2009-04-06_REVISION - C1982056 (20)

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and will be graded and crowned to promote effective drainage. Road construction will require minimal cut and limited fill, so the actual road disturbance area will average approximately 30 feet in width. Cut slopes will be established at a maximum of 1.5H:1V and fill slopes will be graded to 2H:1V or less, with all disturbed slopes to be stabilized by seeding with the topsoil stockpile stabilization seed mixture. For permitting purposes, a road disturbance corridor 50 feet wide has been defined as encompassing all project-related activities, including road construction and soil recovery and handling. Preparation of the ventilation shaft pad and substation area will involve installation of required drainage structures, soil material recovery and stockpiling, excavation and , lining of a collection pit for blind drilling of the shaft pilot hole and shafts, placement and compaction of fill material (from-cuttings pit excavation) to establish level pad working areas, haulage or stockpiling of any excess excavation material, and placement of gravel surfacing material to control dust and sediment from the pad areas. The collection pit will consist=of four cells covering an area of approximately 130 x 520 feet, with a'depth of approximately 10 feet, and is sized to contain all drilling fluids and cuttings from both shafts (total capacity of approximately 12,500, cubic yards). Facility construction details and configuration are illustrated by the design drawings provided in Exhibit 49R. The .cuttings pit and associated foundation area will be inspected during soil material stripping, placement of the liner, and temporary closure, on completion of shaft boring operations. As- built certifications will be provided to the DRMS prior to cuttings placement and following temporary closure. In general, the shaft pad is designed and configured to balance cuts and fills, and minimize any need for borrow material or handling of excess cut material. Prior to drilling the pilot hole for each shaft, a maximum 17.5-inch diameter exploration borehole will be drilled to a depth of approximately 1,360 feet to verify geologic and hydrologic conditions for the shaft site. Any excess water from the exploration borehole will be routed to the previously constructed cuttings pit. The exploration borehole will be completed with a 12- inch diameter steel casing, an 8-inch and two, 2.5 inch diameter pipes will be installed within the casing, and the annulus will be grouted between the borehole and casing. It is anticipated that the 8-inch pipe will be used as a nitrogen injection borehole, and the two 2.5-inch pipes for communication lines. The exploration borehole will provide information on site ground water conditions, however, in the event unanticipated ground water flows are encountered; they would occur during drilling of the pilot holes when the collection pit would have significant excess capacity. The combination of excess capacity and flow controls should be adequate to prevent any off-site discharge. The substation area will be constructed at the same time as the shaft pad, as previously discussed. The substation area will be a 50 x 100 foot gravel-surfaced pad. Pole- or pad- mounted transformers and switch-gear will be installed on the pad, and a grounding field will be established under the near edge of the shaft pad during construction. If transformer pads are utilized, a maximum of three 20 x 20 foot pads would be constructed. The substation area will be enclosed by a chain-link security fence with locked gate, to limit access. A 69KV powerline will be extended up to 3,000 feet to the new substation from the existing Yampa Valley Electric Association line to the northeast. Installation of this line will require placement of approximately 12-16 new powerpoles.