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July 18, 2013

Waterfront tunnel: Bertha's story in her own words

  • The behemoth will be chewing and tweeting as she makes her way under Seattle.
  • mug
    The SR 99 tunneling machine

    It feels like I just got here.

    Maybe you remember that day in early April. Gray skies, news choppers circling, a fireboat spraying arcs of water in the wake of my ship as it rolled into Elliott Bay. Back then I was in pieces, fresh from my manufacturing facility in Japan, little more than the makings of the world’s largest tunneling machine. Now I’m assembled and nearly ready to start digging the 2-mile-long state Route 99 tunnel beneath downtown Seattle.

    As my big day approaches, it’s hard to not get at least a little bit sentimental. I mean, think about it: In a matter of weeks, I’ll be gone. You’ll be cruising along SR 99 near the stadiums. You’ll wind your way around the curvy section of highway that skirts the 80-foot-deep pit where I’ve spent the past few months. Except this time, when you glance into the pit, I won’t be there.

    Instead I’ll be chewing my way through the ground beneath Seattle, monitoring the soil that surrounds me, carefully plodding along, pushing toward the day 14 or so months from now when I’ll emerge just north of the Battery Street Tunnel. You might wonder how I’m doing, just for a second, but mostly you’ll be wondering when all this construction will end and you’ll get to use the tunnel I’m building.

    Photos courtesy of WSDOT [enlarge]
    Bertha was built in Japan and then disassembled and shipped across the Pacific Ocean.

    That’s fine. I understand you have more important things to do than think about me. But here’s the thing: I was sort of hoping I’d get a chance to thank you before I go. I’m digging this tunnel for you, after all. I owe all of this — the media hype, the fancy green paint job, the chance to devour some 850,000 cubic yards of delectable dirt while reshaping the SR 99 corridor — to the good people of Washington.

    So I’m having a party. Come on down to my launch pit from 11:30 a.m. to 3 p.m. this Saturday. You’ll be able see me up close, talk to project staff and learn more about how I work. There will be food trucks on hand in case you want to buy a snack, along with activities for the kids. Lots of people will be there, including Gov. Jay Inslee and Transportation Secretary Lynn Peterson.

    My guess is that most people who attend will focus on my size. At five stories tall and 326 feet long, I’m the largest machine of my kind in the history of planet Earth. But you already knew I was big.

    Bertha is in the launch pit and will start digging later this month.

    What you might not know is that the task I face is as massive as me. Because crews have taken soil samples all along my planned route beneath the city, I know that I’ll have to navigate through eight different soil types. I’ll spend much of my time in undisturbed glacial till that’s ideal for tunneling, but sand, clay and other less predictable soils also await me. Fortunately, the knowledge crews gained from those soil samples informed my design. I was built specifically for the ground conditions I’ll encounter as I dig, and I’ve been working hard to make sure I’m ready for what lies ahead.

    After I was built, I was tested. Then I was tested and tested and tested again. Every hose, every cable, every piece of steel that I’m made of has been through the wringer. Testing will continue even after I start tunneling. In fact, I won’t even become the property of Seattle Tunnel Partners, the Washington State Department of Transportation’s contractor for the project, until after I’ve tunneled about 1,000 feet.

    Of course even the most rigorous testing can’t diminish the fact that I’m an incredibly complex machine. I have lots of moving parts, lots of different components that need to be looked after. Because of that, I feel pretty lucky to be surrounded by a great team that’s had success building similar machines and tunnels all over the world.

    The launch pit is 80 feet deep and 400 feet long.

    The first section of the tunnel route will serve as my training ground. Fill soils dumped in my path by the city’s settlers have been removed or reinforced. Additionally, crews have built a number of protected areas underground — we call them safe havens — that will allow them to inspect my cutterhead to make sure everything is working properly. I’ll push forward about 6 feet per day at first, but by the time I’m deep beneath downtown I’ll dig up to 35 feet per day.

    There will be a number of ways for you to track my journey. The best place is my Web page: http://www.wsdot.wa.gov/Projects/Viaduct/About/FollowBertha. There, you’ll find information about where I am along the tunnel route and what types of ground conditions I’m currently facing. You can also follow me on Twitter — my handle is @BerthaDigsSR99 — where I’ve been providing regular updates about my efforts since December.

    If you’re getting the impression that the tunneling business is difficult, you’re right. Anyone who’s ever plunged a shovel into the dirt can tell you that digging is far from easy. But it’s also rewarding. Just think how great the new SR 99 corridor will be when all of this hard work is done.

    As I prepare to push off, I’m reminded of a quote from Marc Isambard Brunel, the tunneling pioneer who paved the way for massive machines like me. “The world,” Brunel said, after completing the unheard of task of tunneling beneath the River Thames in London in 1843, “has not such another tunnel as this.”

    The same could be said of the SR 99 tunnel, although WSDOT’s goals for the project have nothing to do with breaking records or setting trends. The most vital aims of this undertaking are safety and mobility — you know, the things you think about when you’re sitting in traffic.

    Still, breaking a record along the way won’t hurt. It might even be cause for another party. Meet me at the north end of downtown next fall. You bring the excitement. I’ll bring the dirt.

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