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As the basis for design and construction of two proposed mine ventilation shafts and associated ancillary facilities, <br />TCC conducted geotechnical investigations for the 18 -Left (18LT) Mine Ventilation Shaft Installation. The site <br />was accessed using a Snow -Cat mounted auger, and the geotechnical investigations involved completion of up to <br />eight 4 -6 inch hollow -stem auger sample holes and collection, examination, and testing of the resulting samples. <br />Auger test holes were located by the contractor within the areas defined as the 18LT shaft pad and road areas, as <br />shown on Figure EX49R -F1, and were advanced to depths of 15 -40 feet. On completion of each sample hole, the <br />hole was backfilled with drill cuttings and leveled. Given that all sample holes fall within the 18LT shaft facilities <br />footprint, and shaft facility construction is anticipated within the next six months, further reclamation will not occur <br />unless shaft facility construction is deferred or cancelled. In those circumstances, drill -sites will be seeded with the <br />approved rangeland seed mixture during the first scheduled seeding operations follow the decision to defer of <br />cancel shaft construction, but no later than nine months following completion of sampling activities. <br />In order to reestablish effective vegetative cover, TCC will recover and stockpile a maximum of 18 inches of soil <br />material from shaft disturbance areas. With a total road disturbance area of approximately 0.3 acres, approximately <br />750 CY of soil material will be salvaged from the road corridor, and approximately 12,800 CY from the 5.3 acre <br />shaft pad and associated disturbance areas. Prior to initiation of soil salvage operations, temporary sediment <br />control measures (silt fence, wattles, and/or other, as appropriate) will be installed. Soil salvage volumes are <br />indicated on Table 49A. Soil material from the road corridor and other disturbance areas will be stockpiled in a <br />central soil stockpile areas as shown on the design drawings in Exhibit 49R. Natural vegetative materials (mulch) <br />incorporated into the soil, and seeding with the topsoil stockpile stabilization seed mixture identified on page 2.05- <br />121, will stabilize the stockpiled soil materials. <br />Following soil removal, required drainage and sediment control structures will be constructed or installed. In order <br />to minimize potential environmental and aesthetic impacts, surface drainage will be handled by a downslope <br />drainage collection ditch; a culvert crossing where this ditch intersects the light -use road; Alternative Sediment <br />Controls (ASC's) for the substation and soil stockpile; a partially incised two -cell sedimentation pond <br />downgradient of the pad area; and a discharge control structure (rock check dam) and transition ditch at the outlet <br />of the second sedimentation pond cell. TCC will apply for a modification to its existing CPDS Discharge Permit to <br />include the new discharge point. The limited road drainage will be handled by a designed road ditch. In addition, <br />the pad and light -use road will be gravel- surfaced to minimize erosion and sediment loss, other disturbed areas <br />(including topsoil stockpiles) will be stabilized with erosion control fabric and temporary vegetation, and any <br />structures will be painted in neutral earth -tone colors to blend with the natural surroundings. <br />The light -use road will run along the contour of the low ridge at a relatively flat gradient, and will be gravel - <br />surfaced, so road drainage control requirements are minimal. A typical road drainage ditch design is provided in <br />Figure 2 of Exhibit 8DD, prepared by Water & Earth Technologies, Inc. The only culvert that will be required will <br />be at the point where the light -use road crosses the downslope drainage collection ditch. All drainage calculations <br />and documentation are provided in Exhibit 8DD. <br />Construction of the ventilation shaft light -use road will involve soil recovery and stockpiling, installation of <br />required drainage structure, scarification and re- compaction of surface materials, and placement and compaction of <br />approximately 8 inches of pit -run gravel and 3 inches of suitable road -base material. The road surface will be <br />approximately 24 feet wide, and will be graded and crowned to promote effective drainage. Road construction will <br />require minimal cut and limited fill, so the actual road disturbance area will average approximately 30 feet in width. <br />Cut slopes will be established at a maximum of 1.5H:1 V and fill slopes will be graded to 211:1 V or less, with all <br />disturbed slopes to be stabilized by seeding with the topsoil stockpile stabilization seed mixture. For permitting <br />purposes, a road disturbance corridor 50 feet wide has been defined as encompassing all project - related activities, <br />including road construction and soil recovery and handling. <br />Preparation of the ventilation shaft pad and substation area will involve installation of required drainage structures, <br />soil material recovery and stockpiling, excavation and lining of a collection pit for blind drilling of the shaft pilot <br />hole and shafts, placement and compaction of fill material (from cuttings pit excavation) to establish level pad <br />working areas, haulage or stockpiling of any excess excavation material, and placement of gravel surfacing material <br />to control dust and sediment from the pad areas. <br />MR10 -250 2.05-45.16 12/02/10 <br />