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13 -Left Outbv Utilitv Borehole (MR15-291
<br />As the 12 -Left and 13 -Left Panels approach the mains and the fault -zone, the cross -panel grade increases to the
<br />point where operational stability of the longwall system becomes a concern, particularly during the recovery phase.
<br />In order to address this problem, TC plans to over -excavate the floor at the end of the two panels, and pour a wedge
<br />of concrete to create a more level and stable floor in this area. The 13 -Left Outby Utility Borehole will facilitate
<br />transfer of the large quantities of concrete required for this project from the surface to the underground working
<br />area. TC plans to complete the Utility Borehole, to be located over the 13 -Left Outby entries, extending from the
<br />surface to the existing Wadge Seam workings. The borehole will extend to a depth of approximately 1,270 feet,
<br />will be drilled to a maximum 10 -inch diameter, and cased to a 4.5 -inch diameter.
<br />The proposed borehole will be accessed from the paved County Road (RCR33), using the existing established
<br />access for the 6 -Main North Shaft Facility, with a new light -use road to the borehole pad location, as shown on
<br />Map 24 (2/4) and Figure 49DD-F1. The proposed utility borehole will require upgrading of approximately 1,550
<br />feet of an existing ranch road, and construction of approximately 1,000 feet of new light -use road from the existing
<br />established 6 -Main North access road. A new borehole pad (approximately 200 x 200 ft.) will be constructed to
<br />support the initial drilling, borehole completion activities, and subsequent concrete delivery and transfer operations.
<br />The 13 -Left Outby Utility Borehole installation will consist of the new light -use road and borehole pad; adjacent
<br />soil material stockpiles, and the lined and grouted borehole extending into the 13 -Left Outby mine entries in the
<br />Wadge Coal Seam. The road disturbance corridor will be 40 feet wide, although the actual road surface will only
<br />be approximately 24 feet wide. The total road disturbance will be approximately 2.4acres, and the maximum pad
<br />disturbance will be approximately 1.0 acre.
<br />Site-specific investigations required for design and permitting of the utility borehole include a cultural resource
<br />survey and wildlife consultation. The cultural resource survey results are summarized by the survey report
<br />provided in Exhibit 6T, and a wildlife consultation letter is included in Exhibit 23C. The perimeter of all areas to
<br />be disturbed will be clearly marked and construction drainage control measures (silt fences or wattles) will be in
<br />place prior to disturbance. In order to reestablish effective vegetative cover during site reclamation, TC will
<br />recover and stockpile a maximum of 1.5 feet of soil material from the road and pad disturbance areas. A maximum
<br />of approximately 5,810 cy of soil will be recovered and stockpiled from the road disturbance area, and
<br />approximately 2,420 cy from the pad area. Natural vegetative materials incorporated into the salvaged soil
<br />materials and seeding with the soil stockpile stabilization seed mixture will assist in stabilizing the stockpiled soil
<br />material and preventing erosion or loss of the soil materials.
<br />The proposed pad and road location are on a low -gradient sidehill, so upgradient drainage will be limited. The
<br />limited amount of drainage from upgradient areas will be intercepted and routed around the borehole pad by a small
<br />upgradient diversion ditch on the southwest and northwest sides of the pad. The existing ranch road crosses a small
<br />ephemeral drainage, and the existing culvert will remain in place. The culvert installation will evaluated relative to
<br />condition and cover to carry the anticipated truck traffic, the culvert will be replaced or extended as necessary, and
<br />adequate cover will be placed to carry the anticipated loads, without crushing the culvert. Drainage from the
<br />borehole pad area will be controlled under a Small -Area Exemption, with gravel surfacing on the pad and road to
<br />control runoff and sediment and placement of rigid sediment filter material on the northeast side of the pad area.
<br />The upgradient diversion ditches will drain through rock sediment basins to the undisturbed adjacent lands, and pad
<br />cut/fill areas will be stabilized with temporary revegetation seeding.
<br />Road upgrades and construction will involve soil recovery, scarification and recompaction of surface materials, any
<br />necessary cut/fill work to establish the road profile, and placement and compaction of approximately 3 inches of
<br />suitable road -base materials and 8 inches of pit -run gravel. Given the location of the borehole pad on a low -
<br />gradient sidehill, and the relatively short access road, it is not anticipated that any truck turn -outs will be needed.
<br />The 24 -foot road surface will be graded and crowned to promote effective drainage.
<br />Construction of the borehole pad will involve soil recovery, installation of the upgradient diversions, cut/fill pad
<br />construction, and placement of gravel surfacing material to control dust and sediment from the pad area. Borehole
<br />completion will involve drilling, installing, and grouting a 14 -inch diameter steel surface casing in place to a
<br />maximum depth of approximately 60 feet (dependent on the ground conditions encountered). The borehole will
<br />then be advanced, using directional drilling, to a depth of approximately 1,270 feet to intercept the mine workings.
<br />Water, drilling fluids, and cuttings will be contained within one or more excavated pits or portable steel tanks
<br />(porta-pits) on the borehole pad. The borehole will be drilled at a maximum of 10 inches, and cased and grouted to
<br />MR 15-291 2.05-45.29 12/22/15
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