Contents tagged with sr99

  • + 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 the tunneling machine operate?

    When operating, the SR 99 tunneling machine's rotating cutterhead scrapes away soil, carrying it 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. A conveyor belt that will eventually reach 9,000 feet in length moves 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 (links to YouTube).

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  • + Where will the dirt from tunneling go?

    During tunneling, Seattle Tunnel Partners 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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  • + 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 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).

    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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  • + Why is the tunneling machine named Bertha?

    Naming tunneling machines is a long-running tradition within the tunneling industry. Brenda, Togo, Balto, Rainier and Elizabeth are all names of tunneling machines that are currently or have recently completed tunneling in the Puget Sound region.

    Like most ships, tunneling machines are traditionally named after females and WSDOT chose to follow in that tradition. Bertha’s name was chosen as part of a contest for kindergarten through 12th-grade students. Proposed names had to be female and have significance to Washington state heritage, life, nature, transportation or engineering. Elected mayor of Seattle in 1926, Bertha Knight Landes was the first woman to lead a major American city.

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