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e <br />_.~ hours. Also, for n triangular outflow hydrograph, the relationship <br />between volume of runoff, detention time, volume of outflow and rate of <br />outflow permits the computation of an outflow rate that will yield a <br />desired detention time. Tlie peak outflow rate from the sediment pond <br />for a detention time of 24 hours was found to be 0.01 in/hr and the <br />required detention storage is 0.33 in. All of these runoff depths are <br />converted to volumes by multiplying by the area of the contributing <br />watershed. (Pond 1 34.52 Ac, Pond 3 38.43 Ac, Pond 4 30.61 Ac). <br />SUPiMARY OF REQUIRED SEDIMENT POND CHARACTERISTICS <br />The sediment that will have to be handled by the sediment pond comes <br />from areas A and.8 via direct runoff and from the pit by pumping. It is <br />assumed that the sediment delivery ratio from areas A and B is unity <br />and for the active pit is 0.5. These are values that cause the sediment <br />estimated to enter the ponds to be conservatively large. Further, it is <br />assumed that pi[ water and sediment will be pumped to the settlement basin <br />after direct runoff has been detained for the required time. Thus, [he <br />inflow to the sediment pond from the active pit was no[ considered in <br />detention time computations. Finally, it was assumed that the bulk <br />specific gravity of the sediment is 1.5, which permits conversion of the <br />sediment weights to volumes. In the event of a 25-year or larger preci- <br />pitation event excess pit water accumulation may have to be pumped into <br />the sedimentation ponds as well as into the settling basin. This will be <br />done only after sufficient sediment settling time has elapsed. The storage <br />requ!rements are summarized below: <br />SEDIMENT STORAGE POND 1 <br />. A) From direct funoff (297 tons) 0.15 Ac-Ft. <br />~. B) From pit (delivery ratio 0.5, 6900 tons) 3.38 Ac-Ft. <br />Detention Storage <br />A) From direct runoff (on 41.95 Ac) 1.15 Ac-Ft. <br />