2014-04-25_PERMIT FILE - C1982056A (3)

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approximately 2.3 acres. The light -use road disturbance corridor will be approximately 750 feet long and 40 feet wide. Actual constructed road width (finished top width) is expected to be approximately 24 feet. Refer to Exhibit 49Y, 15LT Ventilation Shaft Installation — Design Drawings, for details on the road, and the road profile and cross - section. The proposed light -use road crosses upland areas where road construction will involve removal of any large vegetation and stripping and stockpiling of other vegetation, soil, and organic materials. In order to reestablish effective vegetative cover, TCC will recover and stockpile a maximum of 18 inches of soil material from shaft and road disturbance areas. With a total road disturbance area of approximately 0.7 acres, approximately 1,700 CY of soil material will be salvaged from the road corridor, and approximately 3,900 CY from the 1.6 acre shaft pad and associated disturbance areas. Prior to initiation of soil salvage operations, temporary sediment control measures (silt fence, wattles, and/or other, as appropriate) will be installed. Soil salvage volumes are indicated on Table 49A. Soil material from the road corridor and other disturbance areas will be stockpiled in a central soil stockpile areas as shown on the design drawings in Exhibit 49Y. Natural vegetative materials (mulch) incorporated into the soil, and seeding with the topsoil stockpile stabilization seed mixture identified on page 2.05- 121, will stabilize the stockpiled soil materials. Following soil removal, required drainage and sediment control structures will be constructed or installed. In order to minimize potential environmental and aesthetic impacts, surface drainage will be handled by an upslope drainage diversion ditch; a culvert crossing where this ditch intersects an existing natural drainage and crosses under the light -use road; and a interceptor ditch and rock -lined sump (Alternative Sediment Controls (ASC's)) on the downslope side of the pad. All drainage calculations and documentation are provided in Exhibit 49Y. Once the pad is constructed, surface runoff from the pad will be limited by placement of gravel surfacing material, and any limited surface drainage from the pad will flow to the cuttings pit. As a limited disturbance area, the pad, ditches, and ASC's will function under a Small Area Exemption to assure effective runoff and sediment control. Road drainage will be minimized by placement of gravel surfacing. Other disturbed areas (including topsoil stockpiles and pad outslopes) will be stabilized with temporary vegetation, and any structures will be painted in neutral earth - tone colors to blend with the natural surroundings. Construction of the ventilation shaft light -use road will involve soil recovery and stockpiling, installation of a 30- inch CMP culvert, scarification and re- compaction of surface materials, and placement and compaction of approximately 8 inches of pit -run gravel and 3 inches of suitable road -base material. The road surface will be approximately 24 feet wide, 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. For permitting purposes, a road disturbance corridor 40 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 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, placement and compaction of fill material (from cuttings pit excavation and site grading) to establish level pad working areas, and placement of gravel surfacing material to control dust and sediment from the pad area.. 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. The cuttings pit will be a single cell approximately 70 x 100 feet, and approximately 8 feet deep, and is sized to contain all drilling fluids and cuttings from the shaft (total capacity of approximately 1,700 cubic yards). Facility construction details and configuration are illustrated by the design drawings provided in Exhibit 49Y. 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. A 69KV distribution line will be extended approximately 1,000 feet to the new ventilation shaft pad from the existing Fish Creek Water Treatment Facility Substation. Because the new pad is adjacent to the powerline feeding this substation, the distribution line can be hung on the existing poles, requiring only two additional poles and pad - mounted transformer at the pad location. MR 12 -260 2.05-45.24 04/12/12