PHOTOS: See what the tunneling machine’s done so far, before its Via-dive

(WSB photos by Christopher Boffoli)

Before the Highway 99 tunneling machine starts its dive beneath the Alaskan Way Viaduct, closing it for two weeks or so starting early Friday, WSDOT gave local news media one more chance for a look inside what’s been done so far. Christopher Boffoli was there for WSB.


Monday afternoon’s hour-long tour was his first visit to the tunnel in more than a year and a half, since September 2014 (see his report here), nine months after the machine stalled (eventually restarting just before last Christmas).


This time, tour participants were NOT taken up to the tunneling machine, which has gone 1,560 feet so far.


The trip to get beneath and clear of the Alaskan Way Viaduct will be almost exactly a fourth of that distance, 385 feet.


While WSDOT promises online progress reports at least once a day once the tunneling machine is on its way, it also is warning not to expect much at the start – the one-sheet given to those on today’s news-media tour says contractor Seattle Tunnel Partners told WSDOT that “mining will be SLOW at first” as the first 10 feet will go through the protective concrete block built at “Safe Haven 3” where the machine has been stopped for six weeks.


More tunnel facts: 232 tunnel rings, each weighing 10 tons, are installed so far; reaching the end of the planned tunnel route will require about 1,450 of those rings.


Christopher says today’s tour “was much more limited than the last one” (the September 2014 tour mentions above) – “this time we were simply walked down to the end of the tunnel and taken about midway under the machine (into the area where all of the trailing gear brings the concrete sections forward for placement) and then were walked back out.”


By the way, WSDOT has completed 400 feet of roadway inside the 1,560 feet of tunnel that’s done so far.


We don’t know yet exactly what time The Viaduct will be shut down on Friday morning – WSDOT says it depends on when Seattle Tunnel Partners are ready to start up the machine. But the plan is for it to be long before the morning commute. If you still haven’t figured out how you’re going to get around without The Viaduct, find all the closure-related info at

13 Replies to "PHOTOS: See what the tunneling machine's done so far, before its Via-dive"

  • miws April 26, 2016 (7:35 am)

    Thanks for another great Tunnel Tour, WSB, and Christopher! 

    As I started to read the article, I was thinking; “Wow, another media tour already?”  Can’t believe the other one was over a year and a half ago!


  • Eddie April 26, 2016 (8:58 am)

    1450 more sets of rings.  There are a few sets (maybe 100??) staged at the south end of the tunnel.  Where are the other 1000+ sets of ring segments staged?

    • Sevenless April 26, 2016 (9:28 am)

      From what I recall when the tunnel plans were originally announced, additional ring segments are being cast as the project progresses and trucked to the site, since there was no need to have all 1500+ sets ready before tunneling started.  Sound Transit did something similar with the U-Link project, temporarily staging the segments at an off-site storage lot on Elliott.

    • Christopher Boffoli April 26, 2016 (9:31 am)

      Eddie:  There actually will be 1,218 more rings installed (232 in place now, 1,450 total when the tunnel is complete).   The concrete segments for those rings are presumably still being staged in the in the southeast corner of site.  That’s where I saw a large number of them during my 2014 tour and where they can be seen if you look at a Google Maps satellite view of the southern end of the project site.   I didn’t see any of the segments during yesterday’s tour but we weren’t really taken by that area.  STP may have drawn down their standing inventory of segments during recent tunneling and may be waiting until the TBM is boring again before replenishing them.  Or they might just be trucking them in as needed.

  • dsa April 26, 2016 (9:52 am)

    Great pictures, on the roof there is a black thing to the left that could be a conveyor belt and on the right a yellow tube which could be fresh air.  Or neither is correct.  CB, do you know?

    • Christopher Boffoli April 26, 2016 (10:42 am)

      DSA:  Yes, the black belt carries tailings away from the cutting face and back out through the tunnel.  As STP’s Chris Dixon explained to me during my 2014 tour, new sections of belt are added as the TBM advances so that by the time the tunnel is complete the tailings belt will be as long as the tunnel itself.  The yellow ventilation duct carries fresh air into the depth of the tunnel. The air flow can be rapidly reversed in the event of a fire to pull smoke out of the tunnel.

  • Michael April 26, 2016 (2:20 pm)

    Thanks for the updates on this project!  I’m looking forward to the daily updates during the closure too.

    This might be a nitpick but why does STP refer to this operation as mining?  They are digging a hole but they aren’t searching for anything of value beyond the hole itself.  Why are they using this term?

    Also, do you know the purpose of the buildings at each end of the tunnel with the yellow stacks?  Is that some kind of exhaust system?

    • WSB April 26, 2016 (2:25 pm)

      I don’t know about the terminology but re: the yellow stacks – ventilation:

      • Anne April 28, 2016 (9:57 am)

        Re the term “Mining”.  While you can mine for something such as copper, lead, etc. by tunneling, you can also mine something.  It’s a military term that was used to refer to tunnels dug under fortifications, walls, etc.  to allow sappers to blow up the wall or dig into a  shielded area and allow infiltrators inside.  So in that respect, STP is mining Seattle.

  • Curious George April 26, 2016 (10:58 pm)

    Has WSDOT or STP relayed what the contingency plan is if Bertha breaks down under the viaduct or if they do see a significant event involving the structural integrity of the viaduct?  Do they stop?  Keep going and let the viaduct remain closed indefinitely or what?  Do they even have a contingency plan?  Given that they have been so reluctant until today to even relay a closure time, I worry they are not planning ahead.  Btw, it closes at midnight, so the closure begins after the Thursday commute.  If you read the signs around WS, you see closing on 4/29.  Wish they’d been more clear about that before I scheduled a bunch of appointments the morning of 4/29 on First Hill 😐  I wrongly assumed Friday Night like normal WSDOT closures.

    • WSB April 26, 2016 (11:04 pm)

      If the Viaduct was considered unsafe, it would stay closed. If the tunneling machine broke down but the Viaduct was fine, they would likely reopen it until they figured out what to do – they’ve said that multiple times. We reported earlier in the week that WSDOT told us 12:01 am was the tentative closure time, but since the day the announcement was made (see the first paragraph of our 4/15 story) they were clear it would be BEFORE the Friday morning commute. The signage currently says 11:59 pm Thursday, which is two minutes before 12:01 am Friday; I think they finally realized it would be clearer if they said “late Thursday night” than continuing to say “before the Friday morning commute” – TR

  • yippee! April 27, 2016 (8:48 am)

    ok Tracy, then I must be dense. I’ve sought the closure time info for weeks, searched for exact time, etc. If there was clarity, I’d have seen it. See, I communicate for a living too. This was sloppy and vague. Your own story said they were waiting for the timing based on what they heard from STP. Why does STP dictate closure timing on a major hughway when Wsdot manages them? Wait, nevermind …i know the answer. And yes, you insulted my intelligence.


  • Denise April 28, 2016 (8:41 am)

    Who thought those yellow stacks were attractive?  I was hoping is was temporary. I see if you are employed by the tunnel once it is finished you will report to the north yellow stacked building. It says you also have parking lot. Is that parking free for employees?

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