WSDOT stated that its completion clears the way for tunnelling to start this summer, once Bertha’s 41 pieces have been reassembled and tested at the bottom of the pit.
Launch-pit construction started last summer in the work zone west of Seattle’s stadiums. Before excavation began, crews drilled more than 200 piles as many as 100ft (30m) into the ground to form the pit’s walls. The perimeter of the pit is 80ft (24m) wide and 400ft (122m) long.
Assembly of the machine started at the south end of the pit shortly after it arrived last month from Osaka, Japan. Now that the front end of the pit is complete, crews have started building the body of the machine near the spot where it will first push into Seattle’s soil.
Crews are also preparing the surrounding area for tunnelling, including strengthening the soil and building protected work areas along the initial section of the tunnel route so they can perform scheduled inspections of the machine before it begins digging beneath downtown. Meanwhile, work continues near the north end of the Battery Street Tunnel to prepare the area where Bertha will emerge at the end of tunnelling.
