Makes one wonder how many railroad bridges are affected, too.
From: The Associated Press
ST. PAUL, Minn. (AP) -- Pounded and strained by heavy traffic and weakened by missing bolts and cracking steel, the failed interstate bridge over the Mississippi River also faced a less obvious enemy: pigeons.
Inspectors began documenting the buildup of pigeon dung on the span near downtown Minneapolis two decades ago. Experts say the corrosive guano deposited all over the Interstate 35W span's framework helped the steel beams rust faster. Although investigators have yet to identify the cause of the bridge's Aug. 1 collapse, which killed at least 13 people and injured about 100, the pigeon problem is one of many factors that dogged the structure. "There is a coating of pigeon dung on steel with nest and heavy buildup on the inside hollow box sections," inspectors wrote in a 1987-1989 report. In 1996, screens were installed over openings in the bridge's beams to keep pigeons from nesting there, but that didn't prevent the building of droppings elsewhere.
Pigeon droppings contain ammonia and acids, said chemist Neal Langerman, an officer with the health and safety division of the American Chemical Society. If the dung isn't washed away, it dries out and turns into a concentrated salt. When water gets in and combines with the salt and ammonia, it creates small electrochemical reactions that rust the steel underneath. "Every time you get a little bit of moisture there, you wind up having a little bit of electrochemistry occurring and you wind up with corrosion," said Langerman. "Over a long term, it might in fact cause structural weaknesses." Langerman emphasized that he wasn't saying pigeon dung factored into the collapse of the 40-year-old bridge. "Let's let the highway transportation and safety people do their job," he said. The problem is familiar to bridge inspectors everywhere. The Colorado Department of Transportation spent so much time cleaning pigeon manure off bridges that it is embarking on a two-year research project looking for ways to keep pigeons away from its spans. "It can be damaging to our structures because it's slightly acidic and it has other compounds in it that can dissolve especially things like concrete," said Patricia Martinek, the agency's environmental research manager. Pigeon guano isn't just a danger to the bridges. In the Denver area, the Colorado DOT pays outside environmental specialists to clean bridges wearing full biohazard suits with respirators because of heightened fears about bird flu and other diseases, said Rob Haines, who supervises maintenance there. Keeping pigeons off bridges usually requires a multi-pronged strategy that can include netting to block holes and surfaces, spikes to keep them from landing, and sometimes poisoning, shooting or trapping the birds, said John Hart, a Grand Rapids, Minn.-based wildlife biologist with the U.S. Department of Agriculture. The problem is that pigeons are naturally drawn to bridges and tall buildings since they're descended from cliff-dwellers, said Karen Purcell, who heads Project PigeonWatch at the Cornell Lab of Ornithology. Bridges offer shelter from predators and flat surfaces for nesting and roosting. "It's a nice fit for them," Purcell said. Meanwhile, the National Transportation Safety Board issued an update on its findings in the collapse Wednesday, saying investigators are looking at whether chemicals used in an automated de-icing system had any corrosive properties. The state Transportation Department wasn't concerned about the system; in fact, the agency is planning to install a similar system on the replacement bridge, said Khani Sahebjam, a state transportation engineer. The de-icing elements are inside the concrete deck, Sahebjam said, so he wouldn't expect them to pose a structural problem. The automated system was triggered by weather conditions and kept the state from having to send crews to spread de-icing chemicals, Sahebjam said.
"Let's hurry up and blame something before they blame us"
BLAME CANADA! (Theme from South Park the Movie)
I know the words are a bit modified but thats the first thing I thought of when I read the report.
Paul
http://www.youtube.com/user/pavabo
http://www.flickr.com/photos/paulvbox
It was also reported a couple weeks ago that pigeon poop obscurred the steel, thus preventing it from being properly inspected. They also complained about too many spriders living on the bridge, and too many spider webs. But these pigeon and spider excuses are so pathetic that I am amazed they are being offered. No matter whether pigeon poop hid defects or cause them, it is the job of the state inspections authority to inspect the bridge and certify it safe. Either move the poop and look at the steel or close the bridge.
There is no pigeon excuse unless inspectors can prove that so many pigeons happened to land on the bridge that their weight overloaded it. And even that should have been taken into account as a design issue.
Speaking of load weight, the NTSB has determined that there was 288 tons of construction equipment and materials on the bridge that was involved with the resurfacing work at the time of the collapse.
I know that bird droppings of most kinds will damage the finish on new cars. If you don't wash it off fairly quickly it will destroy the clear coat and permanently dull the finish.
Bird Guano from a South American Island was mined during the immediate pre-Civil War Era for its Nitrate content to make Gunpowder. Slaves were used for the mining as the life expectancy of the miners from breathing in the Dust was short.
Never too old to have a happy childhood!
I don't think the idea of pigeon droppings playing a role is hogwash. There is a reasonable cause to believe it could have been a contributory factor in some capacity. This is not being toted as an end-all explanation. No one seriously believes this is the central cause. However, this is in no way an excuse for what happened. The authorities knew it was there; it had to be cleaned.
Typical reaction to this sort of thing - Ignore it, and maybe it'll go away.
Give it 40 years of not going away and the result could easily be serious degradation of the structure.
I once encountered a situation where a relief tube in the aft compartment of a KB50 had leaked undetected for an extended period of time. The problem was discovered when the weakened skin blew out, causing a drop in pressurization. The tube was 1/4" in diameter. The area where skin and stringers had been eaten away was about the size of a dinner plate. The hole would have easily passed a softball.
If human urine can do it, I'm sure that pigeon poo can.
Chuck (modeling Central Japan in September, 1964)
tomikawaTT wrote: Typical reaction to this sort of thing - Ignore it, and maybe it'll go away.Give it 40 years of not going away and the result could easily be serious degradation of the structure.I once encountered a situation where a relief tube in the aft compartment of a KB50 had leaked undetected for an extended period of time. The problem was discovered when the weakened skin blew out, causing a drop in pressurization. The tube was 1/4" in diameter. The area where skin and stringers had been eaten away was about the size of a dinner plate. The hole would have easily passed a softball.If human urine can do it, I'm sure that pigeon poo can.Chuck (modeling Central Japan in September, 1964)
How long ago did they retire the KB-50s? I am guessing it was not too long after the KC-135s came along.
"No soup for you!" - Yev Kassem (from Seinfeld)
Bucyrus wrote: But these pigeon and spider excuses are so pathetic that I am amazed they are being offered. No matter whether pigeon poop hid defects or cause them, it is the job of the state inspections authority to inspect the bridge and certify it safe. Either move the poop and look at the steel or close the bridge.
But these pigeon and spider excuses are so pathetic that I am amazed they are being offered. No matter whether pigeon poop hid defects or cause them, it is the job of the state inspections authority to inspect the bridge and certify it safe. Either move the poop and look at the steel or close the bridge.
Bucyrus has it exactly right. If necessary get a fire engine to blast the spiders and the pigeon poop out of there, or put it on a river barge to get the center sections clean; but do your job of actually inspecting the structure.
Next time it might be wise to insist on a design that is less attractive to the birds.
Sounds to me like a case of "passing hte poop", whoops I mean "passing the buck". I recall many times my dog ate my homework during high school, but I never managed to convince my teachers to "give me a pass" for that reason.
Not sure how you get a firehose to a long span of bridge over a river!! Inspectors had to be lowered down the side of the bridge on ropes to look under. They tried in the limited time they had (time is money) to see everything they could, but they apparently couldn't completely clean every piece of the bridge just in case some of the dirt, droppings or whatever were covering an almost microscopic hairline crack or joint problem.
Unfortunately, I'm sure many of the people in the general public who are now complaining that the bridge maintenance and inspection crews were lax were a year ago happily voting for politicians who pledged to not raise taxes even to help boost the crumbling national infrastructure.
tomikawaTT wrote:Typical reaction to this sort of thing - Ignore it, and maybe it'll go away.Give it 40 years of not going away and the result could easily be serious degradation of the structure.I once encountered a situation where a relief tube in the aft compartment of a KB50 had leaked undetected for an extended period of time. The problem was discovered when the weakened skin blew out, causing a drop in pressurization. The tube was 1/4" in diameter. The area where skin and stringers had been eaten away was about the size of a dinner plate. The hole would have easily passed a softball.If human urine can do it, I'm sure that pigeon poo can.Chuck (modeling Central Japan in September, 1964)
Hello,
I work aircraft structures for FedEx and we are involved in a situation similiar to the one Chuck speaks of. I'm repairing a 727-200 that has severe fuselage skin corrosion at the aft lavatory service panel. These panels are deactivated on our aircraft but apparently "blue water" residue from the previous operator of the aircraft seeped down between the stringers and skin and began to do it's damage. The pressure from the corrosion caused the rivit heads to shear and the fuselage skin to bulge outward. I'm now looking at about a two square foot cutout of fuselage skin which is located next to the aft pressure bulkhead, which makes this a complex repair. Waiting on Boeing engineering for a repair drawing. The stresses and pressures caused by corrosion can be enormous. I've seen corrosion areas, usually aluminum or alloy steel, bend and break stainless steel and titanium components that are rather heavy and thick.
Take care and be safe!
Gregory
wjstix wrote: Not sure how you get a firehose to a long span of bridge over a river!! Inspectors had to be lowered down the side of the bridge on ropes to look under. They tried in the limited time they had (time is money) to see everything they could, but they apparently couldn't completely clean every piece of the bridge just in case some of the dirt, droppings or whatever were covering an almost microscopic hairline crack or joint problem. Unfortunately, I'm sure many of the people in the general public who are now complaining that the bridge maintenance and inspection crews were lax were a year ago happily voting for politicians who pledged to not raise taxes even to help boost the crumbling national infrastructure.
There's no shortage of companies with equipment and expertise to clean Bridges and other steel structures. Hydroblasting equipment (basically a super powerfull industrial sized power washer) is used to clean guano, ect. There was an episode of "Dirty Jobs" on the discovery channel where host Mike Rowe demonstrated how it's done. Many of these firms have truck mounted multi jointed telescoping work platforms which can get men and equipment under and into a bridge's structure.
"I Often Dream of Trains"-From the Album of the Same Name by Robyn Hitchcock
Well, you can bet that corrosion due to pigeon guano played some role, be it however small. The problem with this bridge, and with all structures, is that you have to look at all contributing factors and analyze their synergistic effect. Looking specifically at this bridge, you have 40 years of weathering, 40 years of pitting due to pigeon guano, 40 years of high frequency cyclic loading, 40 years of high amplitude (rush hour) cyclic loading, X number of repair/resurface/reconstruction loadings, etc.
The weathering, guano and cyclic loadings reduce the strength of the structure little by little. There was construction loading, coupled with the high amplitude, high frequency loading of rush hour. Put all of that on a weakened structure and you have a recipe for catastrophy.
The cause of the bridge collapse will be revealed, but we already know the reason: lack of adequate quality inspections.
As alluded to above, it is systemic, and systems thinking is what will ultimately provide both the cause(s) and the remediation. I think the most insidious aspect of the systemic failure cannot be attributed to any one factor more than our homosapiens' penchant for taking the easy way out. That applies all the way down the line, from those in charge down to the great unwashed electorate. If I am correct, you should see a lot of squawking and threats and lawsuits and....you name it...from a whole bunch of strata. Finger pointing, head ducking, alliances suddenly where there were none, strange bedfellows very chummy...
But my point is that it really comes down to our preferences for the status quo as we understand it. If we really wanted that to change, and for us to have truly accountable leading engineers, executives, legislators, and such, we know what we have to do.
Krazykat112079 wrote: The cause of the bridge collapse will be revealed, but we already know the reason: lack of adequate quality inspections.
The probable cause sure does point that way, unless something really fluky is found to be a cause that can be said to be an act of god. Bridges start to wear out the day they are opened. That is why there is a federal inspection program in place to guarantee that bridges do not become unsafe. It is similar in its rigid requirements to the federal locomotive boiler code enforcement. You have to learn the condition of all of the metal.
It is quite popular for politicians to blame the people who resisted higher taxes. But that is a worse excuse than pigeon poop. That lame excuse is a political ploy to expand the government on the back of this tragedy. Even MNDOT ran away from the funding excuse because they know that it is a bogus, transparent stunt.
It is true that a bridge will collapse if it is not maintained, and maintenance costs money. But a lack of money cannot possibly be the cause when you have agencies in place that only have the two options:
1) Guarantee the safety of the bridge.
2) Close the bridge.
Our so-called crumbling infrastructure is being used like a cash cow to pull in revenue that can be spent for anything else they happen to want. If they fix the roads and bridges they kill the cash cow. And then they won't have their several hundred millions of dollars that they siphon off the highway budget and spend on bike trails every year in Minnesota, for instance.
Bucyrus wrote: Krazykat112079 wrote: The cause of the bridge collapse will be revealed, but we already know the reason: lack of adequate quality inspections. The probable cause sure does point that way, unless something really fluky is found to be a cause that can be said to be an act of god. Bridges start to wear out the day they are opened. That is why there is a federal inspection program in place to guarantee that bridges do not become unsafe. It is similar in its rigid requirements to the federal locomotive boiler code enforcement. You have to learn the condition of all of the metal. It is quite popular for politicians to blame the people who resisted higher taxes. But that is a worse excuse than pigeon poop. That lame excuse is a political ploy to expand the government on the back of this tragedy. Even MNDOT ran away from the funding excuse because they know that it is a bogus, transparent stunt.It is true that a bridge will collapse if it is not maintained, and maintenance costs money. But a lack of money cannot possibly be the cause when you have agencies in place that only have the two options: 1) Guarantee the safety of the bridge.2) Close the bridge. Our so-called crumbling infrastructure is being used like a cash cow to pull in revenue that can be spent for anything else they happen to want. If they fix the roads and bridges they kill the cash cow. And then they won't have their several hundred millions of dollars that they siphon off the highway budget and spend on bike trails every year in Minnesota, for instance.
Great points. If they need more money for the infrastructure on interstates, why not do what we do in Chicago and charge tolls, i.e. a user fee?
They also do it in downtown New York -- I think the last time I drove over the Verrazano Narrows bridge it cost me $4.50 one-way. And the Golden Gate and Oakland bridges in San Fran.
Maybe this was the cause of the bridge collapse, maybe it wasn't. We will find out when they officially say what caused it. Until the official cause is determined, what caused it will remain a question. In any case, Illinois (and I am sure other states also) is supposed to step up bridge inspections and close any bridge during construction. I don't know if that is possible becuase closing an major highway in this area would cause more traffic on already backed-up roads.
First, call me very skeptical about this. The acid formed is very weak and once it has been reduced chemically, its dried remains should shield the steel from further damage from subsequent droppings.
Second, using the word guano is incorrect unless a pigeon is a bat or seabird. Using an incorrect word tainted the accuracy of the rest of the article.
Like most major failures, the bridge collapse will probably be the result of a series of smaller contributing factors. Remember the plane crash in, IIRC, the Everglades that was the result of a $0.10 light bulb? The cockpit crew was so worried about the indication (or lack thereof) from the landing gear light that no one noticed the plane was losing altitude until it was too late.
As far as the pigeon poop, maybe this is a job for the Mythbusters. Plausible is my guess. BTW, didn't they once do an electochemical experiment about the effect of salsa on the steel bars in a jailhouse?
Jay
I would not be surprised if pigeon poop caused corrosion. Even the spiders might have contributed some detriment with their digestive products. And there would be other types of birds as well, no doubt. Speaking of guano, the bridge was also probably home to a large numbers of bats. I can attest to the fact that bat urine will take solid color stain finish right off of a house. I would assume that the inspectors were not only prevented from seeing the steel because of all this icky stuff, but they also probably felt that it was unfair that they should have to be exposed to it.
It has also been suggested that a de-icing system installed a few years ago that might have caused chemical corrosion. And of course road salt has been implicated as a cause of corrosion. But even though all of this could have been part of the cause, it was the responsibility of the inspection authority to learn the factors leading to a collapse and prevent it. The one good thing about corrosion is that it gives you time to catch it.
So it all comes down to this question:
Why is the public being offered these explanations for a possible cause?
There are two possible answers:
1) Inspection authorities are demonstrating diligence in probing the cause, making an honest effort to satisfy the public's need to know with as much information as possible.
2) Inspection authorities are making a smokescreen to obscure the fact that they failed to perform their job.
If number two being the correct answer is not obvious, it can be arrived at by eliminating answer number one. These inspection authorities are always telling us that they cannot speculate about a cause. They must let their investigation run its course, and it might take a year or more. The new bridge might be up and running before we ever find out why the old one fell down. Moreover, since they are performing a formal investigation, there is no need for them to speculate. In fact, if they did speculate, it might cloud their objectivity with pre-conceived ideas, and thus flaw their investigation. So cognizant are they of the harm of speculation that they even warn the public to not speculate.
And yet, despite all of this stern admonishment against speculation, they are publicly rolling out theories about the role of pigeons, spiders, road salt, and de-icing chemicals. It ought to be pretty obvious that, in the case of this investigation, the need to shield themselves from blame is far greater than the need to learn the cause.
~~~
I wonder what the rate of highway bridge failures is as compared to the rate of railroad bridge failures.
Obviously, there are many more highway structures, but I can think of three or four modern highway failures and no comparable railroad problems (burned bridges don't count).
Is the premise of a much greater failure rate for highways correct, or am I just remembering selectively?
Perhaps the Minnesota DOT would have us believe railroads don't attract pigeons and spiders as highways do!
I personally think the basic design of the bridge in the first place contributed to this unfortunate tragedy.
If you've seen the pictures of the bridge pre-collapse, note the following:
1) The spindly structure of the steel lattice framework beneath the roadbed.
2) The steel is exposed to the elements (note several spots of rusting, especially around the rivet joints).
3) The entire bridge over the Mississippi is held up by four very small concrete posts.
I'm surprised the bridge didn't collapse years earlier. I do see the replacement bridge to be more a traditional reinforced concrete arch structure, something that has lots of structural strength and weather resistance to start with.
Hmm......last I heard (few days ago in various media) here in MN, was that the contractor doing construction on the bridge was being looked at, for overloading the bridge with equipment, materials, etc.........hmmmm........
Mailman wrote: Hmm......last I heard (few days ago in various media) here in MN, was that the contractor doing construction on the bridge was being looked at, for overloading the bridge with equipment, materials, etc.........hmmmm........
At the time of the collapse, there was 288 tons of equipment and supplies that was placed on the bridge by the contractor who was working on the bridge. I wonder what their contract stipulated in regard to the weight of equipment and materials that was permitted to be placed on the bridge during this work. Perhaps the contractor exceeded the stipulation, or maybe the stipulation mistakenly allowed too much weight. Or maybe there was no stipulation.
I overheard someone on talk radio screaming about how the MDOT was responsible because they funded the construction of a "useless" light rail system for the Minneapolis/St. Paul region, and could have used that money for upkeep of the bridges. While disagreeing with the main principle, there is some truth that maintenance and upkeep are the step-children of the transportation budget in most cases. It is tough enough to get tax funding for new roads and bridges where they are needed. Mass transit is often demonized as a waste of money, many voters will reject funding it if they don't think they would use it. But I am sure that a few more folks in Minnesota may be considering it now.
If everybody is thinking alike, then nobody is really thinking.
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