Twenty years after the catastrophic failure of the federal levees protecting the New Orleans area, some experts believe that corrosion is still a major vulnerability within the remade flood-control system.
The U.S. Army Corps of Engineers completed the $12 billion remake of the levee and floodwall system in 2022; the state’s local levee authorities now oversee its upkeep.
The system involves a lot of metal touching a lot of water.
The massive steel pumps that empty the canals, the steel pilings driven deep below the levees — all must contend with the slow and steady threat of brackish water, which is more corrosive than either salt or fresh water, from sources like Lake Pontchartrain.
Corrosion plagues a few parts of the levee system, which was reconstructed after the 2005 flood that left the city 80% flooded after Hurricane Katrina.
When the massive lakefront pumps suffered unexpected degrees of corrosion, the Corps made repairs, but has not yet implemented a final fix.
Questions also remain about the integrity of the levees themselves, which are reinforced by steel piles that are susceptible to corrosion in Louisiana’s moist climate. And yet, only a fraction of those piles were protected according to the Corps’ own standards.
And while the Corps did create a decade-long monitoring program in response to concerns about levee pile corrosion, no results have yet been released.
That leaves some experts worried that another disaster could be brewing. “What I’m talking about here is the corrosion of the levees again, and the possibility of another Katrina,” says Charlie Speed, a materials engineer and former president of the National Association of Corrosion Engineers (now Association for Materials Protection and Performance or AMPP). ‘
Pumps were repaired but will face rust again
Three outfall canals – London Avenue, Orleans Avenue, and 17th Street – run through New Orleans, collecting rainwater pumped by the New Orleans Sewerage & Water Board and funneling it into Lake Pontchartrain. At the tops of the three canals, 17 massive pumps – some of the largest in the world – stand in cavernous cement buildings, primed and ready for the next storm.
During a hurricane, the outfall canal gates are closed to prevent storm surge from Lake Pontchartrain rushing into the canals, which could be overtopped, flooding the city. Once the gates are closed, operators with the Flood Protection Authority turn on the pumps to move water into the lake, to ensure levels in the canals don’t exceed eight feet, their maximum safe limits.
The gate-and-pump system didn’t exist in August 2005, when the London and 17th Street canals breached.
The Corps first installed temporary pumps here, at the end of the outfall canals, in 2006. But almost immediately, the pumps showed signs of rust and corrosion. The Corps had higher hopes for the new, massive pumps that were installed and activated in 2018, with the assumption that they’d be good for 35 years.
But four years later, in May 2022, pump operators with the Southeast Louisiana Flood Protection Authority (SLFPA) noticed that Pump 1 at London Avenue was overheating. They opened it and found it so rusted that a bolt fell out.
“The corrosion had come through, started eating away,” said Corps spokesman Ricky Boyett. That’s when Corps engineers realized that the issue went beyond the London Avenue pump, he said.
The Army Corps began repairs on all 17 pumps in 2023, completing them this spring. Repair crews replaced some carbon steel parts with stainless steel ones, and redid the anti-corrosive coatings. They replaced anything that showed corrosion in crucial underwater areas, like the driveshaft and intake areas.
But the same repairs were done on the temporary pumps. And those repairs didn’t last.
The temporary pumps, which were smaller, were repeatedly removed and repaired due to recurring rust. Pumps were removed about 50 times between 2006 and 2017, according to Matt McBride, a mechanical engineer who’s long been chronicling issues with the pumps.
“The lakefront pumps are, to my mind, the biggest danger,” McBride said. “They rusted out before. They need an inspection program.”
Vulnerabilities tied to flaw in contractor plans
The temporary pumps were vulnerable in part because they were made with carbon steel, which is more vulnerable to rust. In response, the Corps addressed the issue piecemeal, replacing certain carbon steel parts in some places and applying rust-resistant paint in others – rather than replacing all carbon-steel components with stainless steel ones.
The permanent pumps activated in 2018 are also made of carbon steel.
It was a flaw in contractor plans, Boyett said. “When we were evaluating this,” he said, the contractors’ reports advised that “you can combat it with coating and basically not letting the water to the metal. And so that was the big plan.”
The contractor also ran modeling to indicate what would prevent the corrosion for 35 years, he said. “And basically, five years into it, we realized it wasn’t working.”
It’s difficult to know when the corrosion first began on the temporary pumps. But corrosion and rust appeared on elements of the pump station as early as June 2006 – less than a month after installation.
That means the Corps may need to work very quickly to keep the rust from returning.
One possible solution, commonly used by ships and pipelines, is a technique called cathodic protection. It keeps rust at bay by running a very low current through an anode attached to the pumps, causing a metal coating, like zinc, to corrode instead.
During the pumps’ construction, CPRA had suggested use of the technique as state officials repeatedly expressed concerns about corrosion, according to last year’s suit against the Corps, which described CPRA’s concerns about “inadequate cathodic protection.”
The pumps don’t yet have cathodic protection, reported Army Corps Lt. Col. Nathaniel Wonder at the June SLFPA-East board meeting.
Though the cathodic protection work has not yet begun, it should be completed by the end of the year, said Boyett, who explained that the Corps defers more disruptive work until December, after hurricane season ends.
Crews may not be able to add the cathodic protection without pulling the pumps – “the final big piece” of work to do on the pump system, Boyett said. The same contractors who recently repaired the pumps will add the cathodic protection.
Underground piles face corrosion
Rust and corrosion are also a grave concern elsewhere: deep below the levees, where 100-foot long, H-shaped steel piles were driven beneath the ground to support the levees and floodwalls rebuilt after the storm.
State and local agencies have been especially vocal about this vulnerability, because once the construction was complete, the state’s CPRA and Lake Borgne Basin Levee District became responsible for maintaining the floodwalls.
The risk of corroded pilings raises red flags for New Orleans observers because the levees failed in 2005 partly due to the faulty pilings beneath them. Some of the 53 breaches occurred when floodwalls were undermined from below, rather than overtopped, because the Corps did not drive the piles deep enough into the soil, allowing water to seep underneath.
When the levees were reconstructed, the piles were driven to deeper levels. Yet because of moisture in the soil, the new piles face the same corrosion threat as the pumps. Normally, before driving piles into the ground, the U.S. Army Corps of Engineers paints them with an anti-corrosive layer of coal tar epoxy.
But the Corps were on a deadline and on a budget to finish the New Orleans levees. Instead of taking the time to coat the piles, the Army Corps granted the New Orleans district a waiver in December 2009 so they could meet the construction schedule.
The waiver permitted the Corps to skip the coating. To compensate for the inevitable corrosion, they built the piles larger than normally required, adding an extra ⅛ inch of steel which would be deliberately allowed to rust, known as “sacrificial steel.”
All the key players had objections to the decision. SLFPA-East, the Levee Board, and CPRA raised alarm bells, pushing the Corps to adhere to its standard practice and paint the piles.
In 2014, an independent study commissioned by CPRA, performed by The Water Institute of the Gulf, found that using sacrificial steel rather than coating steel piles for corrosion protection was “inconsistent with the current state-of-practice of engineering in this region…the panel is not aware of any modern designs that have used this approach for corrosion protection in the Greater New Orleans region.”
Eventually, the Corps agreed to paint the piles. But most of the piles had already been driven into the ground, because the Corps had continued driving the unpainted piles while the disagreement played out.
In the end, only about 20% of the piles got the anti-corrosive coating.
No details yet revealed from 10-year study of corrosion
In light of all the concerns, the Corps agreed to establish the St. Bernard Monitoring Plan, through a $756,714 contract awarded in March 2015. The plan, which covers only St. Bernard levees, monitors corrosion and troubleshoots the plans – or, as the project description says, “will either confirm the design assumptions or identify them as incorrect.”
Advocates hoped that results from the hard-fought monitoring plan would shed light on corrosion’s threat to the piles beneath the levee system.
But a full decade later, no data from the plan has been made available. The St. Bernard Monitoring Plan remains one of the only contracts out of the 130+ listed for the Lake Pontchartrain section of the Army Corps’ flood protection system that does not have a completion date.
Boyett told The Lens it was a 10-year contract and is now closed out. The Corps expects to release the results by February 2026.
Now that the 10-year St. Bernard monitoring project is complete, Corps officials are preparing to do data analysis and publish a report, said Brad Barth, Chief of Operations with the CPRA. Barth said the CPRA’s concerns remain, and they are “anxiously awaiting” the data analysis. Since the Army Corps hasn’t acted to remediate any problems, he assumes that the piles are performing as expected: “because if they didn’t, they would be out there doing scramble mode and doing something, right?”
The results will be critical for the entire post-Katrina flood protection system, which faces the threat of corrosion as its most serious vulnerability, says Speed, of the Association for Materials Protection and Performance.
The Corps’ waiver decision was based on past Army Corps studies asserting that the agency could reliably predict corrosion rate, and relied in part on data from a 1962 report by the U.S. Department of Commerce. But in 2023, a National Academies of Science study found significant knowledge and research gaps in the methods used to predict the corrosion of buried steel, as developers “are reliant on limited decades-old corrosion-related data.”
As the debate raged in 2015 about the waiver, experts also had warned that corrosion threats would be worsened by subsidence. That’s especially true in St. Bernard, where some levees have already settled several inches, which could lead to voids under the floodwall and expose more steel to air or water, hastening corrosion.
A June study published in Science Advances also took a close look at subsidence, finding that some floodwalls in New Orleans are sinking at a significant rate, and that some of the highest rates of sinking were found at the St. Bernard Parish floodwall. Floodwalls in St. Bernard near Lake Borgne were found to be sinking up to 1.9 inches per year.
As the levees were being reconstructed, Speed joined the levee board and CPRA in calling for the Corps to paint the levee piles. “All the levees’ steel that goes into the ground – the pilings, the sheet piles, the corrugated pile that stabilized the ground, all of it – the standard for the Corps of Engineers in the United States is to paint it,” he said.