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~ .. <br />The Upper Coal member is approximately 220 feet thick, containing shales, <br />siltstones, sandstones, and the 'D", 'E", and 'F' coal seams. The Orchard <br />Valley Mine will be located in the lowermost seam, the °D" seam. At the mine <br />site, the coal is immediately overlain and underlain by shale. See Map 2-10, <br />'Representative Statigraphic Column, Coal Member, Mesa Verde Formation, in <br />Volume 2. The "D" seam overburden ranges from approximately 500 feet to 2,000 <br />feet within the permit area. The thickness of this seam decreases from 26 <br />feet at the outcrop to 8 feet at the northern edge of the permit boundary. <br />The "D" seam dips from the outcrop area in the south five degrees to the <br />north, and the strike is North 88 degrees West. <br />Overlying the upper Coal member is the Barren member of the Mesa Verde <br />Formation. This unit consists of interbedded and lenticular sandstones. <br />siltstones, and shales of varying thicknesses. This unit is thought to be of <br />terrestrial origin and, as a result, the sandstones and the coals are highly <br />lenticular, discontinuous, and of limited lateral extent in outcrop. This <br />unit ranges up to 1,fi00 feet thick and outcrops throughout the southern <br />portion of the permit area. <br /> Three categories of potential aquifers occur in the general area. These are <br /> alluvial and terrace deposits associated with the North Fork of the Gunnison <br /> River, the localized shallow alluvial/colluvial areas in the stream drainages, <br /> and ground water 1n the lenticular sandstones and the Rollins sandstone of <br />• Mesa Verde Formation. <br /> The most significant occurrence of ground water in the general area is <br /> associated with the alluvium of the North Fork of the Gunnison River, located <br /> approximately two (2) miles southeast of the mine portals and 1,500 feet lower <br /> in elevation. Significant alluvial sand and gravel deposits averaging 34 feet <br /> thick exist along the North Fork from the mouth of Terror Creek to the <br /> confluence of the Gunnison River. There are numerous wells in the area which <br /> draw water from this alluvium; well yields range from 5 gpm to 120 gpm, with <br /> average yields of approximately 17 gpm (page 31 of Section 2.04.7, Volume 1). <br /> Steven's Gulch, an ephemeral stream, located in the center of the permit area, <br /> drains an area of 6.0 square miles and contains several reaches of shallow <br /> alluviuun/colluvium. Most of these reaches have little ground water except <br /> during periods of stream flow. The most significant area of <br /> alluvium/colluvium occurs to the NW 1/4 of Section 13, T135. R92W (Steven's <br /> Gulch weltfield), where a 25-foot thick sandstone outcrop has created a <br /> topographic restriction such that a considerable thickness of alluvial sands <br /> and colluvial material have been deposited, Test wells drilled by the <br /> applicant indicate that the alluvium in this area can support a pumping rate <br /> of approximately 28 gpm (Ground Water F{ydrology Appendix, Volume 4). The <br /> applicant has 'nstalled a production well and currently uses this water for <br /> domestic use, dust control, and fire control. <br /> The recharge to the Steven's Gulch well field area is through flow from the <br /> adjacent colluvial deposits and from a leaky pipeline aqueduct. The ground <br />• water flows through the colluvium downslope to the alluvium, where it becomes <br />