PARAMUS, N.J. — The collapse of the huge Interstate 35W bridge in Minneapolis earlier this year may have been caused by what seemed to be a relatively small problem: bird droppings.
Sal Santamaria, vice president of operations for Bird Doctor, Paramus, N.J., said the leavings of pigeons, while unsightly and a major health risk, also can play a major role in the degradation of such structures as roads, buildings and bridges.
“I think they had a real impact on the bridge,” Santamaria said. “Bird droppings are probably one of the worst things when it comes to breaking down metal and paints. You don’t give it credence, but it can be a big problem.”
Officials investigating the bridge collapse — which killed 13 people and injured about 100 — have noted the structure’s ongoing problems with bird dung as far back as the late 1980s.
Santamaria said that if droppings aren’t washed away, they turn into a concentrated salt that, when mixed with water, generates an electrochemical charge — like static electricity — that becomes ten times as corrosive to steel as the normal environment.
This corrosion will continue until the structure is cleaned and repainted, he said.
He noted two jobs Bird Doctor worked on where pigeons destroyed most of a six-story wooden structure and rendered a city park unusable.
In a 2002 project in New York City, the company was called on to exclude birds from a park that had been built underneath a highway. For a half-mile stretch of pavement, city officials had installed basketball, handball and tennis courts, but pigeons roosting above had turned the recreation area into a sanitation district.
“Before the park was open you couldn’t walk or bounce a ball, the droppings were just that bad,” Santamaria said. “What they defecate is horrendous.”
That same year, the company worked on the Weehawken, N.J., water tower, a six-story, 90-year-old structure that had, over the years, accumulated nearly 7,000 pounds of bird droppings.
“(The droppings) had literally collapsed five floors of the building,” Santamaria said.
Bruce Donoho, president of Bird-B-Gone, said other areas such as canopies on gas stations, building roofs and aircraft hangars also are prime pigeon targets.
“Obviously building materials are not as robust as a bridge, you’ll see material fatigue because of pigeons a lot quicker,” Donoho said.
Pigeons, descendants of cliff-dwelling birds, are naturally drawn to bridges, since structures give them safe shelters and flat spaces to build their nests. Santamaria said most of the bridges Bird Doctor works on are covered in droppings 7 to10 inches deep.
And the removal of that much dung is a hazard to technicians, who must wear full protective suits and respirators, and the general public; the droppings harbor bacteria that can cause encephalitis, histoplasmosis and Salmonella food poisoning.
And the nature of a bridge's construction — as well as the construction of the exclusion — can complicate things, said Cameron Riddell, president of Bird Barrier
“A lot of these bridges — a large percentage it’s impossible to know the problems exist. There’s no way to get to them," Riddell said. "How do you clean that out? How do you paint that? The best solution for the budget is to net. "
For more information on bird control, visit www.ppmatools.org.