1986-12-31_REPORT - C1981008 (3)

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3. Site NPDES 004 and 005 NPDES discharge points 004 and 005 (Permit No. CO-0000213; see Appendix 7-6) are located within the East Return Ditch drainage along the central southwest edge of the scraper area as shown on Exhibit 1. To date, neither of these discharge points have been known to discharge. Discharge monitoring reports for the past three quarters of 1986 are provided in Appendix C. Because the present storage capacity and spillway configuration of the ponds are inadequate (see Appendix 7-1 of the Nucla Mine Permit Revision) , these ponds have been redesigned. Up until and upon reconstruction, these ponds will continue to be monitored for flow and quality according to the requirements of the NPDES permit. 4. Site SW-N3 Site SW-N3 is located on Tuttle Draw downstream of mining as shown on Exhibit 1. Flow and quality data have routinely been collected from this site since April 1980; these data are presented in Appendix B and statistically summarized in Table 7. A hydrograph constructed from monthly instantaneous flow measurements is shown in Figure 4. A trilinear plot of the major ions is depicted in Figure 2. As previously described, flow at this site is artificially controlled for most of the year from irrigation return flow from the Second Park lateral irrigation ditch. According to the hydrograph depicted in Figure 4, flow during the summer months is generally between 2.0 and 7.0 cfs, falling to a baseflow during the winter and early spring of less than 1.0 cfs. As can be seen from Figure 5, during the summer a substantial portion of the flow at this site is contributed by flow from the West Return Ditch as monitored at the NPDES 001 discharge point. Because site SW-N3 is located downgradient of mining, a resultant diminution in water quality is expected and evident. Prior to mining, water quality at this location on Tuttle Draw was probably similar to that of present day water quality at 22