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C- 2010 -089 PAR Part 1 <br />New Horizon North Mine <br />23 -Dec -2010 <br />Page 16 of 21 <br />embankment can be used. However, Rule 4.05.9(7)(d) requires that there be at least one foot <br />difference in elevation between the 25 year -24 hour precipitation event water level flowing <br />through the emergency spillway and the top of the embankment. For the sake of clarity, <br />please revise this statement on the fourth page to reflect the rule requirement. <br />12. On the fourth page of Appendix 2.05.3(3) -1, it is recommended that modifications to <br />sediment ponds NHN -001 and NHN -002 be used in order to avoid. short circuiting. Please <br />revise the text to describe which modifications will be used, especially for pond NHN -002. <br />Also for pond NHN -002, please explain per Rule 4.05.6(7) why the spillway pipe could not <br />be located more towards the middle of the pond since it is now positioned very close to the <br />outlet of ditch NHN -002 North. <br />13. Figures 1 -4 of Appendix 2.05.3(3) -1 show that the sediment pond primary discharge pipes <br />will extend beyond the permit boundary. Please revise these figures to show that the <br />discharge pipes will not extend past the permit boundary. <br />14. The submitted pond designs are based only on the 10 year -24 hour precipitation event. <br />Please provide pond designs that also use the 25 year -24 hour precipitation event to show <br />compliance with Rule 4.05.9(7)(d) regarding the minimum elevation difference of one foot <br />between the design event water level flowing through the emergency spillway and the top of <br />the embankment. <br />15. Please confirm that the three riser pipe diameters are different than the barrel diameters for <br />each of the three sediment ponds. <br />16. Please revise the permit text and pond drawings to show that anti- piping barriers will be <br />used on the primary discharge pipes that go through the pond embankment, as required <br />under Rule 4.05.9(2). <br />17. The Sedcad designs contain two runs for the "Collection Ditch Design for Pond NHN -002 <br />South ". The first design run appears to have used parameters from the previous run for <br />"Collection Ditch Design for Pond NHN -002 North ". Please eliminate the incorrect Sedcad <br />design run for NHN -002 South. <br />18. On Map 2.05.3(3) -1, Surface Water Hydrology, the acreage for subwatershed SW -MD is <br />shown as being 103.02 acres. This- watershed is appropriate for the design of culvert C -6 but <br />the design of culvert C -6A should also take into account the subwatershed of Meehan Draw <br />and the undisturbed wetland. Please revise the Sedcad design for culvert C -6A accordingly. <br />19. As was done for the curve number of 91 on the second page of the Pond Design Memo in <br />Appendix 2.05.3(3) -1, please justify the use of the curve number of 79 for the subwatersheds <br />for culverts C -6 and C -6A. <br />20. Please designate the extent of the riprapped section of ditch NHN -002 South Riprap on Map <br />2.05.3(3) -1. <br />21. Please explain how all of the runoff from a subwatershed, such as SW3 -A, can get to the exit <br />culvert of the subwatershed, such as culvert C -7, without downgradient cross ditches that <br />would bring the runoff to the culvert. <br />22. Please explain how the upgradient runoff will be diverted around the disturbed area <br />perimeter collection ditches. <br />23. On page 22 of Section 2.04.7, it is stated that sediment pond NHN -001 is designed to <br />receive pumped pit water and backfill seepage water. Please point out where pumped pit <br />