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SUNDAY MINE COMPLEX-HYDROGEOLOGIC REPORT <br /> Discharge of the M aquifer (Salt Wash) occurs from evapotranspiration, springs and seeps, <br /> discharge to the Dolores River, lateral outflow from the SMC area, and leakage to over and <br /> underlying formations. <br /> N Aquifer <br /> The N aquifer underlies the M aquifer and, in ascending order, consists of the Wingate <br /> Sandstone, the Kayenta Formation, the Navajo Sandstone, the Carmel Formation, and the <br /> Entrada Sandstone, all of Jurassic age (south of the San Juan River the Entrada is not <br /> considered part of the N aquifer) (Avery, 1986). The aquifer, where all units are fully preserved <br /> and saturated may attain thicknesses of between 750 to 1,250 ft (Avery, 1986). <br /> In the SMC area, the N aquifer units are exposed on the northeastern limb of the Gypsum <br /> Valley anticline on the northeast flank of Big Gypsum Valley. The N aquifer lies at considerable <br /> depth under the mined area and Disappointment Valley, but is exposed in the Dolores River <br /> canyon a few miles to the northwest and in tributary canyons a few more miles west. Further <br /> west and north the N aquifer units are exposed in canyons that dissect high mesas. <br /> Jobin (1962) reported permeability of the N aquifer to range between 60 and 400 millidarcys <br /> (0.13 and 0.98 ft/d, respectively). The reported hydraulic conductivity for the Navajo Sandstone <br /> portion of the aquifer ranges from 0.4 to 66.2 ft/d (Cooley and others, 1969). <br /> The principal areas of recharge to this aquifer are in the exposed higher portions of canyons <br /> where stream runoff comes in direct contact with the rock, and in areas where thin alluvium may <br /> cover the aquifer units and store deep percolated precipitation. Discharge of the N aquifer is by <br /> evapotranspiration, discharge at springs, streams and topographic lows, interformational <br /> subflow, and lateral subflow. <br /> The N aquifer is a commonly used groundwater supply source in the region, especially where <br /> depths are reasonable for development and in areas where the D aquifer is thin or not present. <br /> P, C and Redwall Aquifers <br /> Other aquifers in the region and those deeply buried in the area of the SMC include the P, C, <br /> and Redwall aquifers. These aquifers underlie the confining beds of the Chinle Formation and <br /> other separating confining units. The P aquifer consists of the Cedar Mesa Sandstone Member <br /> (where present) of the Cutler Formation or of undifferentiated Cutler Formation, and the C <br /> aquifer consists of the De Chelley Sandstone Member of the Cutler Formation (Avery, 1986). <br /> Western Water& Land, Inc. 19 <br />