2012-09-28_REVISION - M1977307 (23)

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of the Kayenta Formation and is not representative of the entire formation. However, the lowest permeability unit controls flow for the entire formation. For mining to impact the regional groundwater system, mobilized constituents would have to migrate from the upper sandstone unit of the Salt Wash Member through the lower sandstones and bentonitic shales of the lower portion of the Salt Wash, through the impermeable Summerville Formation, the unsaturated Entrada and fine - grained Carmel Formations, and the well- cemented siliceous sandstone and shales of the Kayenta Formation before reaching groundwater in the Wingate Formation. Considering the hydrogeologic constraints, this scenario is not anticipated to occur. 8.3.4 Recharge Based on the well information discussed in Section 8.3.1, the Wingate Formation appears to be the upper -most aquifer in the area. The recharge area for the Wingate Formation would be along the flanks of the Paradox Valley anticline. While the literature indicates that there is insufficient precipitation to recharge the aquifer in the exposed rock outcrops along the Paradox Valley walls, there are numerous faults that run parallel to the valley, over 3 miles to the southwest of the mine site, that may collect the available precipitation and recharge the aquifer. There is evidence to suggest that another potential source of recharge for the Wingate Formation would be from the San Miguel River in the Uravan area. Portions of the Kayenta Formation have been eroded in the valley allowing seepage from the river to enter the Wingate Formation. If it is assumed that the San Miguel River is in hydraulic communication with the Wingate Formation in the Uravan area, the approximate elevation of the river in the area is 4950 ft. Compared to the static water level elevations presented in Table 2, two of the three monitoring wells show lower water level elevations, indicating recharge from the river is occurring and moving westward in the Wingate Formation. 8.4 Groundwater Monitoring Monitoring groundwater quality to specifications of the Resource Conservation and Recovery Act (RCRA) or requirements of the DRMS is difficult. Simple concepts of up- and down - gradient monitoring wells at locations that could provide early warning system were problematic at best and not representative of subsurface conditions at worst. Cotter instructed crews drilling exploration holes for delineation of ore deposits to note zones of "moisture." Figure T2 shows a 3 -D diagram of the site topography and geology including the location of exploration borings that targeted the ore - producing zone in the Salt Wash Sandstone. This moisture data provide valuable insights on the hydrogeology of the region. Figure T2 shows a 3 -D diagram of the site topography and geology including the location of exploration borings that targeted the ore - producing zone in the Salt Wash Sandstone. The upper surface of Figure T2 shows the topography of the site. The middle layer is the ore zones within the upper sandstone unit of the Salt Wash Member of the Morrison O'Connor Design Group Inc. T - 13