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• <br />i <br />present mining of these seams in the Derringer Pit. The TDS measurements (see <br />Figure 4.8-36) for this well show a fairly steady concentration since 1982. <br />Figure 4.8-37 presents the TDS concentration versus time plot for well GF6. <br />The QR aquifer is monitored downgradient of a portion of the mined Enfield pit at <br />well GF6. TDS measurements from this well have been steady except for the 1986 <br />value at approximately 200 mg/l higher <br />if a significant trend is developing. <br />Additional monitoring is needed to define <br />Field pH has varied from 6.4 to 7.9 since 1974 for water from well CAI. These <br />variations are well within the natural range of fluctuation. Values from GE1 <br />gradually declined for several years and seem to have stabilized slightly above <br />neutral. Field pH from well GD2 does not demonstrate a trend. Well GF6 contains <br />water with a pH slightly greater than neutral. <br />The SAR values measured for water from well CAI are low with an average value <br />of approximately 0.3. The early SAR values from well GE1 were close to 20 while the <br />more recent values have been close to 10. The change in SAR values could be caused <br />by an increased rate of movement of ground water in this area due to the drawdowns. <br />These SAR values with the TDS of this water should not make irrigation prohibitive <br />for most soils. The SAR from well GD2 has generally been close to 0.5. The SAR <br />value for water from well GF6 has declined gradually and additional monitoring with <br />time is needed to establish a good mean for this well. <br />4-233y <br />REVISED FFR 1 x'87 <br />