TBM Bertha final breakthrough
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4 Apr 2017: After 1,344 days, mega Hitachi Zosen EPBM Bertha is through to complete excavation of the SR99 Alaskan Way viaduct replacement tunnel in Seattle, Washington. Final breakthrough marked a historic end to the challenging drive that suffered delays caused by union disputes; a serious machine breakdown; a TBM recovery and repair program; the appearance of a sinkhole shortly after restart of the drive. Despite the difficulties, the joint venture team of Dragados and Tutor Perini for the WSDOT client, has remained professional and focused on getting the job done, completing the remaining 8,000ft of advance after restart of the repaired TBM steadily and seamlessly and in 14 months.

STP management changes enable Bertha restart - TunnelTalk, February 2016
Bertha hyperbaric interventions and progress - TunnelTalk, June 2016


TBM Bertha final breakthrough

Sterling Noren reporting for TunnelTalk from Seattle
Project: Alaskan Way Viaduct replacement tunnel, Seattle, USA
Contractor: Seattle Tunnel Partners Dragados/Tutor Perini JV
Client: Washington State Department of Transportation(WSDOT)
TBM: 17.48m diameter Hitachi Zosen EPBM
Internal structures: Upper and lower level road decks, side walls and equipment rooms
Final Breakthrough: 4 April 2017
Days since launch: 1,344 - launch date July 20, 2013
Drive length: 2,850m (9,270ft)
Tunnel lining: Precast segmental lining
Each ring: Nine 2133mm wide x 610mm thick segments
Total rings: 1,426 (13,194 segments)
Schedule: SR99 tunnel programmed to open to traffic in early  019