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• areas A> B and D shown on Exhibit H-1. Runoff from Area B will be collected <br />in diversion B+C and conveyed to Ditch A through the existing drain pipe. <br />Ditch A will collect runoff from Area A, Ditch B and the underdrains in the <br />restabilized mine bench. Due to the haul road being reclaimed runoff from <br />Area D will flow down to Ditch D. Exhibit G has been revised to show the No. 5 <br />Pond location and size. Areas at different elevations were used to calculate <br />the volumes for sediment and water storage as well as 60% sediment level. <br />The primary and emergency spillway design calculations are given on pages C-7 <br />and 8 of Appendix C. Discharge point 001 of NPDES Permit #CO-0033553 will <br />be transferred to this pond once completed. <br />The No. 5 Pond will be excavated below grade. Material excavated <br />will be used to finish the cover on the mine bench stabilization project and <br />to back fill Pond No. 1. The sides of the pond will have 3h:ly slopes. the <br />crest of the embankment between the pond and the creek will be 15' minimum. <br />Being an incised pond no allowance will be made for settlement. A trench will <br />be dug across the embankment to install the 6" class 200 PVC primary spillway. <br />• A concrete water cutoff collar will be poured around the pipe near the center <br />of the embankment. Material excavated from the trench will be compacted as <br />it is being replaced. The emergency spillway will be excavated as a trench <br />across the embankment with pit run gravel placed in the trench as riprap. <br />A 6" valve will be installed on the creek side of the primary spillway to manually <br />control discharge. <br />During reclamation of the haul road the existing diversion will be <br />eliminated. It is impractical to install a new diversion. The reclaimed area <br />of this haul road is small enough that a small drainage area exemption would <br />be a possibility. To a}low partial sediment control for the reclamation road, <br />the runoff from Areas E and F will be collected in Pond No. 3. The pond size <br />will not be altered but the emergency spillway will be reconstructed to handle <br />a 25 year storm event. Calculations for the collection ditches and emergency <br />spillway are shown on pages C-8, 9 and 10 in Appendix C. <br />C~ <br />106ii (Rev. 6-11-86) <br />