Minneapolis Bridge Collapse Might Have Been Caused By Pigeon Dung

PigeonsPounded 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.

"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."

Source: Sfgate
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joe said…
The Bridge collapse was obviously caused by some accelerated structural deterioration that was likely from some corrosive agent. The pigeon droppings left to pile for years can deteriorate steel in addition to carrying diseases and not looking so nice.

This aspect is not commonly known about the pigeons droppings and we won't know for sure soon, or possibly ever whether the bird poop played a pivotal role in this disaster.

The Minnesota DOT could have taken several preventative measures to have controlled the long-term roosting and nesting behaviors of the pigeons by using Bird Netting systems underneath the bridge or Stainless Steel Bird Spikes or even electronic bird dispersal systems that drive birds away from structures.

Other states may now pay closer attention tho detail when it comes to messy pigeons, they can also be deadly.

Joe Seid
Bird-X Inc.
800 662-5021