2009-04-06_REVISION - C1982056 (20)

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have maximum dimensions of approximately 425 x 500 feet (4.5 acres) with cut and fill slopes, and the substation area will be approximately 80 x 125 feet. The substation and powerline disturbance, light-use road, and soil stockpile area will add approximately 1.1 acres of disturbance, for a total disturbed area of approximately 5.6 acres. The light-use road disturbance corridor will be approximately 420 feet long and 40 feet wide (0.3 acres of disturbance). Actual constructed road width (finished top width) is expected to be approximately 24 feet. Refer to Exhibit 25Y, 18LT Ventilation Shaft Installation - Foundation and Road Investigations, Map 24 (Sheet 4 of 4), and Exhibit 49R, 18LT 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 disturbance areas. With a total road disturbance area of approximately 0.3 acres, approximately. 750 CY of soil material will be salvaged from the road corridor, and approximately 12,800 CY from the 5.3 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 49R. 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 a downslope drainage collection ditch; a culvert crossing where this ditch intersects the light-use road; Alternative Sediment Controls (ASC's) for the substation and soil stockpile; a partially incised two-cell sedimentation pond downgradient of the pad area; and a discharge control structure (rock check dam) and transition ditch at the outlet of the second sedimentation pond cell. TCC will apply for a modification to its existing CPDS Discharge Permit to include the new discharge point. The limited road drainage will be handled by a designed road ditch. In addition; -the pad and light-use road will be gravel- surfaced to minimize erosion and sediment loss, other disturbed areas (including topsoil stockpiles) will be stabilized with erosion control fabric and temporary vegetation, and any structures will be painted in neutral earth-tone colors to blend with the natural surroundings. The light-use road will run along the contour of the low ridge at a relatively flat gradient, and will be gravel-surfaced, so road drainage control requirements are minimal. A typical road drainage ditch design. is provided in Figure 2 of Exhibit 813D, prepared by Water & Earth Technologies, Inc. The only culvert that will be required will be at the point where the light-use road crosses the downslope drainage collection ditch. All drainage calculations and documentation are provided in Exhibit 8DD. Construction of the ventilation shaft light-use road will involve soil recovery and stockpiling, installation of required drainage structure, 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,