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Fri April 16 2021

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Final 2000-tonne lift brings TBM Bertha up for repairs - video

1 Apr 15 Seattle Tunnel Partners (STV) has completed a 2,000-tonne lift to bring the front end of the world’s biggest tunnel boring machine up to the surface for repairs.

TBM Bertha is building a tunnel for the US$3.1bn (£2bn) replacement of the Alaskan Way Viaduct in Seattle in the US state of Washington but has been at a standstill for more than a year.

Bertha herself summed up this week's operation on Twitter: “The lift of my 2,000-ton front end is complete. Up next: Further disassembly, then repairs.”

In addition to the cutterhead, the newly removed drive unit section includes motors and parts that enable the cutterhead to rotate. It also houses the main bearing and seal system that will be replaced during repairs.

The crane carrying out the lifting was built by Mammoet. The section began rising from the pit around noon on Monday and was visible at the surface a few hours later. By 9pm local time, the piece had been positioned above the platform and a fresh crew then set it down yesterday.

Crews will continue disassembling the machine’s front end in the coming days, using the gantry crane that completed the lift to arrange pieces on the repair site. Repair work will take place south of the pit beneath a large canopy that will soon be moved into place to protect the workers and machine pieces from the elements.

This was the fourth and final lift to bring pieces of the tunneling machine to the surface.

The repair effort is being led by STP - a joint venture of Dragados USA and Tutor Perini - and manufacturer Hitachi Zosen.

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