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March 20, 2015

Front shield lifted from Bertha pit

By JOURNAL STAFF

Photo from WSDOT [enlarge]

Yesterday crews with Seattle Tunnel Partners lifted the 270-ton front shield off the damaged tunnel machine Bertha and brought it to the surface.

Two more shields, each weighing nearly 100 tons, must be removed before STP can reach the damaged cutterhead and bearing assembly.

The contractor is using a huge crawler crane to remove the shields. The giant red gantry crane next to the viaduct will be used to pull up the 2,000-ton cutterhead assembly.

To prepare for the lift, crews disconnected hoses and cables, and removed eight of the machine's 24 drive motors. The remaining 16 motors, which weigh about 8,000 pounds apiece, will be removed from the rescue pit as part of the cutterhead lift.

STP will repair the cutterhead and main bearings under a metal-framed canopy just south of the pit. The canopy will protect parts and workers from the weather.

All four pieces should be at the surface by the end of this month. Repairs could be finished by late May, and tunneling could resume in August after testing and commissioning.

Bertha broke down in December 2013 after traveling about 1,000 feet along its 9,270-foot route. It has 12 months of tunneling left. STP's latest schedule has the tunnel opening in fall 2017.

Learn more about STP’s repair plan in this narrated video .




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