Nearly two weeks after a 30-foot-wide collapse opened beneath Interstate 44 in downtown St. Louis, crews are almost finished with stabilization. The effort must be complete before officials can determine exactly what caused the cave-in.
The Metropolitan St. Louis Sewer District, among other agencies, has been working to secure the area and develop a repair plan.
"The priority right now, and still is, getting that site safe, so that we can dig down and see what we're dealing with," said Bess McCoy, manager of public affairs for MSD.
McCoy said filling the hole is a necessary temporary step rather than a long-term solution. Stabilization required to execute permanent repairs.
Jen Wade, an area engineer for the Missouri Department of Transportation in the City of St. Louis, emphasized that the ongoing work combines careful consideration with a timely response. "We're not doing any guesswork out there," Wade said. MoDOT collaborated with MSD engineers to develop an engineered plan that ensures structural strength is fully restored around the piers and underground columns before beginning the fix.
When I-44 will reopen is not yet certain.
"We are very near completion with stabilizing the hole, and things are going well," McCoy said. "If they continue to go as planned, MoDOT should be able to make that decision very soon."
On "St. Louis on the Air," Mccoy said the sewer under I-44 where the cave-in occurred received the highest rating on the Metropolitan St. Louis Sewer District's inspection a few years ago. MSD engineers compared the remains of the 10-foot-by-12-foot structure to a crushed soda can.
"Typically, when it's an issue where there was a small defect or something, what you see is kind of a trail of issues instead of it all being in one area," McCoy explained. "From what we can tell, this was probably more just too much weight on top of the sewer, possibly because of that broken water main."
The hole is a cave-in, not a sinkhole. The distinction matters because it affects how engineers approach repairs.
Fletcher Bone, a geologist and environmental program specialist with the Missouri Geological Survey, said a cave-in is typically associated with man-made structures such as sewer lines, stormwater systems or other underground infrastructure. Sinkholes are naturally occurring phenomena, especially in Missouri.
"The implication of having a naturally occurring sinkhole versus a collapse of infrastructure is the size of the infrastructure," Bone said. "It's a 12-foot-diameter sewer drain over there, so the size of the void."
From his perspective, there's been good collaboration between the agencies working to repair the hole.
"Everyone's trying to try to do as best they can as quickly as they can for such a complicated situation. It's just good to see that things are moving way quicker than initially thought," he said.
In the longer term, McCoy hopes for a more holistic, resilient underground infrastructure system for St. Louis. Some of what MSD is doing now involves bringing in new, more predictive technology to spot weak points in the system earlier.
"We've been doing a lot to upgrade our infrastructure, but resiliency also goes to people's homes, how homes are built, how building codes are decided," she said. "We're looking at resiliency as a big picture thing, not just pipes underground."
For more information on the cave-in, including what measures are being taken to remedy it and the potential impact of the hole on nearby residents, listen to "St. Louis on the Air" on Apple Podcasts, Spotify, or YouTube or click the play button below.
"St. Louis on the Air" brings you the stories of St. Louis and the people who live, work and create in our region. The show is produced by Miya Norfleet, Emily Woodbury, Danny Wicentowski, Elaine Cha and Alex Heuer. Layla Halilbasic is our production assistant. The audio engineer is Aaron Doerr.
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