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• HYDROLOGY AND SEDIMENTOLOGY CALCULATIONS <br />Hydrology and sedimentation inputs for each drainage structure are summarized <br />on the SEDCAD+ computer printouts found in Exhibit 1, SEDCAD+ Computer <br />Printouts. Watersheds for all drainage structures are shown on the Postmining <br />Drainage and Sediment Control Map (Map R-1). The following is a summary of <br />the hydrology and sedimentation results for each drainage structure. <br />Pond 4 <br />Peak Discharge (cfs) <br />10-year, 24-hour event 26.36 <br />25-year, 24-hour event 37.45 <br />Runoff Volume (ac-ft) <br />2-year, 6-hour event 0.36 <br />10-year, 24-hour event 2.57 <br />25-year, 24-hour event 3.67 <br />Snowmelt 10.01 <br />Storm Sediment Yield (tons) <br />10-year, 24-hour event 156.4 <br />• 3-Year Sediment Volume (ac-ft) 0.35 <br />Ditch 4-1 <br />Peak Discharge (cfs) <br />10-year, 24-hour event 9.43 <br />Ditch 42 <br />Peak Discharge (cfs) <br />10-year, 24-hour event <br />Upper 9.71 <br />Middle 9.71 <br />Lower 14.81 <br />Pond 5/6 <br />Peak Discharge (cfs) <br />10-year, 24-hour event 16.96 <br />25-year, 24-hour event 30.09 <br />Runoff Volume (ac-ft) <br />2-year, 6-hour event 0.22 <br />10-year, 24-hour event 2.01 <br />25-year, 24-hour event 3.12 <br />Snowmelt 10.28 <br />13 <br />