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Sept. 24, 2021

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The pit and Bertha: Key event in Seattle tunnel project

The Columbian
Published:

SEATTLE — The contractor trying to dig a new highway tunnel under downtown Seattle is ready for a key event in repairing the stalled boring machine known as Bertha, a state transportation official said.

Seattle Tunnel Partners has completed a cradle at the bottom of a 120-foot rescue pit. Now Bertha will have to drill about 20 feet through the pit’s concrete wall to reach it.

The 2,000-ton head of the boring machine will rest on the cradle so it can be lifted by a huge crane to the surface.

The contractor needs to replace bearings and seals and other parts, then lower the cutting head back into the pit so Bertha can continue tunneling.

“They are ready to go on this repair plan,” said Todd Trepanier, the state Transportation Department’s project manager.

He updated the Seattle City Council on Monday on the progress, the Seattle Daily Journal of Commerce reported.

Bertha overheated and ground to a halt in December 2013 about 1,000 feet into a planned 2-mile tunnel. It would carry Highway 99 traffic and allow the state to tear down the aging Alaskan Way Viaduct, which could collapse in a major earthquake.

If Bertha can’t bring itself to bore through the pit’s wall, workers would have to break through the wall from inside the pit.

Seattle Tunnel Partners needs to get Bertha moving again to complete the $2 billion tunnel project by the latest projected opening in late 2017.

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