Tunnel Wall Collapse Swallows Roadway
A sinkhole opened up on a New Orleans street just hours after the mayor and the city’s infrastructure team examined a decades-old underground tunnel nearby.
The cave-in occurred Friday (April 29) on Canal Street, swallowing up a 30-foot section of road surface, NOLA Media Group reported.
Here's a great shot of the reportedly 20-foot-wide sinkhole that has opened on Canal Street in New Orleans. pic.twitter.com/A7V9qP6BHZ— New Orleans Advocate (@theadvocateno) April 29, 2016
Mayor Mitch Landrieu and an infrastructure crew had been in the 50-year-old tunnel that runs beneath the road while inspecting a wall that was reported to be buckling earlier in the month.
According to the area news agency, the wall at the northern end gave way within a few hours of their departure, collapsing the road above it.
"This is nothing short of incredible," Landrieu said. "Unfortunately, it's not a surprise," he added, referring to the overall state of the city’s infrastructure and its unstable soil. "Still, I've never seen anything like it."
Abandoned Expressway Project
The tunnel is said to be a remnant of the subterranean portion of a 1960s-era plan to build the Riverfront Expressway, a six-lane elevated highway designed to run beside the French Quarter.
Although the project was eventually rejected by the Department of Transportation, the city had already constructed a section of tunnel running beneath Canal and Poydras streets, NOLA said.
The tunnel was constructed from concrete supported by steel I-beams, with “temporary” wooden walls enclosing both ends, reports said. These end caps were to be removed when the rest of the expressway was constructed.
The 700-foot-long, 98-foot-wide tunnel, however, was never filled in or reinforced with additional supports; it is still in use as a valet parking area for an area casino.
According to reports, an entire section of the tunnel, braced by steel beams every 10 to 15 feet, had given way.
Need a room for Jazz Fest? How about the Canal Street sinkhole? https://t.co/DhOKIYWc8f#onlyinNola #Nola pic.twitter.com/uZogO7EbrR— WGNO (@WGNOtv) April 30, 2016
No one was reported to be injured as a result of the cave-in. The city had preemptively closed Canal Street in one direction a week earlier, after learning one of the walls was buckling, so engineers could perform their inspection and plan the necessary repairs.
Compromised by Water
Officials attribute the deterioration of the structure to a combination of time, leaking water lines and drainage culverts that run under the street.
Landrieu also pointed to damage to the city's water system after Hurricane Katrina. "We have about 40 percent of our water bleeding out of our pipes under the city of New Orleans," he said.
Director of Public Works Mark Jernigan told The New Orleans Advocate engineers have inspected the rest of the tunnel, as well as the timber wall at the opposite end, “and so far have no concerns about the rest of the structure.”
Constructed from reinforced concrete, the tunnel’s main walls and ceiling were designed to accommodate the weight of the roadways and buildings above, as well as the effects of constant traffic, Jernigan added.
Officials plan to begin repairs immediately, although the sinkhole could continue to expand. They will replace the temporary wood walls with sturdier supports.
"This is not a short term fix,” Landrieu said. “It's a major infrastructure breach that has to be repaired and it's going to be expensive."
The repair period is expected to take three to six months and cost between $3 million and $5 million dollars, according to Cedric Grant, the executive director of the Sewerage and Water Board of New Orleans.