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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />II <br /> <br />Advantages: <br />. Fabrication methods are simple and economical. <br />. Initial cost is usually less than for gate structures. <br />. Reliability is higher than that of sand bags/fill placement. <br /> <br />Disadvantages: <br />. Special lifting equipment may be required for installation. <br />. Advanced flood warning is needed to effectively mobilize personnel/equipment for <br />installation. <br />. Installation time is increased if post sockets need to be cleaned prior to installation. <br />. A storage building is required for the stoplogs, posts, and accessories. <br />. Initial cost is greater than cost for sand bags/fill placement. <br /> <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />Another common type of closure structure that could be used for this project is a gate <br />structure. There are several types of gates such as swing gates, miter gates, rolling <br />gates, and trolley gates. The Rock Island Corps suggested that a swing gate would be <br />an appropriate closure structure for the Boone Street crossing. Swing gates are <br />composed of two or more horizontal girders, vertical intercostaIs, vertical end <br />diaphragms, a skin plate, and diagonal braces. Swing gates are supported on one side <br />by top and bottom hinges attached to a support structure. Swing gate closures consist <br />of a single swing leaf gate for narrow to moderate levee openings, or double leaf gates <br />for wide openings. The double leaf gates require a removable center post or diagonal <br />tie-back linkages. Rubber seals are attached to gates to form a continuous water-tight <br />seal between the gates and supporting walls and sill of the opening. Oosure provisions <br />should include the use of winches or motor vehicles to accomplish closure during <br />strong winds. A typical detail for a swing gate closure structure is shown on plate 3. <br />Advantages and disadvantages of swing gate closure structures are given below. <br /> <br />Advantages: <br />. Skilled personnel and special equipment are not required for operation of a single <br />leaf gate. <br />. Short lead time is sufficient for making closure of a single Ieaf gate. <br />. Storage building is not required. <br />. Reliability is higher than for sand bags/fill placement. <br /> <br />16 <br />