Tough time for crews digging in front of stalled Bertha to make repairs
Jul 28, 2014, 5:44 AM | Updated: Jul 29, 2014, 10:32 am
Digging under Seattle, as crews have learned the hard way, is not easy to do.
The Seattle tunnel drilling machine, Bertha, has been stalled since December of 2013, and now workers are having trouble with the repair pit.
The 120-foot deep pit in front of the giant tunneling machine is harder to dig than expected.
The Seattle Times reports workers are having so much trouble with the pit that it could delay the removal of the 2,000 ton cutter head.
The cutter head removal had been scheduled for late September or October.
The Washington State Department of Transportation said the work is taking longer than expected because crews have to install 11 additional piles, bringing the total to 84. As it is, WSDOT said Seattle Tunnel Partners crews are “working around-the-clock, seven days a week to complete the approximately 31 remaining piles.”
WSDOT said reinforcing the pit with large interlocking piles take longer to install in the self-supporting pit than standard piles.
According to WSDOT, the issues won’t delay the restart of tunnel digging, which is set to begin in March 2015, because Seattle Tunnel Partners built some wiggle-room into the project schedule.
The tunneling machine only made it about 1,000 feet before breaking down in December. The main bearing that drives the machine was damaged and the seals that protect it were leaking.
The state had two options to fix the world’s largest drill, either take it apart and reach the cutter head from the back or dig a pit in front and remove it. Seattle Tunnel Partners chose option B and started digging a giant pit in front of the drill.
WSDOT said crews are working on other areas of the repair schedule while the piles are being built:
-The main bearing has arrived and crews will likely begin its assembly closer to when it’s need this fall.
-The new out seal ring, the thrust seal ring, and bearing block are nearing completion and will be shipped to Seattle after they’re inspected.
-Crews will begin assembling two large crawler cranes in September that will ultimately lift the largest parts of Bertha from the access pit.
-From July through fall, crews will begin assembling the modular lift tower.
The drill is currently stuck in the mud just south of the Alaskan Way Viaduct.
