The TBM is being used on a US$3.1bn (£2bn) project to build a tunnel to replace the Alaskan Way Viaduct in Seattle, USA, but came to a halt in December 2013. She is now emerging into daylight after breaking through into an access pit that will be used to bring her to the surface for repairs (link opens in new tab).
The project's contracting joint venture, Seattle Tunnel Partners, began mining into the southern wall of the SR 99 tunnel access pit earlier this week to help Bertha break through the wall. She moved forward about 10m to reach the access pit before tweeting yesterday: “The top of my cutterhead has broken through the wall."
This is the start of the repair effort being led by STP - a joint venture of Dragados USA and Tutor Perini - and manufacturer Hitachi Zosen. Bertha will continue to move forward in 2m increments, stopping to build rings on her way into the pit. When the front end of the machine is fully exposed, crews will begin the disassembly process. STP has said that taking the machine apart and lifting it to the surface will take significant time and effort.
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