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soil and revegetation study coordinated by Dr. W. Berg, from the physical <br />and chemical properties of three cores, and from the mining plan. The <br />computations were made specifically for the Pit A area of the mining plan <br />but the estimates apply equally well to Pits B and C within the confidence <br />interval of the computations. <br />The quantities of sediment estimated in Table 1 will not be trans- <br />ported to the pit in their entirety because of deposition. This is par- <br />ticularly true for those that accumulate in the active pit because only <br />a portion of the runoff entering the pit will be pumped to the settlement <br />basin. The sediment delivery ratios used in sizing the ponds are dis- <br />cussed subsequently in this report. <br />COt4PUTATION OF RUNOFF HYDROGRAPH <br />The design of diversion channels and sediment ponds requires know- <br />ledge of the quantity and time distribution of runoff. In the absence <br />of runoff data, the hydrograph was synthesized using the USDA-SCS method. <br />Direct runoff to the sediment pond from the Pit A area will be contributed <br />from sub-areas A and B as described in the above section. Runoff pumped <br />from the active pit to the settlement basin can be controlled relative to <br />both timing and rates and was not considered in the runoff computation, <br />therefore. <br />The runoff hydrograph was synthesized by considering areas A and B. <br />An SCS curve number of CN = 10 was assigned to Area A. This value accounts <br /> for the haul roads that occupy a portion of the area and the fact that <br /> the remaining portion will not constitute a "good" hydrologic condition. <br /> Area B is the temporarily reclaimed outflow area and this was assigned <br />• <br /> a curve number of 49. The composite curve number, applicable to the sum <br />~1 <br /> of areas A and B is Cn = 61. <br />