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Construction of the ventilation shaft access road involved topsoil recovery and stockpiling, installation of <br />required drainage structures, scarification and re-compaction of surface materials, and placement and <br />compaction of approximately 8 inches of pit-run gravel and 3 inches of suitable road-base material. <br />• Following topsoil removal, the exposed sub-grade was scarified to a depth of approximately 12-inches <br />and re-compacted to 95 percent of maximum standard Proctor Density (ASTM D698), with random <br />density testing to verify compaction. Road construction required minimal cut and limited fill, so the <br />actual road disturbance area averaged approximately35 feet wide. Cut slopes were established at a <br />maximum of 1.SH:1 V and fill slopes were graded to 2H:1 V or less, with all disturbed slopes stabilized by <br />seeding with the topsoil stockpile stabilization seed mixture. The access road top surface is <br />approximately 24 feet wide and is graded and crowned to promote effective drainage. For permitting <br />purposes, a road disturbance corridor 100 feet wide has been defined as encompassing all project-related <br />activities, including road construction and topsoil stockpiling. <br />Preparation of the ventilation shaft pad involved topsoil recovery and stockpiling, installation of the <br />required drainage structures and sediment pond, grading and compaction to establish a level pad working <br />area, excavation of a temporary underground mine development waste disposal pit for surface collar <br />material and conventional excavation of the shaft, haulage or stockpiling of the excavated borrow <br />material, and placement of gravel surfacing material to control dust and sediment from the pad area. <br />Excavated borrow material from the collection pit was used to construct the embankment of the waste <br />disposal pit, which was constructed in 8 to 12 inch lifts, compacted to 95 percent of maximum standazd <br />Proctor Density. The collection pit is approximately 14 feet deep, is sized to contain all material <br />excavated from the shaft, and is lined with a PVC membrane liner to minimize infiltration of any moisture <br />contained in the excavated material. In the event unanticipated groundwater flows aze encountered during <br />shaft sinking operations, portable pumps will be used to continuously dewater the shaft, with dischazge to <br />one of the utility boreholes, which would route the water back into the abandoned underground mine <br />workings, or to the adjacent ephemeral drainage channel. Facility construction details and configuration <br />• aze illustrated by Maps EX16E-M1 and M2; Map EX49A-M2, Shaft Pad Profiles; and Map EX49A-M3, <br />Waste Disposal Pit Profiles, in Exhibits 16E and 49A. The cuttings pit and associated foundation azea <br />were inspected during topsoil stripping; placement of the liner; and temporary closure, on completion of <br />shaft sinking operations. As-built drawings will be provided to the CDMG prior to cuttings placement <br />and following temporary closure. <br />Primary Method of Construction -Conventional Blind Sink Excavation: <br />The 6-North Mains Ventilation Shaft was developed by conventional blind sinking excavation. Pre- <br />b outing was not required for conventional blind sinking operations. A probe-hole was typically carried <br />down the hole and ahead of the shaft as shaft excavation progresses. Water was grouted off from within <br />the excavated shaft as it was encountered. <br />A shaft collar was excavated to an approximate 20- to 22-foot diameter to competent rock at a depth of <br />approximately 20-25 feet. Material from the collar excavation was placed within waste disposal pit. A <br />surface casing approximately 12-18 feet in diameter (inside) and large enough to accept the shaft casing <br />and conventional drilling and mucking tools was installed in the shaft collar. This surface casing is cast- <br />in-place concrete. A nominal 25 by 25-foot by 4- to 6-foot thick concrete pad was poured to <br />accommodate the winches, drilling, mucking and casing equipment, and headframe. Specialized drilling <br />and mucking equipment in the form of a hoist, headframe, backlog foundation, and muck dumping system <br />were used to excavate the shaft. An additional concrete pad(s), nominal size of 40 by 100 feet by 2 feet <br />thick, was placed to accommodate the hoisting winch, transformers, distribution boxes, operator consoles, <br />surrounding building, and other miscellaneous equipment. <br />MR06-208 2.05-45.6c 07/25/06 <br />