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SUNDAY MINE COMPLEX-HYDROGEOLOGIC REPORT <br /> saturated thicknesses of less than 100 ft in the area. Jobin (1962) estimated a thickness of 100 <br /> ft for the Burro Canyon Formation and Dakota Sandstone in the area of the SMC (Jobin <br /> includes the Cedar Mountain Formation in this thickness, but by convention, this formation is <br /> correlative to the Burro Canyon Formation east of the Colorado River and is not applicable at <br /> the SMC). <br /> Jobin (1962) estimated a permeability of 665 millidarcy (6.38 x 10-4 centimeters/second <br /> [cm/sec] or 1.81 feet/day [ft/d]) in the area near the SMC. Avery (1986) reported hydraulic <br /> conductivity values for the D aquifer of 0.35 and 0.77 ft/d in the Monticello, Utah area. <br /> Transmissivity of the D aquifer is estimated to be 10 to 50 ft2/d (Freethey and Cordy, 1991), <br /> although Jobin (1962) estimated a value of 90 darcy-ft (245 ft2/d). The D aquifer is unconfined <br /> when exposed on the surface or covered with a thin cap of alluvium, but can be confined by the <br /> overlying Mancos Shale, when present. Storage coefficients reported by Avery (1986) are <br /> relatively small, on the order of 1 x 10-5, indicating confined conditions for these values. <br /> The D aquifer receives recharge by infiltration of precipitation where exposed in locations such <br /> as Disappointment Valley and on ridges northeast of Big Gypsum Valley and on high mesas <br /> such as Island Mesa and Horse Range mesa west of the Dolores River. Freethey and Cord <br /> (1991) suggest that direct infiltration of precipitation on exposed rocks is not significant in areas <br /> where winter precipitation does not exceed 8 inches per year. The aquifer is not present in the <br /> area immediately overlying the SMC, but is mapped on the southern and western flank of <br /> Disappointment Valley and within a faulted block immediately northeast of the mines in Big <br /> Gypsum Valley. <br /> M Aquifer <br /> The M aquifer consists of the Morrison Formation, primarily the units of the Salt Wash Member. <br /> Although other sandstone members are present in the Morrison Formation (ascending above <br /> the Salt Wash are the members Recapture and Westwater Canyon Members, and below the <br /> Salt Wash Member, the Bluff Sandstone Member), they do not occur in the vicinity of the SMC. <br /> The M aquifer is confined above by the Brushy Basin Member and below by the Summerville <br /> Formation (Avery, 1986); both of low permeability. Although the Brushy Basin Member is <br /> considered an aquiclude, it does include lenses of perched groundwater in some locales. <br /> Regionally, the M aquifer is not commonly used for domestic water supplies because of its <br /> relative greater depth, low yield, and poor water quality. Weir(1983) reported the thickness of <br /> Western Water& Land, Inc. 17 <br />