Brenda Breaks Through

Brenda (Sound Transit)

Brenda, the Tunnel Boring Machine (TBM) which has been making its way from the Capitol Hill station to the Pine Street stub broke through yesterday monday night. Brenda will now be disassembled and reassembled at the Capitol Hill station where it will begin boring the second tunnel between Capitol Hill and downtown.

Go here to see all the photos.


  1. Gordon Werner says:

    Apparently they won’t begin the second tunnel until early next year

    • Yep – Brenda gets dismembered at the Paramount, trucked back up to Broadway and reassembled and then has at the other tunnel. Frankensteinian or what?

      • Bruce Nourish says:

        I hate to be pedantic, but I’d have to go with the “what”. A TBM being disassembled and reassembled doesn’t seem to have much to do with Mary Shelly’s book.

  2. trevorthebusdriver says:

    Why can’t it go back the other way?

  3. Are tracks laid in the first bore already for rubble removal? I’m just wondering when they can’t just turn it around and bore back to Broadway. Yes it’s a longer distance the dirt has to be moved but I’d wager the primary cost/time is it loading/unloading and not travel time.

    • Gordon Werner says:

      TBMs are very large machines … there is no room at Pine St. to reassemble the TBM … and even if they wanted to there is no place to handle the spoils removal.

      The TBM needs to be disassembled anyway to make sure that all the parts are still ok anyway … so hauling it back up the hill isn’t a real big deal.

      Judging from the CHS … they still have a ton of spoils to remove from the station shell anyway before they can start on tunnel 2

    • Gordon Werner says:

      oh yea … the temporary tracks in the NB tube are used to transport the concrete tunnel wall segments … they will be removed when they begin the final pouring of concrete to create the trackbed until they end up with this:

  4. Sousdesnuages says:

    The Paramount site is a postage stamp compared to the Capitol Hill site. If they wanted to use it as a staging point to launch the TBM back to Capitol Hill, ST would have to tear-up Pine Street again, only a few years after re-surfacing it for the stub tunnel. Relaunching from Capitol Hill is really the only way to go, and the TBMs launched from Husky Stadium aren’t scheduled to arrive until Spring–well after Brenda’s relaunch.

  5. I can hardly wait to ride it.

  6. I asked on the FB page, but…

    How precise is the break-through? Are the TBM operators able to steer to within inches or less of a target? Or is it more like feet?

    • I think its more like millimetres

      • These days, done well, tunnel bores over *hundreds of miles* are usually less than a centimetre off. This being a short bore, it’s probably pretty much 100% accurate.

        I do wonder how the measurement is done. I believe lasers are involved.

  7. But I thought it was not possible to tunnel through the glacial till that makes up Capitol Hill?

    • Maybe they dug out a black hole?

    • Lack Thereof says:

      Glacial till is hard on boring machines. Luckily, these tunnels are quite narrow, which makes the project easier. They’re also pretty short, which means the cutters don’t have to last very long.

      • I was referring to the doom and gloom of the naysayers back in the mid-1990′s.

      • Lack Thereof says:

        There’s still a lot of doom and gloom regarding the 5-story tall one that’s going to go under downtown for SR99. Nothing that wide’s ever been bored before. If they pull it off it will be quite an impressive feat of engineering.

      • The doom and gloom for the SR99 tunnel isn’t the glacial till part, it’s the sand part that’s 80 ft below sea level at the foot of Yesler. In addition it’s the worry about future transverse earthquakes, and state finances.

        Plus if you go read Ben’s post on the Seattle Subway, you’ll see the tunnel we should be digging before the SR-99 one.

  8. I wonder if anyone made a video of the cutterhead breaking through? If there is one I haven’t found it anywhere.

  9. These things really are just moving along swimmingly. Very impressive!

    Definitely helps to lend credence to the assertion that subway-circumference boring is getting easier and cheaper all the time.

    And allows us to imagine — this is essential to Ben’s vision — a long-term program where these things are just always digging somewhere… always expanding the system bit-by-bit, with stations opening a-few-at-a-time behind them, until a network of usable length and breadth and coverage becomes a reality!

  10. Will they start to work on finishing the completed shaft while simultaneously digging the next?

    And when do they start digging to Bellevue?

    • Bellevue tunnel is cut and cover not bored. And the east link project does not start construction until 2015 IIRC.

  11. Does this mean it is too late to revive the First Hill station? ;-)

  12. MarkSJohnson says:
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