• Early warning: Four-day closure of SR 99 coming in late August

    In August, crews working on the North Access contract near the SR 99 tunnel’s north portal will demolish the bridge on SR 99 over Broad Street. Not sure what bridge we’re talking about? Don’t worry. Even the most seasoned SR 99 commuter may not realize they are crossing a bridge at Broad Street.

    That bridge, and Broad Street itself, must be completely transformed to make room for the future connection to the tunnel’s north portal and on- and off-ramps at Harrison and Republican streets.

    Crews have already begun to fill in Broad Street with recycled concrete from the former roadway. Once we close this section of SR 99 to traffic, crews will bring in heavy equipment and demolish the old bridge in about 12 hours. They’ll then spend the next two days adding more fill material to make the new roadway level with the existing lanes of SR 99. After paving the new SR 99 roadway, crews will stripe the lanes and reinstall barriers. Once all of this is completed, SR 99 will reopen.

    Closure information
    Demolishing a bridge and building a new road in its place isn’t easy work. It is especially challenging on a major highway through Seattle. To minimize disruptions to drivers, crews will replace this portion of SR 99 in a mere four days. Drivers should plan ahead for SR 99 closures from Friday night, Aug. 22 to Wednesday morning, Aug. 27.  View a map of the closure. 

    • From 10 p.m. Friday, Aug. 22 to 5 a.m. Monday, Aug. 25 SR 99 will be closed in both directions from the West Seattle Bridge to Valley Street.
      • Northbound SR 99 will be open from South Royal Brougham Way until midnight on Friday, Aug. 22 for exiting Seahawks traffic.
    • From 5 a.m. Monday, Aug. 25 to 5 a.m. Wednesday, Aug. 27 SR 99 will be closed in both directions from the south end of the Battery Street tunnel to Valley Street.

    There’s a lot of other work that will happen on SR 99 during this closure as well, including utility work at Harrison Street, concrete panel replacement in SODO, expansion joint repairs on the viaduct near the Seneca Street off-ramp and removal of ivy and other maintenance on the viaduct.

    We will continue to share information to help drivers plan ahead and get around during the closure.

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  • Contractor announces details of repair work plan for the SR 99 tunneling machine

    Bertha has always been big. The focus now is on rebuilding Bertha and making her better, according to a new repair work plan unveiled Monday, June 16, by Seattle Tunnel Partners, our design-build contractor for the SR 99 Tunnel Project.

    STP’s work plan (pdf 4.8 Mb), which is illustrated in a new animation (view on YouTube or download WMV file), contains four major repair and enhancement elements:

    • Replacing the damaged seal system with a more robust system
    • Replacing the main bearing
    • Installing enhanced monitoring systems
    • Adding steel to strengthen the machine and accommodate the new seal system

    Other major enhancements of the work plan include:

    • Widening the openings at the center of the cutterhead
    • Improving the soil conditioning injection system
    • Installing bit- and wear-resistant steel on the cutterhead
    • Extending the length of the agitator arms in the mixing chamber

    STP will provide WSDOT with additional supporting information about rebuilding the machine in the coming months, in accordance with the design-build contract, to demonstrate how the repairs will meet the contract’s performance and technical requirements, including:

    • An analysis demonstrating that the machine’s structure can withstand all loads from the surrounding ground and its own operation
    • Seal design details and background calculations
    • Design of revised conditioner injection systems and cutterhead openings
    • Updated operations plan including enhanced instrumentation and monitoring for key machine components
    • Complete testing program for all modified machine components prior to restart of mining

    Bertha is currently stopped approximately 60 feet underground between South Jackson and South Main streets. As owner of the machine, STP is responsible for ensuring it functions properly at all times. STP is currently building the underground walls of a circular pit (pdf 2.5 Mb) crews will use to access and repair the machine.


    Links to STP’s plan for repairing Bertha


    Previous updates 

    May 13, 2014 update – Construction of access pit’s underground walls now underway

    May 8, 2014 update - With environmental review complete, access pit construction begins in earnest

    April 29, 2014 update - A summary of change orders on the SR 99 Tunnel Project

    April 21, 2014 update - SR 99 tunneling machine to resume digging in March 2015

    April 3, 2014 update - Setting the stage for Bertha's repairs

    Click here to see a full archive of progress updates

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Program Spotlight

  • Remodeling Bertha’s launch pit

    Seattle Tunnel Partners, our contractor for the SR 99 Tunnel Project, is remodeling the giant concrete box where they assembled, tested and launched Bertha, the world’s largest tunneling machine.  

    Fittingly, Bertha’s launch pit is massive – 400 feet long and 80 feet wide. It was 80 feet deep, but it’s a little shallower now due to the remodel, which is turning the pit into part of the future State Route 99.

    Remodeling the launch pit isn’t too much … more