Laserfiche WebLink
Construction of the ventilation shaft access road will involve topsoil recovery and stockpiling, installation <br />of required drainage structures, scazification and recompaction 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 will be 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 requires minimal cut and limited fill, so the actual <br />road disturbance area will average approximately35 feet wide. Cut slopes will be established at a <br />maximum of 1.SH:1 V and fill slopes will be graded to 2H:1 V or less, with all disturbed slopes to be <br />stabilized by seeding with the topsoil stockpile stabilization seed mixture. The access road top surface will <br />be approximately 24 feet wide and will be graded and crowned to promote effective drainage. For <br />permitting purposes, a road disturbance corridor 100 feet wide has been defined as encompassing all <br />project-related activities, including road construction and topsoil stockpiling. <br />Prepazation of the ventilation shaft pad will involve topsoil recovery and stockpiling, installation of the <br />required drainage structures and sediment pond, grading and compaction to establish a level pad working <br />azea, 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 material, <br />and placement of gravel surfacing material to control dust and sediment from the pad azea. Excavated <br />borrow material from the collection pit will be used to construct the embankment of the waste disposal pit, <br />which will be constructed in 8 to 12 inch lifts, compacted to 95 percent of maximum standazd Proctor <br />Density. The collection pit will be approximately 14 feet deep, is sized to contain all material excavated <br />from the shaft, and will be lined with a PVC membrane liner to minimize infiltration of any moisture <br />contained in the excavated material. In the event unanticipated groundwater flows are encountered during <br />shaft sinking operations, portable pumps will be used to continuously dewater the shaft, with discharge to <br />one of the utility boreholes, which would route the water back into the abandoned underground mine <br />workings. Facility construction details and configuration are illustrated by Maps EX16E-M1 and M2; Map <br />EX49A-M2, Shaft Pad Profiles; and Map EX49A-M3, Waste Disposal Pit Profiles, in Exhibits 16E and <br />49A. The cuttings pit and associated foundation azea will be inspected during topsoil stripping; placement <br />of the liner; and temporary closure, on completion of shaft sinking operations. As-built drawings will be <br />provided to the CDMG prior to cuttings placement and following temporary closure. <br />Primary Method of Construction -Conventional Blind Sink Excavation: <br />The 6-North Mains Ventilation Shaft will be developed by conventional blind sinking excavation. Pre- <br />grouting would not be required for conventional blind sinking operations. A probe-hole is typically carried <br />down the hole and ahead of the shaft as shaft excavation progresses. Water is grouted off from within the <br />excavated shaft as it is encountered. <br />A shaft collaz will be 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 will be placed within waste disposal pit. A <br />surface casing approximately 12-18 feet in diameter (inside) and lazge enough to accept the shaft casing <br />and conventional drilling and mucking tools will be installed in the shaft collar. This surface casing will be <br />cast-in-place concrete. A nominal 25 by 25-foot by 4- to 6-foot thick concrete pad will then be 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, backleg foundation, and muck dumping system <br />will be used to excavate the shaft. An additional concrete pad(s), nominal size of 40 by 100 feet by 2 feet <br />thick, will be placed to accommodate the hoisting winch, transformers, distribution boxes, operator <br />consoles, sun•ounding building, and other miscellaneous equipment. <br />TROS-48 2.05 - 45.6c 09/05/05 <br />