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Update: Highway 99 tunnel machine now a third of the way to the pit

February 18, 2015 9:47 am
|      14 COMMENTS
 |   Alaskan Way Viaduct | Transportation | West Seattle news

(UPDATED LATE WEDNESDAY AFTERNOON with progress report)

9:47 AM: Last week, WSDOT said the Highway 99 tunnel contractor would likely start the process this week of trying to get the tunneling machine to move 20 feet ahead so its damaged cutterhead can be pulled from the 120-foot-deep pit dug next to the Viaduct. This morning, there’s word the process has begun. As of 7 this morning, according to WSDOT’s announcement, the machine had made it about three feet forward:

The machine must mine through 20 feet of unreinforced concrete to reach the pit. The duration of this effort will depend on the machine’s ability to mine through the concrete while operating with a damaged seal system. STP anticipates the machine may overheat, as it has during their most recent attempts at mining. If the machine becomes too hot, they will take a break for it to cool down before resuming.

The image above is from the WSDOT page displaying several “live” construction cameras. (P.S. The south side of the pit, where it’s expected to break through, is on the left side of the photo.)

4:32 PM: WSDOT has just posted another update – saying the machine has now gone six feet.

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14 Replies to "Update: Highway 99 tunnel machine now a third of the way to the pit"

  • bada-bing February 18, 2015 (12:14 pm)

    How long will the breaks need to be between the time they shut her down due to overheating, and the time they can start her up again? And what is the pace of the drilling now (i.e. how long did it take to drill this first 3 feet?)?

    • WSB February 18, 2015 (12:56 pm)

      I don’t believe they know that yet, BB – which is why they’re not guesstimating how long it will take to get the entire 20 feet. I’ll be watching to see if they have Twitter updates between longer web updates – http://twitter.com/berthadigssr99 – so far nothing today but a tweet pointing to the same web update from which we took this info. – TR

  • mike February 18, 2015 (4:53 pm)

    I propose a drinking game. Every time Bertha breaks down, you take a shot. (It’s a very SAFE drinking game!)

  • WSince86 February 18, 2015 (5:17 pm)

    Mike- We’re game for that!!

  • The Future February 18, 2015 (9:07 pm)

    Here’s a short video that shows the future of the tunnel…
    https://animoto.com/play/0J0HCXrgYxfWi72tA63jnA

  • Dixon February 18, 2015 (10:46 pm)

    So what happens if the drill gets stuck under a building as it digs further? Will they need to tear down a building in order to dig a hole to access the drill? w h a t t h e h e l l

  • Dennis February 18, 2015 (11:17 pm)

    @ Dixon: No. It’s been reported before that while the pit is the (relatively) easy way, in a pinch they can dismantle the machine from behind.

  • WsEd February 19, 2015 (8:34 am)

    Dennis,

    I think maybe the pit was a relatively easy way to extend the contract for more cash as well.

  • wakeflood February 19, 2015 (9:08 am)

    I was curious when I read that they’re unsure how the machine will deal with getting through the concrete wall of the extraction pit.

    My first thought would be that if it was a concern, they’d have done something like perforate the shaft where they expect the machine to enter or something like that – picture a voting ballot chad that can be punched out, or similar.

    And then I took a closer look at the picture in the article. Hmmm…looks like there’s a change in color/texture in the wall in a circular shape near the bottom? Does the extraction shaft indeed have a punchout chad? Methinks it might.

    • WSB February 19, 2015 (9:38 am)

      Wake, yes, that’s been part of the WSDOT updates if you click through to read in their entirety. They have chipped away a spot to make it easier for the machine to finish getting through.
      .
      Regarding the discussion of making repairs from behind – yes, WSDOT has mentioned this repeatedly. Haven’t found an exact link and don’t have time to look, have to get on with other things, but it’s been explained before. – TR

  • Peter February 19, 2015 (9:33 am)

    @Dennis: >> in a pinch they can dismantle the machine from behind. << Willing to be corrected, but I don't think that's true. They're using the pit approach because the cutting head is larger in diameter than the tunnel bore, after the concrete wall sections are installed. They'd have to take the cutting head apart to slide it out the back. I doubt that's even feasible, given the massive weight of the cutting head. Even if in pieces.

  • Born on Alki 59 February 19, 2015 (9:49 am)

    I have heard one analogy that making repairs from behind Bertha would be like doing a valve job on a Maserati while blindfolded with the hood closed. I guess anything’s possible with enough time and money.

  • Dixon February 20, 2015 (11:31 pm)

    So if it can be repaired from behind, why was there no progress for a year? If making a pit is the easier path, and it takes a year, if it continues on and starts to head under existing buildings and gets stuck, will there be another year+ delay?

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