• Nov. 24 project update: Video of Seattle Tunnel Partners rotating Bertha's cutterhead

    Commissioning of the SR 99 tunneling machine continues as Seattle Tunnel Partners prepares to resume mining. STP began testing machine components earlier this month as crews continued welding pieces and reconnecting hoses and cables. Last week, STP began rotating the machine’s cutterhead a few degrees at a time, stopping periodically to take measurements before completing a full rotation.
    Tuesday, Nov. 24 marked the first sustained rotation of the cutterhead since the machine broke through the southern wall (links to YouTube) of the access pit on Feb. 19. STP indicated they will rotate the cutterhead in both directions for about one hour at a time. Watch a short video of the cutterhead rotating below.
    During the next phase of commissioning, STP will backfill the access pit with sand and gravel to prepare the machine for mining. STP's most recent schedule shows that the machine will be ready to resume mining on Dec. 23. The state cannot verify the contractor's schedule.
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  • Nov. 12 project update: Tunneling machine testing underway

    Seattle Tunnel Partners and manufacturer Hitachi Zosen have begun testing components of the SR 99 tunneling machine as they prepare to resume mining. A few initial tests were performed last week, and several others are slated to occur in the coming weeks.
    This week’s highlights include tests of various pumps inside the machine, as well as the screw conveyor system that carries excavated material from the cutterhead to the back of the machine and out of the tunnel. All of the tests are being conducted by STP and Hitachi Zosen, who are jointly responsible for ensuring the machine is ready to complete the remainder of the tunnel drive. Future tests will include rotation of the machine’s cutterhead, which, according to STP, will occur in late November.
    Some reassembly work is ongoing. Major components of the machine are in place, but crews continue to weld pieces together and reconnect wires and hoses. STP’s most recent schedule shows that the machine will be ready to resume mining on Dec. 23. WSDOT cannot verify the contractor’s schedule. The narrated video below explains STP’s repair effort in more detail.
    Other work
    STP crews have finished treating the ground north of the access pit. They began injecting grout into the soil there last month to stabilize the area where the machine will exit the access pit. Crews will soon place a thin layer of sand at the bottom of the pit; the rest of the pit will be filled after initial testing is complete. 
    STP crews are also preparing to install glass walls at the operations buildings located at each portal. The north building’s glass will be installed first. Read more about those efforts in this post.
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Program Spotlight

  • Exterior walls for operations buildings prioritize transparency

    As walls are installed at the north and south portal operations buildings in the coming weeks, drivers may be surprised by how little their view inside the buildings changes. The exterior walls of the large fan rooms will be made of glass, providing passersby with a glimpse of the everyday activities that will occur inside these important operation centers.

    The decision to use glass walls arose out of the guiding principles for the operations buildings: to reflect their function and … more