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The water found in the overburden is characterized as very hard, saline, <br />calcium/magnesium sulfate water with neutral pH. TDS levels vary from <br />1494-10074 mg/1 and average 4613 mg/1. Sulfate concentrations are very high, <br />varying from 875 mg/1 to 6872 mg/1 and averaging 3176 mg/1. In some of the <br />overburden wells, sulfate, TDS, manganese and fluoride exceed recommended <br />standards for livestock drinking water. In addition, concentrations of <br />manganese and fluoride exceed the agricultural use standards in some wells. <br />The Dakota coal has been described as an aquifer. Wells completed in the <br />Dakota show water level fluctuations of 1.3 to 14.6 feet. The water table <br />exhibits seasonal fluctuations with high water levels in late fall. The <br />aquifer is recharged from the east north east and discharges to the west and <br />along Tuttle and Calamity Draws. The transmissivity varies from 0.92 to <br />6.0 ft2/day, based on hydraulic conductivity values of 0.04 to 0.34 ft/day <br />(average values of 0.19 ft/day), reflecting moderate flow capabilities. <br />The water quality of the Dakota coal is unacceptable for most uses. The <br />saline, sulfate-based water has TDS levels varying from 1050-4444 mg/1, <br />averaging 2822 mg/1 at New Horizon Mine 2, and TDS levels varying from <br />5438-7100 mg/1 and averaging 6701 mg/1 at Need Horizon Mine 1. The three wells <br />at New Horizon Mine 2 exhibit two distinct geochemical characteristics. Two <br />wells have calcium/magnesium sulfate water with the pH averaging 5.4. One <br />well, 17-P1, is an alkaline sodium sulfate water with the pH averaging 9.2. <br />Iron, manganese, aluminum, fluoride and pH levels exceed recommended water <br />quality criteria for agricultural use, and concentrations of aluminum and <br />fluoride exceed recommended water quality criteria for livestock. <br />The aquifer underlying the coal is identified as the underburden aquifer. The <br />wells in the underburden have been completed 17 to 64 feet below the coal, and <br />samples are representative of water within the lower Dakota Sandstone. This <br />confined aquifer is recharged along the Uncompahgre Plateau to the northeast <br />and discharges towards the southwest. Transmissivity was measured at six <br />sites and varies from 3.0 to 88 ft2/day, averaging 38 ft2/day. Hydraulic <br />conductivity values varied from 0.07 to 4.5 ft/day, averaging 1.6 ft/day. <br />This aquifer is not used locally to any great extent. <br />The water in the underburden is characterized as a hard, moderately alkaline <br />saline water with high sulfate concentrations (average sulfate concentrations <br />of 695 mg/1). Two wells show a calcium/magnesium sulfate type water while one <br />well shows an alkaline sodium bicarbonate type water. The TDS varies from <br />960-2648 mg/l, averaging 1619 mg/l. Dissolved iron levels vary from 0.02 to <br />2.51 mg/1 and average 0.63 mg/l. The sodium bicarbonate well occasionally <br />exhibits pH levels which exceed the recommended agricultural standard. <br />Another well shows manganese levels which exceed the agricultural standards. <br />All wells meet the recommended water quality standards for livestock <br />watering. The underburden aquifer does not produce acceptable water for <br />domestic purposes; TDS, sulfate and ammonia standards are exceeded. <br />Ground water within 150 feet of the ground surface has been only minimally <br />developed for use in the Nucla area. High salinities and occasionally high <br />sodium or sulfate concentrations preclude its use as domestic, agricultural or <br />stock water. In addition, moderate hydraulic conductivities are coupled with <br />low sustained well yields (less than 1.5 gpm), discouraging sustained <br />dependence on wells completed within these aquifers. <br />-8- <br />