Because "the SR 99 tunnel work zone...has changed significantly since July 2013," KaDeena Yerkdan, the manager of communications for the Alaskan Way Viaduct Replacement Program, invited members of the media to tour Bertha on Thursday.
Yerkdan said that Seattle Tunnel Partners (STP), the contractor behind the project, has mined more than 1,000 feet, built several hundred feet of “cut-and-cover” tunnel, and begun the process of building the tunnel’s interior roadway.
“We’ve got a lot of structures work going on at the north end of the tunnel and at the south end of the tunnel,” said project manager Chris Dixon, explaining that since Bertha’s breakdown, STP has had to “re-sequence” its work.
“We planned on getting in 2,000 ft with the tunnel before we started interior structure…but since we’re stopped, we’ve decided to go ahead and advance a lot of the work in the launch pit.”
The “interior structure” is the enormous structure that follows the Tunnel Boring Machine (TBM) all the way to the north end.
According to Dixon, 231 workers were on duty during the week of August 22nd. About half the work force “is gone” since the TBM stopped in December.
So what about Bertha's breakdown? Dixon went into a detailed account of seals overheating and the need to take Bertha out (instead of backing her out) to do repairs. Asked later about the infamous pipe that Bertha ran into, Dixon laughed. "I think everyone knows we hit a pipe," he said. "That’s not a topic of discussion for today.”
Seattle Tunnel Partners plans to extract Bertha in the middle of November and then complete about three months of repairs. Testing will begin in February and, if all goes according to plan, Bertha will begin digging again in March.
Here, a visual account of what's going on below-ground:
Project Manager Chris Dixon goes over the tunnel layout and its current state. "The job's going full speed ahead," he said.
Looking north over the construction site towards the launch pit, the south operations building, the tunnel and Bertha, the tunnel boring machine. "The only thing that's stopped at this time," said project manager Dixon, "is the boring of the tunnel."
The entrance to the tunnel, facing Bertha (north).
Looking south, at what will be the lower level of the tunnel. When completed, the tunnel will measure 57.5 feet in diameter, with 2 traffic lanes and 8 feet of emergency lane on each level.
The thrust jacks which, essentially, push Bertha forward.
The cockpit of the Enterprise? Not quite. The operating room, where workers can control everything from pressure to the direction in which Bertha bores.
Workers water-proofing the walls of the launch pit. The center of Bertha is about 80 feet below sea level.
Exiting the tunnel.
By March of 2015, when it is predicted that Bertha will start digging again, the tunnel boring machine will have been out of commission for about a year.
