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As is evident from the statistical summary of data presented • <br />in Table 19 and the trilinear diagram shown on Figure 1Z, the water <br />quality of Spoils Spring #1 is a Ca-S04 type, almost exactly <br />identical to that of the Highwall Spring. TD:S concE~ntration of <br />Spoils Spring #i is however substantially higher than that of the <br />Highwall Spring having a mean value of 3779 mg/1, ranging from 3566 <br />to 4190. This high TDS concentration explains the resultant effect <br />of mine spoils discharge on the -rater quality of the West Return <br />Ditch as monitored at the NPDES 001 discharge point. <br />Spoils Spring #2 is located approximately 50 yards upstream and to <br />the west of Spoils Spring #1. This spring was noted by the field <br />hydrologist during his fall spring and seep inventory conducted <br />semiannually. The field data collected this September for this <br />spring (see Appendix B) showed a much higher conductivity than for <br />Spoil Spring #1, 4600 umhos/cm @ 17.8°C versus 3000 umhos/cm @ <br />17.8°C. Because flow was extremely low, 0.0008 cfs (less than 0.5 <br />gpm), possibly evaporation and transpiration processes effected • <br />this higher conductivity. Future sampling will better assess the - <br />physical and chemical characteristics of Spoil Spring #2. <br />D. East Return Ditchl - Flow and Quality <br />1. Site NPDES 006 <br />NPDES discharge point 006 (Permit No. CO-0000213; see Appendix <br />7-6) is located along the lower end of the East Return Ditch <br />which flows along the east side of Nucla Mine spoils as shown <br />on Exhibit 1. Flow and quality data have rout•;nely been collected <br />from this site since December of 1982. The data are presented in <br />Appendix B and statistically summarized in Table 20. A hydrograph <br />constructed from weekly and monthly instantaneous flow measurements <br />is shown in Figure 13. A trilinear plot of the major ions is <br />depicted in Figure I1. <br />The flaw data collected from this site again reflect the <br />seasonal effects of irrigation on the hydrologic regime of the , <br />1See footnote on Page 39. <br />62 <br />