MEMPHIS, Tenn. (WKRN) – The United States Coast Guard reopened the waterway underneath the I-40 bridge that’s been shut down in Memphis.
The Hernando DeSoto bridge is closed after crews found it had a major crack in the structure.
There were 62 vessels and more than 1,000 barges in queue Friday morning, all waiting for the waterway to be back open.
TDOT’s Chief Engineer Paul Degges told News 2 they had to do a lot of analysis to see the bridge’s structural stability.
Part of that analysis came after building a computer model of the bridge and taking more steps to ensure its safety before taking that information to the Coast Guard, which controls traffic on the Mississippi River.
“We didn’t have the mathematic and the engineering behind it to where our analysis showed for sure that the bridge was stable in its current condition. We had to actually build a computer model, run the analysis of it and verify the model was correct, and then we had to start taking pieces of the model away where we had the fractured steel,” said Degges. “A fractured beam like we’ve seen here is not very common but it does happen from time to time and this just happened to be the largest bridge in the state of Tennessee.”
He said the bridge was built in the 1960s and early 70s, so there were no computer models when the crack was discovered.
“We’ve had a lot of conversations with experts across the country, and I think what we have found is we don’t know if we’ll ever know what the cause was,” said Degges. “It’s likely due to something in the manufacturing of the bridge back in the 1960s when these bridge components were fabricated and welded together.”
He credited the biannual inspection of the bridge for alerting engineers to the crack.
“What happened on this bridge is a success of the National Bridge Inspection Program. Nobody’s been hurt. There’s been some inconvenience, but the system worked,” said Degges. “There was a bridge inspection being done; a problem was identified, so we closed the bridge to traffic before anybody was hurt.”
He said that’s the same process for every publicly owned bridge in the United States. There are currently 8,420 On-System bridges in Tennessee that are maintained, owned and operated by the state. They include bridges on or over the interstate highway system and the state route highway system. More than 270 of them are considered to be in “poor condition”, but some remain open.
“Even though we have some bridges that are poor in Tennessee, generally they’re old and just because something is old doesn’t mean you throw it away,” Degges said. “We do rehab projects and they still have remaining service life in them.”
He said as some bridges get older, they’ll be inspected on an annual or even semi-annual cycle.
“Typically when you inspect a bridge on those kinds of frequencies, you’re heading towards a closure,” Degges explained.
Degges said in funding was not an issue in Tennessee for the safety of the state’s bridges. TDOT owns about 9,000 of the 20,000 bridges in the state and inspects all of them.
“The public safety is not at risk. We’re going to close a bridge before it becomes a public safety issue,” said Degges. “From a TDOT perspective, we make sure we put money towards making sure our bridges are and the fracture of this steel is not an issue with bridge maintenance.”
He said the issue for Tennessee’s infrastructure is congestion.
“If we start getting a lot of congestion in a location, those are the types of projects that want for money, and that’s a public policy issue,” Degges said. “Certainly, maintaining our assets is a top priority and we do that with the resources available to us, but adding new capacity to the transportation system, that’s the issue that brings about the conversation of additional revenue.”