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Mayflies Plague Bridges

Friday, July 1, 2016

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Despite a short life span, mayflies have a reputation for creating havoc on U.S. bridges in the early summer months, and they’re making their presence known to the nation’s drivers once again.

Photos of the seemingly biblical plague in Illinois have gone viral. And in Pennsylvania, officials are returning to tried-and-true practices for addressing the situation.

Mayflies, also known as shadflies, are aquatic insects that spend most of their lives at the bottom of rivers and lakes. As adults, they emerge from the water in swarms, when triggered by the right temperature, to mate before dying within 24 to 72 hours.

Slick Bridge Deck, Viral Photos

The Havana, IL, Police Department brought nationwide attention to the effect mayflies can have on the nation’s roadways when it issued a warning to area motorists Monday (June 27). News outlets across the country are sharing the photos authorities posted to social media depicting the extent of the infestation.

Following motorcycle accidents caused by the slippery road surface created by crushed insects, authorities issued a warning that the city's Scott W. Lucas bridge had become overrun with the insects, making travel there dangerous.

“At one point they had piled 6 inches high and when ran over, became very slick,” officials claimed on the department’s Facebook page.

Lights-Out Approach

In Pennsylvania earlier this month, transportation officials issued a lights-out order for the Route 462 Veterans Memorial Bridge between Columbia and Wrightsville, PennLive reported.

In mid-June last year, the mayflies that billowed up from the river during mating season swarmed a new lighting system on the bridge. There, too, the flies piled up inches deep and swarms reportedly reduced visibility, causing three motorcycle accidents before access to the bridge was restricted. To combat the problem then, the lights were turned out in an effort to reduce the swarms.

"After that initial onslaught it helped," Columbia Mayor Leo Lutz told the local news source. "We had no safety issues and it seemed to work out real well."

This year, officials took the same precaution in advance of the hatch season, which tends to occur between mid-June and mid-July. The bridge lights could remain off for several weeks during that period.

"We were afraid if we had a major hatch, before we can react to it, there could be several accidents," Lutz said. "We want to avoid that and keep people safe."

Bridge Renovation Proposal

But “lights out” isn’t necessarily the long-term plan in that Pennsylvania town.

One proposed solution, according to Lutz, uses light to the traveler’s advantage.

Officials are considering a plan to install lighting on the arches under the bridge, in an effort to attract the flies to that lighting system and keep them off the bridge.

This proposal could work its way into the Pennsylvania Department of Transportation’s planned reconditioning of the bridge in 2020, Lutz said.

A Good Sign

Despite creating dangerous travel conditions and garnering the attention of local police and transportation authorities (last year, the Huffington Post reported, the Iowa Department of Transportation had to close a bridge over the Mississippi River until a snowplow could clear the knee-deep piles of insects from the road), mayflies' presence is a good thing.

For one, the Pennsylvania Fish and Boat Commission says their presence is a sign of good water quality, Lancaster Online reported.

The need clean water to survive, Kent Johnson, who supervises environmental quality for the greater Minneapolis-St. Paul area, told the Post. And big swarms point to a healthy environment, he said.


Tagged categories: Bridges; Department of Transportation (DOT); Government; Infrastructure; North America; Program/Project Management; Roads/Highways; Transportation

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