2012-06-08_PERMIT FILE - C2009087A (12)

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Peabody Sage Creek Mine — Drainage and Sediment Control Plan Consequently, the designs and as -built plans for these structures presented herewith were adapted from the Seneca II Mine permit — accompanying text in their respective reports was changed to reflect their inclusion in the Peabody Sage Creek permit. Ponds 003 and 004 have been approved as permanent, postmine structures by CDRMS. The existing configurations for Pond 002 and PECOCO were re- evaluated for the Peabody Sage Creek Mine to assure they had sufficient storage capacity to meet the applicable rules and regulations. Design evaluations for these two ponds are presented in this exhibit. Designs for Pond 002, PECOCO and the facility area sumps and portal area sumps are summarized below. Pond design/as -built plan hydrology /sedimentology demonstrations and pond and embankment configurations can be found in the PAP as outlined in Table 2.05.3 - E2-4, Index of Pond Design /As -Built Demonstrations and Drawings. All embankments will be less than 10 feet high (from the upstream toe of original ground to emergency spillway invert elevation). Combined upstream and downstream side slopes of the embankments are designed to be greater than 5H:1 V, with neither slope steeper than 2H: l V. Embankment top widths are generally 15 feet; all crests and outslopes will be vegetated with the approved temporary seed mix. Pond 002 is completely incised — there is no embankment; it was constructed by leaving a portion of the Wadge Pit highwall and letting the pit fill with water. PECOCO Pond was constructed by leaving a portion of the West Lennox Pit highwall open and letting it fill with water; however, there is a low embankment of approximately five feet along the northwest margin of this impoundment. TABLE 2.05.3 -E2 -4 Index of Pond Design /As -Built Demonstrations and Drawings Pond /Sump Hydrology /Sedimentology Pond and Embankment Demonstration Configuration Pond 002 Appendix 2.05.3 -E2.A Map 2.05.3 -E2.A Sediment Pond 002 As -Built (2 sheets) Pond 003 Appendix 2.05.3 -E2.B Map 2.05.3 -E2.B Sediment Pond 003 As -Built Pond 004 Appendix 2.05.3 -E2.0 Map 2.05.3 -E2.0 Sediment Pond 004 As -Built PECOCO Pond Appendix 2.05.3 -E2.D Map 2.05.3 -E2.D PECOCO Pond Spillway Re- design Upper Facilities Sump Appendix 2.05.3 -E2.E1 Map 2.05.3 -E2.El Upper Facilities Sump Lower Facilities Sump Appendix 2.05.3 -E2.E2 Map 2.05.3 -E2.E2 Lower Facilities Sump Portal Area Sumps Appendix 2.05.3 -E2.F Map 2.05.3 -E2.F Portal Area Sumps The principal spillway s for the upper and Lower Facilities Sumps are designed to safely pass the peak runoff from the 10 -year, 24 -hour storm event. There will be no discharge through the emergency spillway. The emergency spillways were designed to safely pass the 25 -year, 24 -hour storm event while maintaining a minimum of one (1) foot of freeboard. The emergency spillways are a trapezoidal open - channel and, with the exception of Pond 002, have 3H:1 V side slopes. The combination spillway for Pond 002 is constructed in TRO1 -10 2.05.3 -E2.10 12/10