Laserfiche WebLink
compaction of approximately 8 inches of pit-run grave] and 3 inches of suitable road-base material. The <br />access road surface will be approximately 24 feet wide and will be graded and crowned to promote <br />effective drainage. Road construction requires minima] cut and limited fill, so the actual road disturbance <br />azea will average approximately 35 feet wide. Cut slopes will be established at a maximum of 1.SH:1 V <br />and fill slopes will be graded to 2H:1 V or less, with all disturbed slopes to be stabilized by seeding with the <br />topsoil stockpile stabilization seed mixture. For permitting purposes, a road disturbance corridor 100 feet <br />wide has been defined as encompassing all project-related activities, including road construction and <br />topsoil stockpiling/windrowing. <br />Preparation of the ventilation shaft pad will involve topsoil recovery and stockpiling, installation of <br />required drainage structures, grading and compaction to establish a level pad working area, excavation of a <br />collection pit for blind drilling of the shaft pilot hole and shaft, haulage or stockpiling of the excavated <br />borrow material, and placement of gravel surfacing material to control dust and sediment from the pad <br />area. Excavated borrow material from the collection pit will be hauled to the nearby Fish Creek Loadout <br />for use in final reclamation. The collection pit will be approximately 100 x 200 x 10 feet and is sized to <br />contain all drilling fluids and cuttings. In the event unanticipated ground water flows are encountered, they <br />would occur during drilling of the pilot hole when the collection pit would have significant excess <br />capacity. The combination of excess capacity and flow controls should be adequate to prevent any ofd=site <br />discharge. Facility construction details and configuration are illustrated by Maps 15-50 and 1 W-50 in <br />Exhibits 16C and 16D. The cuttings pit and associated foundation area will be inspected during topsoil <br />stripping, placement of the liner, and temporary closure, on completion of shaft boring operations. As- <br />built certification will be provided to the CDMG prior to cuttings placement and following temporary <br />closure. <br />Primary Method of Construction -Blind Drilling: <br />Prior to the beginning of the blind drilling process, a .pressurized pre-gout operation utilizing up to ten <br />-" small diameter (2") holes, up to approximately 400 feet deep around the shaft perimeter will be considered <br />and undertaken, as needed, to limit groundwater flows between the shaft and the formations. Individual <br />gout holes would be drilled and a cement grout would be pumped under pressure into each borehole <br />before completing the next hole, to seal any wet zones encountered. Each borehole would be filled with <br />grout and allowed to set-up, effectively sealing the borehole and any fractures or voids in the grouted <br />formation(s). Any surface casing extending above ground surface will be cut-off flush with or below <br />natural ground level. <br />If needed and once the pre-grout operation is completed, a shaft collar will be excavated to an approximate <br />10-foot diameter to competent rock at a depth of approximately 10-IS feet. Material from the collar <br />excavation will be placed within and on one end of the cuttings pit. A surface casing approximately 8 feet <br />in diameter (inside) and large enough to accept the shaft casing and drilling tools will be installed in the <br />shaft collaz. This surface casing will be either steel casing grouted in-place or cast-in-place concrete. A 48 <br />by 24 foot concrete T-shaped pad will then be poured to accommodate the drilling and casing equipment. <br />Specialized blind drilling equipment in the form of an A-leg derrick will be used to drill the pilot hole and <br />excavate the shaft. A nominal 17-1/2-inch pilot hole will then be drilled to an approximate depth of 1,000 <br />feet and surveyed to determine vertical shaft deviation and location underground for mine entry tie-ins. <br />The pilot hole will then be reamed to a nominal diameter of 7.5 feet to accommodate the final steel liner. <br />The reaming technique utilizes an inverted disc cutter equipped hemispherical raise bore head to cut the <br />rock. During the drilling of the pilot hole and the 7.5' diameter excavation, all cuttings will be removed <br />from the excavation using an airlift system, with water (reverse circulation) being the circulation media. <br />t Supplemental water, for drilling and to adjust the density of the drilling medium, may be supplied, as <br />needed, by a small portable pump drawing from Fish Creek under TCC's existing water rights. The <br />TROS-48 2.05 - 45.5 08/22/05 <br />