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Pond No. 004 - East Ditch <br />In order to contain runoff from the existing reclaimed, a contour ditch <br />is required along the reclaimed area east of Pond No. 004, flowing into <br />Pond No. 004 (see Exhibit 13-4). <br />For the design of the contour ditch, the SEDIMOT II model was used to <br />predict the runoff from the watershed (see Addendum D for the batch <br />input and output, respectively). The 10-year, 24-hour precipitation <br />event was used in the design, which is a conservative approach to a <br />temporary ditch. <br />Following is a list of the main input factors which were derived in the <br />same manner to the factors of Pond No. 004: <br />Input East Ditch <br />Precipitation 1,60" <br />Drainage Area 6.3 ac <br />CN 81 <br />L 0.186 miles <br />H 95 ft. <br />tc 0.064 <br />Output <br />Q (cfs) 2.6 cfs <br />Based on these discharges, the Dodson and Associates, Inc.'s computer <br />software was used to design the ditches based on Manning's equation <br />calculations. <br />Two ditch designs are proposed for the east ditches. Based on the <br />critical slope calculations for the ditch, a ditch section will be <br />constructed with riprap or without riprap, depending on whether the <br />ditch's slope is steeper or flatter than critical slope. Each ditch <br />will have a minimum of one foot of freeboard included in the total <br />depth. This will allow the ditch to be field-located as close as <br />practical to the reclamation area, but still control all runoff and <br />• direct the flow to Pond 004 (See Exhibit 13-4). <br />Following is a summary of "Alternative A" and "Alternative B" ditch <br />design to be used for East Ditch. <br />11 <br />