Contents tagged with sr99

  • + 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.

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  • + 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.

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  • + 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. 

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  • + 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).

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  • + Where did the dirt from tunneling go?

    During tunneling, Seattle Tunnel Partners removed 850,000 cubic yards of soil. Clean tunnel spoils were barged to CalPortland’s Mats Mats reclamation facility at Port Ludlow, where they helped fill a gravel quarry.

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  • + Why was the tunneling machine built in Japan?

    As WSDOT's design-build contractor, Seattle Tunnel Partners was responsible for procuring the SR 99 tunneling machine. Hitachi Zosen Corp. was selected as the SR 99 tunneling machine manufacturer ahead of three other American and international firms based on overall technical requirements, support capabilities, price and schedule. Based in Osaka, Japan, Hitachi has successfully built more than 1,300 tunneling machines, a number of them for large-diameter tunnel projects such as this one.  

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  • + Will tolling cause diversion?

    The Advisory Committee on Tolling and Traffic Management reviewed several potential toll scenarios in an effort to meet the Legislature's $200 million toll-funding requirement and minimize traffic diversion. Results from their analysis are available online.  

    In summer 2016, WSDOT commissioned an independent traffic analysis firm to conduct a traffic and revenue study that will inform the toll rate setting process. Learn more about the study at WSDOT's Tolling page

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  • + Will the SR 99 tunnel be tolled?

    In 2013, WSDOT was directed by the Washington State Legislature to raise $200 million from tolls for the SR 99 Tunnel Project. The Advisory Committee on Tolling and Traffic Management studied ways to refine tolling of the SR 99 tunnel to minimize traffic diversion and meet funding goals, and investigate strategies to reduce or mitigate diversion. The committee submitted recommendations in 2014 (pdf 1.8 Mb).

    In summer 2016, WSDOT commissioned an independent traffic analysis firm to conduct a traffic and revenue study that will inform the toll rate setting process. Learn more about the study at WSDOT's Tolling page

    Toll rates for the SR 99 tunnel have not been determined. The Washington State Transportation Commission will oversee the rate-setting process closer to when the tunnel opens to traffic. Tolling is anticipated to start when the tunnel opens to traffic.

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  • + Will the tunnel have mid-town exits?

    The SR 99 tunnel will not have mid-town exits. The tunnel and a new Alaskan Way street are designed to work together to replace the functionality of the viaduct. The tunnel will have the capacity to accommodate trips through downtown, while the rest of today’s viaduct users will access downtown using ramps at either end of the tunnel. Along the waterfront, a new Alaskan Way street will provide several east-west connections to downtown, replacing the function of today’s midtown viaduct on-ramp and off-ramp.

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