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~~~r- <br />2.04.7 HYDROLOGY DESCRIPTION <br />The description of the hydrological conditions that follows is a result of the <br />accumulation of data and observations since the start of mining in 1981. This <br />information is combined with studies conducted by McWhorter (Appendix I) <br />during research of the sub-surface water conditions at the present day Keenesburg <br />Mine location. <br />Subsurface Water Hydrology <br />Four subsurface water systems can be identified to exist in the vicinity of the <br />project site. In order of occurrence (top to bottom) they are situated as follows, I) <br />wind blown sand and Fluvial deposits in and adjacent to Ennis Draw, 2) weathered <br />bedrock (transition) zone consisting of silty clays and sands, 3) unweathered, <br />overconsolidated clays and clay shales, mud stones, clay stones, coal and minor <br />sandstones of the Laramie Formation (excluding the lower Laramie sands) and 4) <br />the Laramie-Foxhills aquifer (which includes the lower Laramie and Fox Hills <br />Sandstone formations). <br />Information regarding subsurface water occurrence is summarized as follows (refer <br />to cross sections on following pages, where aquifer systems are labeled by <br />number): <br />• 1) Surficial -Near Surface Water Occurrence: Unconsolidated fine to coarse <br />grained sands w/occasional 1/8 in. to 1-1/2 in. gravels: silty, clayey. <br />Windblown sands cap these deposits. Subsurface water occurrence as <br />influenced by the Ennis Draw pale channel bedrock structure is restricted to <br />the eastern 1/3 of Sec. 25, T3N, R64W, 6th PM. Subsurface water flow in <br />Ennis Draw is predominantly SE to NW. This unconfined (water table) <br />aquifer, inclusive of the eolian sands adjacent to Ennis Draw, varies from 0 ft. - <br />30 ft. in thickness. <br />2) Bedrock Laramie-overburden) Water Occurrence: Weathered silty clays <br />and sands that over lie unweathered bedrock. Subsurface water resides in this <br />transition zone between the overlying sands and underlying clay bedrock. <br />Groundwater flow is to the northeast across the mine site and is largely <br />controlled by the top of bedrock which also slopes to the northeast. <br />Preferential zones of water migration (higher relative permeability) exist in the <br />weathered bedrock materials. The occurrence of subsurface water is largely <br />unconfined in nature, however, there is some information suggesting that this <br />system can be locally confined. Thickness of these zones is approximately 0 ft. <br />to 20 ft. However, silty clay may cap gravels on the western flank of Ennis <br />Draw. " <br /> <br />48 <br />