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pipeline corridor from the well to the rail spur corridor in the El/2 0£ Section 10 and, <br />1.03 acres for the pipeline corridor that extends southward from Routt County Road 37 to the . <br />rail loop corridor in the E1/2 of Section 15. <br />Due to the shallow slopes, existing and well established vegetative cover, and small <br />drainage area the disturbance azeas associated with the water-supply well and water pipeline <br />do not experience significant soil loss through erosion. To satisfy the intention of Rule <br />4.05.2(3), SEDCAD 4 evaluations were completed to demonstrate that the revegetated azeas do <br />not generate peak settleable solid concentrations in excess of the water quality effluent <br />standard of 0.5 ml/1. The SEDCAD 9 evaluations are presented in Appendix 12-2, Small Area <br />Exemption Demonstrations. <br />Given the limited footprint of disturbance, the stabilized soil and excellent vegetative <br />cover that exists after 25 years, as well as peak settleable solid concentrations less than <br />the applicable standard, the HG Shallow Well No. 1 and associated pipeline corridor can be <br />permitted as small area exemptions. <br />Diversion Ditches <br />A number of runoff collection ditches were constructed inside the facilities area during the • <br />initial construction in 1979-1980. These ditches route surface runoff to one of the <br />sediment ponds or away from the disturbance area. Exhibit 12-2, (Revision 13, dated 06/06) <br />shows the location of these ditches. During the permit transfer process from H-G Coal <br />Company to HGTI, HGTI and CDMG personnel agreed that the existing hydrologic structures <br />required designs, but that the requirement would only be applicable to the drainage ditches <br />and culverts in the facilities area. In order to demonstrate that the drainage ditches meet <br />the intention of Rule 4.05.3, SEDCAD analyses were conducted on the existing diversion <br />ditches. <br />Appendix 12-9, Diversion Ditch and Culvert Design, presents design demonstrations for the <br />facilities area drainage ditches. The ditch designs are summarized in Table 12-1, Facilities <br />Area Diversion Ditches. <br />Existing and proposed culverts within the facilities area are shown on Exhibit 12-2, while <br />rail spur and loop culverts aze shown on Exhibit 12-1, Facilities Map. Culvert design <br />demonstrations are presented in Appendix 12-9, Diversion Ditch and Culvert Design, and <br />sunanarized on Table 12-2, Hayden Gulch Loadout Culverts. <br />New diversion ditches and/or culverts constructed as part of any facility modifications will <br />be designed in accordance with Rule 4.05.3. <br />TR-07 6 Revised D6/06 <br />