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5) In the event that concentrations of F and Mn become elevated in the aquifer after land-application to <br />concentrations greater than predicted, what mitigation measures are proposed? <br />6) The leach tests conducted on the aquifer materials revealed that arsenic is prone to leaching to the <br />ground water after application of the West Pit Water. Amore detailed assessment of this is <br />recommended. <br />7) The applicant should conduct laboratory tests to evaluate the potential for release of contaminants <br />from the aquifer geologic materials as a result of seasonal fluctuations of the water table to address the <br />question of whether alternating cycles of saturation and unsaturation caused by water table fluctuations <br />will enhance contaminant mobility. <br />8) I recommend nested wells to capture both shallow and deep GW quality. Figure G.4-l shows well <br />SLM-2 is screened at two locations; at a depth of 85-95 ft, and at 295-305 feet. There are three closely- <br />spaced clay units logged at 100-140 ft between those two screened intervals that might be causing the <br />deeper zone to be confined, so it is possible that the well is capturing and mixing slightly different water <br />packages. Operator is advised to isolate those zones with nested wells as follows: <br />a. Atop screened interval that captures the zone from SWL down to the top of the clay units <br />at ~ 100 ft. <br />b. A middle screened interval from the base of the clay layers at 140 ft down to the clay <br />layer logged at TD 320 ft. <br />A bottom screened interval below the 320 ft clay layer. <br />The other monitoring wells should be completed to a depth sufficient to capture the water table aquifer at <br />depths slightly below the historic lows for the water table. Along screened interval would probably be <br />acceptable, provided it does not extend below the clay units at 100 ft. <br />9) To monitor the possibility of future changes in background water quality, it would be useful to have a <br />monitoring well upgradient of the pivots. Existing well SLM-1 may satisfy that need, but then again it <br />might be too far away, and should be completed in the appropriate'hydrogeologic intervals. <br />