Feb. 9 project update: Bertha passes beneath the Battery Street Tunnel

Posted on Feb 9 2017 2:55 PM
SR 99 tunnel crews successfully mined beneath the Battery Street Tunnel this week. The top of Bertha, the SR 99 tunneling machine, passed approximately 90 feet below the bottom of the 62-year old tunnel, which will permanently close when highway traffic shifts from the Alaskan Way Viaduct to the new tunnel.
 
The ground along the tunnel route remains stable as Bertha pushes toward the finish line near Seattle Center. Crews are now less than 1,600 feet from the end of the tunnel drive, and the machine is climbing at a steady rate. The distance between the top of the machine and the surface is approximately 115 feet. The tunnel, at its deepest point, is approximately 215 feet deep.
 
Up next for Bertha: a trip beneath Fifth Avenue and the Seattle Center Monorail. The top of the machine will pass approximately 90 feet below the Monorail’s supports.
 
Highway construction
 
While crews inside the tunneling machine are focused on mining, separate crews are hard at work building the double-deck highway inside the tunnel. The new roadway now stretches more than 3,800 feet into the tunnel, near the southern edge of Pike Place Market. 
 
Work has also begun on the mechanical, electrical and plumbing systems within the tunnel. Crews began installing these systems near the stadiums last week and will continue to progress north, even after the tunnel drive is complete. 
 
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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