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11.2.1 Monitoring Well Locations <br />The regional groundwater gradient is assumed to be towards the south based on the <br />topography of the area and available groundwater level data. Therefore, the <br />upgradient monitoring wells will be located north of the underground mine workings <br />and the intermediate and compliance wells will be south of the underground mine <br />workings. Monitoring wells will be screened in the Top Rim sandstone unit of the <br />Saltwash aquifer. This rock unit hosts the uranium ore bodies that have been, and will <br />be mined at the Sunday Mines Group. The following provides additional detail <br />regarding the proposed groundwater monitoring wells. <br />Upgradient Monitoring Well <br />The location for the upgradient groundwater monitoring well was determined in <br />consultation with DRMS based on evaluation of hydrogeology, ore deposit geology, <br />and the location of active and expected future mining areas. Groundwater quality <br />data collected from the upgradient well will be used to support assessment of <br />groundwater conditions in the Top Rim sandstone of the Salt Wash aquifer. Water <br />level data collected from the upgradient well will support further assessment of <br />groundwater flow directions and velocity. Criteria considered by DRMS and Denison <br />in selection of the upgradient monitoring well location included the following: <br />• The well should be located in an area of naturally elevated concentrations of <br />uranium and vanadium to provide a representative measurement of natural <br />background conditions in mineralized areas; <br />• The well should not be located in direct proximity of the underground <br />workings to avoid potential anthropogenic effects to groundwater quality; <br />• The well should be located within the Top Rim Sandstone Unit of the Saltwash <br />Member (the rock unit that hosts uranium mineralization); and <br />• The well should not be located down - gradient from the mine workings. <br />The structural geology of the area essentially truncates the aquifer of interest in the <br />northerly direction as shown on Figure 11 -2. The Top Rim sandstone unit is present in <br />this area, but it occurs at a higher elevation and is not saturated. Rock units <br />stratigraphically below the Top Rim sandstone may be saturated north of the <br />proposed location, but the target aquifer for groundwater quality monitoring is not <br />saturated. Therefore, the structural geology and hydrogeology of the area precludes <br />placement of the upgradient monitoring well further north from the selected location. <br />The upgradient monitoring well will also be located within an area of naturally <br />mineralized rock to provide valid data to assist with both the evaluation of ambient <br />conditions and potential effects of the mining operation on groundwater quality. This <br />limitation precludes placement of the upgradient monitoring well further to the west <br />of the selected location or in a location distal to areas of uranium and vanadium <br />mineralization. Areas of previously mined underground workings are present east of <br />the proposed location. The location for the upgradient monitoring well was selected <br />C \Users\cwoodwardeesIdop \Sundays \FINAL - Environmental Protection Plan Sunday Mines Revised January 2012 docx <br />11 -2 <br />