Grand Isle gets new levees
A new geotube levee is being built along the eastern 6 1/2 miles of beachfront at Grand Isle by the U.S. Army Corps of Engineers. It will replace the levee that was almost entirely destroyed by Hurricanes Gustav and Ike. After the ’08 hurricanes washed the old sand levee across the island, the the corps is building the new levee with tubes 30 feet in circumference and
200 feet long filled with compacted sand. The tubes, made of geosynthetic material, will be connected to each other for the 6 1/2 miles and provide more protection than the old levee did.
The tubes will be placed on a 5-foot-high bed of sand, and 3 feet of sand will be pumped on top. Grass will be planted to help hold it in place.
The town of Grand Isle has already replaced 1 1/2 miles of levee along the beachfront on the western end with a base of heavy clay inside a polyethylene covering. It is called a “burrito” levee because the clay inside the covering resembles a burrito. It likewise will have a 3-foot sand cap with grass planted atop. It will connect to the new levee now being built.
According to Wayne Martin of TinCate Geotubes, similar tubes were used to narrow an area of the Mississippi River at Redeye Crossing in Baton Rouge to help navigation by keeping the water deeper with a more rapid flow. It has helped in other areas of the world for various shoreline-stabilization and wetland-restoration projects,
Martin said the tubes can be installed quickly and are cost-effective. The company is one of the largest synthetic fabrication manufacturers in the world.
The tubes are filled by pumping water from the Gulf of Mexico and mixing it with sand on the beach. The sand-water mixture is then pumped into the tubes, which act as a de-watering mechanism as the water leaches through the tube material. The sand-filled tube then becomes very hard.
The tubes will be coated with a material that will protect them from ultraviolet light and abrasion, Martin said. TinCate is a 300-year-old Royal Dutch company. Its tubes, which have been produced for 40 years, are made in the company’s plant in Commerce, Ga.
Similar tubes were first used in The Netherlands in the 1960s.
The entire levee is expected to be completed by Aug. 31. It will be 14 feet high with the 6-foot-diameter tube resting on a 5-foot sand base and a 3-foot sand cap.
Galveston, Texas, has been protected for years by a geotube levee. The 20-foot surge from the Gulf that hit there during Hurricane Ike did some damage to the levee, but much of it remained in place.