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Smoke billows from a section of an overpass that collapsed from a large fire on Interstate 85 in Atlanta, Thursday, March 30, 2017. Witnesses say troopers were telling cars to turn around on the bridge because they were concerned about its integrity. Minutes later, the bridge collapsed. (AP Photo/David Goldman)
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The inferno that collapsed the Interstate 85 bridge in Atlanta not only could happen in Tennessee, it already has.

But there's not much risk it will occur often.

In August 2014, a tanker truck hauling 9,000 gallons of gasoline hit a bridge support and exploded under the Peytonsville Road overpass on I-65 in Williamson County, killing the driver. The Peytonsville bridge was being replaced, but the intense heat from the burning fuel badly damaged both structures.

"What was left of the bridge was completely demolished for safety reasons, leaving residents, businesses and emergency crews without a simple way to cross I-65 in the town of Franklin," said Jennifer Flynn, spokeswoman for the Tennessee Department of Transportation's Region 2 office in Chattanooga.

But it takes a set of peculiar circumstances to set up such a large-scale catastrophe.

Mainly, "you've got to have a lot of fuel that can burn at a very high temperature," said Ken Flynn, chief of operations for the local TDOT office and Jennifer Flynn's husband.

"Anything will melt if you get it hot enough, especially with accelerants like gasoline or diesel. If they get to 2,500 degrees Fahrenheit, then all kinds of material will start becoming liquid. Mother Nature does it all the time with a volcano and that's what concrete is made of, rock and lime, that will melt if it gets hot enough," Flynn said.

And pouring water on the conflagration may make things worse. Intense heating followed by rapid cooling can cause metal materials to shrink or crack. Flynn said he saw that at the Peytonsville Road scene.

"The beams were just spaghetti — they were wobbly and they weren't straight anymore," he said.

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The same thing happened in April 2007 in Oakland, Calif., when a tanker hauling 8,600 gallons of gasoline flipped and exploded under Interstate 580. Flames shot hundreds of feet in the air and collapsed a three-lane section of highway on to another interstate about 30 feet below. The crash shut down a heavily used commuter route for months.

Georgia officials said the cause of the I-85 blaze is still under investigation, but media reports said a quantity of PVC stored under the bridge caught fire. AJC.com used images from Google Maps Street View to show coiled materials stacked under the bridge that were put there sometime between July 2011 and April 2012.

Jennifer Flynn said the department doesn't allow storage under Tennessee bridges. She said TDOT operations personnel have been put on notice to check the bridges in their areas and make sure they are clear.

"Of course, there may be material and equipment stored under a bridge that is under construction or being widened, like the Olgiati Bridge, but we don't allow material to be stored beneath our bridges on a permanent basis," she said.

The Atlanta collapse is proving just slightly inconvenient for the local office of Groome Transportation, which runs multiple daily shuttles to Hartsfield-Jackson Atlanta International Airport.

John Collison, manager of the Groome office on Ringgold Road in East Ridge, said Chattanooga shuttles won't be much affected because they bypass the collapsed bridge. The only hassle will be extra traffic, he said.

But Groome's Athens office is having to reroute from I-85 to I-20, he said, and the Augusta site is bracing for heavy traffic while I-85 is out of commission.

Contact staff writer Judy Walton at jwalton@timesfreepress.com or 423-757-6416.

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