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Description of the Environment Climate The climate at the Edna Mine is typical of semi-arid steppe regions with more than half of the annual precipitation (16 inches) falling as snow. The temperatures are cool, from 61'F average mean temperature in August, to a cold 18°F average mean in February. Regional winds are from the west. Local topography affects both precipitation and wind direction. Geology The Edna Mine is geographically situated between the drainages of Oak Creek on the east and Trout Creek on the west. Topographically, the permit area is dominated by a north-south trending ridge line. A steep east-facing escarpment extends to Oak Creek, with a more gentle west-facing dip slope from the ridge line west to Trout Creek. Elevation of the area varies from 7,000 to 7,600 feet. Except for surficial deposits, only the coal bearing Cretaceous Mesaverde Group outcrops in the permit area. The Williams Fork Formation and the Iles Formation together comprise the Mesaverde Group. The Williams Fork Formation is separated from the lower Iles Formation by the massive Trout Creek Sandstone Member, the top of which forms the upper limit of the Iles Formation. The coals to be mined at the Edna Mine are all situated within the Williams Fork Formation, approximately 150-225 feet above the Trout Creek Sandstone. The "Middle Coal Group" of the lower coal bearing member include, in ascending order, the Wolf Creek, Wadge, and Lennox coal seams. The Lennox and Wadge seams will be mined in the West Ridge Area. The Moffat pits will recover the Wadge seam only. The major portion of the Edna Mine is located on the eastern limb of the Twentymile Park Syncline, the axis of which trends northwest from the southernmost boundary of the permit area through West Ridge. Two minor faults occur in the Moffat Area of the mine site. Landscape character in and near the Edna Mine results mostly from moderate folding of strata followed by differential erosion of interbedded resistant and non-resistant layers of various thicknesses. The southern portion of the permit area, West Ridge, consists of large areas of previously strip-mined land characterized by spoil ridges from a dragline operation conducted prior to enactment of the Surface Mining Control and Reclamation Act (SMCRA>. Ground Water Monitoring and on-site investigations have identified four aquifer systems at the Edna Mine. These units are: 1) Trout Creek Sandstone, 2) Wadge Coal and overburden, 3) Quaternary alluvium, and 4) replaced spoils. With the exception of the Quaternary alluvium and replaced spoils, it is thought that each of the identified aquifers are hydrologically discontinuous with each other, due to the relatively impermeable nature of the intervening strata. The consolidated aquifers of Twentymile Park basin are generally recharged at their outcrops near the edge of the basin. Flow direction from the recharge -~-