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~ • • <br />~ I'~ <br />' degrees. The ground water gradient has a similar direction of dip, but allower gradient <br />(approximately 4.5 degrees). <br />We have evaluated whether the existing monitoring wells can adequately monitor ground water <br />' quality downgradient of the tailings facility and collection pond. To evaluate this, a dispersion <br />' analysis using atwo-dimensional analytical model was conducted to assess if there was a point <br />source of leakage within the tailings facility and/or collection pond whether that leak would be <br />observed at the three existing monitoring wells (M-9, M-12 and M-13). <br />' For this analysis, we used the aquifer characteristics derived from the pump tests and input a <br />lateral dispersivity of 100 feet and a transverse dispersivity of 30 feet. For a given minimum <br />' distance of 550 feet from the collection pond pool to downgradient well M-9, it Bs expected that <br />a point source of contamination would have dispersed through an aquifer width of approximately <br />' 2,400 feet. Therefore, some portion of the plume created by that point source would be <br />observed at well M-9. Similarly, for a point source leak from the tailings facility to the nearest <br />' monitoring well (eitfter M-12 or M-13) the minimum distance travelled would be approximately <br />1,000 feet and, given the dispersivity analysis, it is expected that the lateral dispersion in the <br />' aquifer over that distance would be approximately 2,800 feet. This amount of dispersion would <br />result in the plume being observed in the monitoring wells regardless of where in the tailings <br />facility the leak would occur (due to the geometry of the wells with respect to the tailings <br />facility). <br />In either instance, based on the spacing of the tluee existing downgradient monitoring wells, <br />' these wells would observe cyanide contamination if it entered the upper water-bearing strata of <br />the Santa Fe Formation. <br />1 <br />In addition to evaluating the existing wells' capability to monitor ground water quality <br />' conditions, we have used the aquifer hydraulic characteristic data derived from the pump tests <br />' (Table 2) to evaluate whether the installed monitoring wells would be capable of providing <br />hydraulic control in the event that contaminants are observed in the local ground water table, <br />' 7 <br />1 <br />