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Sandstone Member, the top of which fortes 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 ]50-225 feet above the Trout Creek Sandstone. The "Middle Coal Group" of the lower coal bearing member include, in ascending order, the Wolf Creek, Nadge, and Lennox coal seams, 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, Nest Ridge, consists of large areas of previously strip-mined land which remains as spoil ridges left by a pre-SMCRA dragline operation. Ground Water The Wadge coal seam, its overburden, and the immediate underburden are all water-bearing. However, the first rock unit below the Wadge Coal with any significant potential as a regional aquifer is the Trout Creek Sandstone. Generally, the Wadge Coal, the overburden, and the immediate underburden all have limited ability to transmit significant quantities of water, The Trout Creek Sandstone, a 100 foot thick sandstone unit which is persistent throughout much of northwestern Colorado, underlies the pit bottoms by approximately 750-225 feet. This regionally significant sandstone aquifer will not be physically disturbed by the Edna Mine. Because of the interbedded nature and low permeabilities of the rock units situated stratiaraphically between the Wadge Coal and the Trout Creek Sandstone, little hydrologic communication between these units is expected. The alluvial bodies located adjacent to Trout Creek and Oak Creek are considered locally important aquifers. These alluvial systems are in direct hydrologic connection with the associated stream channel. The bedrock formations generally plunge beneath or subcrop under the Trout Creek a77uvium, Following mining and the disruption of the overburden, it may be possible for water percolating through the spoils to enter the Trout Creek alluvial aquifer. Surface Water The permit area lies in the upper Yampa River basin and is drained by several ephemeral streams which flow into Trout Creek and Oa Y, Creek. These are both perennial streams which flow in a northeasterly direction toward the Yampa River. The ephemeral streams draining the permit area flow predominantly west-northwest into Trout Creek, which follows the western permit boundar~~. -b-