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02 April 2015: Chris Dixon, Project Manager for construction JV Seattle Tunnel Partners (STP), and Jeroen van Kooperen, Project Manager of specialist crane-lift subcontractor Mammoet of the Netherlands, describe in detail the plan and the successful process of lifting the main drive unit and cutterhead of TBM Bertha, a lift of some 2,000 tonne, to the surface ahead of repairs to the main bearing seals of the mega 17.5m diameter EPB machine and replacement of the main bearing with the spare. Repairs are to take place for a planned restart of tunnel boring in August this year.

References
Unique gantry for mega-TBM lift - TunnelTalk, March 2015
TBM Bertha repair strategy - TunnelCast, April 2015
Alaskan Way mega-project procurement - TunnelTalk, October 2010

Snapshot

Sterling Noren, TunnelTalk
Project: Alaskan Way Viaduct replacement tunnel, Seattle
Contractor: Seattle Tunnel Partners Dragados - Tutor Perini JV
Client: WSDOT
TBM supplier: Hitachi Zosen 17.48m EPBM
Date of breakdown: December 2013
Nature of problem: Machine overheating
Diagnosis: Ruptured bearing seals
Bearing manufacturer: Rothe Erde of Germany
Replacement bearing: Spare bearing available as part of the contract
Access method: 24m diameter x 36m deep (80ft x 120ft deep) recovery shaft Started in May 2014 Completed Feb 2015
Revised schedule: Repairs to be completed and anticipated restart of boring by August 2015
Original contract delivery date: November 2016