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• minus 3 inch coal into a truck for delivery. The plus 3 inch coal is currently <br />sold as lump coal, but as production increases, a crusher may be installed to <br />crush this excess lump down to a minus 3 inch size. This crushed coal would then <br />all be conveyed into trucks. Since the run of mine product is sold, no coal reject <br />is made. Surface disturbance is minimum. Due to recent difficulty in stabilizing <br />the immediate mine roof, Blue Ribbon may be required to bring a small amount of <br />the roof rock to the surface for storage. If this requirement arises, the mine <br />will present this topic at a later date. <br />(4) Ponds, Impoundments and Diversions <br />Sediment control on and around the surface disturbance area consists <br />of diversions, collection ditches and sediment ponds. The majority of unaffected <br />surface drainage is diverted around the disturbed area. The disturbed area drainage <br />is collected into ditches and diverted to sediment ponds prior to discharge into <br />Hubbard Creek. <br />• Appendix C (revised 1/22/82) contains calculations performed by Ute <br />Engineering for runoff from the disturbed and undisturbed areas. The calculations <br />are based upon sub areas as shown on Exhibit H. Other assumptions include a 10 <br />year 24 hour storm event of 1.7", CN's of 77 for undisturbed areas and 89 for <br />disturbed areas. The ditch and culvert sizes to handle the runoff are calculated <br />in Appendix C and shown on Exhibits G, G' and H. The ditches and culverts to <br />convey runoff from areas 2, 5 and 7 were recalculated for the mine bench stabilization <br />project in 1984-1985., For detail, see "Sediment Control Comments and Calculations" <br />Map B and Appendix 1-B of the Blue Ribbon Technical Revision Request for Mine Bench <br />Stabilization. <br />The Hubbard Creek crossing culvert was installed in 1980 and no calculation <br />for sizing is available. Calculations are shown on pages P-1 through P-8 in Appendix <br />C for Hubbard Creek. <br />These calculations indicate that the Hubbard Creek Culvert will pass <br />the 10 year 24 hour storm event of 838 cfs but not the 20 year 24 hour event of <br />• <br />105 (Rev. 8/30/8 0 <br />