2009-10-16_PERMIT FILE - M2009082 (13)

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Pond 5C has a surface area of 2 acres and an available storage volume for storm water capture of 11.4 acre-feet above the normal pool. The contributing drainage area to this pond includes Subbasin RB14 for a total drainage area of 65 acres. Comparison of Existing, Mining, and Reclaimed Conditions Mining operations and site reclamation either will not change or will significantly reduce the drainage area and historical runoff leaving the site from each of the nine historical basins. At Design Point DP1 which includes Subbasins H1, RB1, and RB2, the peak flow rate reduces from the historical condition rate of 203.0 cfs to a reclaimed condition rate of 69.5 cfs. The drainage area contributing to flow leaving the site reduces from the historical condition of 194 acres to a reclaimed condition of 134 acres. The Phase 1 mining condition is the same as the historical condition. At Design Point DP2 which includes Subbasins H2, P1-14, R133, and R134, the peak flow rate reduces from the historical condition rate of 87.9 cfs to a reclaimed condition rate of 63.5 cfs. The drainage area contributing to flow leaving the site reduces from the historical condition of 159 acres to a reclaimed condition of 107 acres. The Phase 1 mining condition is the same as the historical condition. At Design Point DP3 which includes Subbasins H3, RB 13, and RB 14, the peak flow rate reduces from the historical condition rate of 283.0 cfs to a reclaimed condition rate of 125.8 cfs. The drainage area contributing to flow leaving the site reduces from the historical condition of 196 acres to a reclaimed condition of 131 acres. The Phase 1 mining condition is the same as the historical condition. At Design Point DP4 which includes Subbasins H4 and R1312, the peak flow rate for both reclaimed and Phase 1 mining conditions remains unchanged from the historical condition rate of 122.1 cfs. The drainage area contributing to flow leaving the site remains unchanged from the historical condition of 97 acres. At Design Point DP5 which includes Subbasins H5, R1315, R1316, and R1317, the peak flow rate reduces from the historical condition rate of 20.2 cfs to a reclaimed condition rate of 11.2 cfs. The drainage area contributing to flow leaving the site reduces from the historical condition of 28 acres to a reclaimed condition of 12 acres. The Phase 1 mining condition is the same as the historical condition. At Design Point DP6 which includes Subbasins H6, R139, RB9, RB 10, and RB 18, the peak flow rate reduces from the historical condition rate of 24.7 cfs to a reclaimed condition rate of 9.7 cfs. The drainage area contributing to flow leaving the site reduces from the historical condition of 57 acres to a reclaimed condition of 30 acres. The Phase 1 mining condition is the same as the historical condition. At Design Point DP7 which includes Subbasins H7 and RB11, the peak flow rate for both reclaimed and Phase 1 mining conditions remains unchanged from the historical condition rate of 11.4 cfs. The drainage area contributing to flow leaving the site remains unchanged from the historical condition of 22 acres. -13- Revised Preliminary Drainage Report.doca