• Nov. 21 project update: Bertha nearing the tunnel’s deepest point

    Seattle Tunnel Partners passed the 60 percent mark of tunnel boring last week. As of this morning, crews had mined 5,774 of 9,270 feet and installed 880 of 1,426 concrete tunnel rings. 
    Bertha, the SR 99 tunneling machine, is located near Virginia Street, between First and Second avenues. With the top of the cutterhead now approximately 210 feet below the surface, crews are nearing the deepest point of the tunnel drive. 
    STP will continue mining and other construction activities through Wednesday before securing the work zone for the holiday weekend. Work will resume on Monday.
    Happy Thanksgiving from the Alaskan Way Viaduct Replacement Program team.
    — more —

    Order: 1

  • Nov. 7 project update: Girders arrive for future off-ramp

    Large bridge girders began arriving Monday in the work zone near the stadiums. Crews will install the girders this week on the new bridge that will serve as the off-ramp from northbound SR 99 to South Dearborn Street after the tunnel opens to traffic.
    The bridge will include 14 girders in all. The four largest girders will be installed overnight Tuesday, requiring crews to close the left lane of northbound SR 99 between South Holgate Street and Railroad Way South from 9 p.m. Tuesday to 5 a.m. Wednesday.
    You can see regularly updated images of the girder installation on our south-end construction cameras.
    Off-ramp girders
    Crews are installing bridge girders near the stadiums as part of the South Dearborn Street Off-ramp Bridge Project. This post explains how this "flexible" bridge will use new technology to stand up to earthquakes. This folio provides a detailed technical description of the materials being used.
    — more —

    Order: 1.1

  • Nov. 3 project update: Bertha passes the one-mile mark

    Seattle Tunnel Partners passed the 5,280-foot mark of the SR 99 tunnel on Thursday morning. Less than 4,000 feet now separates the front end of Bertha, the SR 99 tunneling machine, from the receiving pit (links to YouTube) near the Space Needle where Bertha will emerge at the end of tunneling. Bertha’s cutterhead is located more than 200 feet below First Avenue, just north of Stewart Street.
    The one-mile point in Bertha’s journey also marks the tunnel route’s departure from the ground beneath First Avenue. While First veers northwest at Stewart Street, Bertha will continue pushing north toward the receiving pit. By passing Stewart Street, Bertha entered Zone 7 of the tunnel drive
    How do crews steer the five-story-tall tunneling machine toward the finish line some 4,000 feet to the north? We asked Jerry Roberge, one of Bertha’s operators, that very question. Jerry’s answer, along with exclusive footage from inside the tunnel, can be seen in the video below.
    — more —

    Order: 1.2

Program Spotlight

  • Coming to the south portal: A “flexible bridge” to stand up to Seattle’s next big earthquake

    When the SR 99 tunnel opens to traffic, drivers on northbound SR 99 will use a new off-ramp near the stadiums to reach downtown Seattle. In addition to linking travelers to their destination, engineers and researchers hope the new ramp will provide a link to something else: earthquake-resistant bridges.

    By combining memory-retaining metal rods and a bendable concrete composite, the future off-ramp will become the first bridge in the world built to sway with a strong earthquake and … more