2016-08-12_REVISION - C1982056 (2)

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utilizing small rock -lined sediment traps to control discharge and sediment. Drainage from the borehole pad area will be controlled under a Small -Area Exemption, with gravel surfacing on the pad and road to control runoff and sediment, stabilization of cut/fill areas with temporary revegetation seeding, and control of runoff from outslope areas by the perimeter ditch and sediment traps. Drainage designs for the culverts and diversion ditch are provided in Exhibit EX49EE. Borehole completion will involve drilling, installing, and grouting steel surface casing in place to a maximum depth of approximately 60 feet (dependent on the ground conditions encountered). The boreholes will then be advanced, to depth to intercept the Wolf Creek mine workings. Water, drilling fluids, and cuttings will be contained within one or more excavated pits or portable steel tanks (porta-pits) on the borehole pad. The surface casing for the larger utility borehole will be 32 -inches in diameter. If dry, this borehole will be drilled to 22 -inches and cased to 16 - inches, or if wet, 30 -inches and cased to 24 -inches. The surface casing for the smaller utility borehole will be 24 - inches. The smaller utility borehole will be drilled to 22 -inches and cased to 16 -inches if wet. If dry, this borehole will be drilled to 13.75 -inches. A 6.675 -inch and 3.5 -inch carrier pipe will be placed and grouted in either the 16 - inch casing (wet) or 13.75 inch (dry) borehole. The larger carrier pipe may be used for grouting, material transfer, or other utility needs. The smaller carrier pipe may be used as a power drop or for a communications line(s). Power to the 9 -East Utility Borehole Installation will be provided by a branch -line from the existing nearby powerline, extending from 990 to 1,700 feet, depending on which pad location is selected. Powerline construction will require placement of from 14 to 34 power -poles, dependent on which pad location is selected and power -pole spacing (50 to 75 feet). A switch and transformer on the Yampa valley Electric line at the connection with the branch -line, and a drop -line at the pad location will provide power to the electrical equipment skid and portable skid -mounted exhauster units. Three concrete equipment pads will be constructed on the 9 -East Utility Borehole pad; a 7'8" x 6'6" x 1' Borehole Collar Pad; a 26'6" x 15' x 1'6" Blower Skid Pad; and a 31' x 15' x 1' Electrical Equipment Skid and Transformer Pad, as shown by construction drawings in Exhibit 49EE. The 9 -East Utility Borehole Installation will remain in place until it is no longer needed to support ongoing operations (estimated life of approximately 3 -years), and will then be reclaimed. Reclamation will involve plugging and sealing the boreholes, breaking -up and hauling the concrete pad materials off-site, removing the powerline, regrading the pad and road, drainage reestablishment, soil material replacement, and reseeding. MR16-302 2.05-45.31 08/12/16