Contents tagged with sr99

  • + 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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  • + Why was the tunneling machine built in Japan?

    Based in Osaka, Japan, Hitachi Zosen has successfully built more than 1,300 tunneling machines, a number of them for large-diameter tunnel projects such as ours. It is critical that we ensure the manufacturer of the SR 99 tunneling machine, which is the world’s largest boring machine to date, is at the leading edge of the industry, with expertise in producing similar large-scale machines. 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.

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  • + How many local jobs are created through the SR 99 Tunnel Project?

    Construction to replace the Alaskan Way Viaduct is boosting our local economy in many ways. Seattle Tunnel Partners (STP), the joint venture that is building the SR 99 tunnel, includes several local firms, such as Frank Coluccio Construction, HNTB Corp and Malcolm Drilling Company. Seventy-five percent of STP’s subcontracts – including contractors, consultants and suppliers – are with firms located in Washington state. At the height of construction, the viaduct replacement will sustain nearly 3,900 jobs.

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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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