1986-12-31_REPORT - C1981008 (3)

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As is evident from the statistical summary of data presented in Table 19 and the trilinear diagram shown on Figure 12, the water quality of Spoils Spring #1 is a Ca-SO4 type, almost exactly identical to that of the Highwall Spring. TDS concentration of Spoils Spring #1 is however substantially higher than that of the Highwall Spring having a mean value of 3779 mg/l , ranging from 3566 to 4190. This high TDS concentration explains the resultant effect of mine spoils discharge on the water quality of the West Return Ditch as monitored at the NPDES 001 discharge point. Spoils Spring #2 is located approximately 50 yards upstream and to the west of Spoils Spring #1. This spring was noted by the field hydrologist during his fall spring and seep inventory conducted semiannually. The field data collected this September for this spring (see Appendix B) showed a much higher conductivity than for Spoil Spring #1, 4600 umhos/cm @ 17.8°C versus 3000 umhos/cm @ 17.8°C. Because flow was extremely low, 0.0008 cfs (less than 0.5, gpm) , possibly evaporation and transpiration processes effected this higher conductivity. Future sampling will better assess the physical and chemical characteristics of Spoil Spring #2. D. East Return Ditch - Flow and Quality 1. Site NPDES 006 NIPDES discharge point 006 (Permit No. CO-0000213; see Appendix 7-6) is located along the lower end of the East Return Ditch which flows along the east side of Nucla Mine spoils as shown on Exhibit 1. Flow and quality data have routinely been collected from this site since December of 1982. The data are presented in Appendix B and statistically summarized in Table 20. A, hydrograph constructed from weekly and monthly instantaneous flow measurements is shown in Figure 13. A trilinear plot of the major ions is depicted in Figure 11. The flow data collected from this site again reflect the seasonal effects of irrigation on the hydrologic regime of the 1See footnote on Page 39. 62