2011-11-28_PERMIT FILE - C1992081A (10)

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pipeline corridor from the well to the rail spur corridor in the El /2 of Section 10 and, 1.03 acres for the pipeline corridor that extends southward from Routt County Road 37 to the rail loop corridor in the E1 /2 of Section 15. Due to the shallow slopes, existing and well established vegetative cover, and small drainage area the disturbance areas associated with the water - supply well and water pipeline do not experience significant soil loss through erosion. To satisfy the intention of Rule 4.05.2(3), SEDCAD4 evaluations were completed to demonstrate that the revegetated areas do not generate peak settleable solid concentrations in excess of the water quality effluent standard of 0.5 ml /1. The SEDCAD4 evaluations are presented in Appendix 12 -2, Small Area Exemption Demonstrations. Given the limited footprint of disturbance, the stabilized soil and excellent vegetative cover that exists after 25 years, as well as peak settleable solid concentrations less than the applicable standard, the HG Shallow Well No. 1 and associated pipeline corridor can be permitted as small area exemptions. Diversion Ditches A number of runoff collection ditches were constructed inside the facilities area during the initial construction in 1979 -1980. These ditches route surface runoff to one of the sediment ponds or away from the disturbance area. Exhibit 12 -2, (Revision 14, dated 03/07) shows the location of these ditches. During the permit transfer process from H -G Coal Company to HGTI, HGTI and CDRMS personnel agreed that the existing hydrologic structures required designs, but that the requirement would only be applicable to the drainage ditches and culverts in the facilities area. In order to demonstrate that the drainage ditches meet the intention of Rule 4.05.3, SEDCADt analyses were conducted on the existing diversion ditches. Appendix 12 -4, Diversion Ditch and Culvert Design, presents design demonstrations for the facilities area drainage ditches. The ditch designs are summarized in Table 12 -1, Facilities Area Diversion Ditches. Existing and proposed culverts within the facilities area are shown on Exhibit 12 -2, while rail spur and loop culverts are shown on Exhibit 12 -1, Facilities Map. Culvert design demonstrations are presented in Appendix 12 -4, Diversion Ditch and Culvert Design, and summarized on Table 12 -2, Hayden Gulch Loadout Culverts. New diversion ditches and /or culverts constructed as part of any facility modifications will be designed in accordance with Rule 4.05.3. MR -15 6 Revised 03/07