Design for Rapid Levee Construction Shaves Off Decade in Schedule
Dwayne Smith, a senior engineer at URS Corp., San Francisco, is a geotechnical program manager on a levee enlargement project in New Orleans that is shaving a decade off the time it normally takes to build and consolidate such a structure.
Archer Western Contractors Ltd., Atlanta, holds the $114.9-million contract to deliver the 7.54-mile stretch of what will be some of the most massive earthen levees in the Greater New Orleans Hurricane and Storm Damage Risk Reduction System. The levees are built on soft, marshy soils in eastern New Orleans. From toe to toe, they are 320 ft to 360 ft wide, with elevations varying from 18-plus ft to 25-plus ft.
URS developed the design and specifications using Smith’s system, which layers a sand blanket, geotextile fabrics and rock over a landscape studded with 300,000 fabric-tape wick drains—almost nine million linear ft—to rapidly draw moisture from the soggy soil. It’s one of the largest projects in terms of square footage and number of holes ever done in the U.S., says Mark Palmatier, president and owner of U.S. Wick Drain, the wick installation supplier and contractor.
“When you put up to 30 ft of fill height on those soft soils, it would no doubt cause a slope failure,” explains Smith. Normally, such a levee would take 10 to 11 years of gradual buildup and consolidation to stabilize. However, by using Smith’s design, the U.S. Army Corps of Engineers is achieving that in 60 to 90 days. An array of monitors validates performance as the levee grows.
“Its really going well,” says John Grieshaber, chief of the execution support division in the Corps’ Hurricane Protection Office in New Orleans. He says the design is helping the Corps deliver promised levels of protection by June. He adds that he never thought he would see such a levee built this fast “on virgin marsh.”