• *** Canceled *** Daytime closure of southbound SR 99/Aurora Avenue North in South Lake Union set for Feb. 19

    Feb. 18 update: A planned closure of southbound SR 99 on Sunday, Feb. 19 has been canceled due to anticipated weather. The closure will be rescheduled for a later date. The original notice is below.
    Crews working for WSDOT will close a half-mile stretch of southbound State Route 99/Aurora Avenue North near South Lake Union this Sunday, Feb. 19. 
    All southbound lanes of the highway between Valley Street and the south end of the Battery Street Tunnel will be closed from 8 a.m. to 5 p.m. Sunday; the northbound lanes will remain open. 
    During the closure, crews will restripe and reopen a portion of Harrison Street that has been closed due to SR 99 tunnel construction. When Sunday’s work is complete, drivers will have access to and from SR 99/Aurora Avenue North at Harrison Street. 
    This work is weather-dependent and could be rescheduled in the event of rain.
    Closure map
    Southbound SR 99 closure map
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  • Feb. 9 project update: Bertha passes beneath the Battery Street Tunnel

    SR 99 tunnel crews successfully mined beneath the Battery Street Tunnel this week. The top of Bertha, the SR 99 tunneling machine, passed approximately 90 feet below the bottom of the 62-year old tunnel, which will permanently close when highway traffic shifts from the Alaskan Way Viaduct to the new tunnel.
    The ground along the tunnel route remains stable as Bertha pushes toward the finish line near Seattle Center. Crews are now less than 1,600 feet from the end of the tunnel drive, and the machine is climbing at a steady rate. The distance between the top of the machine and the surface is approximately 115 feet. The tunnel, at its deepest point, is approximately 215 feet deep.
    Up next for Bertha: a trip beneath Fifth Avenue and the Seattle Center Monorail. The top of the machine will pass approximately 90 feet below the Monorail’s supports.
    Highway construction
    While crews inside the tunneling machine are focused on mining, separate crews are hard at work building the double-deck highway inside the tunnel. The new roadway now stretches more than 3,800 feet into the tunnel, near the southern edge of Pike Place Market. 
    Work has also begun on the mechanical, electrical and plumbing systems within the tunnel. Crews began installing these systems near the stadiums last week and will continue to progress north, even after the tunnel drive is complete. 
    Progress updates are posted on Mondays and Thursdays at our Follow Bertha page. You can also follow Bertha on Twitter @BerthaDigsSR99.
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  • Jan. 17 project update: Tunneling crews resume mining

    Seattle Tunnel Partners resumed mining late Monday following 10 days of hyperbaric maintenance on Bertha, the SR 99 tunneling machine.
    Crews replaced approximately 300 of the nearly 500 scrapers on Bertha’s cutterhead during the hyperbaric maintenance period. As this post explains in more detail, the scrapers line the sides of the cutterhead spokes. STP also conducted other important inspections and maintenance during this time.
    Completing routine maintenance is an important part of ensuring that the machine continues to operate properly. STP will continue to perform inspections and maintenance as needed over the remainder of the tunnel drive.
    Crews are less than 2,500 feet from the receiving pit near Seattle Center where Bertha will emerge at the end of tunneling. The top of the cutterhead is located approximately 160 feet below Third Avenue in Belltown. 
    Progress updates are posted on Mondays and Thursdays at our Follow Bertha page. You can also follow Bertha on Twitter @BerthaDigsSR99.
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Program Spotlight

  • Getting to know the SR 99 tunnel's biggest fans

    Clean air is a critical element of a safe and well-functioning tunnel. In the new SR 99 tunnel, a complex system of fans will push and pull air into and out of the tunnel to ensure fresh air during routine operations and in emergencies.

    The first element of the tunnel’s ventilation system is the very traffic that uses it. Vehicles traveling through the tunnel will act like pistons, pushing fresh air into the tunnel. But when that piston effect needs a boost, the tunnel will turn to … more