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<br />The volume of ground water stored in the Piceance Creek structural basin, <br />~ <br />-J whose porosity is due mainly to fracturing of various formations, has been estimated <br />~ <br /> <br />~l to be as small as 2.5 maf and as large as 25 maf. Until a map of the porosity of <br /> <br />the permeable section of the structural basin is completed, a more accurate estimate <br /> <br />cannot be made. In any event, only an unknown portion of the ground water in <br /> <br />storage would be physically recoverable and, in turn, only a fraction of that <br /> <br />amount is apt to be economically recoverable. <br /> <br />With respect to the structural basin's water quality, it is generally rather <br /> <br />poor, although it varies from place to place and from one geologic unit to another. <br /> <br />In the upper aquifer, total dissolved solids are generally less than 2,000 mg/l. <br /> <br />Total dissolved solids concentrations in ,the lower aquifer may range from more <br /> <br />than 30,000 mg/l (very saline water) in the northern part of the structural basin <br /> <br />to as low as 1,000 mg/l in the southern and southeastern parts of the structural <br /> <br />basin. Water of such quality, which will probably have high fluoride and boron <br /> <br />concentrations also, would have to be processed before being applied to any <br /> <br />industrial use or before being discharged to surface streams (e.g., as a means <br /> <br />of disposing of excess mine drainage water). <br /> <br />Since the oil shale resource (i.e., the Mahogany Zone) lies between the two <br /> <br />aquifers in the Piceance Creek structural basin, it is likely that ground water <br /> <br />will be an important consideration in the development of an oil shale industry, <br /> <br />whether used as a source of supply or not. For example, dewatering of mines and <br /> <br />underground retorts could produce amounts of water significantly in excess of a <br /> <br />plant's consumptive use requirements. Disruption of artesian conditions also has <br /> <br />legal ramifications, as discussed below. Finally, the quality of the ground <br /> <br />water has cost implications for its use and disposal, while preventing the mixing <br /> <br />of waters of differing quality in the upper and lower aquifers after mining of <br /> <br />the Mahogany Zone will be difficult. It must be emphasized, however, that ground <br /> <br />water conditions can vary substantially from site to site. Thus, these general <br /> <br />conclusions must be regarded with caution until more definitive data has been <br /> <br />collected. <br /> <br />cx <br />