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Pea C ENERGY <br />Twentymile Coal, LLC <br />RECEIVED <br />SEP 0 )' Z010 <br />Jared Ebert DMSION OF RECLAMATION <br />MINING AND SAFETY <br />Colorado Division of Reclamation, Mining, and Safety <br />1313 Sherman Street, Room 215 <br />Denver, Colorado 80203 <br />(303) 866-3567 X8134 <br />29515 Routt County Road 27 <br />Oak Creek, CO 80467 <br />970.879.3800 <br />September 5, 2016 <br />RE: Twentymile Coal, LLC - Foidel Creek Mine (Permit No. C-82-056), Technical Revision <br />(TR16-86) SWMD Thickener Underflow Borehole <br />Jared: <br />Twentymile Coal, LLC (TC) requests CDRMS approval of a Technical Revision to our existing <br />approved Permit for construction, operation, and reclamation of a new thickener underflow borehole, <br />pipeline, and associated ancillary equipment and facilities in the Southwestern Mining District <br />(SWMD). The new thickener underflow installation is needed both as backup for the current system, <br />and to replace the existing 1 MN Borehole and/or 2MN Borehole at some point in the future, if and <br />when either of these boreholes is no longer functional. <br />The SWMD Thickener Underflow Borehole installation will be located near the west entrance to the <br />main Foidel Creek Mine site. In order to provide some flexibility, TC is permitting two alternate <br />borehole locations, although only one will be constructed and developed. Borehole location SWMD-1 <br />1 is located on the west side of Routt County Road RCR27 between the west entrance and the Fish <br />Creek Borehole road. SWMD-2 is located on the east side of RCR27, is accessed from the Fish Creek <br />Borehole road, and the pad will be located on the west side of the road. The SWMD Thickener <br />Underflow Borehole will extend from the surface into the sealed SWMD mine workings <br />approximately 750 to 850 feet, depending on which location is selected. <br />Installation of the SWMD Thickener Underflow Borehole will involve placement of construction <br />erosion controls (silt fence and/or straw wattles), removal and stockpiling of soil materials and the <br />limited vegetation from the existing pad area and road margins, minor fill placement (if necessary) and <br />grading to establish a level drill pad, placement of gravel surfacing at the access point, excavation of a <br />temporary cuttings pit on the drill pad, and drilling and casing of the borehole. Upon completion of <br />drilling and casing operations, the cuttings pit will be allowed to dry -out, material excavated from the <br />pit will be replaced and graded, and the pad surface will be graveled to control erosion and sediment <br />and provide an all-weather operating surface. The completed Thickener Underflow Borehole <br />installation will include an access road, soil material stockpiles; a leveled pad (maximum 250' x 170'), <br />an 18 -inch cemented surface casing (60 feet deep), a 12 -inch cased borehole, and a covered 8 -foot <br />diameter CMP manhole with lightning protection. <br />The pipeline installation will involve removal and windrowing of soil materials; trenching in most <br />areas; placement of suitable bedding materials; placement, connection, and pressure testing of the <br />pipeline; backfilling and compaction of suitable fill materials around and over the pipeline; backfilling <br />and compaction of the trench; re -grading; replacement of soil materials; and re -vegetation of all <br />