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2.05.6 (3)(b)(vi) <br /> RESPONSE continued ` <br /> The Twenty Mile sandstone is the only unit with a permeability <br /> and an aeral extent (see Exhibit BB (Exhibits Volume II) ade- <br /> quate to be considered a significant aquifer. The recharge of <br /> the Twenty Mile sandstone will be protected by not disturbing it <br /> during the mining process. Horizontally, it will be isolated from <br /> the disturbed area by several hundred feet of natural topo- <br /> graphy. Vertically, it will be isolated from the disturbed area <br /> by 200 to 300 feet of material of low permeability (K=0.02 to 0.12 <br /> gal/day/ftx). While it is debateable if this portion of the for- <br /> oration is an aquifer within the definiton provided in the <br /> Colorado regulations, it will be treated as such in responding to = <br /> the above question. The recharge to these strata, which will be <br /> disturbed in the mined area, will be restored due to: <br /> o The post-mining topography will approximate the <br /> pre-mining topography, minunizing long-term impacts <br />•__ on the precipitation/ infiltration/runoff relationships in <br /> the permit area. <br /> o The topsoil will be replaced and vegetation reestab- <br /> lished, minimizing long-term impacts on the surface _ <br /> detention and infiltration characteristics of the permit <br /> area. <br /> o The spoils, even though partly compacted during the <br /> reclamation process should retain permeabilities greater <br /> than those of the undisturbed materials below them. <br /> The near surface, lenticular sandstones are within the upper <br /> Williams Fork Formation, but have been listed separately because <br /> they are the source of three springs adjacent to the permit area. <br /> These sandstones originate above the mined area. The springs <br /> associated with them will partially dry up during active mining <br /> and will approach their original flow rates as the ~ site is re- <br /> claimed. <br />