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In some instances, the mining will cause the drainage area to change <br /> during the life of the sediment structure. When the pit moves into the <br /> watershed, runoff is intercepted by the pit and diverted away from the <br /> structure. In these cases, a conservative procedure was used; the <br /> structure was analyzed for the largest anticipated drainage area that <br /> will contribute runoff to the structure. This condition usually occurs <br /> at the start of mining and again during the reclamation period. <br /> Following is a summary of the SEDIMOT II input values used in the Design <br /> Report and the As-Built Report (see the Design Report for the derivation <br /> of the input values): <br /> 10-Year, 24-Hour = 1.60 inches <br /> 25-Year, 24-Hour = 1.80 inches <br /> 100-Year, 24-Hour = 2.40 inches <br /> SCS Type II Storm <br /> CN = 83 <br /> k = 0.24 <br /> Disturbed Hydrograph (No. 1) <br /> tc = 0.194 hr. <br /> (1) MUSLE = 0.138 ac-ft. or 260.77 tons <br /> Specific Gravity = 2.5 <br /> Submerged Bulk S.G. = 1.25 <br /> LS = 2.62 <br /> CP = 1.00 <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. <br /> The inputted soil particle distribution is as follows: <br /> 3 <br />