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-8- <br />The flow of water in Terror Creek and in the North Fork of the Gunnison River <br />are strongly influenced by irrigation structures along these stream courses. <br />The Overland Ditch intercepts and distributes water from the upper reaches of <br />Terror Creek. The flow in the North Fork is controlled by Paonia Reservoir <br />and water withdrawals by several irrigation ditches: the Fire Mountain Canal, <br />Stewart Ditch, Farmers Ditch, and Paonia Ditch. In addition, a pipeline <br />aqueduct used by the Pitkin Mesa Pipeline Company follows Steven's Gulch <br />through the permit area. <br />There are many springs and ponds within the permit and hydrologically <br />adjacent area. It appears that, based on available data, that most of these <br />springs and ponds are intermittent and depend upon seasonal precipitation and <br />recharge from shallow colluvial/alluvial sources. <br />The Orchard Valley Mine lies on the southeast margin of the Piceance Basin. <br />Sedimentary rocks ranging from late Cretaceous to early Tertiary age, and <br />dipping 5 degrees North, are exposed in the mine areas. <br />Structural-stratigraphic cross-sections and isopach maps are presented in <br />Volume l0A (Confidential Appendices), and the mine area geology is presented <br />on Map 2-2. <br />Coal is to be produced from the Mesaverde Formation, a 2,500-foot-thick <br />sequence of sedimentary beds overlain by the Ohio Creek Congolomerate and <br />underlain by the Mancos Shale. The Mesaverde Formation is composed of four <br />members; the Rollins sandstone, the Upper and Lower Coal members, and the <br />"Barren" member. <br />The lowermost member of the Mesaverde Formation, the Rollins sandstone, is a <br />white to buff-colored, well-sorted, medium-grained sandstone, ranging from 150 <br />feet to 200 feet thick in the permit area. The Lower Coal member overlies the <br />Rollins sandstone and consists of interbedded sandstones, siltstones, coals, <br />and shale. The unit averages 265 feet thick in the permit area and bears <br />three significant coal seams--the "A", "B", and "C" seams. <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, Mesaverde 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 88o West. <br />Overlying the upper Coal member is the Barren member of the Mesaverde <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 1,600 feet thick and outcrops throughout the southern <br />portion of the permit area. <br />r.__ <br />