• July 7 project update: A splash of color for the south portal

    This week, the muted tones of the south portal construction area will welcome an accent of yellow. The infusion of color will come courtesy of four 40-foot-tall, brightly painted steel ventilation stacks that are to be installed at the south portal operations building.
    The stacks are central to the tunnel’s ventilation system, which will be capable of removing 1.4 million cubic feet of air per minute should it be necessary. The operations buildings at each end of the tunnel will house operating systems, including safety, lighting and communications. Additionally, they’ll provide space and access for the very thing that inspired the colorful stacks – WSDOT’s yellow maintenance vehicles. Like all aspects of the design, the color palette was developed with guidance from the Seattle Design Commission.
    SR 99 tunnel south operations building image
    WSDOT and Seattle Tunnel Partners worked with the Seattle Design Commission on the final look and color scheme of the tunnel operations buildings.
    Manufactured in Longview, Wash. with American-made steel, the stacks will be delivered by truck to the work zone over the next few days. Crane crews will then hoist them into place before bolting them to the building’s steel frame. If the stacks had their own baseball card, here are some facts that might appear on the back:
    • Height above street level: 102 feet
    • Weight: Approximately 30,000 pounds of steel
    • Diameter: 10 feet
    • Thickness: Three-eighths of an inch
    • Professional debut: July 7 to 8, 2015
    • Position: Vertical
    • Birthplace: The stacks were manufactured in Longview, Wash. by Wayron, a DBE firm based there.
    The north portal operations building will also have four yellow ventilation stacks, but their delivery date has yet to be determined. Both buildings were the subject of this post back in April. Crews have made substantial progress on the structures since then, with the ventilation stacks being the most visible markers of that progress to date.
    SR 99 tunnel ventilation stack installation
    Seattle Tunnel Partners began installing ventilation stacks at the south operations building on July 7.


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  • Summer is the season for Milepost 31

    Hoping to catch a glimpse of SR 99 tunnel construction? Summer is an ideal time to visit Milepost 31, our project information center, located at 211 First Ave. S. in Seattle’s Pioneer Square neighborhood. Our free public tours give visitors a great view of the work site from a section of the Alaskan Way Viaduct that has been permanently closed to traffic. 

    Tours depart from Milepost 31 Tuesday through Saturday. Advance registration is required. Each tour is a half-mile round trip, and visitors must be able to walk over uneven ground and climb up and down 50 stairs.

    After the tour, stick around to look at the exhibits about the people and projects that shaped Pioneer Square. Learn how natural forces and people transformed Seattle’s landscape over time, and get an inside look at the SR 99 Tunnel Project.

    No speaker series in July

    Normally we host a monthly speaker series in conjunction with Pioneer Square’s First Thursday Art Walk, but due to the holiday we won’t be hosting the event in July. Milepost 31 will remain open until 8 p.m. on July 2 for the Art Walk. The center will be closed on July 3 and 4. Speaker Series will resume on Aug. 6.

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  • June 5 project update: Installation of new seal system underway

    Seattle Tunnel Partners has begun installing the SR 99 tunneling machine’s newly redesigned seal system. Crews lowered the new outer seal ring into place Wednesday, marking the first new piece to be installed in the machine as part of STP’s effort to resume tunneling.
    The new outer seal system arrived in October and was stored on-site prior to Wednesday’s installation. The new inner seal system arrived last week and is currently being installed. Made in Japan by manufacturer Hitachi Zosen, the new seal system will be easier to access should the need arise.
    Crews look on as the tunneling machine’s new outer seal ring is moved and placed on the cutterhead.
    We will continue to provide updates as we receive them.
    Digging into STP’s repair plan
    You can continue to track STP’s work on our time-lapse cameras and follow @BerthaDigsSR99 on Twitter for updates. Don't forget to check out the other resources we've created to give you a fuller understanding of Bertha's story:


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Program Spotlight

  • Making progress on the south end

    If you regularly drive SR 99 near the stadiums, you’ve probably noticed a lot of changes to the roadway during the past 16 months. For example, crews divided the northbound and southbound lanes into two separate roadways near South Atlantic Street to make room for more construction. And you’ve no doubt witnessed huge changes taking place in the work zone on either side of the road. Did you know that crews have been hard at work completing the southern portion of the SR 99 tunnel … more