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• were performed utilizing the SEDCAD+ computer model developed by Civil <br />Software Design, as was Magpie Creek Diversion. <br />SEDCAD+ is a hydrologic and hydraulic calculation model designed for use <br />on IBM compatible personal computers. The SEDCAD+ model calculates runoff <br />and peak flow via a numerical modeling technique based on user inputs of <br />a design storm, i.e., rainfall amount and duration, selection of rainfall <br />distribution, and convolution increment. Hydrographs are developed on a <br />subwatershed basis with the input of area, time of concentration, SCS <br />curve number, and selection of one of three dimensionless double triangle <br />unit hydrograph shapes. Routing of hydrographs is accomplished by <br />Muskingum's method. In a similar manner, SEDCAD+ performs sedimentology <br />calculations on a subwatershed basis, however, sediment yield values <br />required for Sedimentation Pond No. 4 were performed by hand. Sediment <br />yield values are not required for the diversions and ditches. <br />Inputs to the hydrology component of the SEDCAD+ computer model include: <br />• o Precipitation Distribution <br />o Storm Duration <br />o Return Period/Precipitation <br />o Hydrograph Response Shape <br />o Drainage Basin Area <br />o Time of Concentration <br />o Curve Number <br />Input values used for each structure are shown on the SEDCAD+ printouts <br />contained in their respective design calculations section in the following <br />text of this exhibit. <br />Precipitation Distribution <br />A precipitation distribution is input to model the runoff hydrograph. <br />SEDCAD+ allows the user to choose between the SCS Type I and Type II <br />• storms. For the Southfield Mine area the SCS Type II storm was input. <br />5 R Revised - December, 1991 <br />