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COAL <br />COMVAN d� <br />5731 State Highway 13 ♦ Meeker, Colorado 81641 <br />September 19, 2013 <br />Mr. Rob Zuber <br />Environmental Protection Specialist <br />Colorado Division of Reclamation, Mining & Safety <br />Department of Natural Resources <br />1313 Sherman Street, Room 215 <br />Denver, CO 80203 <br />♦ 970- 824 -1200 <br />R� 1013 <br />SEA <br />OMSM10N f ve 4ev <br />�tv <br />RE: Colowyo Coal Company L.P., Mine Permit C -81 -019, Technical Revision No. <br />100 (TR -100), Highwall Mining Revision <br />Dear Mr. Zuber, <br />Colowyo Coal Company L.P. (Colowyo) received your letter dated September 13, <br />2013 which contained adequacy comments for TR -100. Colowyo has included the <br />Division's original comments and has the following responses: <br />1. In the report by Agapito Associates, Inc. (AA), there is no mention of potential <br />impacts of highwall mining the G78 Seam under the previously mined E Seam <br />along the North End Wall in the South Taylor Pit. Please add a discussion of <br />these potential impacts on future G78 panels. <br />Response: There is no mention of potential impacts of highwall mining in the <br />G78 Seam under the previously mined E Seam along the North End Wall in the <br />South Taylor Pit due to the large interburden spacing between the G78 Seam <br />and the E Seam which results in no impact or interaction between the seams. <br />Figure 6 on page 9 indicates the G7 to E Seam interburden thickness is <br />approximately 180 to 200 feet with a projected G7 coal seam thickness of <br />approximately 6.5 to 8.5 feet (Figure 3 page 6). Note that only the G7 coal <br />seam will be mined in this area due to the G7 and G8 coal seams splitting <br />apart. Utilizing the interburden thickness -to -lower seam mining height ratio <br />of 2.0 and assuming a G7 average seam thickness of 7.5 feet gives an <br />interburden thickness of only 15 feet. Per AA's recommendations on page 60 <br />under Multiple -Seam Mining, "Past mining experiences and numerical <br />modeling analyses indicate that seam interaction effects are minimized as <br />long as interburden thickness -to -lower seam mining height ratio of 2.0 or <br />greater is maintained. Where this is the case, panels in each seam can be laid <br />out independently... ". Due to the massive interburden thickness between G7 <br />and E Seams of approximately 180 to 200 feet when only 15 feet is required to <br />A mining property of Western Fuels - Colorado, A Limited Liability Company <br />