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Structures P-1, P-2, P-3, P-4, P-5, P-6, P-7, P-8, P-9 are designed <br />as below-grade dug-out type pools and have no embankments greater <br />than ten feet associated with them. These structures were designed <br />to not qualify as impoundments. Because these structures are <br />below-grade, no settling is expected. Runoff from undisturbed <br />areas is diverted through the mine area with a bermed ditch, shown <br />on Drawings D-4-8 and D-4-6. Cross-sections of the dewatering <br />device used in these ponds to achieve the required detention time <br />are shown on Drawings D-4-5 and D-4-6. Each pond is equipped with <br />an emergency spillway, as shown on the drawings, sized to pass the <br />25-year, 24-hour storm. <br />The refuse disposal pond, shown on Drawings D-4-9 and D-4-10 is <br />located at the toe of the refuse disposal site. Drawings D-4-9 and <br />D-4-10 shows the cross-section of the pond, design details, and <br />construction elevations. Calculations, short circuiting analysis <br />and computer print outs used to design the pond are included in <br />Appendix 4-B. All ponds will be inspected quarterly and these <br />• reports forwarded to the division upon completion. The stability <br />analysis of the dam is discussed in the geotechnical investigation <br />by Chen and Associates, Appendix 4-C. <br />According to Mine Subsidence Engineering Company's Subsidence <br />Report, none of the sediment ponds is constructed above undermined <br />areas. <br />~~ <br />4-18 <br />10-02-92 <br />~~ <br />