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Why is Bertha stuck? WSDOT's 5 levels of tunnel-drilling hell

What exactly went wrong with Seattle's tunnel boring machine? Five different scenarios WSDOT may face this week.
Tunneling crews discuss their progress as they operate Bertha, the world’s largest tunneling machine, in November 2013.

Tunneling crews discuss their progress as they operate Bertha, the world’s largest tunneling machine, in November 2013. Photo: WSDOT

The world's largest tunnel machine, Bertha, is stuck 60 feet beneath Downtown Seattle. The tunnel contractor has drilled down, pumped out and pressurized a gap in front of the machine and is sending divers down 24/7 to try to figure out what brought the machine to a standstill nearly seven weeks ago.

According to the Washington State Department of Transportation (WSDOT), diver teams are working in shifts examining the cutterhead from an approximately 14-inch vertical crawlspace created between a claylike Bentonite barrier sprayed into the ground ahead of Bertha and the top half of the towering, five-story tall behemoth.

Depending on what they find, here are five potential scenarios for Bertha's future, ranging from inconvenient to disaster:

Scenario One: Pipe Gone Wild.

Divers may find more remnants of the 8-inch diameter steel pipe tangled within the cutterhead of the machine. If so, they'll need to clear it out and determine how badly the cutterhead may have been damaged by the encounter. That will take time, but the bigger question will be how much metal junk remains in the 9,000 foot path ahead of the machine. If there is more, then finding it, removing it — and being certain about it — will take time and resources.

Scenario Two: Big Rock Indigestion

Divers may find large rocks or boulders jammed into the machine. In that case, the fix may be to change some of the soil cutting teeth back to disc-style rock cutters like those used when the machine launched from its concrete starting pit. Disc cutters can break rocks, provided they can get a purchase on and exert enough pressure to do it. If not, then some other plan will be needed to remove large rocks. Bertha does not have a secondary rock crusher mechanism as do some other TBMs.

The tunnel route is a diverse patchwork of ground conditions including "non-cohesive" sandy, gravelly, clayish earth, all below the water table. Similar to the metal pipe, it is hard to know beforehand how many rocky boulders lurk in the mix along Bertha's path.

Scenario Three: A Bearing Surprise

At the core of any TBM is the vital main bearing. There is a small chance, observers worry, of problems related to those that Bertha's builder, Hitachi Zosen, had and fixed during testing of the machine at the factory. Bertha is a giant, and the pressures at the bottom of the machine vary significantly from those at the top of the machine, but TBMs are routinely built to cope with that fact.

It would take something truly extraordinary to prang the main bearing, but if it were damaged, it would be a major showstopper. UK Tunnel expert Alastair Biggart: "The heart of… any TBM, is the main bearing. If this should be damaged during tunnelling it is a major problem for the project. It is possible to change a main bearing within the tunnel, but extremely time consuming and expensive."

Scenario Four: The Biggest Problem

If the divers take a good hard look and don't find any obvious problems, that could mean the problem is Bertha's design itself. This would be the biggest problem of all. TBM selection is often the most crucial decision of a tunnel job. The situation in Seattle may turn out to settle a contentious technical question: Which of two competing types of machines was best for this job?

Tunneling here is known to be tricky. "We can never take for granted the tendency of the soils in Seattle to misbehave if given the opportunity," consulting project managers from the firm Hatch Mott MacDonald wrote in a report to WSDOT.

To this day, there is industry disagreement about what machine design is best for Seattle's conditions. In its "design-build" process, WSDOT specified a category of machine (closed face pressurized), but left the design choice up to the main contractor. Two different types of machines were contenders for the work: An Earth Pressure Balance machine (which Bertha is) or a Slurry/Slurry Mixshield machine. There are important technical differences between the two and each has vocal proponents.


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Comments:

Posted Mon, Jan 20, 5:27 p.m. Inappropriate

Soil doesn't misbehave. How does someone uttering such nonsense get quoted?

Posted Mon, Jan 20, 10 p.m. Inappropriate

It was obviously a figurative way of saying that the soil behavior is difficult to predict.

NotFan

Posted Tue, Jan 21, 6:47 a.m. Inappropriate

Expect more of the same from the apologists.

Posted Mon, Jan 20, 10:22 p.m. Inappropriate

Here's one thing they will not, not, NOT do: Admit that they completely screwed this up from the very start and go to Plan B, which at this point should be a cut-and-cover tunnel wide enough for six lanes and the railroad tracks, topped with a surface artery.

This would involve facing facts, which in my years in Seattle I have rarely if ever seen anyone in local or state government ever stoop to doing. Nope, they'll string this out long enough to put us on the hook for that machine, at which point our troubles will REALLY begin.

NotFan

Posted Tue, Jan 21, 9:57 a.m. Inappropriate

Recommended reading:
"This Land was made for you and me, (but mostly me)"

An 'illustrated' guide to the outrageous display of obscene wealth by the world's one percent.
Bruce McCall and David Letterman.

Seattle's fraction of one percent worst pricks have revived a 60-year old plan to demolish Pioneer Square and rebuild. Demolition will commence within 10 years after Bertha finishes boring the slow but sure instrument of death and destruction -(cue show of crockadile tears for national sympathy)- along with BAGS OF MONEY! for rebuilding. Seattle will repopulate with even stupider people with even more worthless college diploma slips.

Wells

Posted Tue, Jan 21, 3:54 p.m. Inappropriate

Koo Koo

acbytesla

Posted Mon, Jan 20, 10:38 p.m. Inappropriate

Yeah those misbehaving soils are really getting out of hand.

Posted Tue, Jan 21, 3:36 a.m. Inappropriate

This is the first article that actually seems to be truthful as opposed to being just a smear job.
Herrenknecht has been criticizing the choice of using an EPBM since the beginning. But FUD (Fear, Uncertainty and Doubt) campaigns are not unusual in a sales battle.

Mixed Slurry machines spray a Bentonite slurry to front of the machine to stabilize the ground and put pressure on the soil. The slurry mixes with the muck and together they are piped back to a treatment/separation plant where the muck and the bentonite are separated and the bentonite is the pumped back to the cutterhead.

Mixed Slurry operates well in in sandy gravel soils but is not suitable in clay silty type soils.

Bertha is an EPBM machine which seems to be the TBM of choice in the Seattle area as are 80 percent of the TBMs chosen for this area. In fact all of the TBMs chosen by Sound Transit for the downtown to University rail links were EPBMs.

An Earth Pressure Balance Machine uses a combination of compressed air and forward movement to match the pressure and type of soil it is carving through. If it is say a hard rock face it will assert a great deal of forward pressure and slowly grind the rock away with cutter wheels. The softer the ground in front, less forward pressure is asserted to reduce the chance of ground movement.

It's easy and natural to second guess the TBM choice. I'm sure it is possible that the engineers MAY be worrying about that choice. I'm amazed that there isn't a stone crusher in the plenum. That surprised the editor of Tunnel Talk who called it "brave" on her tour of Bertha.

There is a real science in building tunnels, far more than most people realize. It's not like it was a hundred years ago where hundreds of men would toil with hand tools to build a tunnel. Only 24 men/women operate Bertha and build the the tunnel behind her.

But to allow those 24 people and Bertha to create that tunnel under Seattle, a significant amount of work and the right choices have had to have been made ahead of time. For example a thorough site investigation along the route analyzing the soil in as many places as reasonably possible along the route. Then as the author notes, choosing the right type of TBM for the route or varying the route to get the right kind of soil for the TBM.

TBM tunneling is great when everything goes as expected. It is the safest and most effective method of building underground infrastructure in the world today. The problem with TBM tunneling is when problems arise and you encounter the unexpected. It takes both engineering know how and unfortunately time and money to resolve those problems. That is why tunneling projects usually have a significant contingency fund.

This delay is frustrating and I understand people panicking but I refuse to second guess engineers who know far more than I do.

Everybody take a deep breath and keep your fingers crossed.

acbytesla

Posted Tue, Jan 21, 8:25 a.m. Inappropriate

Yes, it's a good idea to take a deep breath and relax. I have no idea how much information is being withheld. However, the situation and engineering are complex and I'm in no position to second guess the prognosis.

pragmatic

Posted Tue, Jan 21, 9:21 a.m. Inappropriate

Thanks for an informed overview of the issues.

Now back to the usual channel of arm waving from folks with no background, knowledge, education, experience, or credentials in engineering or tunneling - which of course provides no obstacle to try and express their uninformed opinion.

Lily32

Posted Tue, Jan 21, 10:05 a.m. Inappropriate

So says the bimbo front desk secretary cheerleader clique.

Wells

Posted Tue, Jan 21, 11:07 a.m. Inappropriate

Your welcome Lily32. I just hope to provide some balance to the crazy Chicken Littles that are screaming "the sky is falling" and ready to string up WSDOT employees just because it suits their political leanings.

acbytesla

Posted Tue, Jan 21, 3:51 p.m. Inappropriate

Some people like to throw a damp blanket over a raging fire in hopes to put it out.

Some people like to fan the flames and make the fire burn brighter.

Some people like cost effectiveness and have to scream bloody loudly in this City/State to get anyone to listen.

Bertha is a Bore that is failed. A financial mess of a muddy bowl of Seattle sludge. $4 billion and climbing for 2 miles of low-traffic carrying capacity.

For those who don't seek public answers related to cost overruns, staying on budget and exposing why many, many millions of dollars have been wasted by WSDOT serious mistakes -- you are the Ostrich of Seattle with its proverbial head in the sand. Call you Ostrich Pollyanna, and you can proclaim 'All is well, all is well, the engineers know more than we do'.

The Wizard of Oz must be right around the corner.

Posted Tue, Jan 21, 3:58 p.m. Inappropriate

The time to have stopped the deep bore tunnel has long since passed.

I would think that someone who goes by the handle "commonsense" would actually have some.

It is more than reasonable to ferret out waste and evaluate cost over-runs, but to do so with virtually no information is reckless and disingenuous.

acbytesla

Posted Wed, Jan 22, 1:54 p.m. Inappropriate

Which means that no "ferreting" will ever be done, because there'll never be enough information. That's how the "progressive" city and state governments work. Who knows whether Wells's disaster scenario will play out? I tend to doubt it, but you never know. What I'm much more confident of is that WSDOT will make sure that we're on the hook for that machine, at which point the money will really, really start adding up.

This project is going to be a fiscal disaster. And for what? A tunnel that skips downtown and carries one-third less traffic than what it replaces. And which does nothing to solve the other big issue on the waterfront, the train tracks.

Leave it to the "progressive" Seattle city and Washingtom state governments to study all the options; pick the worst and most expensive of the bunch; screw up the execution; and then lie to everyone about it.

NotFan

Posted Fri, Jan 24, 8:06 p.m. Inappropriate

1/3 less traffic being moved. Downtown a snarl of stopped vehicles.

And this is improvement? How?

Posted Wed, Jan 22, 11:50 a.m. Inappropriate

Has it been determined that the pipe was a problem? or that it contributed to the problem? was the pipe something that Bertha should have handled easily?

kieth

Posted Thu, Jan 23, 9:08 p.m. Inappropriate

Bertha was not designed/made to handle steel.

sarah90

Posted Tue, Jan 21, 10:12 a.m. Inappropriate

"My TBM is bigger than your TBM"

-- WSDOT

crossrip

Posted Tue, Jan 21, 10:12 a.m. Inappropriate

Bertha is stopped because the volume and affects of overflowing subsurface water is beyond predictions. Pumping this water out as fast as it refills the drill head area (to investigate and repair) has caused measurable soil settlement. Bertha will descend another 60' or so further down through likewise unpredictable water tables. The affects this could have upon soil stability is finally being questioned now that a barely controlled flooding situation has occurred.

The construction companies, engineering firms and public agencies are quietly (stealthily) reconsidering the bore tunnel as the wrong type for the soil conditions. They know it's still possible to construct the 'stacked' Cut-Cover/Seawall (see FEIS) by directing the completed 800' of DBT (with a lot of construction disruption, boo frickin hoo), to the cut-cover/seawall south portal near Jackson and finish that tunnel-type to its Pike Street north portal. Ongoing construction work at Aurora can lead to a Battery Street tunnel extension to Harrision and a more ideal SR99 southbound entrance (according to WSDOT studies).

WSDOT honchos hate winning THE WORST DOT contests repeatedly and will defiantly insist public safety is their 1st priority when the exact opposite is closer to the truth. People die. Who cares? Not Warshdot.

Wells

Posted Tue, Jan 21, 10:56 a.m. Inappropriate

I wonder if you have inside knowledge or are posting without a clue. TBMs regularly deal with high groundwater conditions. From my understanding the level of groundwater HAS NOTHING to do with Bertha being stuck at the present time.

That said Wells, I know don't know. Still, I do believe that you are full of it. That you are running your mouth instead of your brain. But I guess time will tell if I owe you an apology. Or not.

acbytesla

Posted Tue, Jan 21, 12:04 p.m. Inappropriate

Could you possibly use YOUR brain? If my detailed, analytical prediction proves correct about the high risk and probability of cataclysmic catastrophe, Seattle loses Pioneer Square, The Underground, innumerable buildings along the bore tunnel length, high-rise condos and many lives of those inside when the Big 9.0 hits and foundations suddenly fail.

"Uh, like, uh, yer just speck-ulatin, man,
like, uh, so like whatever."

At least I have something in me other than clueless obeisance
to authority-approved spokesperson bimbos pleased as punch to blithely support
any construction project that comes with a pittance paycheck.

Wells

Posted Tue, Jan 21, 1:39 p.m. Inappropriate

Who's detailed analytical prediction? Chicken Little? You remind me of the guy standing on the corner of the street with the sign that says "The world is coming to and end Monday. crossed out. Tuesday crossed out, Wednesday crossed out. etc., etc., etc., etc.

There are countless engineers and geologists that have done mountains of study who know more than you or I. People have been saying that California is going to slide into the sea for as long as I can remember too.

Seattle is a city with many 20 to 40 story buildings built above that route and no one is seriously worried that the ground conditions below it are going to make them all come crashing down.

I have no idea what is the problem with Bertha is, but I am a construction project junky. I follow great engineering feats from the Gothard tunnel to the new Hong Kong Airport and as bad as the problem with Bertha seems right now to the people in the cheap seats, it is nothing compared to problems that have delayed countless other projects.

Why not wait until we know something before we panic?

acbytesla

Posted Fri, Jan 24, 8:18 a.m. Inappropriate

Isn't this the guy with a political science degree making believe he's an engineer or geo-tech?

Lily32

Posted Tue, Jan 21, 11:55 p.m. Inappropriate

I've explained many times here and on other websites just how the extreme displacement of underground water causes siltration and cavernous collapsable voids beneath buildings. That alone should be enough for anyone to perceive mortal danger inherent with the bore tunnel.
Acbytesla, you remind me of clueless consumers of corporate media who expect any dazzling technofix just beyond the horizon will solve the world's problems.
You are correct only about being a junky.

Wells

Posted Wed, Jan 22, 12:23 a.m. Inappropriate

There is no doubt that there are dangers in tunneling, but you are showing yourself to be Chicken Little. Extensive surveying of the ground conditions have been made along the route.

Lest ye forget, TBMs are busy boring under San Francisco, London, NYC, LA, Mexico City, Kuala Lumpur, Rio di Janeiro and countless other cities. There are more than two dozen hard at work through out India building subways and the same is true for China.

Really the only thing unique about Bertha is her massive size,

acbytesla

Posted Wed, Jan 22, 12:26 a.m. Inappropriate

There is no doubt that there are dangers in tunneling, but you are showing yourself to be Chicken Little. Extensive surveying of the ground conditions have been made along the route.

Lest ye forget, TBMs are busy boring under San Francisco, London, NYC, LA, Mexico City, Kuala Lumpur, Rio di Janeiro and countless other cities. There are more than two dozen hard at work through out India building subways and the same is true for China.

Really the only thing unique about Bertha is her massive size.

acbytesla

Posted Thu, Jan 23, 12:37 p.m. Inappropriate

ACbyTesla. What are you, some medieval monk expounding "Lest ye forget?" Should Bertha be referred to in the feminine "she"? How is Bertha in any way feminine?

Chicken Little, as the story goes, was gently tapped by a falling leaf, and reacted as if the sky was falling. The comparison is ridiculous. The bore tunnel risk is extremely high, because of its size, its location beneath vulnerable buildings, soil conditions, the inappropriate seawall replacement technique, and because its traffic management outcome is worse.

Wells

Posted Thu, Jan 23, 9:16 p.m. Inappropriate

Oh so what, Wells. You were not listened to. You were not in charge. You are not in charge now, and you can do nothing about it. It really doesn't matter if every single person in Seattle reads what you have to say; in fact, most of us have read it a zillion times and we're tired of it. Enough. If you can't stand to watch what happens, move somewhere else.

sarah90

Posted Sat, Jan 25, 9:23 a.m. Inappropriate

Are you an engineer or a geologist Wells? And what "extreme displacement"? An Earth Pressure Balance Tunnel Boring Machine is designed to match the pressure not "displace" it Too much forward pressure can "create" a blowout and too little can cause a sinkhole.

And a funny think about that dazzling technofix, they usually do solve the world's problems. For example, take a look at the latest Gates Foundation letter. It highlights the fact that many nations that were "labeled" poor in 1990 are considered middle class today. The number of infants that died before the age of 5 then as compared today has dropped from over 10 percent to 5 percent.

Ten years ago, Solar energy was considered a pipe dream, far too expensive to compete with fossil fuels like coal. Today, it is on par with this dirty fuel.

Say what you want, but TBM tunneling is revolutionizing the world. There are hundreds of them building subways, road and water tunnels throughout the world. And they are doing it in almost every possible geological conditions from Manhattan's Schist Granite, to Kuala Lumpur's Karstic Limestone to glacial till in Norway and Finland to chalky deposits under London to the sandy soils of Qatar.

I'm a strong believer that we advance socially and technologically by being brave and imagining and doing great things. It is far better to say "why not" and then do it, then sit back and do nothing.

acbytesla

Posted Sun, Jan 26, 9:43 a.m. Inappropriate

abyctesla says "I'm a strong believer that we advance socially and technologically by being brave and imagining and doing great things. It is far better to say "why not" and then do it, then sit back and do nothing."

Nothing in any of your posts indicates an appropriate awareness of actual dollars spent in relation to mobility gained.

The bore tunnel is too expensive for what it *may* deliver, in relation to what it actually will cost us. A new viaduct, even built after all this bore mess/fiasco, will still be far, far less expensive, and move more vehicles.

It is absurd that economics are not being discussed.

Posted Thu, Jan 30, 3:30 p.m. Inappropriate

Commonsense. That has never been my argument. Our leaders took ten years to decide on a course of action and that was after countless community hearings, dozens of studies on mobility and environmental considerations as well as a ballot proposal to scrap the project by bicycle Mayor McGinn. This was decided upon. Get over it.

They have already spent more than half the money on THIS project including building the on ramps, off ramps, a railway overpass, built the tunnel boring machine, built the launch pit, built the substation to support it and most of the tunnel segments to line the tunnel.

At some point you need to look at this as a fait acompli. That it would undoubtedly cost far more to scrap this project at this point and find some kind of alternative. And you also have to come to the conclusion that we are living on borrowed time? Personally, I'd hate to see the viaduct fall down while people are driving on it or under it.

I'm confident that from an engineering standpoint that the tunnel, when it gets completed will be as safe as any building in Seattle

acbytesla

Posted Thu, Jan 30, 4:30 p.m. Inappropriate

abcytesla,

What was never your argument? That affordability and economics should be the prime method of deciding whether the bore tunnel ever made any sense?

As to continuing forward because "our leaders took ten years to decide on a course of action and that was after countless community hearings, dozens of studies on mobility and environmental considerations as well as a ballot proposal to scrap the project by bicycle Mayor McGinn. This was decided upon. Get over it." ... my, oh my. This is complete pap, and you know it.

I'm surprised your fingers don't rise up from your keyboard and slap you in the face.

The public has been misinformed, and ignored for far too long on this project. It's time for a complete audit, and full public disclosure on costs, cost overruns, what individuals have shares/ownership in real estate that will benefit from this tunnel completion, how much over budget this project will be, and just where in hell will all the excess traffic that the tunnel cannot handle actually go?

Posted Mon, Feb 3, 5:54 p.m. Inappropriate

I have never been arguing what was the best solution to replacing the crumbling viaduct. I'm sure that there were less expensive alternatives to the deep bore tunnel. But that was then. This is NOW.

My argument is that scrapping the project and going back to square one is more likely to be more fiscally irresponsible than moving forward and resolving whatever is the current problem.

The decision was made and project moved forward with the design and engineering work and now much have the construction has been started and well under way.

Granted, I could end up eating my words, because we won't know until it is completed. But the same is true if we scrap and take some other route.

acbytesla

Posted Tue, Jan 21, 10:27 a.m. Inappropriate

"My megaproject financing plan is murkier than your megaproject financing plan."

-- WSDOT

crossrip

Posted Tue, Jan 21, 11:46 a.m. Inappropriate

I am posting without a clue. But my naive noodle compares this with dental work, only on a much larger scale. We are praying that the problem solvers are experienced and sensitive dentists.

We have a lot to lose. My naive noodle worries that Seattle will float away into the Puget Sound, but of course I haven't a clue.

When I first came to Seattle there were lots of pilings in Lake Washington...rusted out...seven years old, I believe. (this was in 1973.) The sky had fallen and the bridge improvement had come to a complete halt.
Nothing new under the sun?

Just saying. No clue.

sgh

Posted Tue, Jan 21, 3:53 p.m. Inappropriate

Indeed. No clue was had by politicians then too. The ramps to nowhere ...

Posted Fri, Jan 24, 3:01 p.m. Inappropriate

Great comments on this story. There are and have been so many screw ups by WSDOT on past projects. Remember the indian burial sites in Port Angeles for the Hood Canal Floating Bridge Dry Dock. What kind of Risk Management do they consider when attempting some of these projects? Then there is the 520 Floating Bridges that may not float being built. Both of these past projects have cost the taxpayers money and given WSDOT a black eye. I hope the people keeps the government employees at the upper level accountable!

Posted Fri, Jan 24, 8:11 p.m. Inappropriate

The fact that this tunnel will move far fewer vehicles each day than we move today, and cost us more than ANY other road project ever just gags me. How can this scenario make sense to anyone?

2 miles of road, at more than 4 billion $$$. $4,000,000,000 and climbing due to very poor management by WSDOT. That's crazy.

Posted Thu, Feb 13, 2:43 p.m. Inappropriate

Delete

acbytesla

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