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i 1 <br />' 5.1.2 Characterization oP the West Pit Hydrologic Regime <br />' To further characterize and understand the ground water in the West Pit, additional monitoring <br />wells will be constructed and completed in the saturated portion of the backfilled materials. <br />' These installations will assist (1) identifying the saturated portions of the backfilled materials, <br />(2) developing additional static water elevation data for construction of the potentiometric <br />map, (3) characterizing the magnitude and direction of ground water flow within the pit, (4) <br />estimating the volume of storage within the pit, (5) estimating the volume of unsaturated <br />' material in the pit and (6) evaluating water quality data. Currently, two monitoring wells (BF- <br />1 and BF-2) are completed in the backfill materials of the West Pit. Seven additional <br />monitoring wells will be completed through the complete thickness of the backfilled materials <br />' (estimated to be 60 to 100 feet) (Table 2). Special attention will be paid during drilling <br />relative to the nature of the backfilled materials, e.g. Santa Fe Formation versus pink gneiss. <br />In addition, one pre-Cambrian aquifer monitoring well will be installed upgradient of the <br />backfilled pit as shown in Figure g• This well will be completed to re-establish upgradient <br />water quality. -~ `~~~ ~~ t~^-~~.2 Q~ ~~-e~•~ -^~ <br />' Each of the wells will be constructed as possible multiple purpose installations (with the <br />exception of the upgradient pre-Cambrian well) serving future uses as either monitoring, <br />interceptor or injection wells for longer term response actions. Each of the wells will be <br />' completed consistent with the construction details shown in Figure 9 and will be pump tested <br />to evaluate aquifer hydraulic characteristics. Water sample collections will be taken from each <br />' of the completed following development and analyzed for the parameters givQn in Table 3. <br />Each well will be surveyed for horizontal and vertical control to accurately locate the well and <br />' provide water level elevation data. <br />' 5.1.3 Downgradient Flow Evaluation <br />Hydraulic and water quality characterization of downgradient ground water in the vicinity of <br />monitoring well M-11R will be conducted to evaluate the areal extent of pote¢ttial elevated <br />TDS and sulfate concentrations in the Rito Seco alluvium. Four alluvial monitoring wells are <br />proposed to be installed upgradient and downgradient of M-11R to define the hydraulic <br />gradient and extent of movement of elevated concentrations. These wells will be completed <br />1 <br />19 <br />1 <br />1 <br />