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SUNDAY MINE COMPLEX-HYDROGEOLOGIC REPORT <br /> connection existed between salt-affected groundwater and overlying sediments including the <br /> Salt Wash sandstones. <br /> Over geologic time, continued uplift and erosion saw the development of the Dolores River <br /> basin and substantial exposure of the Salt Wash on the west limb of the Disappointment Valley <br /> syncline. Recharge of the Salt Wash is more prevalent in these highlands to the west and also <br /> where the river was in contact with the formation. The Salt Wash is confined above by several <br /> hundred feet of siltstones and mudstones of the Brushy Basin Member and below by the <br /> Summerville Formation consisting of similar fine-grained sediments. Migration of groundwater <br /> by vertical flow paths to or from the Salt Wash is therefore expected to be minimal. <br /> Hydraulically, the SMC area is essentially bound to the northeast by a high hydraulic divide and <br /> to the southwest and west, by the Dolores River, which may act as a constant head or <br /> discharge boundary or both. <br /> Groundwater Flow <br /> Potentiometric head in the SMC area in the Salt Wash is indicated by groundwater levels in <br /> monitoring wells, from past observations of levels of flooded mine workings, and from recent <br /> vent shaft water levels. The elevation of the Dolores River is also a potential head boundary. <br /> Despite divergent groundwater elevations measured in the monitoring wells, the head indicated <br /> in the West Sunday and Sunday Mine is approaching 5,500 ft amsl, which is near the same <br /> elevation of the Dolores River located a few miles west (the elevation of the river west of the <br /> SMC is between 5,400 and 5,500 ft amsl). This indicates that the hydraulic gradient between the <br /> mines and the river is small or almost flat. The static potentiometric surface in the area of the <br /> SMC will be best realized after seepage into the mines has ceased and water levels in <br /> monitoring wells show stable levels. <br /> It is postulated that groundwater flow in the Salt Wash in the area between the SMC and the <br /> Dolores River is somewhat stagnant which is conceivable in a synclinal setting. Recharge and <br /> flow from the river toward the syncline axis (northeast) is possible, and discharge and flow to the <br /> river may also occur in the opposite direction. The small gains that may occur in the Dolores <br /> River in this region may be from groundwater inflows from the high mesas on the west side of <br /> the river. Figure 12-1 and Figure 12-2 illustrate planar and cross section schematic <br /> representations of conceptual groundwater flow in the vicinity of the SMC. <br /> Western Water& Land, Inc. 51 <br />