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Small Area Exemptions <br />Topsoil Stockpile: There are three topsoil stockpiles within the permit area. Two of the <br />stockpiles (TS-1 and TS-3) and a portion of the third stockpile (TS-2) do not drain to <br />sedimentation ponds (see Exhibit 12-2, Surface Water Control Plan Map). In order to <br />demonstrate that these piles meet the intention of CDMG Rule 9.05.2(3), SEDCAD+ analyses <br />were conducted. These demonstrations are presented in Appendix 12-2, Small Area Exemption <br />Demonstrations. <br />The status of the stockpiles has not changed since their construction in the late 1970's <br />except for the establishment o£ vegetative cover. A similar demonstration was made by Yampa <br />Mining Company for the topsoil stockpiles at the H-G Mine surface mine (approved CDMG Permit <br />C-60-003). Nany of the parameters used in the H-G Mine demonstrations were borrowed for the <br />Loadout small azea exemption demonstrations based on similar seeding dates, rates, etc. Due <br />to the shallow slopes, existing, well-established vegetation cover, and small drainage areas <br />none of the stockpiles exhibit a soil loss through sediment erosion. Consequently, the <br />topsoil piles have been permitted as small azaa exemptions by CD[+G. <br />The following briefly describes the input and output from the small area exemption SEDCAD+ <br />analyses. <br />Input Suimnary <br />10-yr. 24-hr Precipitation 1.6 in. <br />CN Factor 46 <br />K Factor 0.25 <br />CP Factor 0.075 <br />Output Sun¢nary <br />Runoff Volumes and Sediment <br />Topsoil Pile 1 0.0 <br />Topsoil Pile 2 0.0 <br />Topsoil Pile 3 0.0 <br />Substation; There is an electrical substation located in the northwest corner of the <br />facilities area as shown in Exhibit 12-2, Surface Water Control Plan Map. The substation is <br />enclosed within a 30 by 90 foot area which is graveled and fenced. Also associated with the <br />substation is a small disturbance area outside the chain-link fence. Runoff from the <br />substation area does not drain to the Truck Loop Pond and is controlled using a sediment <br />fence. The location of the sediment fence is shown on Exhibit 12-2, Surface Water Control <br />TR-06 3 Revised OS/OS <br />