Geotextile tubes help stem beach erosion
Early this year, in Sea Isle City, N.J., severe beach erosion caused by strong coastal storms consumed a wide path of dunes with heavy vegetation and damaged the beach. City officials were particularly concerned about an 18-unit condominium complex that was situated only about 50 feet behind the dunes.
The city decided to use high-strength polyester Geotex tubes made by Synthetic Industries, Chattanooga, Tenn., to erect an “artificial dune” to protect the condos. Workers constructed a temporary road to the beach and began hauling in equipment for its construction. A crane lifted rocks and debris from the site so that the tubes could be placed on the beach without being punctured.
With the help of front end loaders, back hoes, dump trucks and hydraulic equipment, a six-man crew filled up the tubes with trucked-in sand. About 300 feet of the tubes, each 30 feet in circumference, were filled. The ultraviolet-resistant tubes are designed to resist pressures, abrasion, tearing and puncturing during filling and placement.
The process began with the digging of a trapezoidal trench 1 foot below grade, onto which a “scour apron” was placed. The apron served to reduce local erosion caused by the flow of water during the filling process. Three tubes then were set onto the apron, and a sand-and-water slurry was trucked and pumped into the tubes.
Each tube was pumped full, with tube heights reaching 5.5 to 6 feet and widths of 12 to 13 feet. The water percolated out through the fabric, leaving dense, sand-filled structures.
The 900 feet of tubing contained nearly 1,900 cubic yards of sand when full. After the tubes were completely filled, they were covered with an additional 1 to 2 feet of sand, creating an 8-foot high dune along the beach.
Within three weeks, the tubing had been successfully placed at a cost of $163,398 – much less than traditional rock or concrete measures would have cost. Valuable shoreline was restored, and the condominium complex was protected.