Risk to levees remains same each day, not worsened
Published 12:01 am Saturday, May 21, 2011
NATCHEZ — Risk of levee failure remains as floodwaters from the Mississippi River recede, U.S. Army Corps of Engineers officials said Friday.
But the risk, at least, does not grow worse as record-high water levels linger with each passing day, said James McRae, a project engineer with the Corps who is based in Vidalia.
“Every day the water is at this level, it’s the same amount of risk,” McRae said.
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Since the Concordia Parish levees are already saturated, they will be in no more danger in two weeks than they are now, McRae said.
“We won’t necessarily be worse off (in two weeks), but (the parish) is still an area of great concern,” he said.
McRae said the same number of people monitoring seepage and sand boils will stay on task until river levels are no longer a risk to levees.
A sand boil results when pressure from the river forces water under the levee, displacing soil and forming a hole. Boils can be addressed by building a ring well of sandbags around them, allowing the water pressure to equalize before the boil is plugged.
McRae said different risks are associated with a slow and a fast water recession. “It’s a double-edged sword,” McRae said.
If the river falls out very quickly, it could cause sloughing off, like a landslide. If the river level has a slow fall, additional seepage and sand boils will continue to remain a problem for longer.
McRae said as long as the levees were not in danger of being overtopped, the crest level does not really affect their strength, just the timing.
“We had protection to a higher crest, but we’re definitely glad to see the crest at a lower level because (the river will be) at historic river stages for a reduced period of time,” he said.
McRae said all is being done to prevent any risk failure in the levees.
“The levees are strong, and we’re taking measures to locate seepage and address sand boils, as required,” he said.
He said sand boils at the Vidalia Canal and north of Lake St. John are being treated with sandbags.
Those areas, he said, were problem areas in 2008 and during other previous floods.
“Some of these sand boils have been around for years,” McRae said.
Representatives from agencies such as the Fifth Louisiana Levee District, the Louisiana National Guard, the Louisiana Department of Transportation and Development and the Louisiana Department of Fisheries and Wildlife are patrolling sand boils day and night and air patrols are also monitoring them, he said.
“We are experiencing nothing on ground that would indicate any kind of (levee) failure possibility,” McRae said.