Contents tagged with sr99

  • + How many lanes will the tunnel have?

    The tunnel will have two 11-foot travel lanes with an eight-foot safety shoulder and a two-foot shoulder in each direction that will ensure enough space for all vehicles and legal size trucks.

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  • + Who will pay for the cost associated with the tunneling machine stoppage?

    WSDOT does not believe the state or taxpayers will be responsible for costs associated with the current delay. Earlier this year, Seattle Tunnel Partners requested $125 million in additional compensation. WSDOT denied that request after determining it had no contractual merit. The process for resolving disputes within the tunnel contract is prescriptive. It requires multiple steps by both parties. Should Seattle Tunnel Partners continue to pursue entitlement related to the stoppage, it will take time to resolve.

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  • + When will the SR 99 tunnel open to drivers?

    Seattle Tunnel Partners is working to meet the November 2016 opening date as originally proposed by WSDOT. They are looking at ways to streamline their construction schedule in order to recover as much as five months.

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  • + What work is happening while tunneling is on hold?

    Construction is taking place at the north and south end of the SR 99 tunnel. The north portal is taking shape near the Space Needle, including construction of the pit where the SR 99 tunneling machine will emerge at the end of tunneling. Crews are also building the cut-and-cover tunnel that will connect the bored section of the tunnel to SR 99/Aurora Avenue North.

    Crews at the south portal are continuing to work on the south portal operations building, which will control safety features, lighting and ventilation within the future tunnel. Work is also focused on the south cut-and-cover tunnel that will connect the new south-end SR 99 roadway with the bored section of the tunnel.

    Crews in Frederickson, Wash. continue to produce the concrete tunnel segments that are pieced together to form the exterior walls of the SR 99 tunnel.

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  • + How will the tunneling machine be repaired?

    In mid-April, Seattle Tunnel Partners provided WSDOT with a schedule that outlines the necessary steps for repairing the SR 99 tunneling machine and resuming tunneling by the end of March 2015.

    Seattle Tunnel Partners is building a 120-foot-deep circular pit (pdf 2.5 Mb) in front of the machine, which is located about 60 feet below the surface in a fenced off construction zone between South Jackson and South Main streets. When the pit is complete, the machine will tunnel forward into it. Crews will then partially disassemble the machine and make repairs and enhancements. Seattle Tunnel Partners' work plan (pdf 4.8 Mb), which is illustrated in an animation (view on YouTube or download WMV file), contains four major repair and enhancement elements:

    • Replacing the damaged seal system with a more robust system
    • Replacing the main bearing
    • Installing enhanced monitoring systems
    • Adding steel to strengthen the machine and accommodate the new seal system


    You can watch crews work via our construction cameras.

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  • + Why has tunneling stopped?

    Tunneling began in summer 2013, just west of the stadiums. In December 2013, Seattle Tunnel Partners stopped tunneling approximately 1,000 feet into the tunnel drive after experiencing increased temperatures in the machine. While investigating the cause of the high temperature readings, Seattle Tunnel Partners discovered damage to the machine’s seal system and contamination within the main bearing. Seattle Tunnel Partners plans to make repairs and enhancements to the machine and resume tunneling in March 2015. The tunnel is scheduled to open to drivers in 2016.

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  • + When will the viaduct be closed?

    For the most part, SR 99 remains open during construction thanks in part to a construction bypass roadway that connects SR 99 in SODO to the viaduct along the waterfront. The viaduct is closed for two weekends a year – generally in the spring and fall - for inspection and maintenance. We also have a few planned closures due to construction activities such as when the tunneling machine tunnels beneath the viaduct. For any type of planned closure, we provide advance notice to the public so they can plan their trips accordingly.

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  • + How does the tunneling machine operate?

    The SR 99 tunneling machine was built specifically for the ground conditions beneath Seattle. The machine’s cutterhead will chip away the ground as it rotates and carry excavated soil back through the machine using a spiral screw conveyor. Curved concrete panels are installed behind the machine’s front end to form rings that serve as the machine’s exterior walls. Ring by ring, the machine pushes forward while the tunnel takes shape in its wake. The machine will dig an average of 35 feet per day. A conveyor belt, that will eventually reach 9,000 feet in length, will move excavated soil from the front of the machine out of the tunnel to barges waiting at nearby Terminal 46.

    The tunneling machine uses a laser as a reference as it moves forward through the earth. Projected from a fixed point behind the machine, the laser is received by a guidance system at the front of the machine that is precisely calibrated to the tunnel’s predetermined path. The guidance system is referenced by the machine’s operator to ensure the machine remains on course. The operator steers the machine by making slight adjustments with each push forward. To learn more about how the machine operates watch the tunneling machine video.

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  • + Where will the dirt from tunneling go?

    During tunneling, crews will remove 850,000 cubic yards of soil. Clean tunnel spoils will be barged to CalPortland’s Mats Mats reclamation facility at Port Ludlow where they will help fill a gravel quarry.

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