1988-04-11_PERMIT FILE - C1981008A (9)

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the Nucla mining area. This well was not completed until late summer, 1987. Only one chemical analysis (Appendix 7-4) was performed during the remainder of 1987. A trilinear diagram for the analysis is presented in Appendix 7-3. The well location is shown on Exhibit 7-1. The spoil aquifer exhibits a calcium magnesium sulfate water type during the irrigation period. The TDS concentration was 3,076 mg/l and the pH was 7.0. A summary of the trace elements analyzed at Well GW-N27 is presented in Table 7-8. Manganese levels in the spoil aquifer exceed the CWQCC agricultural standard; however, the water is suitable for use as livestock drinking water (Table 7-9). Measurable trace metal concentrations in the spoil aquifer are boron, cobalt, fluoride, iron, lithium, manganese, nitrate, vanadium and zinc. Nucla East Mining Area. Well GW-N22 monitors the water quality in the alluvial aquifer along Calamity Draw. A statistical summary of the water analyses performed on water sampled from this well is presented in Table 7-16. Trilinear diagrams representing analyses performed during periods of irrigation and no irrigation are presented in Appendix 7-3. The individual water quality analyses for Well GW-N22 are presented in Appendix 7-4. The well location is shown on Exhibit 7-1. The alluvial aquifer along Calamity Draw has a calcium magnesium sulfate water type both during periods of irrigation and no irrigation. A slight lowering of TDS occurs during non-irrigation periods. The mean TDS when irrigation is occurring is 3,349 mg/l and the mean TDS during periods of no irrigation is 3,204 mg/l . Schoeller diagrams representing mean milliequivalent values at Well GW-N22 for the two above-referenced time periods are presented on Figure 7-8. Only very slight chemical changes are apparent between the two time periods. Calcium and sodium concentrations increase slightly during periods of no irrigation. The pH of the water at Well GW-N22 ranges from 7.2 to 7.7 with the mean value being 7.41. A larger water quality data base is necessary to determine if there is any seasonal water quality variability in the alluvial aquifer irrespective of the general irrigation effects. There is a suggestion of chemical trends during periods of irrigation. Calcium and bicarbonate levels are decreasing slightly with time. A summary of the ranges in concentration for trace elements analyzed at Well GW-N22 is 7-50 Revised 04/11/88