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limited ground water that may be suitable for domestic and stock use, the <br />extensive shales in the upper part of the formation act as relatively <br />impermeable barriers to the subsurface movement of water and the Mancos Shale <br />can be considered as an impermeable, confining layer underlying the tdesaverde <br />Group. <br />The Trout Creek sandstone underlies the Wadge coal seam and is separated from <br />the coal by 150 to 300 feet of interbedded shales, siltstones, sandstones and <br />coals within the permit and adjacent areas. The latter acts as an aquitard <br />for the artesian Trout Creek sandstone aquifer east of the mine. The 7rrout <br />Creek sandstone provides recharge to alluvial aquifers and base flows to Trout <br />Creek and its tributaries. The sandstone is an important regional bedrock <br />aquifer within the Twentymile Park Synclinal Basin. This sodium <br />bicarbonate-based water has TDS values of approximately 900 mg/l. It is used <br />for industrial (mining), domestic, and irrigation ground water supplies. <br />The Wadge coal overburden aquifer is composed of the coal and 75 feet of mixed <br />shale and interbedded and lanticular sandstones. The permeability of this <br />aquifer ranges from 0.001 ft/day to 0.5 ft/day. Generally, areas of shallow <br />overburden have the highest permeabilities which decrease with increasing <br />overburden thickness. <br />There are three aquifers of interest in the Hayden Gulch permit area. There <br />are two aquifers in the Williams Fork which flow through the lenticular and <br />intertedded sandstones associated with the coal bearing zones: The upper coal <br />aquifer and the lower coal aquifer. These localized aquifers dip 4°-8° to the <br />northeast towards the watering trough syncline. The Twentymile Sandstone is <br />regional aquifer which lies 250' below the lower coal and is approximately 100 <br />feet thick. It is separated from the coal aquifer by interbedded sandstone <br />and shale beds which are moderately impermeable. <br />Twentymile Sandstone is recharged southwest of the mine. Transmissivity <br />values of 1-2 gpd/ft were recorded in addition to a storage coefficient of <br />0.01, at one well at the mine. The storage coefficient seems somewhat low in <br />comparison to other recorded values of the Twentymile Sandstone, indicating <br />that this well might be completed in a zone overlying the Twentymile <br />Sandstone. This calcium bicarbonate water has concentrations of ammonia, <br />iron, manganese and sulfate in excess of receiving stream standards. The <br />neutral water has total dissolved solids concentrations ranging from 612-1700 <br />mg/1. <br />The lower coal aquifer is defined as the fifth coal seam and the underlying <br />sandstone strata; this zone ranges in thickness from six (6) to eight (8) feet <br />in permit area. Transmissivity levels vary from 0.1 to 6.92 gpd/ft and <br />storage capacity was 0.01. This calcium bicarbonate water has concentrations <br />of sulfate, ammonia, iron and manganese in excess of receiving stream <br />standard. Conductivity levels range from 1.14 - 2.05 mmhos/cm and the pH is <br />8, slightly alkaline. <br />-14- <br />+ ~- <br />