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Florida Erosion and Sediment Control Inspector's Manual " <br /> Design Criteria <br /> 4 <br /> Maximum Drainage Area <br /> Unless the structure is designed as a permanent pond by a qualified professional engineer, <br /> the maximum allowable drainage area into the basin shall be 150 acres (61 ha) . <br /> Basin Capacity <br /> The design capacity of the basin must be at least 134 cubic yards or 3600 cubic feet per <br /> acre (252 m3/ha) of drainage area measured from the bottom of the basin to the crest of <br /> the principal spillway (riser pipe) . Sediment should be removed from the basin when the <br /> volume of the basin has been reduced to 55 cubic yards per acre ( 104 M3/ha) of drainage <br /> area . The elevation of the sediment clean out level should be calculated and clearly ` <br /> marked on the riser. In no case shall the sediment clean out level be higher than one foot <br /> (30 cm) below the top of the riser. (See Plate 4 .26a) . <br /> Basin Shape <br /> To improve sediment trapping efficiency of the basin , the effective flow length must be <br /> twice the effective flow width . This basin shape may be attained by properly selecting the <br /> site of the basin , by excavation , or by the use of baffles . See Appendix 1 . 26A for design <br /> details. <br /> r <br /> r <br /> 67 C.Y./ AC." DRY "STORAGE <br /> r <br /> DEWATERING <br /> DEVICE <br /> 67 C.Y./ AC. .:..... .......... ::_ ...... ::....: <br /> " WEr " STORAGE <br /> SEDIMENT CLEANOUT POINT « <br /> ( ' WET " STORAGE REDUCED <br /> TO 34 C.Y./ ACRE) <br /> r <br /> a <br /> Plate 4.26a Sediment Basin Storage Volumes <br /> Source: Virginia DSWC <br /> 4-80 <br /> r <br />