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March 24, 2015

STP lifts Bertha's last shield

Photo from WSDOT [enlarge]
Next up is Bertha's 2,000-ton cutterhead and drive unit assembly.

On Monday Seattle Tunnel Partners lifted the third shield section off Bertha, the damaged tunnel machine stuck along the Seattle waterfront in Pioneer Square.

In the next week or two crews will lift Bertha's cutterhead and drive unit assembly that weighs 2,000 tons.

The front shield was removed to reach the drive unit. It was cut into three pieces, with the 270-ton upper body lifted last Thursday and the 80-ton left side body lifted on Saturday. The right side body lifted Monday weighs 90 tons.

The lifts were performed with a Demag CC-2800 crawler crane that has a capacity of 660 tons. A modular lift tower will be used to extract the cutterhead/drive unit.

The front shield supports the ground as the machine tunnels, and protects Bertha's mechanical systems.

Hitachi Zosen, the machine's manufacturer, will add more than 100 tons of steel to the bearing block and front body for extra strength and to reconnect the drive unit to the front shield.

Berth's bearing seals and possibly other components were damaged in late 2013. Hitachi Zosen will install a new main bearing and bearing seal system. The work will be performed under a canopy that is 50 feet tall, 60 feet wide and 70 feet long.

STP hopes repairs will be finished by late May and tunneling will restart in August. STP's latest schedule has the tunnel opening in fall 2017.




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