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• For rule 4.23.2(6)(d), subsidence resulting from auger mining to any powerline s, buildings, <br />or other surface facilities is not predicted to occur based on the engineering design <br />analysis conducted by SCC. The auge[ panel design information is based on the engineering <br />report entitled •AUyer Panel Design Study for Seneca II-W and Yoa st Mines, Seneca Ceal <br />Company' prepared by Mr. Graeme Boyd, Highwall Mining Services, Inc. of Brisbane, Australia. <br />Mr. Boyd has prepared numerous highwall studies throughout the world and the pillar spacings <br />between each auger hole was based on a hole diameter of 6 feet and a corresponding design <br />factor of safety of 1.50 for pillar stability resulting in zero subsidence. <br />Finally, rule 4.23.2 (~) requires that auger mining shall be conducted in accordance with the <br />approved backfilling and grading requirements of 4.14. No changes to the currently approved <br />backfilling and grading plans are proposed due to the auger mining operations. <br />Geology <br />Site spec if is geology within and adjacent to the permit area is presented in Tab 6 of the <br />permit application package. Mr. Boyd was given an electronic copy of our geologic model <br />covering the proposed auger operations and surrounding areas to conduct his study. <br />• Seam to be mined: Wadge <br />Wadge Thickness: '7 to l4' <br />Height of highwall: The highwall height will vary from '10 to 15o feet. The maximum <br />overburden depth encompassing the auger recovery area will be 300 feet. <br />General cha racteriatics of the strata: The coal seam dips to the west at e° to 12°. The <br />overburden material consists mainly of thin [o Chick sandstones and are interbedded with <br />shales, siltst ones, thin and thick coal seams. <br />Hydrology <br />Ground Water <br />The proposed auger mining will remove a small portion of the Wadge seam in comparison to <br />mining that has already occurred upgzadient. The existing monitoring wells will be used to <br />monitor for any measurable ground water impacts throughout the life of the mining operation. <br />Any additional impacts to [he downgradient Wadge coal aquifers from the auger mining will be <br />negligible (unmeasurable) for the following reasons: <br />• 1. The total area of additional disturbance is quite small in comparison to the strip mined <br />pits. <br />2. The Wadge coal have very low transmissivities. <br />12-1-2 Revised O1/O1 <br />