Program Spotlight

Latest updates on the Alaskan Way Viaduct Replacement Program

  • The choreography of a concrete pour

    This week, at the south entrance to the bored tunnel, Seattle Tunnel Partners is pouring concrete for a section of the future southbound highway. On one hand, the pouring of concrete (also known as a "concrete placement”) is nothing extraordinary – it’s a common occurrence on a project that will use enough concrete to build nine football stadiums. But their frequency belies the complex choreography that goes into executing each pour successfully. Since concrete plays … more

  • Making progress on the south end

    If you regularly drive SR 99 near the stadiums, you’ve probably noticed a lot of changes to the roadway during the past 16 months. For example, crews divided the northbound and southbound lanes into two separate roadways near South Atlantic Street to make room for more construction. And you’ve no doubt witnessed huge changes taking place in the work zone on either side of the road. Did you know that crews have been hard at work completing the southern portion of the SR 99 tunnel … more

  • Temporary tunnel access ramp helps Seattle Tunnel Partners rearrange work

    This week, crews working for Seattle Tunnel Partners inside the bored tunnel finished building the 400-foot-long ramp shown below. You might be wondering: Why is the ramp necessary? After all, crews completed more than a thousand feet of the tunnel without one. Turns out the ramp is part of STP’s plan to complete work now – while the SR 99 tunneling machine is being repaired – that was originally scheduled to be done after tunneling was complete. 

    Looking north … more

  • Paving the way to the SR 99 tunnel

    Crews working for Seattle Tunnel Partners have reached a concrete milestone at the SR 99 tunnel’s south portal.

    As shown in the aerial photo below, crews are building the cut-and-cover section of the tunnel in SODO, just west of Seattle’s stadiums. Earlier this month, they successfully poured the final sections of northbound mainline roadway concrete for this 1,500-foot-long stretch of the future highway. 

    Sections of cut-and-cover tunnel at both portals will … more

  • Tunnel’s two nerve centers taking shape

    State-of-the-art systems will be the key to maximizing safety and efficiency inside the SR 99 tunnel. Lighting and intelligent transportation systems (video cameras, traffic counters, variable message signs, etc.) will help ensure smooth traffic flow, while the ventilation, drainage and fire-suppression systems will help the tunnel meet the highest safety standards. To manage these systems, we’ll need nerve centers at each end of the tunnel. While they’re hard to see now, those … more

  • A look inside the new-look SR 99 tunnel

    Not long ago, you might have been able to fit a five-story building inside the cavernous circumference of the SR 99 tunnel. Not anymore. From the south end of the tunnel to the back end of Bertha, the SR 99 tunneling machine, crews have filled the tunnel with long stretches of walls and roadway sections of the future underground highway. The series of photos below shows just how much the landscape inside the tunnel has changed. 


    In the first photo, you are looking … more

  • A tunneling breakthrough near the stadiums

    Seattle Tunnel Partners is preparing for Bertha to break through the southern wall of the SR 99 tunnel access pit, but another, lesser known tunneling breakthrough has already occurred approximately 2,000 feet south of the pit. Earlier this month, crews demolished the temporary wall separating two sections of cut-and-cover tunnel under construction to the west of the stadiums. A cut-and-cover tunnel is just what it sounds like – dig a trench, then build a floor, walls and a … more

  • New time-lapse video highlights crane construction

    Crews have spent the past several months assembling the massive red crane that will lift Bertha to the surface for repairs. As STP prepares to move the machine into the pit, crane crews are also making final preparations. We put together a new time-lapse video to illustrate how the crane came to be. This post explains the assembly process in more detail. Don’t forget about our time-lapse cameras, which will give you a good view of STP’s work to repair Bertha. … more

  • 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

  • New pavement and walls add shape to the tunnel’s future north portal

    At the construction site for the SR 99 tunnel’s north portal, imagining the future is getting easier. While it all looks like one project, north portal construction is comprised of two separate contracts. Roughly everything south of the tunnel entrance near Harrison Street is part of the main tunnel contract being completed by Seattle Tunnel Partners. North of the tunnel entrance, crews working for Atkinson Construction are building the lanes and ramps  that will connect … more