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When the U.S. Army Corps of Engineers agreed last fall to apply protective coating to sheetpile that would be used to shore up a key New Orleans canal, the agency apparently did not mean all of the metal.
Photos show, and the Corps confirms, that it is painting only the top several feet of the steel sheetpiling that is being used to upgrade the London Avenue Canal.
At the request of the Southeast Louisiana Flood Protection Authority-East, USACE said in December that the $17.9 million contract to improve the canal’s floodwalls and levee would include applying protective coating to 6,000 feet of sheetpile.
Time Crunch
Local authorities and the Corps have been locked in a protracted dispute over whether the steel used in the $14.4 billion Hurricane and Storm Damage Risk Reduction System (HSDRRS) for southeast Louisiana should get protective coating. The system includes five parishes, 350 miles of levees and floodwalls, and 73 pumping stations.
The Corps, which built the levee system that failed during Hurricane Katrina, opted last year to forego coatings in favor of oversized pilings with an extra 1/8-inch layer of sacrificial steel on about 23 miles of new levee encircling St. Bernard Parish, which was hit hardest by Katrina.
The Corps said that the system would be difficult to complete on time if it was coated. The Corps declined to discuss the cost of coating vs. sacrificial steel, but said that the difference was negligible and that either option was acceptable.
Corps: ‘Not at Risk’
However, a Corps spokeswoman said in December that the steel on the London Avenue Canal project would get coating, because local authorities had requested it and because there was time to do so.
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Photos: Steve Beatty
Photos show partially coated steel to be used in the London Avenue Canal project. |
Now, the Corps says that only the top portion of the piling—the part above the water table—requires coating, so that is what the agency is doing. However, the Corps is not using oversized steel or additional steel thickness on the canal project, as it did on the new St. Bernard Parish levee, a spokeswoman said.
Nor is the Corps using cathodic protection or concrete encasement on the sheetpile, she said. The same process is being used on remediation of the Orleans Avenue Canal, the second of three so-called Outfall Canals that drain water from the city into Lake Pontchartrain.
“It is standard to only coat the top portion of the pile with the coal tar epoxy,” Nancy Allen, public affairs officer for the USACE Hurricane Protection Office (HPO) in New Orleans, wrote in an email. “This is being done across the Hurricane and Storm Damage Risk Reduction System in any instance where coated steel (H piles, sheet piles, etc.) is being used.”
Allen said the coal tar epoxy was sufficient to inhibit corrosion. “The local sponsors are well aware that the industry standard only calls for coating the top portion of the piles,” she added. “The portion of the pile that is below the water table is not at risk of corrosion.”
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Coal tar epoxy will provide sufficient corrosion protection, USACE says. |
Seepage Remediation
Allen noted that the Outfall Canal remediation and the St. Bernard floodwalls “are vastly different.” Although part of the same system, “the outfall canal work is remediation for seepage and stability issues. We are driving sheetpile to cut off seepage.”
She added: “There is existing levee or floodwall in place, and the only purpose of the outfall canals at this point is interior drainage. After Hurricane Katrina, gates and pump stations were installed at the mouths of each of the three canals to block hurricane surge, making the existing levees and floodwalls a secondary line of protection.”
‘An Imprudent Decision’
Members of the SLFPAE did not respond Wednesday (March 16) to a request for comment. Last year, however, local and regional officials demanded that the project steel be coated.
"We have counseled them for months that ... the use of untreated steel in the marine environment was an imprudent decision, and we asked people with more expertise to look at it, and they agreed it was imprudent," levee commissioner Steve Estopinal, an engineer and surveyor, told the local newspaper last summer.
"We want future steel coated, and if the external peer review comes back and agrees with us . . . the federal government should be required to pay for the [monitoring] and maintenance of those walls." Estopinal called the use of untreated pilings "a design flaw."
Estopinal sponsored a successful resolution to fast-track an external peer review of the situation. That review "is being processed by the Army Research Organization's contracting department,” Allen said Wednesday.
Corrosion Control Options
Col. Robert Sinkler, Commander of the USACE HPO, reviewed for the authority the corrosion-inhibiting measures being used on the project. They are, he said:
• Over-sized cross-sections of piles
• Coal tar epoxy or other coating
• Application of a polyethylene sleeve
• Zinc coating
• Electro-chemical (cathodic) protection
• Casting in cement, mortar or concrete
Sinkler said that the system’s design guidelines did not specifically address corrosion.
A USACE official said in September that coating the pilings “would have overwhelmed the coatings industry."
Canal Project
Two of the three major breaches during Katrina occurred on the 15,000-foot-long London Avenue Canal, with much of the problem later traced to seepage, Allen said.
The goal of the six-month canal project is to repair and shore up the weakest sections of floodwall and levee to increase the “safe water” level in both channels to eight feet. The current elevation at London Avenue is capped at five feet.
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