Sinkholes: A Part Of Daily Life In New Orleans

Aug 1, 2016

New Orleans’ streets drew national attention this spring after a giant sinkhole opened up downtown during JazzFest. Since then, several more holes have made it into local news - in Uptown and Mid city.

New Orleanians are used to complaining about persistent potholes in all parts of the city - but, sinkholes are a different animal.

I met Tulane University professor Alex Kolker at Constance and First Streets Uptown - where a big hole in the middle of the street was slowing down traffic. It’s about two feet wide and a foot deep. We watched as drivers figured out what to do. They slowed down guided their wheels over the hole.

It’s a pretty familiar scene here in New Orleans. Drivers dodge gaping holes in city streets on the way to work - eventually learning where they are and adapting commutes accordingly.

Kolker is a professor of earth and environmental science at Tulane. He studies the coast. And he gets excited about these holes. He likes to figure out how they formed. This one, he says, was probably caused by a broken pipe. He inspects the buckled street, and notes that the sinkhole is in a larger depression about the width of a house. Diagnosis - it was caused by a few factors. One of those is subsidence, which is the sinking of the ground.

“We’re getting some erosion, which is the wearing away of the surface sediments - so the ground sinks from underneath, probably as pipe has collapsed and then the edges erode as cars drive their tires over them,” says Kolker.

Alex Kolker is a professor of earth and environmental science at Tulane University. He says this sinkhole in Uptown was probably caused by a pipe leaking underground.
Credit Tegan Wendland / WWNO

It’s a sinkhole, not a pothole. The distinction is important. Potholes form on the surface - sinkholes form when space opens up underground and the surface sinks. They’re less predictable and more dangerous. They can happen suddenly.

It turns out New Orleanians talk about these problems a lot online - so from Facebook posts and blogs I made a list and went to check a few out, with Kolker as my sinkhole doctor. This one is Broad Street and Esplanade.  

“That’s impressive! That’s very impressive,” remarks Kolker. “You can actually see some of the historical layers, there’s a shell layer - a bunch of oyster shells with some other shells mixed in – and there’s a lot of of asphalt on the edge of the hole, slumping down into the hole.”

Diagnosis - sinkhole. The shell was probably used to pave the road decades ago. Shell is weaker than pavement - it breaks down over time - then water seeps in and washes it away, creating a hole. The ground sinks.

This sinkhole on Broad Street was likely caused by the compaction and erosion of a layer of oyster shells beneath the surface, which formed a hole and then the pavement collapsed.
Credit Tegan Wendland / WWNO

But this is not news in this city. Cedric Grant, director of the Sewerage and Water Board, says it’s time to address what’s underneath, not just pave over.

“Oyster shell. That used to be the standard. It was probably pretty good for 50 years. But 50 years has passed and it’s time to go deal with it!” Shells aren’t the only problem, “Sand used to be a standard - but it doesn’t take much for sand to wash out.”

Grant says most of the road problems we have today are because of decisions engineers made long ago, and leaky pipes - damaged by the flooding from Hurricane Katrina. Several feet of floodwater weighed down the ground and broke and shifted the pipes. Water flows out and scours away those layers underneath the top pavement.

The city just received $1.2 billion from FEMA to help replace many roads and pipes.

But that’s no comfort to Hiltraud Reeder, a German tourguide. We met her outside her house near Bayou St. John, where she stood in a yellow nightie looking down at a gaping hole in the street. “I am furious at this! My goodness gracious, I can't even get in and out of my driveway!”

Reeder says a big hole opened up outside her house back in April and she’s made endless calls to the city to get it fixed.

Kolker takes a look. It seems the city started on some work...then hit a snag. “Now this is a big one! I’m not sure what is the hole and what the city has carved out after. It’s square and even…”

Diagnosis - sinkhole or pothole, and cause? Unclear. Regardless, the problem is similar to the other two we saw - more leaking pipes and old infrastructure.

And even when this hole is filled, there will likely be many more to come. Because New Orleans continues to sink. Kolker explains, “It’s hard to reverse subsidence. But we can slow it by holding water in the ground.”

Rain gardens help. And special pavements that let water through. He says the city would be wise to better track sinkholes and which areas are sinking fastest. But...messed-up streets? Not going away.

People like Reeder might be inconvenienced and frustrated - but would never consider moving. “Not out of New Orleans, no, no no. I really love living in New Orleans and it would be paradise on earth if the city would just help us!”

Mayor Mitch Landrieu says he’s trying to help. He launched an initiative last year called Fix My Streets Nola which is working to get 1$0 billion to upgrade the city’s aging infrastructure.

Grant says it’s just going to take time. “This is a generational challenge. This is not something that happened overnight and it can’t be fixed overnight.”

He points to new technology, like flexible piping that would bend as pavement sinks instead of breaking, and sonar leak-detection would let workers fix pipes before sinkholes collapse.

There are just spot fixes - no comprehensive funding to dig up and re-do all the city streets. So for now, stay wary of the errant hole. 

Support for WWNO's Coastal Desk comes from the Greater New Orleans Foundation, the Coypu Foundation, and the Walton Family Foundation.