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<br />' The salinity hazard to crops is considered to be very high. This well was not <br />used for the 1986 irrigation season for this reason. The water quality of <br />this well in contrast to the other Fox Hi11s well is a sodium sulfate type. <br />It was later found that the casing had been corroded and breached by carbon <br />dioxide gas found within the Laramie formation. <br />The Laramie formation overlies and confines the Fox Hi11s sandstone with <br />sequences of shale, sandstone and coal. The coal is the only isolated unit <br />that is considered an aquifer. The overlying interbedded shales and <br />sandstones are grouped together and labeled as the overburden aquifer. From <br />pump tests, the coal aquifer appears to be confined and the overburden aquifer <br />unconfined. Generally the water quality of the coal aquifer is much better <br />than the overburden aquifer. The total dissolved solids concentration in the <br />coal aquifer is are approximately 1500 mg/1 and in the overburden <br />approximately 7000 mg/1. Pump, slug and recovery tests show transmissivities <br />(T) in these two aq fifers to be poor to infeasible for use as a domestic water <br />source (T = .011 ft~/min - .00017 ft2/min.) <br />During Quarternary times the Laramie Formation was eroded and streams cut into <br />the formation. Gravels were deposited in these channels. Later Aeolian sands <br />were deposited as dunes modified the topography with a blanket of sand. The <br />gravels of these ancient streams are very permeable and have been identified <br />as an aquifer. In the area of the Keenesburg Mine, Ennis Draw is a buried <br />stream channel containing gravels. The operation has avoided mining through <br />the gravels and intercepting its flow, but in 1986 the water on the gravels <br />was used for irrigation. The gravels are generally only about 12" thick, thus <br />the transmissivity in relation to the permeabilities is very low. It is <br />estimated that about 6 acre feet of water flows through the gravels of Ennis <br />Draw annually. The water quality of Ennis Draw is suitable for irrigation and <br />stock watering with total dissolved solids in the range of 750-1000 mg/l. The <br />Aeolian sands do not appear to be an identifiable aquifer but may hold limited <br />water in isolated pockets. <br />The 4 aquifers discussed are hydrologically independent of each other. The <br />Fox Hills sandstone has a gradient that flows to the north. The coal aquifer <br />has a northeast trending anticline through the northwest portion of the permit <br />area causing. Flows to the northeast and southwest along the axis. The <br />Laramie overburden has a ground water gradient that flows to the northwest. <br />The gravels of Ennis Draw transport ground water in a northerly direction. <br />-10- <br />