Laserfiche WebLink
Description of the Environment <br />Climate <br />The climate at the Edna Mine is typical of semi-arid steppe regions with more than half of <br />the annual precipitation (16 inches) falling as snow. The temperatures are cool, from 61oF <br />average mean temperature in August, to a cold 18~F average mean in February. Regional <br />winds are from the west. Local topography affects both precipitation and wind direction. <br />Geoloev <br />The Edna Mine is geographically situated between the drainages of Oak Creek on the east <br />and Trout Creek on the west. Topographically, the permit area is dominated by a <br />north-south trending ridge line. A steep east-facing escarpment extends to Oak Creek, with <br />a more gentle west-facing dip slope from the ridge line west to Trout Creek. Elevation of <br />the area varies from 7,000 to 7,600 feet. <br />Except for surficial deposits, only the coal bearing Cretaceous Mesaverde Group outcrops <br />in the permit area. The Williams Fork Formation and the Iles Formation together comprise <br />the Mesaverde Group. The Williams Fork Formation is separated from the lower Iles <br />Formation by the massive Trout Creek Sandstone Member, the top of which forms the <br />upper limit of the Iles Formation. The coals to be mined at the Edna Mine are all situated <br />within the Williams Fork Formation, approximately 150-225 feet above the Trout Creek <br />Sandstone. The "Middle Coal Group" of the lower coal bearing member includes, in <br />ascending order, the Wolf Creek, Wadge, and Lennox coal seams. The Lennox and Wadge <br />seams were mined in the West Ridge Area. The Moffat pits will recover the Wadge seam <br />only. <br />The major portion of the Edna Mine is located on the eastern limb of the Twentymile Park <br />Syncline, the axis of which trends northwest from the southernmost boundary of the permit <br />area through West Ridge. Two minor faults occur in the Moffat Area of the mine site. <br />Landscape character in and near the Edna Mine results mostly from moderate folding of <br />strata followed by differential erosion of interbedded resistant and non-resistant layers of <br />various thicknesses. The southern portion of the permit area, West Ridge, consists of large <br />areas of previously strip-mined land characterized by spoil ridges from a dragline operation <br />conducted prior to enactment of the Surface Mining Control and Reclamation Act <br />(SMCRA). <br />Ground Water <br />Monitoring and on-site investigations have identified four aquifer systems at the Edna Mine. <br />These units are: 1) Trout Creek Sandstone, 2) Wadge Coal and overburden, 3) Quaternary <br />alluvium, and 4) replaced spoils. With the exception of the Quaternary alluvium and <br />replaced spoils, it is thought that each of the identified aquifers are hydrologically <br />na me 6 Permit Rev~s~on o. <br />