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FINDINGS OF THE COLORADO MINED LAND RECLPMATION DIVISION FOR THE TRAPPER MINE I. Legal, Financial and Compliance Information (Rules 2.03, 2.07.6 2.07.6(9) and 2.07.6(h The only modifications to this section is to change the previously approved 10,355 acres of the permit area to 10,451 acres in this revision. V. ~drologic Balance: Surface Water (Rules 2.04.5, 2.04.1, 2.05.3(4 2~5: €f3 al nd~715 The Division has reviewed Sections 2.7, 4.8 and Appendices P and Q of the permit and permit revision applications for compliance. The sediment control system at the Trapper Mine includes a series of diversions, sediment ponds, and one inactive pit to control sediment generated at the site. The Soil Conservation Service method was used for estimating peak flows. Routing procedures for pond designs and simple nomographic techniques for culvert sizing have been used. The method used for sediment yield estimation was one proposed by the applicant which assumes that sediment yield is directly proportional to the annual runoff for all disturbed sites. The Division has verified the estimates as generated by this method based on values generated by other methods. Information on this method is contained in Section III of Appendix Q of the original permit application. The operator used an estimate of 2.0 inches of precipitation fora 25-year, 24-hour storm for design purposes. Diversion and Collection Ditches The majority of existing and proposed ditches at the Trapper Mine site divert the runoff from active pits into downstream sediment ponds. Trapper Mining, Inc. has produced estimates of the peak flows to be expected from the 2-year, 24-hour storm and had adequately designed the ditches to convey these flows. Several sections of ditch had slopes which exceeded 1%, increasing the possibility of erosion. In discussions with the Division and based on additional information incorporated into the permit, it was demonstrated that these areas would not experience erosion as designed. Sediment Ponds All ponds have been found to be adequately sized to provide for treatment of both sediment and flood volume resulting from the 10-year, 24-hour storm. All ponds have been professionally certified.