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' SUMP <br />It will be necessary to construct a sump at the end of Stage <br />2 to collect runoff from disturbed areas which cannot be <br />ditched to sedimentation ponds. Designated as Sump D, it is <br />located near Pond B, as shown on Plate 17 Ditch D will <br />intercept runoff along 'tann Draw and direct it into [he sump. <br />This sump mill provide storage for approximately 0.37 acre- <br />feet, which includes 0.11 acre-feet of sediment storage and <br />0.26 acre-feet for the 10-year, 24-hour storm runoff from <br />3.44 acres. Runoff into the sump will be pumped into Pond B <br />before being discharged into ?iann Draw. The sump will be <br />approximately 7~ feet square and 3-feet deep. <br />REQUIRED SEDIME~TATIO~ VULUi`tE5 <br />The C~iLRB provides for two methods to compute required <br />sedimentation volumes. The first is the product of 0.1 acre- <br />feet per acre and the total number of disturbed acres during <br />the mining and reclamation activities. An alternate technique <br />utilizes the Universal Soil Loss Equation, gully erosion <br />rates and sediment delivery ratios. The second method was <br />applied in this analysis. The Universal Soil Loss Equation is <br />used to estimate the gross soil erosion: <br />A = R K L Vm <br />s <br />where: A = average annual soil loss per unit of area, <br />tons per acre <br />R = rainfall factor <br />K = soil erodibility factor <br />1,s = dimensionless length slope factor <br />Vm = erosion control factor <br />M <br /> <br />