

Under Seattle, a Big Object Blocks Bertha. What Is It? - petethomas
http://www.nytimes.com/2013/12/20/us/under-seattle-a-big-object-blocks-bertha-what-is-it.html

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jasonkester
Amazing that they managed to fill two whole pages of speculation about what
might be under that bit of Seattle without once mentioning the giant
underground city that actually _is_ under that bit of Seattle. Or at most a
few blocks away:

[http://en.wikipedia.org/wiki/Seattle_Underground](http://en.wikipedia.org/wiki/Seattle_Underground)

They talked to the local city librarian, so clearly she must have mentioned
the tourist attraction where you can go down and see all the buildings that
sank into the mud before they decided to raise the street level, oh, around 45
feet.

So now when they're digging a new tunnel 45 feet under that spot, it's tough
to understand why they're in any way surprised that they hit something
building-ish.

~~~
ryanthejuggler
I laughed when I saw the map. Compare [1] from the article with [2], which
mostly corresponds to the location of the Seattle Underground.

I went on the Underground tour earlier this year. It's really interesting and
pretty funny too; after a large earthquake at one point they used the tunnels
to hide a lot of the debris. I'd definitely recommend the tour; that said, I
would definitely _not_ want to be down there when something like this hits the
wall!

A big object blocks Bertha. What is it?
[http://lmgtfy.com/?q=Seattle+Underground](http://lmgtfy.com/?q=Seattle+Underground)

[1]
[http://graphics8.nytimes.com/images/2013/12/20/us/20tunnel-g...](http://graphics8.nytimes.com/images/2013/12/20/us/20tunnel-
graphic/20tunnel-graphic-popup.jpg)

[2]
[https://en.wikipedia.org/wiki/Pioneer_Square,_Seattle](https://en.wikipedia.org/wiki/Pioneer_Square,_Seattle)

~~~
arbuge
We (my family, i.e.) personally found that tour rather short and significantly
overpriced at $17 for about 75 minutes... in spite of that it was packed with
tourists who paid extra for priority seating at the start of the tour (which
isn't worth anything in practice). A real money spinner.

~~~
colanderman
Overpriced? Sure, but having been on that tour, I would regret having _not_
taken it. Really interesting history, and where else do you get to see an
honest-to-goodness sunken city? I'd pay similar money (or more) to go on a
(legal) tour of, say, disused NYC subway tunnels, a deactivated nuclear plant,
an abandoned mine, a shipwreck, or Kowloon Walled City (when it existed).

EDIT: Indeed, the Wieliczka salt mine (which, for me, was a similar experience
to the Seattle underground) costs about $25 USD: [http://www.wieliczka-
saltmine.com/visiting/tourist-route/vis...](http://www.wieliczka-
saltmine.com/visiting/tourist-route/visitor-s-guide/check-prices)

------
ghshephard
I find it fascinating that the pressure is so high in their (relatively
shallow) drilling area that the people doing the inspection have to go through
decompression chambers. I'm trying to visualize how that could be, but I'm not
sure what's going on - is there basically a "perfect seal" in the front of the
drill head they don't want to break? And if so, won't the bore holes they are
drilling do just that?

That's the most interesting part of the article for me.

~~~
abduhl
Large TBMs like this generally allow access to what is called the face (the
area being excavated) via a double bulkhead system. The ground conditions in
Seattle require that the machine be able to control the rate of excavation at
all times such that a large sink hole does not form due to uncontrolled loss
of ground. This is done by keeping pressure on the face.

The pressures required to keep the face stable are a function of the soil
properties, lithology, and groundwater. The typical way for someone to access
the face is to pressurize ahead of the machine head with gas and have workers
enter under pressure (known as a dive or an intervention). Workers generally
are limited in how long they can be under pressure and must go through
decompression.

Edit: real quick calculation on my phone puts them at about 70 psi or 4.5 atm
of pressure to do a manned intervention, possibly higher for safety

Disclosure: underground tunneling is my profession.

~~~
timr
I've always wondered how they get the kind of seal necessary to maintain that
kind of pressure ahead of a tunneling machine. Is the drilled surface smooth
enough to provide that kind of seal?

~~~
abduhl
I typed up a rant about boring vs drilling and the correct terminology but it
sounded super nerdy after reading it.

I'm not really qualified to answer your question as I'm not as intimate with
the machines as I am with the ground/structure side. Most likely the seal is
maintained by the machine being too big for the hole being cut or by
inflatable packers. The walls of the bore can range from extremely smooth to
not smooth at all depending on ground conditions.

Sorry.

~~~
StavrosK
Are you saying that drilling tunnels is really boring?

------
wittekm
Let me answer.

"Chris Dixon, the project manager at Seattle Tunnel Partners [...] said he
felt pretty confident that the blockage will turn out to be nothing more or
less romantic than a giant boulder, perhaps left over from the Ice Age
glaciers that scoured and crushed this corner of the continent 17,000 years
ago. " ~ The article.

~~~
Zikes
Which is why there will never be a followup.

"Mystery Object Found to be Benign, Everyday Rock" does not make for a great
headline.

Edit: I may be underestimating NYT's ingenuity a bit. I suppose "Big Bertha
Resumes Drilling After Penetrating Ancient Glacial Super Rock" would serve the
purpose.

~~~
BrandonMarc
"Subterranean Seattle Drilling Engineers Use This ..."

(wait for it)

"... One Weird Trick ..."

(ah, there it is)

"... To Conquer Ancient Mega Boulder Behemoth"

Yep. _That 's_ a headline.

~~~
Raphael
Glacial tills hate them!

------
bcbrown
> A secret subterranean heart, tinged with mystery and myth, beats beneath the
> streets in many of the world’s great cities.... Now Seattle, at least for
> now, has joined that exclusive club.

That lead is funny in light of
[http://en.wikipedia.org/wiki/Seattle_Underground](http://en.wikipedia.org/wiki/Seattle_Underground)

~~~
D9u
I thought the same. The old underground Seattle used to be a tourist
attraction 40 or so years ago. What's new about this?

~~~
sirmarksalot
Still is. The Seattle Underground Tour is still one of those go-to tourist
activities, like Pike Place Market and the Boeing Factory Tour.

~~~
jffry
To be fair, the Boeing Factory Tour is pretty cool, even if it is a giant
propaganda movie.

~~~
MartinCron
I think a better tourist attraction is the Museum of Flight at Boeing Field.
All sorts of gorgeous aircraft in there.

~~~
jffry
True. Up there with the Udvar-Hazy Center outside of Washington, DC, and the
USAF Museum in Ohio.

------
astrobe_
> Tourists seek out the catacombs of Rome, the sewers of Paris

I think it's the opposite: the catacombs of Paris are quite famous (at least
in France), and the ancient sewers of Rome are likely to be visited, since
sewers are a Roman invention IIRC.

------
adamnemecek
I got curious how the machine works and I found this video

[http://www.youtube.com/watch?v=Dk-8Q42NCSQ](http://www.youtube.com/watch?v=Dk-8Q42NCSQ)

Pretty fascinating stuff.

~~~
ph0rque
Thanks for the video, I'm sure my kids will love watching it with me.

The one idea I had was wouldn't it be cool if they could somehow use the
material they've cut through in the cement tunnel that they are building.

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wreegab
> "The object’s composition and provenance remain unknown almost two weeks
> after first contact"

Anyone else thought "Arthur C. Clarke" when reading this part?

~~~
joseph_cooney
I heard a choir of discordant voices, and pictured something smooth,
rectangular and black.

------
jonhohle

      > In October, workers walked through the first
      > rings of the highway tunnel being built under
      > Seattle’s waterfront toward the _boring_ machine
      > called Bertha.
    

What's so boring about a huge, self-propelled drill making a gigantic hole
under a city? … oh (facepalm)

------
cdcarter
I haven't been able to tell from any reports yet. What is it about this object
that they weren't able to discern existing through sonar/ultrasound/core
samples/whatever pre-engineering I imagine these sorts of projects do? Is it
that it's just so far down? Or do we not even know?

~~~
abduhl
A couple things:

1\. We generally do a boring every couple hundred feet along an alignment for
tunnels. The bore hole is about 2" in diameter. You can imagine that we miss
white a bit of subsurface detail. We rely on experience and local geological
history for fleshing out the details and putting things in context. Sometimes
we just flat out miss things. 2\. Geophysics methods (sonar essentially) is
not very good at telling you what something is past "hard", "soft", or "void".
In a glacial till you get a lot of all three.

~~~
001sky
Is inconsistency of substrate enough to be a problem? Like if you put marbles
in a food processor?

~~~
abduhl
I don't understand your question. A problem for what? For the geophysics
methods or for the TBM?

Geophysics methods give a measure of density based on wave
reflection/refraction and are therefore at the mercy of energy absorption of a
given material. Resolution is a function of energy and so the ground smears in
your results. The variability of the ground may or may not pose a problem to
the geophysics methods used, it depends on how they do it.

For the TBM, inconsistency in the ground can obviously pose problems. Based on
what I know about this project (which is not much), Bertha has mixed face
tooling on its cutter head but is primarily a soil machine. This means that
large boulders can pose a problem as the cutter head isn't designed to deal
with massive, hard objects most likely. The way most of these soil machines
work is that they have a cutter head with tooling that essentially scrapes the
soil and there are windows in the head that open to an area behind the cutter
head which the soil moves through before being spit out as muck from a
conveyor or screw jack. This area behind the cutter head generally has a
system to crush large rocks that enter this area into sizes that are fit for
the muck system. The problem arises when you have a rock too large to fit
through the window as the cutter head isn't really equipped to bust up rocks
(for multiple reasons).

Let me know if that didn't answer your question.

~~~
dreen
So what is the typical procedure when encountering a large boulder? Get people
there and just drill through it manually? Or would they have to completely
remove the entire boulder? (how?)

~~~
abduhl
Access the face and bust up the obstruction so that it can be ingested or sink
a shaft and remove the obstruction vertically.

------
micro_cam
As a former Seattleite I think there is a decent chance this is just another
one of restaurateur Ivar Haglund's futuristic adds like the Billboards for
submarines [1]. Perhaps a literal acer of clams.

[1]
[http://seattletimes.com/html/localnews/2009889864_ivar18m.ht...](http://seattletimes.com/html/localnews/2009889864_ivar18m.html)

(the underwater billboards did turn out to be a Hoax/Stunt that were not
actually put there in 1954.)

------
fixedd
>> "I’m going to believe it’s a piece of Seattle history until proven
otherwise," said Ann Ferguson, the curator of the Seattle Collection at the
Seattle Public Library

It is exactly what my biases would lead me to believe it is, without evidence,
unless you go to the effort to prove otherwise.

~~~
VBprogrammer
That's pretty harmless in this case, the necessity of getting though it means
they will have to find out what exactly it is.

Perhaps 'hope' would have been a better choice of word.

------
nmc
I am the only one seeing the paywall?

~~~
adamnemecek
Open it in private browsing mode.

~~~
nmc
Oh, I had never tried the "privacy mode" of Firefox! Thanks for the heads up!

However why is this working? I already had disabled JS, so the only thing I
can think of is my location (Europe), but "privacy mode" will not prevent
anyone from seeing my IP, so... wtf?

EDIT: cookies, of course! I had forgotten I already read the NYT recently.
Thanks!

EDIT': confirmed by disabling "privacy mode" again, deleting cookies did it.

~~~
adamnemecek
I'm pretty sure that it's based on cookies. They let you read some number of
articles per month for free and once you hit that number, they show the
paywall.

------
teh_klev
Maybe they've bumped into the last tunnel boring machine left behind by
ancient space travellers :)

[https://www.youtube.com/watch?v=4i4DSvRoKQc](https://www.youtube.com/watch?v=4i4DSvRoKQc)

------
sinkasapa
It is actually happening.

[https://en.wikipedia.org/wiki/Boneshaker_%28novel%29](https://en.wikipedia.org/wiki/Boneshaker_%28novel%29)

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auctiontheory
Reminded me of this episode of Star Trek:
[https://www.youtube.com/watch?v=39roz9jQfzE](https://www.youtube.com/watch?v=39roz9jQfzE)

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snogglethorpe
Uh-oh... oO;

[http://www.youtube.com/watch?v=l7JY9xtpCxY](http://www.youtube.com/watch?v=l7JY9xtpCxY)

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HPLovecraft
[http://www.imdb.com/title/tt0062168/](http://www.imdb.com/title/tt0062168/)

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stuaxo
Do the conspiradroids think it is a UFO yet ?

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vivin
I hope it is an ancient alien space ship.

