Contents tagged with sr99

  • + 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).


  • + 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.


  • + 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.  


  • + Will the SR 99 tunnel be tolled?

    The 2012 Legislature directed WSDOT to collect tolls in the SR 99 tunnel in order to fund ongoing tunnel maintenance and raise $200 million to repay construction bonds used to build the tunnel. Tolls could also pay for future tunnel operations and maintenance costs, similar to other toll facilities in Washington. Tolling of the SR 99 tunnel is anticipated to begin after the tunnel opens to drivers

    The Washington State Transportation Commission is responsible for setting toll rates and is in the process of analyzing potential toll rates. They will oversee the toll rate-setting process in 2018.


  • + 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.


  • + 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.


  • + Will there be restrictions on freight using the tunnel?

    Most freight will be able to use the SR 99 tunnel. Vehicles hauling hazardous or combustible materials will be prohibited from the tunnel, similar to current restrictions in the Battery Street Tunnel and on the viaduct during peak hours. These vehicles will take I-5 or Alaskan Way along the waterfront, as they do today.