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For Rules 4.23.2(4) and 4.23.2151, special plugging procedures are not proposed for this set <br />of auger (highwall miner) holes. The holes will be plugged by backfilling operations as a • <br />normal part of the highwall miner and reclamation operations. Drainage from these holes will <br />not be a problem as discussed in the Hydrology Section. <br />For Rule 4.23.2(6) (dl, subsidence resulting from auger (highwall miner) mining to any <br />powerlines, buildings, or other surface facilities is not predicted to occur based on the <br />engineering design analysis conducted by SCC. If subsidence does occur there are no <br />structures that will be highwall mined underneath. If cracks do occur on the surface SCC <br />will repair them. As per accordance with the MSHA ground control plan, pillar strengths <br />were designed with a minimum safety factor of 1.5. <br />Finally, Rule 4.23.217), requires that auger (highwall miner) mining shall be conducted in <br />accordance with approved backfilling and grading requirements of Rule 4.14. In certain <br />areas, highwall mining and retention of mine haul roads will preclude rough backfilling and <br />grading within 180 days of final dragline coal removal. SCC has requested a variance from <br />the contemporaneous reclamation requirements of Rule 4.14.1 for these areas, as outlined in <br />the Tab 19 text discussion. <br />2.0 GEOLOGY <br />Site specific geology within and adjacent to the permit area is presented in Tab 6 of the <br />permit <br />application package. <br />• Coal seams to be mined: Wadge and Wolf Creek <br />Wadge Thickness: 8' to 15' <br />Wolf Creek Thickness: 6' to 19' <br />Height of highwall: The highwall height will vary from 30' to 150'. The maximum <br />overburden depth encompassing the highwall miner will be approximately 460 feet. <br />• <br />• General characteristics of the strata: The coal seam dips to the west at 8 to 20 <br />degrees. The overburden material consists mainly of thin to thick sandstones and is <br />interbedded with shales, siltstones, and thin and thick coal seams. • <br />TR-25 12-2-3 Revised 09/04 <br />