SEATTLE (AP) — The Washington state Transportation Department says the contractor building a highway tunnel under downtown Seattle has finished digging a 120-foot-deep pit that can be used to access and repair the broken tunneling machine.
State officials say Seattle Tunnel Partners' crews removed the final scoop of soil Friday. They've moved about 20,000 cubic yards of material since mid-October. Next they'll build a concrete cradle at the bottom of the pit to support the tunneling machine called Bertha. The contractor hopes Bertha will be able to chew through the pit's 20-foot-thick concrete southern wall to reach the access pit. If that doesn't work, the contractor will create the opening.
Once Bertha is in the access pit, workers will use a massive red crane to hoist the tunneling machine's front end to the surface for repairs.
The plan is to move Highway 99 under the city, replacing the aging Alaskan Way viaduct. The tunneling machine broke down in December 2013 after drilling about 1,000 feet of the 2-mile tunnel.