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ti <br /> RULE 4 PERFORMANCE STANDARDS <br /> r=�„.;mak :,. ,, �� �;��.:. w_w,., .•� »rte.,. �,*�� r�c�,�,...,, ,��c�,. a ._a <br /> 4.23.8 Prevent Pollution of Surface and Groundwater and to Reduce Fire Hazards <br /> Ground water in the pit or highwall mining holes will not be problematic being that the Colowyo <br /> pits are essentially dry(minor perched aquifers with limited seasonal flows)and are located above <br /> the first regional aquifer(Trout Creek) by a substantial distance. Ground water flow regimes and <br /> the negligible impact that Colowyo's surface mining activities have on ground water as a result of <br /> mining these target coal seams/rock interburdens are detailed extensively in Permit Section <br /> 2.04.7(1). From this extensive body of data and from experiences to date with mining activities, <br /> no toxic forming or acid forming water discharge is anticipated from any of the highwall openings. <br /> Should toxic forming or acid forming water discharges be encountered,the opening exhibiting the <br /> discharge will be backfilled within 72 hours of completion. <br /> Colowyo will backfill each highwall miner entrance hole within 30 days following coal extraction. <br /> All highwall miner entrance holes will be further buried by pit backfill during the normal backfill <br /> sequence for the pits to remain in compliance with Rules 4.05.1 and 4.05.2. Ground water <br /> hydrologic regimes will be re-established in the backfilled pits with no anticipated detrimental <br /> effects from the highwall miner holes. <br /> 4.23.9 Division shall prohibit Auger(Highwall Mining) Mining <br /> There is no probable reason to prohibit the highwall mining in light of no anticipated adverse <br /> impacts to water quality, fill stability, pit backfilling, increased resource recovery, and highwall <br /> mining is designed for zero subsidence to prevent disturbance or damage to powerlines,buildings, <br /> or other surface facilities. <br /> 4.23.10 Backfill and Grading Requirements <br /> Highwall mining will be conducted in accordance with the backfilling and grading requirements <br /> of 4.14. <br /> 4.23.11 Highwall Shall be Eliminated <br /> Highwall mining is proposed to occur in areas previously mined with adequate material on hand <br /> to backfill the pits with proper static safety factors for stability to the approved postmining <br /> topography thereby eliminating all highwalls. Any minimal spoil material generated by the <br /> highwall mining operation will be buried at depth in the pit backfill. All coal seams mined will be <br /> adequately covered by pit backfilling in conformance with the permitted PMT and reclamation <br /> plan. No remnant highwalls will be left at conclusion of the reclamation activities and no spoil <br /> material will be place on any outslopes. <br /> 4.24 Operations in Alluvial Valley Floors <br /> The field investigation described in Section 2.04.7 and 2.06.8 resulted in no identification of <br /> alluvial valley floors in the general area,which would be adversely affected by mining operations. <br /> Therefore, no special performance standards for operations in the alluvial valley floors are <br /> Rule 4 Performance Standards 4-75 Revision Date: 12/20/19 <br /> Revision No.: TR-135 <br />