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<br />. <br /> <br />~ <br />~ <br />~ <br />~ <br /> <br />to 4,000 AF/yr, while more impermeable rocks in Tract C-b would give <br />less than 1,000 AF/yr and produce a well drawdo<;n from 2 to 6 times <br />greater than Tract C-a (Brown et al., 1977). Test wells into the <br />Uinta Formation in the north-central part of the basin yield up to <br />300 gpm (U.S. Bureau of Land Ugmt., 19767), In the lower aquifer, <br />yields from the Parachute Creek Member of the Green River Formation <br />are as high as 1,000 gpm but in the deeper Evacuation Creek Member, <br />lower rock permeability reduces yields to 100 gpm or less (Coffin, <br />1971). One study (Brown et al., 1977) concluded that the more <br />prodigious lower aquifer is not significantly connected with the <br />upper aquifer in oil shale Tract C-a. Therefore, recharge rates <br />are low and long-te~ yields may be meager. This lower aquifer <br />isolation may be repeated at other locations in the basin but this <br />is uncertain (Brown et al., 1977). <br /> <br />. <br /> <br />Water quality from bedrock aquifers varies as to location in <br />the Piceance Creek Basin and geologic unit from which water is with- <br />drawn. Dissolved solids increase from less than 2,000 mg/liter at <br />the fringes of the basin to about 40,000 mg/liter (brine water) at <br />the center of the basin (U.S. Bureau of Land Mgmt., 19767; Andrews, <br />1975). Total dissolved solids also increase toward the northern <br />portions of the basin (Weeks, 1976). Average dissolved solids of <br />samples drawn from the upper aquifers (Uinta Formation and upper <br />part of Parachute Creek Me~ber) ranged from 345 to 2,180 mg/liter <br />(U.S. Dept. of the Interior, 1974). From the lower aquifer (lower <br />Parachute and Evacuation Creek members), samples varied from 250 to <br />63,000 mg/liter (Coffin, 1971). Weeks (1976) reports upper aquifer <br />TDS generally are less than 2,000 mg/liter while water in the lower <br />aquifers may contain more than 30,000 mg/liter TDS (very saline <br />water) in the northern part of the basiu to as low as 1,000 mg/liter <br />in the southern and southeastern parts of the basin. <br /> <br />Sodium and magnesium bicarbonates and sulfates coomonly com?rise <br />as much as 50 percent of ion concentrations in the upper aquifer. <br />The lower aquifer is high in sodium bicarbonates but low in sulfates <br />(Andrews, 1975). Health and environmental concerns have been expressed <br />about the high fluoride content (5 mg/liter) of the lower aquifer, <br />which also has large concentrations of such trace elements as boron, <br />barium, and lithiu= (Weeks, 1976; Andrews, 1975; Brown et al., 1977). <br />The concentrations of such ions would render water from the lower <br />aquifer unfit for irrigation or stock consumption and would add to <br />the costs of water processing, <br /> <br />It is not expected that alluvial aquifers in the Piceance Creek <br />Basin will be a significant source of water supply for oil shale <br />operations since their use would decrease stream flo~ (Brown et a1., <br />1977). Furthermore, the areal extent of alluvium in the valleys of <br />Parachute, Piceance, Yellow, and Roan creeks is small. Alluvial <br /> <br />. <br /> <br />D-14 <br />