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<br />. <br /> <br />( <br /> <br />, <br />~ <br /> <br />SWDP 1150-2-1 <br />26 May 78 <br /> <br />9. RIVER AND CHANNEL CROSSING CRITERIA. <br /> <br />a. Pipeline Crossings Under Rivers and Channels. Bury the pipeline <br />so that: <br /> <br />(1) The minimum cover between the top of pipe and the river or <br />channel bottom should conform to the following criteria: <br /> <br />(a) Three feet if the bottom materials do not erode during flood <br />discharges. <br /> <br />(b) Five feet if the bottom materials are erodible during flood <br />discharges. <br /> <br />(c) Determined case by case when under navigation channels, but <br />generally at least 7 feet below the authorized channel depth to protect <br />the pipe from overdepth maintenance dredging operations, <br /> <br />(2) The pipeline should be maintained at the minimum cover level <br />for the full length between top of bank lines. <br /> <br />(3) The pipeline shall be suffiCiently anchored or encased to <br />prevent floatation. <br /> <br />( <br /> <br />(4) The pipeline shall be kept straight for a minimum of 15 feet <br />beyond the lands ide of the levee toe. <br /> <br />(5) Contour along the pipeline crossing shall be restored to <br />preconstruction elevations. Any material not required for backfill <br />shall be removed and disposed of so as not to affect the hydraulic <br />capacity of prescribed navigation channel dimensions. <br /> <br />b. Pipeline Crossings Over Rivers and Channels. <br /> <br />(1) Non-navigable Waterways - A minimum freeboard will be provided <br />between the low point of the crossing and the design water surface <br />elevation of 3 feet or to the top of any levee, whichever is higher. <br /> <br />(2) Navigable Waterways - A US Coast Guard permit will be required. <br />Clearances over such waterways will be established by the US Coast Guard <br />on a case-by-case basis, <br /> <br />(3) The obstruction caused by the supporting bridge and its piers <br />should not exceed 10 percent of the floodway waterway area. No longitudinal <br />cross-bracing will be used. In all cases, final plans will have to be <br />submitted with appropriate hydraulic computations to identify the effect <br />the proposed work will have on flows and floodway capacity. <br /> <br />6 <br />