2020-03-11_REVISION - C1981035 (2)

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Water contained in the sediment pond will not be discharged into the Hay Gulch Ditch, but allowed to evaporate. The only water to be discharged from the ponds will be from precipitation events approaching or exceeding the ten year, twenty-four hour storm event. The ponds are described in Section 2.05.6 and are designed to manage the precipitation events as required by regulation and in accordance with the requirements of GCC Energy's N.P.D.E.S permit No. CO-G-850001. PONDS, IMPOUNDMENTS, AND DIVERSIONS DRAINAGE PLAN The drainage plan for the King II Mine consists of diversion of uncontaminated water originating upstream of the mine yard, through the yard to the discharge point at the south end of site. Runoff generated on the yard itself will be collected and routed through the sedimentation pond. Refer to 2.05.6 (Hydrologic Balance) Appendix 10 & 11 and Maps King II- 007 A thru G for a detailed description of Mine Surface Drainage and Sediment Pond design and descriptions. The sediment control system for the King II Mine is comprised of undisturbed area drainage ditches and one sediment pond. Designs for sediment control system structures are included in Appendix 11. Small Area Exemption #1 is approximately 1.3 acres of the disturbed area which lies below the sediment pond, consisting of the haul road between County Road 120 and the north end of the Sediment Pond. Runoff from this area will tend to collect and drain along the haul road bypassing the sediment pond. Alternate sediment control measures are used in this area. These measures consist of the use of rock check dams, rock filters and gravel surface. This area is too small and too flat to run a SEDCAD demonstration. This runoff flows into the area on either side of the haul road. UNDISTURBED AREA DRAINAGE DITCHES Two undisturbed area drainage ditches convey undisturbed surface flow around the disturbed area of the mine surface facilities and return the flow to the native surface drainage channel below the mine bench. The ditches encircle the mine disturbance. One ditch conveys surface flow along the west side of the mine facilities to the native channel, while the corresponding ditch drains east and south above the mine portal and down the east side of the mine bench and surface facilities to the native channel. These open earthen channels are sized to contain the precipitation events as required by regulation. The channels are stabilized with a combination of vegetation and riprap (where necessary). TR-29 proposes to convey part of the east clearwater ditch via two 24" culverts as shown on map King II-007 (TR-29) & King II-007A (TR-29. GCC Energy, LLC King II Mine Section 2.05.3 Page 5 February 18, 2020 (TR-29)