Oh, this is going to be hilarious until someone gets killed. Imagine that, the State has played credulous hacks such as Tom "Tunnell" Rasmussen and Jean Godden for fools. Who could have guessed? I think this is all McGinn's fault. If it weren't for all his nay-saying, the unstable glacial till soils would never have threatened to collapse.
Insert "Quartermass and the Pit" reference here...
Best Sawant quote ever!!
Giant eyeroll at that last sentence. This situation is farcical enough without injecting that sort of imagery.

As long as Ms. Sawant has speculated wildly, I'll speculate a little less wildly (and as a non-engineer) and say that the catastrophic failure likely refers to the access pit itself, not the whole adjacent area of downtown.

Look, they were pumping groundwater around the access pit to lower the soil-saturation zone. This produces a shallow inverted cone of desaturated soil centered on the pit. It reduces the amount of water pouring in if they get to the point where Bertha's in the pit and being worked on, but before that it reduces the lateral forces on the concrete columns that surround the pit. Concrete is strong in compression, weak in tension ( pulling or bending), which is why rebar is usually added. I'm guessing there is little or no rebar in the pit columns (because Bertha has to chew its way in, and then back out again).

They had to stop pumping because it was causing problematic surface subsidence near the edges of the cone (under the viaduct and Pioneer Square), and they must now presumably pump groundwater at a greatly reduced rate, or not at all. So groundwater rises again around the pit and lateral (inward) forces on the pit columns increase. I think the main catastrophic failure they fear (other than the viaduct collapsing, of course) is that of the rescue pit—unreinforced columns crack and collapse inward, quickly followed by an inflow of saturated soil.
@4) The most enlightening part of your cute little essay: you are a "non-engineer". It isn't just that you are not an engineer - you are a "non-engineer". Well, your opinion costs nothing and it is worth that price!

Great reporting, Sydney!

Re: Did the facts change? Or did the language change to cover up the facts?

Risk assessment is not "facts" it's engineering judgement. Which can change. Because it's a risk assessment about the future, not a history lesson. Just sayin'

And I AM an engineer, so I know from engineering judgement.
@7, I'm not engineer...but I am a litigator (who has worked with a number of engineers as experts on cases). If someone is hurt, or something goes wrong...that's the kind of language I would use to tear an engineer a new asshole during a deposition/trial.
Does Sawant know that Atlantis is fictional ?

pg 482 indicates that buildings were planned for up to 1 inch of settlement as a part of the tunnel. How many buildings have already exceeded that and who owes money on that ?…
Dewatering is part of the excavation. Trying to say it wasn't caused by the excavation, but the dewatering is some smarmy distinction-smithing. A lawyer friend of mine lables that as a distinction without a difference.
They would not be dewatering if they weren't digging.
@1, I'm sure we can blame McGinn for swearing that, if elected, a tunnel would not be built and then being ineffective at actually achieving that campaign promise.
Is that council meeting being streamed online?

@12 But that would be stupid.
@12 You could, but that would be stupid.
You know, it's possible this asteroid is not entirely stable.
@4 That soil has to come from somewhere. While smushing anyone and anything inside the access pit would be pretty catastrophic for residents of that pit, I think anything sitting on top of the soil surrounding the pit would probably not fare well, either.
Freezing the ground around the repair pit is a good (but more expensive) way to keep the water and soil in place and reduce localized subduction.
@8, do you consider it part of your profession to tear people a new asshole for exercising their professional judgement (actually DOING their professional work)? I presume that's a matter of speech.

Exercising judgement is the only way to do risk assessment about a potential future event. Unless you know of another way? Maybe you could share what that is!
@18, but think of the gribbles that would die!
@18: I was wondering about that. Time for ice-9?
Engineering is not as precise a science as some people seem to think it is.

An engineer predicts the likelihood of failure based on past knowledge, and stress of concrete and other materials, and soil conditions, and so on. But it is an estimate, not a guarantee. Nothing can be predicted with 100% accuracy. So they dig/build that pit, and they throw enough concrete at it that they are pretty sure it will hold, but there is always some chance that there is some factor that wasn't predicted, or something fails. Sometimes new information changes that prediction, or factors change and they have to re-evaluate.

Engineering is messy. Live with it.
Lol@Sawant saying she used to be an engineer and they're not prone to hyperbole.

I think we've heard enough hyperbole from Sawant to see those two statements can't fit.
@17, you're absolutely right. Catastrophic collapse of any size is to be avoided.

@18, etc.: They're developing the expertise at Fukushima right now………
*munches popcorn amusedly*
Good grief if the media doesn't just love a potential "catastrophic failure". It reminds me of all the local news stations that annually predict a potential snowmageddon of epic proportions and we get a half inch of snow while the media talking heads appear on the TV for the non event like the idiots they are. Nothing attracts the media like a problem or potential problem with a public works project and the second and third guessing starts along with all of the finger pointing.

Rarely is a large complicated Public works project without a problem(s) and the tunnel is no exception. It was to be expected but if we sat back as we Seattlites frequently do and listened to all of these non-engineering types spread there doom and gloom we would still be staring at the viaduct and have no plan to replace it, sort of like we did with the monorail. Brains a lot more intelligent and experienced than those at the Stranger are working to resolve the Big Bertha problem as they did with the Big Dig in Boston. Give them a chance.
Aaaah, another mountain out of a mole hill from The Stranger on this issue. When the tunnel is done, I will read these articles and chuckle to myself.
Ok, from the perspective of someone who has some expertise.

First, Catastrophic Failure is likely to be limited to just the pit. However, that's bad enough, as economically and practically, it would finish both Bertha and the deep tunnel. We could still dig them out, but the repair would probably cost more than the original project.

Second, with this kind of excavation, dewatering needs to take place whether digging is happening or *not*. without it, The Pit will turn into The Pond, in short order, to be replaced by The Bog, as the shoring fails and the immediate vicinity slumps into it.

(I remember watching this play out when I was doing soils testing at Magnuson park. I worked there when they were converting it from an naval air station to a park 30-odd years ago. They hit a spot with ground water rapidly up-welling through a gravel seam in the glacial till. They tried to ignore it by just scooping out the muck that came up - they were trying to put in a drainage catch basin, ironically. I watched in mixed amusement and alarm as what was supposed to be a 10x10x20 deep hole turned into a 100' diameter 10' deep pit, as the quicksand rapidly undermined and consumed the pit walls. Eventually, they trucked in about 50 tons of Bentonite, and built a pad which they could drop pipe and basin on. They then quietly re-filled the pit with gravel and sand and walked away from it...)

Freezing is a good engineering move, but not so much for dewatering as it would be for securing the pit structurally. Even frozen, you'd still need to be pumping like mad to keep the pit dry - water will be upwelling from the bottom of the dig.

The best *technical* choice I see from a speed and engineering standpoint, but one that is both hella dangerous and expensive, is the pre-20th century one - caissons. Pressurizing the excavation (it would need about 3 atmospheres) would keep most of the water out and help stabilize things generally, but anyone working would need to go through end-of-shift decompression or suffer the bends. However, doing so would have allowed them to get to the cutting head quite rapidly via a small access tunnel. What would happen from there is a separate question.

This is such a total mess, and (to no one in particular) I told you so... more than once! Far less risky options existed and were very deliberately marginalized and ignored; as a result, we now end up with the worst of possible outcomes - millions in wasted effort, no viaduct, and traffic forced into overcrowded transit and surface streets.
@26 What resolved the Big Dig was $10 billion in Federal funds. Do the brains you are referring to have influence over billions of Federal dollars? If not, it may not matter how smart they are.
#9, Atlantis technically isn't fictional. It was just poorly recalled fourth hand information. Solon visited an Egyptian temple that tells a story of the Santorini explosion (inaccurately, as it was written down centuries after the event), going so far as to use the Egyptian word for Thera in the story. It is this second hand story that Solon told Plato and Plato retold. We've found the temple and the story. Atlantis isn't fictional. It is a matter of already discovered archaeology combined with early "telephone" errors. Plato likely used the story for political ends, but the story had an element of truth to it deep down.
Armchair Engineers and Chicken Littles are part and parcel to all large engineering project. Seattle's tunnel project is no different with complainers and nay-sayers in high gear at this point in the Viaduct replacement project.

Boston's Big Dig is an amazing feat of engineering and construction. Cost? 14 Billion. More expensive than the Panama Canal and Hover Dam combined. The project cost is paid but once, the improvements to Boston will benefit the city for the next 150 years and more.…
"sinks into Elliott Bay like Atlantis."

Atlantis sunk into Elliott Bay?
#31, nobody call The Big Dig an amazing feat of engineering and construction with a straight face. You also neglect to mention that the bid for The Big Dig was 2.8 billion or so. That's 5 times the price due to cost overruns. Are you honestly suggesting that if Bertha ends up costing 5 times more than the original bid it will still be worth it to the region? How can you justify such a statement?
Is STP paying for the new water mains, or do they have an insurance policy?
The hell with Tom Rassmussen. This situation cries out for comment by Tom Tomorrow!!!
I have personally worked with WSDOT engineers, and project managers. As such, I am confident this project will be a colossal failure and will be abandoned at great monetary and psychological expense to the City of Seattle and Washington State in general.
What MORE could I wish for? Ice cream and a pony; it's what I've been asking for all along!

@31, i'm so glad to see our nation expending its best and brightest minds as well as 10's of billions in pubic capital to complete monumental feats of engineering so we can have a couple underground roads.....
The tunnel option for Seattle urban planning says, if they put a man on the moon, we can put 10 pounds of shit in a 5 pound bag.
Assuming the tunnel is someday completed (ha ha!), how long before it is flooded by rising sea level? I recall during the debates about its merits that the service life wasn't expected to be that long. Anyone, anyone?
I was wondering what all the hubub was. I then realized, you're building a tunnel. All this time I thought it was a giant funnel.
@31 …uh correction to your $14b price tag on the Boston Big Dig - It won’t be paid off till 2038 and at that point w/ interest it will ultimately cost an estimated $22 billion!!!

"The Big Dig was the most expensive highway project in the U.S. and was plagued by escalating costs, scheduling overruns, leaks, design flaws, charges of poor execution and use of substandard materials, criminal arrests, and one death. The project was originally scheduled to be completed in 1998 at an estimated cost of $2.8 billion (in 1982 dollars, US $6.0 billion adjusted for inflation as of 2006). However, the project was completed only in December 2007, at a cost of over $14.6 billion ($8.08 billion in 1982 dollars, meaning a cost overrun of about 190%) as of 2006. The Boston Globe estimated that the project will ultimately cost $22 billion, including interest, and that it will not be paid off until 2038. As a result of the death, leaks, and other design flaws, the consortium that oversaw the project agreed to pay $407 million in restitution, and several smaller companies agreed to pay a combined sum of approximately $51 million."

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