A partial bridge collapse on I-75 in Chattanooga, Tennessee, left one person with critical injuries on Monday, April 1, but some authorities say it’s very fortunate and unusual the incident didn’t result in multiple fatalities.
A long section of concrete rail fell from the I-75 overpass along the northbound section of the highway at the I-24 split, which Chattanooga Mayor Andy Berke said is “one of the most heavily trafficked intersections in the country.”
The concrete rail fell onto the highway below about 11:30 in the morning. The driver of a car that slammed into the concrete debris was taken to a Chattanooga hospital in critical condition. That person is expected to survive, but information about the extent and nature of the injuries was not released.
Jim Hall, a former National Transportation Safety Board (NTSB) chairman who lives in the area, told Chattanooga’s News Channel 9 that he has investigated several bridge collapses and similar accidents around the country and rarely saw an outcome in which there were not multiple deaths.
“We are a very blessed community that we did not have multiple fatalities. I’ve been around the country and events like this usually end up with multiple fatalities and a much worse situation,” Mr. Hall told News Channel 9.
The Tennessee Department of Transportation (TDOT) said the last time the 60-plus-year-old bridge was inspected was in July 2018. It was found to be structurally sound.
“It had normal problems that an older bridge would have, but there was nothing structurally wrong with it,” TDOT regional bridge manager Steve Hutchings told the Chattanooga Times Free Press. “There was no reason for us to suspect anything like this would happen. Everything was in good condition.”
TDOT officials later reported that they suspected the bridge collapse was caused by an illegally oversized truck that damaged the structure from underneath.
Speaking at a conference about the bridge collapse, TDOT Deputy Commissioner and Chief Engineer Paul Degges said the five steel reinforcing strands were cut through in a manner that was consistent with being struck by a large load, the Times Free Press reported.
TDOT engineers found the reinforcing strands at the center of the bridge collapse investigation were not rusted and the nuts that held them in place were in good condition.
Officials think an oversize truck hit the overpass in the hours or days leading up to the bridge collapse, cutting through five of the 23 strands “like someone took scissors through it,” Mr. Degges explained.
The cables were each damaged in the same location on the lowest side of the bridge, “making it improbable that the collapse was caused by anything other than a collision,” TDOT officials said, according to the Times Free Press.
Video surveillance of the overpass may have been captured by traffic cameras, but officials aren’t legally allowed to use such footage for investigative purposes.
Mr. Degges said statewide about 50 bridges are struck every year, usually because they are hauling loads that are too tall or wide. Most of those collisions, however, are minor.
The bridge is slated to be replaced as part of an interchange redesign later this year, but the state is taking measures to add temporary repairs to the overpass. Those reinforcements will take about two weeks.