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<br />Proposed Decision and Findings of Compliance July 2018 <br />Permit Renewal No. 7 P a g e | 53 <br />XVIII. Subsidence Control - Rule 4.20 <br /> <br />The Permit was found to comply with Rule 4.20 as well as Rule 2.05.6(6). <br /> <br />Colowyo is mainly a surface coal mining operation. A small area was auger mined (see XXI <br />below). The potential for subsidence over the auger mining was not considered a significant <br />concern. The possibility of large scale pillar failure over an area sufficient to produce surface <br />effects was considered very low (CTL/Thompson, Inc., “Auger Mining Analysis,” February 5, <br />1996). <br /> <br />A truck parking lot exists above a highwall mining area of the South Taylor Pit. Colowyo has <br />designed the highwall mining in this area to minimize the impacts to the lot. The plan includes <br />driving one highwall mining entry as deep as possible (under the lot), leaving the designed web <br />pillar, driving the next entry and stopping it short of the lot, leaving another web pillar, than starting <br />the process over again. Although there is no current requirement for monitoring of subsidence by <br />Colowyo at the Mine, Colowyo is monitoring the possible movement or subsidence of the truck <br />parking lot through visual inspection; this is done to meet Mine Safety and Health Administration <br />(MSHA) requirements. <br />XIX. Coal Exploration - Rule 4.21 <br /> <br />Coal exploration outside the Permit boundary is not authorized by the mining permit with the <br />Division, and is not addressed in this finding. <br />XX. Concurrent Surface and Underground Mining - Rule 4.22 <br /> <br />No concurrent surface and underground mining is planned for the permit renewal period. <br />XXI. Auger Mining - Rule 4.23 <br /> <br />No auger mining is currently proposed in the mine plan. However, auger mining was done in 1993 <br />in the Section 11 Pit. Further, highwall mining in the East Pit, West Pit and South Taylor Pit has <br />been approved (PAP, Section 4.23). Highwall mining was not originally permitted for the South <br />Taylor Pit during the Permit Revision No. 2 review process, leading to the Division adding <br />Stipulation 9 to the permit. This stipulation was terminated with the submission of TR-77, which <br />permits limited highwall mining in the South Taylor Pit area. <br />XXII. Operations on Alluvial Valley Floors - Rule 4.24 <br /> <br />The Permit was found to be in compliance with Rule 4.24. <br /> <br />Information related to alluvial valley floors is found in Sections 2.04.7, 2.06.8 and 4.24; Exhibit <br />7; and Maps 7, 11, 11A, 11B, 11C, 12, 12A, 12B, 12C 17, 32 and 37 of the PAP. A detailed <br />summary of alluvial valley floors identified during the original permitting of the Mine can be found