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.


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

    In 2014, Seattle Tunnel Partners requested $125 million in additional compensation related to the stoppage. 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. Ultimately, the responsibility for costs associated with the delay will be determined through the project's design-build contract. 


  • + Did other work continue during the tunneling stoppage?

    Construction at the north and south ends of the SR 99 tunnel continued throughout the stoppage. Crews built ramp and roadway connections at each portal. They also continued work on the operations buildings that will control safety features, lighting and ventilation within the future tunnel. 


  • + How was the tunneling machine repaired?

    Seattle Tunnel Partners built a 120-foot-deep pit in front of the machine. When the pit was complete, the machine tunneled forward into it. Crews then partially disassembled the machine and made repairs and enhancements. This narrated video (links to YouTube) explains the repair process in detail. The machine mined out of the pit in January 2016 and completed the SR 99 tunnel drive in April 2017.


  • + Why did tunneling stop in December 2013?

    Tunneling began in summer 2013just 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, STP discovered damage to the machine’s seal system and contamination within the main bearing. STP has since completed repairs and enhancements to the machine and resumed tunneling. Their latest construction schedule is available here.


  • + Will the viaduct close during construction?

    The viaduct closes for two weekends a year – generally in the spring and fall  for inspection and maintenance. The project also includes planned temporary closures due to construction activities, such as the 10-day closure that occurred in April and May 2016.

    Aside from planned closures, SR 99 will remain open during construction thanks in part to a construction bypass roadway that connects SR 99 in SODO to the viaduct along the waterfront. 


  • + How does a tunneling machine work?

    When operating, the SR 99 tunneling machine's rotating cutterhead scraped away soil, carrying it back through the machine using a spiral screw conveyor. Curved concrete panels were installed behind the machine’s front end to form rings that serve as the machine’s exterior walls. Ring by ring, the machine pushed forward while the tunnel took shape in its wake. A conveyor belt that eventually reached 9,000 feet in length moved excavated soil from the front of the machine out of the tunnel to barges waiting at nearby Terminal 46.

    The tunneling machine used a laser as a reference as it moved forward through the earth. Projected from a fixed point behind the machine, the laser was received by a guidance system at the front of the machine that was precisely calibrated to the tunnel’s predetermined path. The guidance system was referenced by the machine’s operator to ensure the machine remained on course. The operator steered the machine by making slight adjustments with each push forward. To learn more about how the machine operated watch our tunneling machine video (links to YouTube).