2015-08-04_REVISION - C1982056 (2)

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Peabod ��1111 ENERGY Twentymile Coal, LLC 'ECFIVF_D AUG 0 4 2015 29515 Routt County Road 27 Oak Creek, CO 80467 970.879.3800 Mr. Jared Ebert, Environmental Protection Specialist July 30, 2015 Division of Reclamation, Mining, and Safety Division of &esatety��n' 1313 Sherman Street, Room 215 Nlinin9 Denver, Colorado 80203 (303) 866-3567 X 8120 RE: Twentymile Coal, LLC - Foidel Creek Mine (Permit No. C-82-056), Minor Revision (MR15-289) —10- East Mid -Panel Emergency Air Borehole Dear Mr. Musick: Twentymile Coal, LLC (TC) requests CDRMS approval of a Minor Revision to our existing approved Permit for installation, operation, and reclamation of a new emergency air borehole, to be located over the Wolf Creek 10 -East Gateroad. The purpose of the borehole is two -fold; to obtain additional geologic information in this area; and to provide an emergency air -hole for air, supplies, and communications in this portion of the Wolf Creek Reserve, as a safety consideration, given the distance from existing ventilation and emergency escape hoist capabilities. The borehole will extend to a depth of approximately 1,600 feet, will be drilled and subsequently reamed to a 8.75 -inch diameter, and cased to a 4.5 -inch diameter. Initial drilling will focus on core recovery with a 3.5 to 4.0 inch corehole to depth. In the event any significant quantities of water are encountered during drilling, the option exists of drilling a large (11.0 to 13.0 inch) diameter borehole to a depth of approximately 800 feet, and placing and grouting in a 8.625 inch casing. The proposed borehole would be accessed from the paved County Road (RCR27), using an existing established ranch access (Camilletti Road) and existing ranch roads to within less than 0.25 mile of the borehole location. Drilling is planned for late summer, and the remaining distance to the borehole is along a ridgeline, so no additional road construction is planned, as shown on Map 24, and in Exhibit 53. The proposed borehole will not require any new road construction, however, a new borehole pad (maximum of approximately 200 x 200 ft.) will be constructed to support the initial corehole drilling and subsequent borehole completion activities. The 10 -East Emergency Air Borehole installation will consist of the existing road access, the new borehole pad; adjacent soil material stockpiles, and a cased and grouted borehole extending into the Wolf Creek Coal Seam. As an emergency air borehole, following drilling and completion the site would be accessed only in an emergency, and would not be accessed on a regular basis, so there would be no need to establish and maintain a long-term access road. The proposed pad and existing road locations are on a minor ridgeline, so upgradient drainage will be limited. The limited amount of drainage from upgradient areas will be intercepted and routed around the borehole pad by a small upgradient diversion ditch on the north and east sides of the pad, and the road will not cross any natural drainages, so no culvert installations will be needed. Drainage from the borehole pad will be controlled under a Small -Area Exemption. The 10 -East Emergency Air Borehole installation will remain in place until it is no longer needed to support ongoing or anticipated future mining operations. Reclamation of this installation will involve plugging and sealing the borehole, regrading the pad, soil material replacement, and reseeding.