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USGS WELL SELECTED ANALYSIS lon A r 12, 94 Jul 21, 94 Increase Calcium 189.8 386.3 196.5 Magnesium 57.4 122.7 65.3 Nitrogen-Nitrate 6.9 26.98 20.08 Sodium 494 598 104 Sulfate 1298.4 2]06.9 808.5 Total Selected Ions 2058.5 3261.88 1203.38 It is not possible that the increase in ion content was due to fertilization since records show that the fertilizer applied was 18%N and 46% P, which is a common single chemical fertilizer using di-ammonium phosphate. The only ions added to the ground were (NH.)" and (PO, )-' . A quick check of the lab analyses shows that these ions did not increase at all for the samples in question. The sulfate anion in combination with calcium, magnesium and sodium were primarily responsible for the increase. This increase could not have come from the Rimrock pit altering the flows of water in the Engleville Mine workings since all encountered entries were dry and the historic quality of the Engleville Mine discharge does not contain such a high salt level. In general, the ions that showed increases were already present in the water in significant levels. It appears that the water increased in salt content through concentration, possibly due to evaporation of the shallow water near the USGS well during the dry 1994 year. The ion increase was relatively proportional to the pre-luly 21, 1994 sample concentration. Also, the ions which increased are not dangerous or toxic. The other holes have not experienced this increase in specific conductance because the water levels are much deeper from the surface and would not be affected to the degree experienced at the USGS well. For the reasons stated above, it is not believed that the Rimrock Mine has affected the prevailing hydrologic balance during 1994. Since the mine has been reclaimed and vegetation has been restored, it is not expected that the hydrologic balance can be affected in future years.