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.
Never too old to have a happy childhood!
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.
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.
"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
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.
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