Slashdot Mirror
Big Dig - One of Engineering's Greatest Mistakes?
Enggirl1 writes "Design News discusses Boston's Big Dig and begs the question - is it one of engineering's greatest failures? The article reveals that forums and blogs are popping up all over the Internet as vehicles for engineers and contractors to discuss, under the guise of anonymity, their skepticism, thoughts and reactions to one of the biggest infrastructure failures in the news today." From the article: "One blogger, whose profile notes that he is an ICC Reinforced Concrete Special Inspector and an ICC Pre-stressed Concrete Special Inspector, among other specialties, says he has nearly 20 years of experience performing both placement and post-placement inspections of rebar, post-tensioning systems, concrete, masonry, etc. He says if structural engineers who specify epoxy for dowels and the like believe that the work is being done correctly then they live in a world unfamiliar to him."
Rock bolts are a staple in the mining industry. There are darn few failures. Of course the rock bolts are specified by engineers who work for the mining company and installed by miners whose safety depends on them. You tend to do things better if your life depends on it.
In the case of the big dig, you have contractors who are trying to make the maximum possible amount of money. I also bet that there weren't enough government inspectors or that they weren't properly qualified. Cutting costs is just as dangerous in the government as greed is in the private sector. The Canadian province of Ontario laid off all their government water inspectors and a bunch of people died in the town of Walkerton. If you don't give folks the tools they need to do a job then you shouldn't be surprised if the job doesn't get done.
The concrete ceiling tiles were used to create a separate space for supplying air to the tunnel. This is typically how you would do it in a building. In the case of the Chunnel between England and France, they dug a separate tunnel for that purpose. People have wondered why the panels had to be made of concrete. Something lighter would have worked just as well and might have been cheaper and safer.
The big dig is still open and operating. That's hardly a failure.
y _collapse
Even if it eventually is a failure, the Hyatt Regency skywalk collapse in Kansas City killed more people.
http://en.wikipedia.org/wiki/Hyatt_Regency_walkwa
If engineers signed off on the use of the epoxy for the panel supports then those engineers are at fault. Engineers don't hand off designs to construction crews and wipe their hands of it from then on. They have to approve changes in the design and do their own inspections of the construction to make sure it meets the design.
"throws in numbers" and tosses together a design, then sends it out with the engineer's seal on it. Or when an engineer refuses to sign off on an incomplete or incorrect design, the manager brings in a new graduate because they're more "cooperative" (read: will sign anything to get a paycheck) and they go ahead and build it that way.
I'm not saying those things don't happen. I'm saying that they are highly illegal and not common place. Signing off on a design for an engineer is like preparing legal documents without being a lawyer or giving medical advice without being a doctor.
To sign off on any engineering or construction documents, an engineer must be licensed as a Professional Engineer (PE). The requirements vary by state but in most states new engineering graduates do not qualify to be PEs. The norm is an engineering student must pass an exam (FE) near graduation, then work under a licensed PE for several years, then pass the PE test. In most states like MA, it is 4 years minimum between passing the FE and even qualifying to take the PE test. Engineers who are not PEs can do some of the work in construction and design fields but are expressly forbidden to do certain things like sign off on plans.
I agree with you that management is most likely to blame but for another reason. As projects like this become complex, it requires very good management to ensure that the important details are not overlooked. With as many problems as the Big Dig seemed to have before completion, it would seem that the management was not up to the task.
In the case of the collapse, I think the most likely scenario is that the specifications were wrong or changed at a later date. The load required was specified to be 1/2 of what it needed to be. The engineer approved a wall thickness of so many feet that was later modified and built without approval. The specifications for the wall never included withstanding water (hydrostatic pressure), etc.
Well, there's spam egg sausage and spam, that's not got much spam in it.
As usual with engineering disasters of this sort, the failure seems to have been caused by a confluence of lesser mistakes that would not have been tragic in isolation. The root causes, however, seem to be:
Anyone who has lived in Boston can tell you that this is only the latest in a string of cost overruns and management failures. The actual mode of failure (i.e. the bolts) and the immediate causes of that failure should not overshadow the idea that the contractors who screwed this one up should be held responsible. The ongoing investigations should reveal whether the contractors were merely incompetent or whether they willfully ignored problems like these and crossed their fingers that nothing would happen.
Friends don't let friends misuse the subjunctive.
Posting anon here - I worked on the Big Dig (environmental) during peak construction (1997-2000) and I'm currently contracting with another MA state agency, and I don't want to ruffle any state feathers. I also want to write a book someday ;)
First a couple of general statements:
Now back to the facts - I have no knowledge of roof panel construction (I spent little time in that area), but I will note that working on the project during 1999 and 2000 was an interesting experience. Already at the point there was heavy pressure on project managers and contractors to reduce costs (this was before the national stories hit that led to the ouster of James Kerasiotes). It got to the point that office supplies were locked up - you had to get the office manager's permission to get a notebook or pens!
In any event, I wouldn't be surprised at all if cost pressures let to reduced safety factors, etc. The construction site was also the source of many stories about various screw-ups that I won't get into here (wait for my book!). There was of course several times that money was spent to shut people up (at least once against my direct recommendation), but the PTB felt it was needed for the project to move along smoothly. I suppose that it would have been better for B/PB to take the Vista approach, and wait for the tunnel to be "finished" but that wasn't going to happen because of the political pressures.
Now was the project a failure? I'll just say this - is used to take me 1.5 to 2 hours to drive from Braintree to Cambridge during midday traffic. I did the same trip a month or so ago during a Friday afternoon rush hour in abut 20-25 minutes.
One of the problems with the Big Dig ceilings is that some of the engineers that designed it have never actually built anything. These guys must not have ever gotten their hands dirty on an actual jobsite. Their the guys in ties, hard hats and a slight look of confusion on an actual site. The book says epoxy has the strength, it must, use it. When the accident occured and it first came out that the bolts were epoxied in place, my first thought was "what kind of idiot makes suspended ceilings out of concrete, then tries to epoxy them in place?" Epoxy is a wonder material, but this is just so obviously not a smart use for it. No, i'm not an engineer.
s /2006/07/28/bolt_system_graphic/
I've got a running bet with anyone that'll take it that the Big Dig is closed down in less time than it took to build the beast.
My wife is a news designer for the Boston Globe, she made this graphic to explain what happened, it's pretty cool. No complaints about it being in Flash, that's what she uses:
http://www.boston.com/news/traffic/bigdig/article
Enjoy,
Josh
gigantino.tv - Heavy but weighs nothing.
If a typical vehicle is 5 metres long and the distance between vehicles is 10 metres then an object with no dimension will have 1/3 chance of hitting something.
Except that a sheet of concrete which drops in front of your car may be almost as bad as one which lands on you, and if the sheet is (say) 2 metres across it is almost certain to land on something because the lanes will be only 3-3.5 metres wide.
http://michaelsmith.id.au
I have a hard time in believing that the screw-up happened in the actual design. A professional engineer knows that he can be sued for malpractice and can go to jail for signing off a design diagram that is faulty.
The second aspect of the construction is the actual assembly of the project. There could be a problem here. According to a reputable source, about 14% of the laborers in the construction industry are illegal aliens. In some segments (e.g., roofing workers), the percentage of illegal aliens can be as high as 29%.
Most illegal aliens are people who hail from Mexico and who cannot read, write, or speak English. Even if we assume that they are all honest, they can still make honest mistakes when they cannot comprehend English. The warnings on the construction material, the recommendations on the construction material and the construction equipment, the instructions for assembly, and the like are all likely to be written in English. If you have no English skills, the probability of a screw-up is very high.
Watering lawns, trimming hedges, picking fruits, etc. do not require knowledge of English to do well. From a quality perspective, an illegal alien can do good work on such absolutely no-skill-required jobs.
However, welding a joint on a drawbridge, properly fastening a bolt to hold up a concrete ceiling, etc. might require some ability to comprehend English and might even require some minimal skills that a high-school education would provide. Most illegal aliens from Mexico do not have a high-school education. On any project that involves public safety, an English-speaking, literate, educated worker is much more preferable than a non-English-speaking, illiterate, uneducated worker.
"Man, we've been building stuff for like 5 thousand years. Stuff we built 5 thousand years ago is still standing."
Some of the things we built 5000 years ago is still standing. Consider, for example, the Seven Wonders of the Ancient World; only one of them is left, wich gives us a 14.2% success rate. I'm not sure I like that number when it comes to something to be used on a daily basis.
No one talks about the pyramid they built 5100 years ago that fell down after 21 years
That's just because it's no longer news: Collapsed pyramid
My father was an architect for many years and he has many examples of going to inspect sites and finding that the construction crew had misunderstood or wilfully ignored the specifications for critical structural components: columns incorrectly constructed for the projected load, or a pile of roof components rusting in a corner of the site and clearly not installed in the almost-completed roof. Building workers are fairly hazy on the niceties of engineering and are on the kind of contracts that make it attractive to get as much money for doing as little work as possible; they do, generally, though, have a "comfort zone" of familiarity with traditional construction techniques which is why most regular construction projects don't fall down.
Anyone specifying a new or unusual process has to be aware of the fact that the typical construction worker won't believe it's important to follow the rules exactly, won't understand which parts of the process are most vital and won't be around at the end of the project to take any responsbility. If you have a design that depends on technology unfamiliar to the people who're responsible for implementing it, then you need tight supervision during the build and tight inspection afterwards. You often don't get either - the foremen are on bonuses to accelerate the construction phase and the people most qualified to inspect afterwards are the people who designed the structure in the first place.
Of course there are many projects which are simply not feasible using traditional construction, but for those that are, any apparent savings from using new technology can be negated by the costs of ensuring it's correctly applied.
Anyone who has to build something that will be used by someone else should be subscribed to the Risks-Forum digest.
It's titled, "Forum On Risks To The Public In Computers And Related Systems", and relates a lot of computer and general engineering related risks. Risks that either wind up killing or seriously injuring people. It's been going since 1985, and is a good read just to open your mind to what might happen.
As so many headlines on Fark read, "What could possibly go wrong?". This should always be the first thought for any engineer when they are tasked to do something.
You are in a twisty maze of processor lines, all alike.
There is a lot of hype here.
I'd trust a kid "off the farm" to be able to do construction work before about anyone else the same age. You grow up building and repairing big structures, welding, operating equipment that costs as much as most folks houses, etc you appreciate how to do things properly. Any random 20 year old kid off a farm might easily have ten years experience in what would be considered adult professional work in most of the trades. He's grown up wiring at high voltages, working on very large and complex plumbing installations, doing all sorts of carpentry, cement work, equipment maintenance, etc. It's a pretty thorough and complex process to keep a large farm operating. And today's farm kids are using automated and computerized devices, all the way to GPS enabled equipment that uses robotic steering. maybe it is past time to put that "country bumpkin" meme to rest, it no longer applies.
With that said,back on subject, that entire big dig project has a long history of controversy and accusations of weirdness around it. I am (somewhat) surprised it has taken this long to start to fall apart.
As to the illegals versus legals and so on, it's a crapshoot. I have worked on jobs with illegals that were a menace,totally incompetent and dangerous to be around, hired merely because it was a body to throw at a job for cheap pay obviously. A few have been quite good from recollection, most are pretty common, some skills, but a lot of enthusiasm. They come from a culture of lower resources, recycling old junk more, cob jobbing as normal, etc. I think it is just too large a variable to really be able to quantify it adequately. What can't be denied though, is that hiring illegals in a general sense is a cost cutting measure so the boss class can skim a few more bucks off the project, and when that becomes the primary focus on a job, the job suffers. Jobs should cost what they cost, not the lowest crap possible then cut corners from that point. You get your "problems" then. When you have something as important as a big dig styled project, you shouldn't screw up. If it is deemed to be unaffordable to do correctly, don't do it.
If your new garage roof sags and leaks after a few years because you hired the local cut rate guy with his "crew" of casual pickups from the home depot parking lot..well, it's no big deal to anyone but you and not a major threat. Something like the big dig is a totally different situation.
The amazing thing about the Big Dig is that it just isn't that big. It really is only a couple of tunnels under downtown Boston. Are they "big" tunnels? Yes - but not $14.6 billion worth! The T tunnels are much more extensive.
Remember the Denver International Airport boondoggle? For the price of the Big Dig, they could have had 3 DIAs.
When I lived in Boston, they were talking about extending the "Silver Line". Note: the "Silver" line is just a bus, unline the Red, Orange, Blue, or Green lines. The good people of Boston are expected to pay $700 million dollars for a BUS!
Sure you do, all the time. Look at the aerospace industry where the failure of a single faulty weld could lead to the deaths of hundreds of people. Same thing with bridges, tunnels, etc. It would be nice if we never had other peoples lives in our hands when making design decisions but that's just the way it is.
It may be true in aerospace, but it is not, or should not be true in civil engineering.
In aerospace, if your manufacturing something, it is a repeatable process, subject to testing and inspection. When it's not, you're talking about the Space Shuttle -- a job for test pilots, not civilians.
It is true that sometimes civil engineering designs have single points of failure that result in fatalities. But where you have a choice, it's better not to. For example, expansion joints were responsible for the bay bridge collapse in the Loma Prieta quake. But current design practices avoid them; it turns out they just aren't necessary. If they hadn't been used, the section of bridge would not have collapsed, killing one person.
Construction workers expected to work in uncomfortable and dirty environments and still do good work? Yea you're right, that is just unheard of (sarcasm). Drive around some construction sites when it's 100 degrees out and look at the work some of those guys are doing and the conditions under which they are doing it. Then tell me it was somehow a mistake to have construction workers on the Big Dig working in an "uncomfortable and dirty environment".
I know you want to rant about construction workers, but if you stop for a second, you'd realize what I'm saying isn't that construction workers should be allowed to do shoddy work. What I'm saying is that good design should assume that shoddy work will be done a certain fraction of the time. Sometimes you can't, in which case you'd better make (a) sure it is possible to inspect the work and (b) that the inspection is done. Clearly one or the other wasn't true in this case.
Factor of safety is completely the wrong way to think about it. The infamous pedestrian walkway collapse in the Kansas City Hyatt was caused by a steel contractor substituting a two hanging rods for a single rod supporting two levels. They wanted to avoid having a long threaded section, which might be damaged and create installation problems. However this change meant that the entire weight of structure was being borne by the upper join, not 50%. So if they were shooting for a 4x factory of safety, they really only had 2x. And with 2000 people crowding on the walkway to observe a dance below, it was supporting far more more weight that anybody thought it would need to bear. The result: the walkways collapsed, killing 114 and injuring an additional 200.
The lesson here is that your safety factor calculations can be rendered completely worthless by some small detail.
In this case: if the bolt to rock joint is 4x as strong as it "needs to be", it doesn't help at all when the bolt is improperly installed, because instead of being bonded to solid rock, it could be bonded to compacted dust particles lining the hole instead of the rock. You could have used a design that was rated at 1000x the required strength and it wouldn't matter at all, because the friggen bolt is expoxied to compacted dust, not rock.
I have a friend who worked on parts of the project. He'd look at a girder, and say, it needs to be ten inches, so let's make it a foot. Then the design would pass through several hands, each adding a bit of safety to it, and before you know it you have a 36" girder where a 10" girder would do. This kind of thing does nothing for safety; in fact, by draining resources from the project, it undermines safety, which would have been better served by spending the money elsewhere.
Post may contain irony: discontinue use if experiencing mood swings, nausea or elevated blood pressure.