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RULE 4 PERFORMANCE STANDARDS <br />4.23.5 Undisturbed Areas of Coal Shall Be Left in Unmined Sections <br />As for the CDRMS Rules (Rules) requirement for leaving undisturbed areas of coal in unmined sections, <br />Colowyo contends that this application of the Rules does not apply since the seams to be highwall mined <br />are being accessed from active surface pits that by this Permit and other applicable sections of the Rules <br />are required to be backfilled and fully reclaimed. Hence should undisturbed barrier areas of coal be left <br />for some future access, these potential portal areas would be inaccessible for future generations because <br />they would be buried under the pit backfill. Additionally and importantly, as discussed above, due to the <br />many geological reasons, there is not economical coal to be recovered from "behind" the areas slated to <br />be highwall mined. <br />4.23.6 Abandoned or Active Underground Mine Workings <br />To Colowyo's knowledge, no abandoned or active underground mine workings have ever existed or <br />currently exist in any of the coal seams in the areas proposed to be highwall mined. No highwall mining <br />will be allowed to take place within 500 feet of any abandoned or active underground mining operation. <br />4.23.7 Surface Mining Activities and Highwall Mining <br />The highwall mining shall follow the surface coal mining activities in a contemporaneous manner <br />consistent with the applicable requirements of CDRMS Rule 4. Due to active pit progressions and <br />sequencing of mining (in addition to meeting the Permit requirements for contemporaneous reclamation), <br />it is required that highwall mining occurs timely if not immediately following conclusion of pit mining <br />activities. Also, as described more fully in 2.06.9(2), the need to backfill, ie, contemporaneously reclaim <br />the pits, is mandatory for Colowyo in order to build the pit floor from which to work from to mine the <br />successively higher (in the geologic column) coal seam. Hence successful highwall mining is in part <br />dependant upon timely and successful contemporaneous reclamation of the pits. <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 pits are <br />essentially dry (minor perched aquifers with limited seasonal flows) and are located above the 1st regional <br />aquifer (Trout Creek) by a substantial distance. Ground water flow regimes and the negligible impact that <br />Colowyo's surface mining activities have on ground water as a result of mining these target coal <br />seams/rock interburdens are detailed extensively in Permit Section 2.04.7(1). From this extensive body of <br />data and from experiences to date with mining activities, no toxic forming or acid forming water <br />discharge is anticipated from any of the highwall openings. Should toxic forming or acid forming water <br />discharges be encountered, the opening exhibiting the discharge will be backfilled within 72 hours of <br />completion. <br />Colowyo will backfill each highwall miner entrance hole within 30 days following coal extraction. All <br />highwall miner entrance holes will be further buried by pit backfill during the normal backfill sequence <br />for the pits to remain in compliance with Rules 4.05.1 and 4.05.2. Ground water hydrologic regimes will <br />be re-established in the backfilled pits with no anticipated detrimental effects from the highwall miner <br />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 impacts to <br />water quality, fill stability, pit backfilling, increased resource recovery, and highwall mining is designed <br />for zero subsidence to prevent disturbance or damage to powerlines, buildings, or other surface facilities. <br />Rule 4 Performance Standards 4.23-2 Revision Date: 6/23/08 <br />Revision No.: MR-91