Program Spotlight

Latest updates on the Alaskan Way Viaduct Replacement Program

  • The mood around the office

    He was smiling, but you could tell he was tired. Like many of our tunneling experts, he’d been working long hours lately. Still, tired or not, he was genuinely amused when he dropped into our office to share some news.

    “Did you see the Seattle Times?” he said. “People are voting on what they think stopped Bertha. (Seattle Seahawks cornerback) Richard Sherman is winning.”

    He paused.

    “I’m glad people are having some fun with this,” he … more

  • The beauty of barging

    On Nov. 23, crews started barging soil from the tunnel dig site to a disposal facility near Port Ludlow. Adding barges to the fleet of trucks hauling away soil has greatly improved the speed and efficiency of the tunneling operation.

    The reason for that is simple: Bertha is moving a lot of soil – soil that has to be taken away to make room for more soil. If crews removing it can't keep up with Bertha, the bin where the soil is stored gets full and the machine has to slow down. … more

  • Why bridges (and overpasses) are like butterflies

    Over the weekend, crews closed State Route 99 through downtown Seattle for an important reason: the South Atlantic Street overpass needed space to emerge from its cocoon. Don’t worry, it wasn’t flying anywhere. And it isn’t nearly as colorful as a butterfly. Still, you’ll notice a huge difference the next time you take SR 99 through SODO.

    For nearly a year, hundreds of steel and timber beams, and acres of plywood and foam spanned the highway in roughly the same … more

  • Tunneling in Seattle started long before Bertha

    Seattleites were digging tunnels long before Bertha, the SR 99 tunneling machine, came along. Folks started transforming subterranean Seattle in 1894, with construction of a sewer tunnel not far from the SR 99 tunnel’s north portal construction site. Since then the city has seen – or not seen, as the case may be – construction of more than 40 miles worth of tunnels.

    Last month marked the 109th anniversary of the historic breakthrough on the Great Northern Tunnel, which … more

  • Happy Birthday, Bertha Knight Landes – you were one of a kind

    Saturday, Oct. 19, marks the 145th birthday of Bertha Knight Landes, after whom the SR 99 tunneling machine was named.

    Ms. Landes didn’t dig any tunnels, but there’s no question she broke ground. Elected mayor of Seattle in 1926, she was the first woman to lead a major American city. During her two years in office she battled bootleggers, cleaned up corruption in city government and put the city’s finances in order.

    She was active outside of politics, too, playing … more

  • Bertha breaks 200-foot mark

    Bertha, the SR 99 tunneling machine, has passed the 200-foot mark as she continues her dig toward the north end of downtown Seattle.

    By the end of her shift on Oct. 8, Bertha had traveled a total of 209 feet and the top of her cutterhead was about 20 feet below the surface. She averaged nearly 14 feet of digging per day over the past week.

    Bertha is still making her way through fill soil that crews have injected with grout to provide additional strength. She’ll pass into … more

  • Bertha picking up speed

    It was a good first week back on the job for Bertha, the SR 99 tunneling machine.

    Bertha dug 64 feet between Sept. 23 and the end of the month, averaging about 11 feet of excavation per work day. Add that to the 24 feet she traveled prior to the monthlong stoppage in mining, and Bertha had traveled a total of 88 feet by the start of October.

    The end of September brought with it an important milestone: installation of the first permanent tunnel ring. Now that Bertha is building rings … more

  • Tunneling will close the SR 99 Alaskan Way Viaduct for one to two weeks, likely in early 2014

    More than 1,000 feet of soil separates Bertha from the spot where she’ll pass beneath the Alaskan Way Viaduct a few months from now. That gives drivers plenty of time to prepare for Bertha’s big crossing, which will require an extended around-the-clock closure of the viaduct.

    Crews will close the viaduct for one to two weeks to allow Bertha to tunnel beneath the structure (pdf 913 kb). The machine could reach the viaduct in early 2014, but a specific date for the … more

  • Remembering Bertha’s roots: two years of SR 99 tunnel construction in the books

    Time-lapse video highlights the hard work that led up to Bertha’s July 30 launch


    A lot can happen in two years. Just ask Bertha, the SR 99 tunneling machine.

    Two years ago this week, Bertha existed only on paper and her launch-pit site was little more than a field of dirt where the south end of the viaduct once stood. Our contractor, Seattle Tunnel Partners, had just received the go-ahead to complete final design and begin building the SR 99 tunnel.

    Then this … more

  • Desperately seeking soil: As we expected, Bertha is off to a slow (but good) start

    After slogging through 15 feet of concrete, Bertha gets a taste of the good stuff – but why did it take so long?

    Engineers depend on math. It is the thing that, more than any building material, gives shape to their designs. Want proof that what you’re building matches the design? Check the plans, do the math.

    But when it comes to tracking the progress of Bertha, the SR 99 tunneling machine, you can’t rely on an equation. Yes, we told you that Bertha would average 6 … more