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• a drainage area of 247.54 acres, the amount of sediment estimated to <br />accumulate in the sediment pond each year is: <br />21 tons/acre/year x 247.54 acres x O.EC = 3,119 tons/year <br />Assuming a density of sediment of 80 pounds per cubic foot, the volume is <br />77,975 cubic feet per year or 1.8 acre-feet per year. <br />A total of 5.04 ac-ft. of storage is provided for sediment storage in Pond <br />008. This will provide for approximately three years of sediment storage. <br />Peabody will restore adequate sediment storage to the pond when the <br />available sediment storage becomes 2.0 ac-ft. or less (40 percent <br />remaining sediment storage). Periodic sediment Surveys will be conducted <br />to determine available storage. <br /> <br />Particle Size Distribution <br />The particle size percent finer distribution of the soils in the Pond 008 <br />• watershed was determined based on representative soil samples taken in the <br />area . <br />TABLE 7-6e-6 <br />Particle Size Distribution <br />Particle Size (mm) Percent Finer <br />12.700 100 <br />11.200 97 <br />2.000 91 <br />1.000 87 <br />0.500 84 <br />0.250 82 <br />0.106 79 <br />0.045 56 <br />0.020 40 <br />0.010 31 <br />0.005 24 <br />0.002 17 <br />0.001 14 <br />• <br />0.0001 0 <br />The specific gravity and submerged bulk specific gravity were estimated to <br />be 2.5 and 1.25, respectively. <br />7-6e-9 <br />