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1111 Peabodq <br />Twentymile Coal, LLC <br />29515 Routt County Road 27 <br />Oak Creek, CO 80467 <br />RECEIVED 970.879.3800 <br />Jason Musick DEC 10 2013 December 6, 2013 <br />Colorado Division of Reclamation, Mining, and Safety <br />1313 Sherman Street, Room 215 DMSION OF RECLAMATION <br />Denver, Colorado 80203 MINING AND SAFETY <br />(303) 866 -3567 X8134 <br />RE: Twentymile Coal, LLC - Foidel Creek Mine (Permit No. C -82 -056), Minor Revision <br />(MR13 -273) 2 Main North Thickener Underflow Borehole <br />Jason: <br />Twentymile Coal, LLC (TC) requests CDRMS approval of a Minor Revision to our existing approved <br />Permit for construction, operation, and reclamation of a new thickener underflow borehole and <br />associated ancillary equipment and facilities at the 2 Main North (2MN) location. The new thickener <br />underflow installation is needed to replace the existing 6RT Borehole, given that we have experienced <br />some restriction of the underground flow -path for the tailings slurry, and a resultant rise in water levels <br />in the associated portion of the abandoned and sealed 6RT mine workings. <br />The 2MN Thickener Underflow Borehole installation will be located near the north edge of the <br />existing Mine Facilities Area, between the existing Weld Shop and the Twentymile Railroad Spur and <br />will be accessed by a short (550 feet) access road from the existing mine road. At this location, the <br />elevated rail bed forms a substantial berm between the proposed borehole location and Foidel Creek, <br />which is north of the railroad spur. The Thickener Underflow Borehole will extend approximately 150 <br />feet from the surface into the existing active 2MN No. 6 Mine Entry. From this location, the coal <br />slurry will be piped underground approximately 2,650 feet and 3,850 feet, respectively, to horizontal <br />boreholes into the sealed 7 -Right and 8- Right Panels in the Eastern Mining District (EMD). The <br />existing 6RT Thickener Underflow Pipeline runs through the proposed borehole pad, iso only a short <br />pipe- section will be required to connect the borehole to the pipeline, and any excavation for the <br />connecting line will be within the pad area. Due to concerns with reliability an d wear, the existing <br />pipeline will be cut at the new borehole location and an abrasion resistant elbow will be installed for <br />the connection. The remainder of the 6RT pipeline will remain in place for possible future use, and <br />will be plugged at the cut location. <br />Installation of the 2MN Thickener Underflow Borehole will involve placement of construction erosion <br />controls (silt fence and /or straw wattles), removal and stockpiling of soil materials and the limited <br />vegetation from the short access road and pad area; minor cut/fill work and grading to establish a level <br />drill pad; placement of gravel surfacing on the access road; excavation of a temporary', cuttings pit on <br />the drill pad; excavation for the access manhole and pipeline connection, drilling and casing of the <br />borehole; installation of an access manhole, and completion of the pipeline connection. The <br />connecting pipeline will be a double HDPE pipe system, with a 8.625 -inch carrier pipe inside a 12.0 - <br />inch containment pipe, buried approximately 5 -feet deep. On completion of drilling and casing <br />operations, the cuttings pit will be allowed to dry -out, material excavated from the pit will be replaced <br />and graded, and the pad surface will be graveled to control erosion and sediment and provide an all- <br />