• Jan. 30 project update: Access pit excavation complete

    Seattle Tunnel Partners has completed excavation of the 120-foot-deep pit that will be used to access and repair Bertha, the SR 99 tunneling machine. Crews removed the final scoop of soil from the pit on Friday, Jan. 30. Approximately 20,000 cubic yards of material was removed from the ground over the course of excavation, which began in mid-October. 
    With excavation complete, crews can begin construction of the concrete cradle at the bottom of the pit. The cradle will support the machine after it moves through the pit’s southern wall, which is about 20 feet thick. 
    STP plans to tunnel through the concrete wall. The length of time it takes Bertha to reach the pit will depend largely on her ability to mine through and digest the concrete. If she’s unable to mine through the wall, STP will create an opening from within the pit to give her an unobstructed path forward. Once inside the pit, crews will use the massive red gantry crane pictured below to hoist the front end of the machine to the surface for repairs. This narrated video (links to YouTube) explains the repair process in detail. You can also watch raw video of pit excavation on YouTube.  
    The dewatering system that controls groundwater in the pit will continue to operate at its current level as STP proceeds with its repair work. Settlement levels near the pit remain stable.
    Crews building the highway inside the tunnel are also preparing for a big milestone: the first concrete pour on what will become the southbound lanes of the tunnel. Here’s what the southbound roadway currently looks like:


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  • Jan. 27 project update

    Last week, we shared with the public that the dispute review board for the SR 99 tunnel contract had heard and made recommendations on a request by Seattle Tunnel Partners for a differing site condition at the tunnel launch pit. A differing site condition can occur when: 1) actual subsurface or latent physical conditions encountered at the site differ substantially or materially from those indicated in the contract, or 2) unknown conditions at the site are unusual in nature and differ materially from those ordinarily encountered in the type of work.
    To clarify, this dispute is related to a differing site condition experienced while building the launch pit; it is not related to the stoppage of the tunneling machine or recent settlement near the access pit. And, there are funds set aside within the existing project budget to deal with differing site conditions.
    There has been interest from the public in being able to review the board’s recommendations, which are attached to this WSDOT memorandum (pdf 880 kb). Because these recommendations are technical in nature, there may be questions about what they mean.
    As we review the board’s recommendations on the differing site condition in the launch pit and determine our next steps, we will use the terms in the contract to reach the best possible outcome for taxpayers as we continue to build this critical safety project. We will not be offering our opinions of the board’s recommendations or speculating on next steps until our analysis is complete.
    It is also important to remember that the board’s recommendations are just that, recommendations. They are not binding. While STP requested $20 million in compensation for this differing site condition, the board’s recommendations did not address the cost and schedule impacts. Thus it is too early to speculate as to the cost and schedule impacts of this recommendation, should it be accepted by WSDOT.


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Program Spotlight

  • Information for residents and businesses in Pioneer Square

    Recently, our team detected approximately one inch of ground settlement near the pit Seattle Tunnel Partners is building to access and repair the SR 99 tunneling machine. Settlement was also detected on the Alaskan Way Viaduct and some of the buildings that we are monitoring; the amount of settlement lessens in the surrounding area. Our experts are still analyzing data and conducting daily inspections of the viaduct, but the initial settlement we reported publically on Dec. 5 has since … more