of the machine that remains in the ground. A series of tests will follow to ensure the TBM is ready to resume tunnelling.
Tunnelling is expected to resume in late November.