Tunnel machine Bertha has resumed digging in downtown Seattle, near Columbia Street, after its work underneath the Alaskan Way Viaduct and a rest break.
Tunnel machine Bertha has awakened after 4½ days of crew rest and maintenance.
The Highway 99 tunnel-boring machine has just passed the 2,000-foot markon its 9,270-foot journey from the stadium area to South Lake Union, the state reported.
That puts the machine beyond the earthquake-proofed Western Building and heading toward Columbia Street, where the route passes below the old Alaskan Way Viaduct onramp. No lane closures are planned there, because the tunnel is considered deep enough to avoid risk to the ramp foundations.
Muck dropped steadily Wednesday morning from a conveyor belt onto a barge at Terminal 46 for shipment to an abandoned quarry.
Seattle Tunnel Partners (STP) is hoping the 57-foot, 4-inch diameter machine finishes drilling by December.
STP stopped the machine early Friday at 1,995 feet, and restarted late Tuesday, reaching a total 2,008 feet as of 5 a.m. Wednesday, said Laura Newborn, spokeswoman at the Washington State Department of Transportation. Earlier this spring, Bertha passed underneath the viaduct foundations, digging 24 hours a day.
The dig began July 30, 2013, but lost two years because of machine damage and overheating — followed by a prolonged operation to build a vertical access vault, lift the 4-million-pound front end, replace the damaged main bearing assembly, and add steel to stiffen other front-end parts.
Bertha has pushed forward at an above-average pace of close to 40 feet per day since April, as it moves from soggy waterfront soil into firmer downtown clay.
STP is seeking compensation from the state and project insurers totaling more than $200 million, a dispute that could linger after the estimated spring 2018 grand opening.