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SEDIMENT POND NO. 002 <br />The design of Sediment Pond No. 002 (Wadge Impoundment) was evaluated to <br />provide the information on storage capacity, detention time and the <br />efficiency of Pond 002 to satisfy the sedimention pond regulation <br />(4.05.06). Exhibits 7 -8 and 7 -9 were modified to supply the information <br />needed for the review of the storage capacity and outflow <br />characteristics of the principal spillway. <br />The drainage area of Pond 002 is 2098.92 acres, see Exhibit "7 -7 ", <br />Surface Hydrology Map, Drainage Area II. For design reasons, 859.93 <br />acres is considered to be undisturbed ground and 1239.09 acres is <br />considered to have been disturbed and reclaimed during the life of Pond <br />002. The curve numbers and "k" factors for the individual soil types <br />were taken from Tables 7 -6 -1 and 7 -6 -2 respectively. The weighted <br />curve number for the.watershed was determined to be 67 and the weighted <br />"k" factor was calculated as 0.25 (see Tables 1 and 2). <br />The time concentration, tc, is defined as the time required for water to <br />flow from the hydraulically most remote point in the watershed to the <br />watershed outlet (pond). The runoff time of concentration was <br />calculated using the following formula (Barfield et al, 1981). <br />tc = <br />L O .8 (S + 1) 0.7 <br />1140 YO.5 <br />where L = <br />hydraulic length of watershed = 13300 ft. <br />Y = <br />average watershed slope = 31.5% <br />S = <br />maximum retention <br />s = <br />1000 - 10 = 1000 - 10 = 4.93 <br />TN 67 <br />then tc = <br />(13300) 0.8 (4.93 + 1) = 1.08 hr. <br />1140 (31.5) <br />The unit hydrograph type that was selected to be used in the SEDIMOT II <br />model was for a disturbed drainage condition since over half of the <br />watershed was disturbed. <br />Next, a particle size- percent finer distribution of the soil type in the <br />Pond 002 watershed was determined. This was done from a soil sample <br />7 -6a -2 Revised 8/27/86 <br />