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recommended standards for livestock drinking water. In addition, concentrations of manganese <br />and fluoride exceed the agricultural use standards in some wells. <br />The Dakota coal has been described as an aquifer. Wells completed in the Dakota show water <br />level fluctuations of 1.3 to 14.6 feet. The water table exhibits seasonal fluctuations with high <br />water levels in late fall. The aquifer is recharged from the east north-east and discharges to the <br />west and along Calamity Draw. The transmissivity varies from 0.92 to 6.0 ft2/day, based on <br />hydraulic conductivity values of 0.04 to 0.34 ft/day (average values of 0.19 ft/day), reflecting <br />moderate flow capabilities. <br />The water quality of the Dakota coal is unacceptable for most uses. The saline, sulfate-based <br />water has TDS levels varying from 1050-4444 mg/l, averaging 2822 mg/1 at New Horizon Mine. <br />Three wells at the New Horizon Mine 2 exhibit two distinct geochemical characteristics. Two <br />wells have calcium/magnesium sulfate water with the pH averaging 5.4. One well, 17-1 1, is an <br />alkaline sodium sulfate water with the pH averaging 9.2. Iron, manganese, aluminum, fluoride <br />and pH levels exceed recommended water quality criteria for agricultural use, and concentrations <br />of aluminum and fluoride exceed recommended water quality criteria for livestock. <br />The aquifer underlying the coal is identified as the underburden aquifer. The wells in the <br />underburden have been completed 17 to 64 feet below the coal, and samples are representative of <br />water within the lower Dakota Sandstone. This confined aquifer is recharged along the <br />Uncompahgre Plateau to the northeast and discharges towards the southwest. Transmissivity <br />was measured at six 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. This aquifer is not used <br />locally to any great extent. <br />The water in the underburden is characterized as hard, moderately alkaline saline water with high <br />sulfate concentrations (average sulfate concentrations of 695 mg/1). Two wells show a <br />calcium/magnesium sulfate type water while one well shows an alkaline sodium bicarbonate type <br />water. The TDS varies from 960-2648 mg/1, averaging 1619 mg/l. Dissolved iron levels vary <br />from 0.02 to 2.51 mg/1 and average 0.63 mg/l. The sodium bicarbonate well occasionally <br />exhibits pH levels that exceed the recommended agricultural standard. Another well shows <br />manganese levels that exceed the agricultural standards. All wells meet the recommended water <br />quality standards for livestock watering. The underburden aquifer does not produce acceptable <br />water for domestic purposes; TDS, sulfate and ammonia standards are exceeded. Measurable <br />trace element concentrations in the underburden aquifer include aluminum, arsenic, boron, <br />cadmium, copper, fluoride, iron, lithium, manganese, mercury, nitrate, vanadium and zinc. The <br />highest concentrations of arsenic, mercury and copper were measured in the underburden aquifer <br />at the New Horizon 2 mining area. <br />Ground water within 150 feet of the ground surface has been only minimally developed for use <br />in the Nucla area. High salinities and occasionally high sodium or sulfate concentrations <br />preclude its use as domestic, agricultural or stock water. In addition, moderate hydraulic <br />conductivities are coupled with low sustained well yields (less than 1.5 gpm), discouraging <br />sustained dependence on wells completed within these aquifers. <br />13