• Plan ahead: Semiannual viaduct inspection closure set for Halloween weekend

    October is here, which means the semiannual inspection closure of the Alaskan Way Viaduct is just around the corner.
    Both directions of SR 99 will be closed between South Spokane Street and the north end of the Battery Street Tunnel from 6 a.m. Saturday, Oct. 31 to 6 p.m. Sunday, Nov. 1. Please plan ahead and be prepared for additional congestion as a result of this closure.
    Closing the viaduct will allow crews to perform maintenance and thoroughly inspect the structure, as they do each spring and fall. Read our viaduct safety fact sheet (pdf 2.9 Mb) to learn more about what we do to keep the viaduct safe and open to drivers until the tunnel project is complete.  
    Viaduct inspection
    Survey crews walk the viaduct during a previous inspection.
    — more —

    Order: 1

  • Milepost 31 Speaker Series: How changing transportation technologies have shaped Seattleā€™s waterfront

    The SR 99 tunnel will pass through a landscape that has been radically transformed. Go back 160-odd years and high tide laps at the foot of the bluff below Pike Place Market and tide flats reach all the way to the base of Beacon Hill. Join us at 6 p.m. on Thursday, Oct. 1 at Milepost 31, as historian Jennifer Ott discusses how changing transportation technologies – from canoes to container ships – have helped shape Seattle’s waterfront.
    Ott is an environmental historian with a particular interest in Seattle's history of moving dirt, rerouting waterways and leveling hills. She is a staff historian for and has written for Seattle Magazine and the Oregon Historical Quarterly.
    Viaduct construction
    Alaskan Way Viaduct construction, circa 1952.
    About our Milepost 31 speaker series

    We host a monthly speaker series at Milepost 31 to give visitors more insight into our work to replace the viaduct and the history of the Pioneer Square neighborhood. The event is held in conjunction with Pioneer Square's First Thursday Art Walk

    6 - 6:30 p.m.
    Thursday, Oct. 1
    Milepost 31211 First Ave. S., Seattle
    Admission is free

    After the talk, be sure to leave enough time to explore the rest of the First Thursday Art Walk in Pioneer Square. Milepost 31 is open Tuesdays through Saturdays from 11 a.m. to 5 p.m., and stays open until 8 p.m. on First Thursdays. Free parking is available for First Thursday art walk patrons in Pioneer Square. Please visit for more information about participating garages.
    — more —

    Order: 1.1

  • Sept. 8 project update: Final three pieces of tunneling machine safely in the access pit

    Seattle Tunnel Partners has successfully lowered three large pieces of the SR 99 tunneling machine’s front shield into the access pit for reassembly. On Saturday, Aug. 29 and Monday, Aug. 31, respectively, crane crews from Mammoet lowered two 98-ton side body pieces:

    Side body piece being lowered into the access pit

    On Friday, Sept. 4, the 278-ton middle shield was lowered. Our construction cameras will show you a photo sequence of Friday's lift and lowering. Here's a capture from the camera:

    top shield being lowered

    With all major components of the machine now in the pit, crews are focusing on reassembling the machine and preparing for the testing phase of the repair effort. Crews will spend the coming weeks welding pieces back together, in addition to the lengthy task of reconnecting the hundreds of wires and hoses that are integral to the tunneling operation. STP and manufacturer Hitachi Zosen will conduct a series of tests following reassembly to ensure the machine is ready to resume mining.

    You can continue to track STP’s repair effort on our time-lapse camera and follow @BerthaDigsSR99 on Twitter for updates.

    — more —

    Order: 1.2

Program Spotlight

  • Another underground connection at the south portal

    Future connections between the SR 99 tunnel and city streets are continuing to take shape at the south portal, even if they're only partially visible from the surface. Drivers passing overhead didn't know it, but Seattle Tunnel Partners recently demolished a temporary wall separating the future mainline section of the tunnel from the on-ramp that will one day allow travelers to access northbound SR 99 from the stadiums.

    The first photo shows the view from inside the cut-and-cover … more