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USDA Handbook No. 282 formula, then adjusts each segment with a factor, and finally provides <br />a weighted average for the compound slope. <br />The above described method was applied to a 65 foot upper segment at repose angle (77%) <br />followed by an 85 foot flat bench at 1%, resulting in a weighted average LS of 9.0. Several <br />possible combinations of a single L and a single S were then examined for input into SEDCAD <br />to arrive at a similar LS factor. It was found that a single line with L of 145 feet with a drop of <br />45 feet, producing a S of 31% produces a LS of 10. 1, which is slightly higher than the calculated <br />value of 9.0 for the actual compound slope. That line also happens to be close to a simple <br />straight line from the crest of one bench to the crest of the next one lower down the face, so it has <br />some physical relevance to the actual spoil pile face. The L and S of 145 feet and 31%, <br />producing a LS factor about 12% greater than the actual compound concave slope calculated <br />were then conservatively used in the modeling of all spoil pile faces. <br />Embankments for sediment ponds all have 3H:1 V downstream slopes 15 foot crest widths and <br />other dimensions as shown on the individual design drawings, with slotted riser service spillways <br />and open channel emergency spillways. Individual design drawings are provided for each pond <br />as discussed below. <br />One sediment pond in the West Side System, designated as the Sidehill Pond, is formed mainly <br />as an incised pond with 2.5H:1 V cut slopes and a small earthen embankment on 3 sides. <br />The elevation of the lowest hole in the slotted risers, which sets the permanent pool before storm <br />inflow, has been set to provide the maximum sediment storage in all ponds. Details regarding <br />pond dimensions, normal pool, inflow volumes, sediment storage levels and effluent quality are <br />presented on Exh. 7-23C, Table 1 below. <br />The West side system consists of two sediment ponds and the associated collector ditches. The <br />upper pond, designated as the Sidehill Pond, is formed primarily as an incised pond with a low <br />surrounding earthen berm, while the lower pond, designated as the Section 26 Pond, is formed by <br />an embankment. The West Side ponds are depicted on Exh. 7-23, Figures C5 and C6 below. <br />The East side system consists of three sediment ponds in series and associated collector ditches. <br />The uppermost structure is the Section 36 Pond, which is contributory to the Middle Pond, which <br />in turn flows northward to the lowermost Section 25 Pond. All of the East side ponds are formed <br />by an earthfill embankments. The East Side ponds are depicted on Exh. 7-23, Figures C7 , C8, <br />and C9 below. <br />Runoff from the temporary spoil pile is generally collected by a series of collector ditches as <br />described in Part B of this submittal. The series of collector ditches which route runoff from the <br />spoil pile to the ponds is shown on Exh. 7-23, Figures B 1 and B2. <br />The design storm for the sediment control evaluation is the 10 year, 24 hour storm. All ponds <br />route the 10 year, 24 hour storm without engaging the emergency spillway, and the lowermost <br />ponds in each system release water at settleable solids concentrations less than 0.5 mg/1, as <br />described in the SEDCAD output results. The ponds were then all checked to ensure the <br />Exh. 7-23C-2 Revision Date: 11/09/15 <br />Revision No.: PR -04 <br />