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Sediment Control Structures <br />• Beyond the specified land management practices, several silt <br />fence type of fabric berm breaks would be constructed as the <br />primary structural treatment to augment an existing silt fence. <br />Sediment storage was very conservatively modeled since the <br />algorithms do not account for storage along the earthen berm <br />segments of the structure. Due to the topographic variability <br />all runoff cannot reasonably be directed to the existing <br />structure. Therefore, filter fabric berm breaks will be <br />constructed in isolated areas requiring individual treatment in a <br />manner commensurate to the predicted flow. <br />Description/construction of structures <br />A minimum of 40 linear feet of filter fabric will be used in <br />filter fabric berm breaks and silt fence. This equates to <br />approximately one (1) linear foot per 750 ft'. Field fitting of <br />these structures will occur based on this guideline. <br />Construction of such berm breaks entails entrenching filter <br />fabric along the upstream side of the berm outlet. Small brush <br />or other appropriate porous and supportive material is placed in <br />the outlet behind the fabric. The fabric is then draped over the <br />supporting material and anchored on the downstream side. Berms <br />are constructed along the downstream toe of the watershed area to <br />collect runoff and direct it to the outlet structures and silt <br />fence. <br />The existing silt fence, shown on Map 89, was constructed along <br />• the lower most toe of the drainage area immediately following the <br />emergency sealing of the portals. <br />Structure maintenance <br />At the dimensions specified above, a minimum of 1.1 inches (0.09 <br />feet) of fabric is required above the sediment storage elevation <br />to pass the l0yr-24hr event. Excess sediment will be removed <br />from behind the structures to maintain adequate storage volume. <br />• <br />