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the San Miguel River. As no major tributaries occur in this reach, the flow and TDS from records at this station were used in the analysis. The maximum concentration of TDS recorded at Station SW-N3 from all monitoring conducted to date is 330D mg/1. This maximum value was chosen for use in the analysis. Streamflow in Tuttle Draw at SW-N3 has ranged from a minimum of 0.02 cfs to a maximum of 9.4 cfs when water quality samples have been collected. Although a load calculated from the maximum flow at maximum TDS concentration would give the "worst-case" condition for the mine effluent, this was not considered representative of the inverse relationship between dissolved solids and streamflow. The mean flow at Station SW-N3 is 2,D cfs, with a standard deviation of 1.8 cfs. This flow value was chosen for use in the analysis as a conservative estimate for calculations TDS load. Based on the data described above, the following loads more calculated for the San Miguel River and Tuttle Draw. San Miguel River at Uravan 9.4 cfs x 3600 mg/1 x D.0027 = 91.4 tons/day Tuttle Draw below Nucla Mine 2.0 cfs x 3300 mg/1 x 0.0027 = 17.8 tons/day These results indicate that the effluent from the Nuc1a Mine could comprise 20 percent of the TDS load in the San Miguel River at Uravan under low-fl ow conditions. In interpreting these results, a comparison of concentration is instructive. The mean concentration of TDS in the river under low-flow conditions is greater than the maximum TDS concentration recorded to date from the mine. This indicates that under most flow conditions, the mine contributes water with a TDS less than the river. When the reverse condition is evident, the volume of river water would serve to dilute the flows from the mine. In fact, the mean concentration of TDS as reported by the USGS at the Uravan Station, 647 mg/l, supports this conclusion. It is apparent that even when maximum expected concentrations and flows are loaded into low flow conditions in the San Miguel, significant dilution occurs which immediately mitigates the TDS effect under worst case conditions. It does not appear that any of the beneficial uses of the receiving stream would be affected, and material damage of water outside of the permit area would not occur, Additional considerations of the potential degradation of water Duality from heavy metals and other trace elements due to mining are not significant. Increased sediment loading from disturbed areas are adequately mitigated by the sediment ponds and other aspects of the sediment control system. No significant changes to surface water quantity have been identified. Therefore, the impacts to the surface water system will be insignificant. _1 g_