MEMPHIS, Tenn. — A consulting inspector discovered a "significant fracture" Tuesday that has indefinitely closed a bridge that carries Interstate 40 over the Mississippi River from Memphis in Tennessee to West Memphis in Arkansas.
The crack in the Hernando de Soto "M" Bridge, officials said, is on a beam that is crucial to the bridge's structural integrity and is located near the middle of the "M."
"This fracture had the potential of becoming a catastrophic event," said Lorie Tudor, director of the Arkansas Department of Transportation.
That possible catastrophe was prevented, she said, due to maintaining routine inspections of the bridge, which were underway Tuesday when the crack was discovered. Officials said it is most likely the fracture is due to bridge fatigue; the bridge has been open to traffic for nearly 50 years and remains an important component of regional logistics.
Inspections, both of the crack and other parts of the bridge, are ongoing. The outcome will dictate when traffic — on both land and water — can resume along the bridge's path.
Because the bridge straddles state lines, Tennessee and Arkansas split responsibilities. Arkansas maintains the required inspections, said Clay Bright, commissioner of the Tennessee Department of Transportation. Tennessee maintains repairs. Costs are split.
Traffic will remain closed while a physical inspection takes place over the next three or four days, Tennessee Department of Transportation officials said Wednesday. Officials hope to have a written report in about two weeks.
“Right now we just don’t know” how long the bridge will be closed, Paul Degges, chief engineer with the Tennessee Department of Transportation, said during a press conference Wednesday.
Closure could create backlog of boats
No one seems to know how long the river will be closed to traffic, but the longer the closure lasts, the more economically damaging the crack will be, said Mark Mestemacher, co-owner of St. Louis, Missouri-based Ceres Barge Lines and barge consulting firm Ceres Consulting. A closure that lasts a couple of days could create a backlog of boats at the bridge; a closure of more than a week could begin to be felt more widely, derailing the shipment of corn and beans from the port of New Orleans.
"It's too early to tell," Mestemacher said of the economic impact of the closure. "Is it shut down for half a day? For a full day? I don't think they know that."
He added: "I don't want to get in a panic mode. Until they tell us what's what, there's nothing we can do."
Degges said the department will likely know more about when barge traffic can reopen sooner than when vehicular traffic can resume.
Crack is in middle of 'M' on steel box beam
While cracks in steel bridges do occur, it is uncommon for the crack to be found in such a significant structural area, officials said.
“There’s a lot of components to this bridge," said Steve Frisbee, assistant chief engineer for operations at the Arkansas Department of Transportation. "It’s just that this is a key, one of the two key components.”
Michael Baker International, a Pittsburgh-based engineering consulting firm, will assess the crack and required repairs, officials said Wednesday, analyzing the structure to see if it is safe for inspectors or construction, and determining when barge traffic can resume. That inspection will include looking for additional cracks, which sometimes have to be found by completing an X-ray of the steel beams. Inspections will also model different scenarios for the bridge to inform repair.
Degges, the Tennessee Department of Transportation engineer, described the crack found on the bridge. Theoretically, he said, it could have occurred minutes after the last routine inspection was completed in 2019. He believes the crack has been there for at least a week.
The crack does have some rust. Officials said it is unlikely the crack is a result of any damage from the winter storm earlier this year or a result of the retrofitting done to the bridge to help it sustain any potential earthquake damage.
Degges explained the structure and the crack like this: The box beam is made of steel panels that are a little under 2 feet wide and about 32 inches tall. Those four plates of steel are welded together, but three of the plates have separated, by a fraction of an inch. The bottom, fourth piece of the box beam has a crack that's about 20% the width of the steel, he said.
"For any type of beam, steel beam in particular, if it's a one-tenth of one millimeter, if it's not connected, it doesn't carry load," Degges said.
Frisbee, with Arkansas, described the beam as about 50% cracked through.
"It’s just the size of this crack is more than what’s normal, so we have to get the load off of it," he said. "Being that it’s over the river, that makes it a challenge."
Michael Baker International has completed inspections in recent years and was completing the first day of inspections Tuesday when a member of the team discovered the crack, Bright said.
Follow Laura Testino on Twitter: @LDTestino
This article originally appeared on Memphis Commercial Appeal: I-40 bridge crack: Hernando de Soto Bridge reopening timeline unclear