Ship Island is a barrier island located 12 miles off the US Gulf coast near Gulfport, Miss. It is approximately seven miles long, 1/8-mile wide and predominately barren of grass and foliage. It also offers the only deep-water harbor between Mobile Bay and the Mississippi River. During Hurricane Camille in 1969 the island was severed, effectively forming two separate islands – East Ship Island and West Ship Island. No perrmanent inhabitants reside on the islands and the only permanent structure is historic Ft. Massachusetts, built in 1861.
As part of a $300 million project to make Ship Island whole again, the U.S. Army Corps of Engineers began dredging sand from the sea floor and placing it on the north shore beach of West Ship Island in August 2011. Since the dredging activity would create significant turbidity that could damage prized sea grass beds, the Corps identified a need for a turbidity barrier with a high UV resistance and a vertical curtain having a small aperture size to sufficiently contain suspended sediment, yet allow water to pass through. A continuous and secure anchorage system to the seabed, in addition to high upper buoyancy, was necessary due to frequent tropical storms, including possible hurricanes. Accurate and sustainable placement was paramount whereby the vegetation it was intended to protect was not damaged.
The stringent Corps requirements necessitated a radical change in design from past turbidity barriers. Buoyancy tubes were previously available in only a few common diameters. Water depth, current velocity, tidal range and weather conditions necessitated infinite buoyancies to suit site-specific conditions. To solve this problem, a buoyancy tube sleeve was fabricated in the desired diameter from heavy woven geotextile fabric with an ultra-high UV resistance and then filled with spray injected foam. Once the foam expanded, it embedded into the fabric weave, creating an extremely strong buoyancy unit. A continuous and secure anchorage system was also required to prevent displacement of the barrier which could damage the sea grass. Previously used chain ballasts and cables attached to anchors in the sea floor would not provide an adequate bottom seal, thus allowing suspended sediment to escape underneath. This method of anchorage required expensive components, as well as extensive time to install. To address this concern, an anchor tube sleeve constructed also of heavy woven geotextile fabric was attached to the bottom of the filtration curtain. Once the barrier was positioned in the desired location, the tube was then filled with sand hydraulically with a small pump creating an extremely secure anchorage system. As with the upper buoyancy tube, infinite anchor tube diameters were possible to provide the necessary ballast to suit site-specific conditions.
A total of 5,500 linear feet of TITANBoom® was installed, and though it was intended to perform for only five months per the contract requirements, it functioned as specified for the 12-month project duration. During this time, the turbidity barrier withstood the impact of a Category I hurricane, as well as several tropical storms. Since there was no displacement of the barrier during the term of the contract, no damage to the sea grass beds occurred. This is also the only known instance where a turbidity barrier withstood a hurricane with no noticeable damage or displacement. Once the barrier system was removed and brought ashore upon contract completion, the empty anchor tube was removed from the barrier and disposed of. The turbidity barrier could then be shipped to the manufacturer for installation of a new anchor tube, permitting it to be reused on a future project. Product cost, as well as both installation and removal time, was significantly less than previously used turbidity barriers. Additional savings were realized since no maintenance was required during the lifespan of the turbidity barrier. Due to the superior performance of TITANBoom®, it has set a new industry standard for turbidity barriers used in severe marine environments, resulting in a new Class IV category.
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