Program Spotlight

Latest updates on the Alaskan Way Viaduct Replacement Program

  • The story behind the north portal's signature tree

    The signs of summer are everywhere. There’s more sun in the sky and more boats in the water. There’s also more of something that most folks wouldn’t even know to look for: leaves in one of Seattle’s newest trees.

    Allow us to introduce you to the Garry Oak, the area’s only native oak species. Native Garry Oak prairies were once commonly found in Western Washington. This particular Garry Oak was planted this spring a few blocks east of the Space Needle, … more

  • What to expect from Bertha as tunneling continues

    We’ve been hearing a lot of forecasting lately from members of the public tracking Bertha’s progress. We’ve said this before, but now that Seattle Tunnel Partners crews have passed the 25 percent mark of the tunnel drive, it’s worth repeating: Trying to predict future progress is tempting, but there’s no simple equation for doing so.

    Tunneling progress depends on a number of factors, including soil conditions and the need to stop tunneling when Bertha … more

  • Inside tunneling under the viaduct

    After nearly a week of tunneling under the Alaskan Way Viaduct, crews are steadily continuing Bertha’s underground drive towards downtown Seattle. This video gives you a behind-the-scenes glimpse into how the new tunnel is being built, showcasing the complex operations involved in this project. Massive concrete ring segments are transported to Bertha’s segment erector where they are lifted into place, allowing the machine to push forward while the excavated soil is transported … more

  • #99closure feature: Drone footage inside the SR 99 tunnel

    Just a few days before the SR 99 tunneling machine started tunneling under the Alaskan Way Viaduct, the Washington State Department of Transportation flew a video-equipped drone through the SR 99 tunnel to show Seattle Tunnel Partners’ construction progress. There has been continued interest in seeing what has been built below ground and this video gives a glimpse of the tunnel as well as the nooks and crannies of the complex tunneling machine.

    On an average day, the tunnel is … more

  • #99closure feature: Removing soil from the tunnel

    More than 850,000 cubic yards of soil will be removed from the ground during the course of tunneling. To put that in perspective, imagine this: If you piled that soil on the turf at nearby CenturyLink Field, the pile would be about 400 feet tall – more than 100 feet taller than the stadium’s roof.

     

    Excavated soil travels via conveyor belt from the front of the tunneling machine to a barge waiting at the north end of Terminal 46. When the barge is full, it travels … more

  • #99closure prep: Analyzing traffic patterns on the Alaskan Way Viaduct

    Measuring traffic on the SR 99 Alaskan Way Viaduct isn’t as simple as you might think. Traffic volumes vary along the structure. For example, more vehicles drive the section south of downtown than the section near the Battery Street Tunnel.

    But no matter how you add things up, the end result is the same: thousands of vehicles will be forced to find other routes when the viaduct temporarily closes on April 29. And that will equal congestion and frustration, especially for … more

  • Ordinary maintenance, extraordinary conditions

    With Bertha, the SR 99 tunneling machine, having safely reached her planned maintenance stop, Seattle Tunnel Partners is preparing to complete up to one month of planned maintenance. While the maintenance is routine, some of the methods crews will use to complete it are anything but. That’s because they’ll be performing some work in hyperbaric conditions as they get Bertha ready to tunnel beneath the Alaskan Way Viaduct and downtown.

     

    Hyperbaric conditions are those … more

  • Tunnels and earthquakes

    Seattle is prone to earthquakes, so it’s not surprising that one of the most common questions we receive is this: Will the tunnel be safe in an earthquake? 

    All modern structures in the area – including bridges and highways – must be designed with earthquake safety in mind. But geotechnical and structural engineers agree that tunnels are among the safest places to be during an earthquake. 

    Some folks find this counterintuitive. How is it safe to be … more

  • Good news for SR 99 commuters: first phase of lane closures wrapping up early

    Last week we reported that crews were making good progress as they worked to install sign foundations on SR 99/Aurora Avenue North in Seattle. Turns out good progress leads to good news: the first phase of sign foundation work is finishing ahead of schedule. By Friday afternoon, median lane closures should be removed and the southbound bus-only lane will be restored to normal operations.

    It may be tough to tell, but the new foundations for each sign on SR 99 extend 14 to 18 feet … more

  • Sign foundation work progressing well on SR 99 in Seattle

    If you’re a regular user of SR 99/Aurora Avenue North between the Aurora Bridge and just north of Mercer Street, we’d like to thank you for doing your part to help keep traffic delays to a minimum during the past two weeks.

     

    Crews are around the halfway mark for the first phase of sign foundation installation work happening on this stretch of SR 99 and are pleased with the progress they’ve made. Work is continuing on schedule and crews expect to move into the … more