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SUNDAY MINE COMPLEX-HYDROGEOLOGIC REPORT <br /> the Salt Wash Member to be between 15 and 152 ft thick in a study area extending from <br /> Monticello to Moab, Utah. Whereas, Avery (1986) reported a maximum thickness of 490 ft in <br /> eastern San Juan County, Utah,just west of the SMC area. Freethey and Cordy (1991) <br /> estimate that the saturated thickness of the M aquifer in the area surrounding the SMC is less <br /> than 100 ft. <br /> The Salt Wash and other sandstone-rich members of the Morrison Formation are composed of <br /> interbedded fine to medium-grained sandstone and claystone. Cadigan (1967) conducted an in- <br /> depth study of the lithology of the Morrison Formation and described the Salt Wash Member as <br /> 60% sandstone, 39% siltstone, claystone, and mudstone, and 1% limestone and miscellaneous <br /> rocks. <br /> Jobin (1962) studied the transmissivity of rocks associated with uranium deposits on the <br /> Colorado Plateau. He constructed transmissivity isopleth maps of the region for multiple <br /> geologic formations. Jobin's map (Jobin, Fig. 32, 1962) indicates that sandstones of the <br /> Morrison Formation in the vicinity of the SMC have a permeability of 0.115 darcys; when <br /> converted to hydraulic conductivity for water under standard conditions, this value is equivalent <br /> to 1.106 x 104 cm/s or 0.31 ft/d. <br /> The M aquifer receives recharge by infiltration of precipitation where exposed in locations of <br /> higher elevations where precipitation is substantial, from infiltration from the Dolores River in <br /> places where the river overlies the Formation, and from lateral and vertical subflow from <br /> adjoining saturated formations. The amount of exposed Salt Wash Member is limited in the <br /> study area. Only a few discontinuous exposures occur on the southwest flank of Big Gypsum <br /> Valley near the SMC. Recharge by infiltration of precipitation is expected to be minor in the mine <br /> areas. <br /> However, significant exposure of the Salt Wash Member occurs a few miles to the west in the <br /> Dolores River canyon and further west where the Formation forms bedrock on the upper slopes <br /> of tributary drainages to the river. These areas likely serve as main recharge locations for the <br /> Salt Wash, provided precipitation exceeds approximately 8 inches of normal winter annual <br /> precipitation as suggested by Jobin (1962). In addition, the M aquifer may receive recharge from <br /> the Dolores River where the Salt Wash Member forms bedrock under the river at, and south of, <br /> Slick Rock, Colorado, for approximately one mile. The Salt Wash may also receive recharge <br /> from lateral inflow from outside the SMC area, as well as interformational inflow from adjoining <br /> formations. <br /> Western Water& Land, Inc. 18 <br />