Jan. 13 project update: Hyperbaric work continues

Posted on Jan 13 2017 8:56 AM
Seattle Tunnel Partners is making good progress as they continue performing hyperbaric maintenance on Bertha, the SR 99 tunneling machine. Since the maintenance period began on Jan. 5, crews have replaced 250 cutterhead tools (see example below) over the course of 184 hours of hyperbaric shifts. This maintenance is critical as STP prepares for the final 25 percent of the tunnel drive.  
Some of the cutterhead tools replaced during this maintenance stop
The work is taking place in the chamber behind Bertha’s cutterhead, as shown in this image (PDF). As the video below explains, working in this environment is similar to performing an underwater dive.  
STP will resume tunneling when the maintenance period is complete. The top of Bertha’s cutterhead is located approximately 160 feet below Third Avenue, about halfway between Blanchard and Bell streets. Crews are less than 2,500 feet from the receiving pit near Seattle Center where Bertha will emerge.
Progress updates are posted on Mondays and Thursdays at our Follow Bertha page. You can also follow Bertha on Twitter @BerthaDigsSR99.

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