43 Replies to “U-Link Update”

      1. Yep. It completed the SB bore a couple months ago. They took it apart adjacent to the PSST, trucked it back to Cap Hill, and send ‘er on it’s merry way again!

  1. Does anyone know if Balto & Togo are going to have break-throughs like Beacon Hill, or is it going to be more similar to Brenda, where when she reached the end, they mined the wall from the other side?

    1. I can understand modern day surveying using lasers and digital mapping software to plot things, but how in the heck did hard rock miners work towards the middle of long tunnels in the 1800’s and meet up with great precision (off by mere feet)?
      Just amazing with simple optical transits of the day. Any surveyors want to take a swing at this?

      1. Yeah, they had some VERY talented engineers and surveyors back then, didn’t they? Another group who were very talented were the navigators on ocean going boats way back when.

        Truly amazing how utterly intelligent some people are. Math is tough for many/most people to learn, yet some people are so smart they dreamed the stuff up!

        The older I get, the more I realize how stupid I really am….

      2. Historical underground surveying techniques are a very interesting topic. I suggest Googling it. :-)

        One thing: the surveyors were employed *constantly* in the old days, rechecking their sight lines after every foot of digging or so. So the decreased accuracy of the old equipment was partly made up for by a *lot* more measuring. Nowadays fewer surveyors are employed for fewer hours per week.

      3. Careful, proper use of surveying equipment will indeed provide such accurate results. When I took Surveying II during my sophomore year of college, we had to do an elevation traverse over a mile in length around the campus using a transit (not one of those new-fangled total stations — we’re talking the old-school equipment that surveyors have been using since the dawn of the practice, or perhaps just a little bit thereafter). Even as unskilled novices in the use of this gear, my team achieved a delta of only 0.02′ upon our return to the starting point — less than one-quarter of an inch. If a bunch of college kids can do that over a mile, it’s evident what trained, experienced surveyors can accomplish over much greater distances.

  2. I have been critical of ST for being years late and way over budget (based on the original 1996 proposal and vote)on this project so I think it only fair to say on the second attempt — Hey, nice job so far. I am impressed with the progress and the lack of serious issues. Fingers crossed.

  3. Do they have people in parallel working on each section of the project. What I mean is, for example, are people laying track and hanging wire in the sections that are already bored? If not, then what are the waiting for?

    Honestly, I love this progress but I’m really confused why it will take another 4 years to get done. I assumed that tunneling would be the hard part, but I guess there are other limiting factors? The stations maybe? In which case why didn’t they start those sooner?

    1. I’m no expert, but here goes:
      1) The boring operations send the dirt back out the tunnel and bring the tunnel liner segments in via a temporary railway laid behind the TBM. Obviously this is constantly in use, so there’s no opportunity to install the final rails and other systems while boring continues.
      2) They haven’t really been able to start actually constructing the stations (other than excavation) because the station shells are needed for TBM staging for the dirt and lining segments. The latest update shows UW Station at 21% complete, FWIW.
      3) Systems installation and testing takes a long time. The overhead needs to be properly connected, provide appropriate power at all locations, be grounded properly, etc. The signalling system needs to be installed, connected to the existing network, and tested. They need to run test trains through under a variety of conditions (fast, slow, emergency braking, etc.)

      I’d love to have it open tomorrow too, but it just takes time.

      1. Re: 1), the exception is the first bore done by Brenda. They could start doing other things there.

        Re: 2), they can’t start building CHS until the tunneling is done. I don’t think that’s the case for UWS.

      2. Ah yeah thanks forgot about Brenda being reassembled for the second bore. Since the CHS station box is tied up supporting Brenda and awaiting the arrival of Togo and Balto, I doubt they have the space to stage the tunnel finishing contractor into the completed bore.

      3. Construction of UW station is about 20% done, so they are proceeding with that phase (for reasons mentioned, Cap Hill station construction has not started).

        The webcam on Sound Transit’s website clearly shows the concrete station work done to date at UW station.

    2. There are a host of temporary features happening during construction, with supply trains delivering segments, ventilation shafts, construction of cross passages connecting the stations and muck conveyors that installing rail and systems becomes impossible. There’s simply too much congestion. Which is why they are typically last in the tunnels.

      Besides you don’t want systems in there installing in advance before you have your base slab set and final established feeds for systems, electrical, plumbing, etc.

    3. Re: 1) They are getting that first bore Brenda bore done immediately for testing the floating slab segment. This is key to the vibration mitigation required for going under the UW. Engineers need the results ASAP.

      Once the tunneling is done, that contractor will vacate the premises, and deliver Sound Transit three tunnels that are nothing more than funny looking circular tubes. Then the next contractor will come in, pour the invert slab (which gives part of the tunnel a flat bottom to put stuff on) with rebar sticking out, walkways, and tunnel systems (signals, lights, coaxial cables, etc). Finally, the last contractor will come in, install the plinths that attach to the previously poured rebar (this allows for extremely precise alignment control), all the rail stuff onto the plinths, the floating slab segment for testing, the Xover at UWS, and signals. The OCS gets installed at some point, I just don’t remember when. At this point, I believe the track work contract (U260) hasn’t been sent for bid yet.

      1. OCS is one of the last things installed because it would otherwise get in the way of all the other construction work that needs to be done in the new tunnels

      2. After the main excavation work….

        All the concrete pouring takes quite a long time.

        The rail, signals, electrical, and finishes go startlingly fast.

        Then the testing and debugging takes much longer than you might think.

  4. Once these are finished, is the concept to keep these moving to Roosevelt and beyond? Seems like an opportunity to save cost while these are still mobilized, even if station construction were to lag for a long time

    1. Nope, the design beyond UW Station isn’t finalized yet, plus they haven’t even started site preparation or station excavation. Consequently there is nowhere to launch the TBMs from, and even if there was they don’t know exactly where they’d be going. The preliminary drawings don’t provide enough level of detail, and aren’t completely accurate anyway (for example, the station box for Brooklyn has been moved slightly east and the north portal shifted further north from what was assumed in the EIS). Most TBMs are custom-built for the requirements of a particular job too, taking into account bore diameter, intended use, soil type, depth and length of the bore, etc., so no guarantee the three current TBMs are even suitable for use elsewhere.

      1. TBM’s are also usually in pretty bad shape when they’re completed with their jobs. They’re meant to be a custom-built (as Jason said), single-use piece of equipment. Beacon Hill Station was a fairly short bore, so refurbished machines worked just fine and saved a little money. No idea if the ULink machines will still be useable or able to be refurbished but the NLink reaches are probably too far to do the job in a reliable manner.

        One of the newer practices for disposing of TBM’s is after completing the job, make a sharp turn, dig a few hundred feet, and seal the TBM underground in solid concrete. Quite the appropriate tomb.

      2. they are going to use the outer shell of Brenda (stuff behind the cutting head) as part of the tunnel itself where it connects with the Pine St. Stub tunnel IIRC

      3. Reminds me of Mary Anne, Mike Mulligan’s steam shovel, that became the boiler plant for the last building she dug out.

      4. Ha. I just read that story to my kid and was thinking the same thing when I read about the TBM’s fate.

      5. Actually, TBMs are usually reused. They have essentially three components:
        (1) The “shield”, which doesn’t really take much wear and can last a really long time; it lasts like a building.
        (2) The mechanics and motors, which take more wear, but likewise last a long time
        (3) The grinding faces, which need to be replaced after pretty much every job

        So, 2/3 of a TBM is generally reusable, and sinking it in the wall is a waste. They are generally assembled in place (because they’re so huge) so reassembling with a new cutting head is not a big deal.

  5. Once these machines end up in Seattle, why have them stop? Just have one continue to Ballard from Westlake and the other head to West Seattle and get ready for our next subway line: The Green Link (WStoBallard)

    1. Well, they’d have to find somewhere to launch it for the parallel 2nd Ave tunnel; you couldn’t just have the thing thrashing through open space in Westlake, hilarious as that may be.

      Also, West Seattle would be elevated south of Downtown all the way across the bridge, and then bore underground just west of Delridge.

    2. In fantasy it would be great. In reality, nobody has given the contractor millions of dollars to do it. ST2 does not have money for it. The routes have not been engineered, or the station locations decided. It would have to go out to a competitive bid. No contractor would dig a route that hasn’t been engineered and the soils known as much as possible.

      We could bypass some of these if a billionaire offered to pay for the engineering and construction privately, and ST just signed off on the route. But no billionaire has stepped up for Link yet, and if one did, we’d have to make sure he doesn’t adversely affect the route location.

      1. Why haven’t we appealed to any billionaires?

        Anyway, what if the TBM went rogue? o_O

  6. Wow, I was about to weigh in on what happens next in the tunnels and why it takes awhile but other commentors pretty much nailed it. Although your date for the holethrough is a little optimistic. Togo is transitioning from clay into less cohesive materials that could slow progress a little bit. But mid-March should be an exciting time. And yes, it will mine right into the CH staion box. Wrapping up the mining portion of the project is a huge milestone. We’re looking forward to getting a look at Togo’s cutterhead again!

    1. Bruce, what does a guy have to do to get an invite to Togo’s breakthrough? I’d give my left arm to see that, or if left arms aren’t your thing I could probably think up something less messy.

    2. while we all can agree that construction takes time … why 4 years though … I think that is the real question …

      1. 4 years gives time for unforeseen problems (like a TBM getting stuck).

        I’m optimistic that the stations will be ready to open before 2016, given the success so far of the critical boring operation.

        But then there is also the issue of what needs to be done for UW Station for the North Link extension before it gets sealed in by station construction. What is the plan for the TBMs between UW Station and Brooklyn Station?

      2. Brent, IIRC there will be a shaft at the north end of the station at Husky Stadium to extract the TBMS coming from Roosevelt (via Brooklyn). I assume there will be enough empty space beyond the platform to get them out without affected operations.

  7. I remember seeing engineering drawings for the Husky Stadium station a long time ago … in the drawings there was a pocket track located in the station for train storage. Is this still the case?

    also … since “North Link” is going to happen … will they need to dig a new shaft to insert the TBMs for those tunnels north of the Husky Stadium station? or has such a provision been made in the existing station pit design? (like they did with the Pine St. Stub Tunnel)

    1. I thought I heard the pocket track was dropped, but I’m not positive.

      For North Link, I think they’ll have two pairs of TBMs. One pair launches at Roosevelt, continues through Brooklyn, and is extracted from a shaft at the north end of the station at Husky Stadium. I believe this shaft is part of the station construction. The other pair launches near Northgate and is extracted at Roosevelt.

      1. Since the distance from the north portal to Roosevelt is so much shorter, I could see that being done with one TBM like the CHS to Westlake tunnels. Maybe ST will write the bid documents without specifying how many TBMs to use, but just state the timeframe needed and then let the contractors figure it out.

Comments are closed.