• March 23 project update: Getting ready for Bertha’s breakthrough

    Seattle Tunnel Partners is making final preparations for the SR 99 tunneling machine’s arrival at the disassembly pit near Seattle Center. Because mining rates will continue to vary as crews approach the pit, we can’t predict when Bertha’s breakthrough will occur. As of this morning, the cutterhead was approximately 320 feet from the finish line. We will continue to provide regular progress updates along the way.
    We recognize that there is great interest surrounding this stage of the project, and we are working on ways to share this historic moment with the public. We will be activating a new time-lapse camera as well as streaming video of the disassembly pit prior to breakthrough. These cameras will offer the best view of Bertha’s arrival in the pit. We will also continue to share photos and provide frequent updates via social media, including daily progress updates. For safety reasons, the public will not be allowed in the construction zone during the breakthrough. 
    Look for more updates soon about the breakthrough sequence, the process for disassembling Bertha and the work that remains before the tunnel opens in 2019.
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  • March 9 project update: New 360-degree video takes you inside the tunnel as Bertha enters Zone 10

    The countdown is on as Bertha, the SR 99 tunneling machine, mined into the 10th and final zone of the 9,270-foot tunnel drive this week. With 1,294 concrete tunnel rings installed in the ground behind her, Bertha is less than two blocks from the disassembly pit where her journey will end.
    How is the interior of the tunnel shaping up? And how is Bertha doing? It’s probably best if we show you. Click below to join Program Administrator Joe Hedges on a 360-degree tour of the project. Move your smartphone up and down to move around the tunnel. Or, if you’re on a computer, grab the picture with your mouse for a 360-degree view of the work that’s happening out of sight, underneath Seattle.   
    Looking ahead
    It’s still too early to predict when Bertha will reach the disassembly pit. Seattle Tunnel Partners’ most recent schedule shows that tunnel boring is slated to end in May, but mining rates will continue to vary based on maintenance needs and ground conditions.
    There’s still plenty of work to do after tunnel boring is complete. STP will begin disassembling the tunneling machine soon after the cutterhead breaks into the pit. They will remove the machine in small pieces and haul them away by truck, a process that will take several months.
    Meanwhile, crews will continue building the double-deck highway inside the tunnel. This work is completed in different stages, as shown in our weekly interior structures report. The roadway deck is now at the southern edge of Pike Place Market, or nearly 50 percent complete.  
    Crews are also installing mechanical, electrical and plumbing systems that must be completed before the tunnel can open to traffic. This is a big job that is scheduled to last well into 2018. 
    As construction continues, WSDOT and STP will begin an extensive commissioning program. This involves a series of thorough inspections, tests and quality verification procedures to ensure the tunnel systems are functioning properly.  
    Based on STP’s schedule, the tunnel is projected to open in early 2019. 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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  • March 6 project update: Bertha on the move again

    Seattle Tunnel Partners resumed mining today after conducting additional survey work to verify Bertha’s position and to make necessary adjustments to complete the tunnel drive. Crews performed routine inspections and maintenance while mining was stopped, including the replacement of cutterhead tools.  
    As of this afternoon, Bertha was tunneling north toward the intersection of Denny Way and Sixth Avenue North, less than 1,000 feet from the disassembly pit. 
    STP stopped mining on Feb. 28 after survey data indicated the tunneling machine may be several inches off the tunnel alignment. Three independent surveys confirmed the 57.5-foot machine was approximately six inches off alignment.
    STP designers made a slight change to the tunnel alignment between the machine’s current location and the end of the tunnel drive. Adjustments are common during tunneling, including on this project. STP made a similar adjustment to correct Bertha’s course after the machine mined out of the access pit following repairs. 
    Crews steer Bertha (links to YouTube) based on information they receive from its onboard guidance system. The system is now set to the new tunnel alignment.
    According to STP’s most recent schedule, Bertha will arrive at the disassembly pit in May. 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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Program Spotlight

  • Getting to know the SR 99 tunnel's biggest fans

    Clean air is a critical element of a safe and well-functioning tunnel. In the new SR 99 tunnel, a complex system of fans will push and pull air into and out of the tunnel to ensure fresh air during routine operations and in emergencies.

    The first element of the tunnel’s ventilation system is the very traffic that uses it. Vehicles traveling through the tunnel will act like pistons, pushing fresh air into the tunnel. But when that piston effect needs a boost, the tunnel will turn to … more