July 19 project update: Seattle Tunnel Partners resumes mining

Posted on Jul 19 2016 9:27 AM

Seattle Tunnel Partners resumed mining yesterday following a month of routine and hyperbaric maintenance on Bertha, the SR 99 tunneling machine. Crews inspected and repaired machine components as needed during the maintenance period, which started on June 23.

The maintenance period included more than 40 shifts of work under hyperbaric conditions, changing cutting tools and performing other maintenance in the space behind the cutterhead. In all, STP changed 33 of more than 700 cutting tools.

What’s next for Bertha?

Tunnel boring is one-third complete. The machine is located approximately 120 feet beneath Spring Street, tunneling north toward First Avenue. At its deepest point near Virginia Street, the machine will be more than 200 feet below the surface.

STP expects to stop two more times for maintenance before they reach the future north portal, near the Space Needle. You can continue to follow tunneling progress at our Follow Bertha page , and on Twitter @BerthaDigsSR99

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