May 11 project update: Bertha fully beyond Alaskan Way Viaduct

Posted on May 11 2016 3:33 PM

Bertha’s passage beneath the Alaskan Way Viaduct has officially come to an end, but Seattle Tunnel Partners has decided to continue mining a bit farther before taking a short break.

By early Wednesday morning, crews had tunneled 385 feet since the underground maintenance stop near Yesler Way. That put them clear of the fourth and final viaduct column the machine had to pass to complete its journey under the elevated structure. STP decided to mine beyond 385 feet in order to reach a better location for the machine to stop while crews take a few days to rest after mining around the clock since April 29.

SR 99 was closed for 10 days while Bertha tunneled beneath the viaduct. WSDOT reopened the highway on Sunday evening based on STP’s tunneling progress and the continued stability of the ground and viaduct. Monitoring of the structure and ground will continue throughout the remainder of the tunnel drive.

Look for another progress update next week.

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