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impoundments. These calculations, presented in Appendix A, Drainage Design Information, <br />• indicate that with minor modifications, regulatory compliance can be achieved for both <br />categories. Upon reestablishment of effective drainage Rockcastle, therefore, proposes to retain <br />Pond 4 as a livestock watering tank. Required Pond 4 modifications will include: <br />• Extension of the existing riser 1.5 feet so that the riser crest is above the 10-year, <br />24hour water level. <br />• Cut two additional discharge orifices in the existing riser, one at the design <br />sediment level and one at the permanent storage elevation. The existing orifice <br />will be permanently plugged and the orifice at the permanent storage level will <br />be temporazily plugged until the end of the reclamation liability period. <br />• Relocating and reconstructing the north inlet (CMLRD designation 4C-3); and <br />• Regrading, reseeding and placing additions[ riprap as necessary on the south inlet <br />(CMLRD designation 4C-1). <br />The modified configuration of Pond 4 and detailed design information aze presented by <br />Appendix A, Drainage Design Information and by the Pond 4 Design Map (Map R-3). The <br />following summarizes considerations for Pond 4 relative to compliance with applicable <br />• permanent impoundment criteria: <br />a) Water Quality: No water quality data for Pond 4 is available since the pond has <br />never discharged. However, water monitoring data and observations of <br />postmining drainage conditions for other pit areas with similar topography, soils, <br />spoil materials, and vegetation which have been reclaimed for approximately 5-10 <br />years provide a reasonable basis for assessing probable postmining drainage <br />considerations for Pond 4. Inflow to the pond would come primazily from spring <br />snowmelt runoff and to a lesser extent, from stormwater runoff from adjacent <br />reclaimed areas. Given the gradient of both reclaimed and undisturbed slopes <br />within the Pit 4 drainage area and the physical chazacteristics of overburden <br />materials, a significant portion of any precipitation received <br /> <br />~~~,..~,~, 3R Revised -May 1992 <br />ov~v~ ~ <br />