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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/l and average 4613 mg/l . Sulfate concentrations are very high, <br /> varying from 875 mg/l to 6872 mg/l and averaging 3176 mg/l . 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/l , <br /> averaging 2822 mg/1 at New Horizon Mine 2, and TDS levels varying from <br /> 5438-7100 mg/l and averaging 6701 mg/l at New 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/l 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 />