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discontinuous with each other, due to the relatively impermeable nature of the intervening strata. The consolidated aquifers of Twentymile Park basin are generally recharged at their outcrops near the edge of the basin. Flow direction from the recharge area is toward the center of the basin and may discharge into the Fish Creek alluvial aquifer. Locally, some of the smaller, laterally discontinuous aquifers discharge into the alluvium of Trout Creek, Middle Creek, and Foidel Creek. The alluvial aquifers are locally recharged by the bedrock aquifers, as well as by direct infiltration from precipitation, irrigation return flows, and surface runoff. The alluvial water is discharged into the adjacent stream or consolidated aquifers, or may flow out of the basin via the Trout Creek alluvium which discharges into the Yampa River alluvial system. The Trout Creek Sandstone, which is thought to be a regionally significant source of ground water, is usually characterized by sodium-sulfate type water with an average total dissolved solids (TDS) concentration of about 1040 mg/l. The Wadge Coal and overburden units are marginally acceptable as aquifers at the Edna Mine site, however they are included in this discussion because this unit as a whole is considered to be an aquifer at other mine sites within Twenrymile Park. Aquifer properties were determined from single-hole aquifer tests. These tests indicate that the transmissivity of the coal and overburden varies from 0.7 ftZ/day to 39 ftz/day. These values indicate that the aquifer is marginally useful as a water source in this area. The Wadge Coal water chemistry is calcium/magnesium bicarbonate to sodium sulfate, with TDS values varying between 490 mg/l and 570 mg/I. Ground water quality in the Wadge overburden decreases in the downdip direction. Up-gradient monitoring locations indicate that the water is of moderately good quality, characterized by low Sodium Absorption Ratio (SAR) values and moderate levels of total dissolved solids. The down-gradient monitoring wells, however, show increasingly higher levels of total dissolved solids. This trend applies primarily to the Moffat Area, where undisturbed conditions exist. The vertical migration of water from the Trout Creek Sandstone to the Wadge Coal, due to mining related disturbances is not expected to occur, primarily due to the thick sequence of relatively impermeable interburden. The two alluvial aquifer systems present within the Edna permit area are the Oak Creek and Trout Creek alluvial aquifers. Both of the alluvial aquifers are in direct hydraulic communication with each associated stream. na me 7 Permit evision o.