The Army's ship-to-shore Modular Causeway System -- which consists of a roll-on, roll-off discharge facility, or RRDF, and floating causeway -- is used when port facilities are not available. The RRDF enables ships to offload vehicles and equipment to landing craft offshore. The causeway, a floating pier, enables the landing craft to discharge those vehicles and equipment ashore when the gradient is too shallow to allow them to land directly on the beach.
The causeway is essentially a floating pier that stretches outward from a beach, Masengale explained, allowing ships that can't actually get to the beach itself to load or unload vehicles and cargo offshore. At the causeway's seaward end is a wide area onto which vehicles and equipment can be unloaded and then driven directly to shore. The causeway is especially valuable if existing port facilities are unusable because of damage or enemy action.
The basic causeway pieces are a 40-foot-long by 8-foot-wide by 4-foot-deep rectangular center section and two 20-foot-long by 8-foot-wide by 4-foot-deep end sections. When joined, the three sections form an 80-foot-long unit. Three completed units, joined along their long sides, form an 80-foot-by-24-foot segment called a "section." Multiple sections are then joined together to form the causeway, which can extend up to 1,500 feet offshore.
The 331st Transportation Company is the only floating causeway company in the Army. This unit provides the ability to set up a temporary beach site floating causeway pier, a rapid discharge sealift interface between RO/RO ships and literage and direct ship-to-shore movement of cargo using causeway ferries. A key element in the causeway assembly process is the side-loadable warping tug, or SLWT, the craft used to move the causeway sections and tend the completed structure. Though the barge-like SLWT is ungainly looking -- it's 85 feet long, rectangular, low to the water and has a small pilothouse set off to one side -- it's actually well suited to the job. The swiveling heads on its two water-jet propulsion units make it more maneuverable than it looks, and in favorable seas a good coxswain can move the floating causeway sections around with relative ease.
The Improved Navy Lighterage System [INLS] program was the result of the Joint (Army and Navy) Modular Lighterage System (JMLS) Advanced Concept Technology Demonstration program that took place from 1997 through 2000. NAVFAC investigated improvements to the JMLS, and starting in September 2002, proceeded under the INLS name. The INLS consists of four platforms: roll-on roll-off discharge facility, causeway ferry, floating causeway, and warping tug. Each platform comprises a group of interoperable and interchangeable floating modules. The INLS side connector is used to connect modules to create the two subsystems: roll-on roll-off discharge facility and floating causeway. The floating causeway supports the discharge ramp from the cargo ship and transfers rolling stock across undeveloped shoreline.
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