• May 26 project update: Bertha reaches Western Avenue

    Seattle Tunnel Partners crews have successfully tunneled beneath the Columbia Street on-ramp to the Alaskan Way Viaduct. Bertha, the SR 99 tunneling machine, passed approximately 50 feet below the structure’s foundations and is now beneath Western Avenue, heading toward Marion Street. The on-ramp, like the viaduct, remains stable.
    As of May 26, Bertha had traveled a total of 2,255 feet. She is in zone 3 of the tunnel drive. The top of the tunneling machine is now more than 100 feet below the surface. 
    Look for another progress update on Tuesday, May 31, following the holiday weekend.  


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  • May 18 project update: Bertha passes 2,000-foot mark

    Seattle Tunnel Partners resumed mining late Tuesday evening following a break for rest and routine maintenance.
    Bertha has now installed 300 concrete tunnel rings and traveled more than 2,000 feet from the launch pit west of the stadiums. Her journey is more than 20 percent complete. She is approaching the start of Zone 3, which will take her beneath the Columbia Street on-ramp to the viaduct and, later, beneath Western Avenue. Look for twice-weekly updates on the Follow Bertha page.
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Program Spotlight

  • Inside tunneling under the viaduct

    After nearly a week of tunneling under the Alaskan Way Viaduct, crews are steadily continuing Bertha’s underground drive towards downtown Seattle. This video gives you a behind-the-scenes glimpse into how the new tunnel is being built, showcasing the complex operations involved in this project. Massive concrete ring segments are transported to Bertha’s segment erector where they are lifted into place, allowing the machine to push forward while the excavated soil is transported … more