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tc = [11.9(L 3]0.385 <br />• H <br />where: <br />L = hydraulic length = 0.186 miles <br />H = watershed height = 95 ft. <br />tc = 0.064 hr. <br />SEDIMENTOLOGY <br />The SEDIMOT II computer program was also utilized to calculate the <br />sedimentology of each watershed using the modified universal soil loss <br />equation (MUSLE). Usinq a density of 87 lbs/cubic foot, 65.46 tons or <br />0.035 ac-ft. of sediment will be deposited in this pond as the result of <br />a 10-year, 24-hour storm. A total of 0.11 ac-ft. or 3.i MUSLE IO-year, <br />24-hour storm event equivalent storage is provided for sediment yield. <br />Peabody will restore adequate sediment storage to the pond when the <br />available sediment storage becomes 0.035 ac-f t. or less. <br />• <br />Particle Size Distributions <br />The particle size distribution for this sediment pond was taken from <br />Simons, Li and Associates (Design of Sediment Control Measures for Small <br />Areas in Surface Coal Mining). This distribution is representative of a <br />sandy loam soil similar to those described in Tab 9 of the current Nucla <br />Mine Plan. The inputted soil particle distribution is as follows: <br />Particle Size Percent Finer <br />2.0000 100.0 <br />1.0000 100.0 <br />0.1000 85.0 <br />0.0500 80.0 <br />0.0020 20.0 <br />0.0001 0.0 <br />The specific gravity of the soil and the submerged bulk specific gravity <br />. were estimated based on the reference cited above and are 2.5 and 1.25, <br />respectively. <br />7 <br />