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1) Surficiel - Neer Surface Water Occurrence: • Unconsolidated fine to coarse grained sends w/occasional 1/8" to 1-1/2" gravels; silty, clayey. Windblown sands cap these deposits. Subsurface water occurrence as influenced by the Ennis Draw peleo channel/bedrock structure is restricted to the eastern 1/3 of Sec. 25, T3N, R 64W, 6th PM. Subsurface water flow in Ennis Draw is predominantly SE to NW. Thies unconfined (water table) aquifer, inclusive of the eolian sands adjacent to Ennis Draw, varies from O ft. - 30 ft. in thickness. 2) Bedrock (Laramie-overburden) Water Occurrence: Weathered silty clays and sands that overlie unweathered bedrock. Subsurface water resides in this transition zone between the overlying sands and underlying clay bedrock. Ground-water flow is to the northeast across the mine site and is largely controlled by the top of bedrock which also slopes to the northeast. Preferential zones of water migration (higher relative permeability) exist in the weathered bedrock materials. The occurrence of subsurface water is largely unconfined in nature, however, there is some information suggesting that this system can be locally confined. Thickness of these zones is approximately O ft. to 20 ft. However, silty clay may cap gravels an the western flank of Ennis Draw. 3) Unweathered Bedrock (Laramie-Overburden) Water • Occurrence: Overconaolidated clays and clay shales are the predominant lithology. No flows have been observed from these materials as permeabilities are very low and resist vertical and horizontal migration of subsurface water from the overlying weathered bedrock. However, very Ssolated zones of silty, sandy rock types representative of channel type environments may produce small quantities of water (.Sgpm). The occurrence of water in the coal seam (thickness=7 ft.) ie restricted to the lower 1'-2', and appears only as visible surface moisture. Subsurface water in the unweathered bedrock (thickness = 45-70 ft.) and the coal seam is considered to be confined end separate from one another. 4) Laramie-Fox-Hills Aquifer Water Occurrence: These deposits consist of massive fine grained sends and ailtatonea. The No. 7 coal seem to be mined is separated from the underlying Laramie and FoxHills sandstone by 100 to 200 feet of Laramie clays and clay shales. The Laramie-FoxHilla aquifer will not be affected by the ash disposal operation. Thickness of this confined aquifer is approximately 35'. • -26-