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mine site. By mid sunnier, flow generally peaks between 0.6 and • <br />1.0 cfs; base flow during the winter is usually less then 0.05 cfs. <br />There is no indication that base flow has detecta.bly changed during <br />the past five years. Discharge from the NPDES 006 discharge point <br />contributes approximately 10 percent of the flow to Tuttle Draw as <br />measured at site SW-N3. <br />The effects of raining on the diminution of waiver quality in the <br />East Return Ditch appear to be significantly less that those <br />described at site NPDES 001 for the West Return Citch. This <br />conclusion is drawn from the fact that: the mean TDS <br />concentration is 1520 mg/1, significantly lower than at NPDES 001, <br />and the fact that the mean water quality is a Ca-Mg-NC03 type <br />showing a significantly lower percent of SOq anion tfran shown at <br />NPDES 001. <br />2. Site SW-N4 <br />Site SW-N4 is located on the East Return Ditch irrmrediately • <br />above its confluence with Tuttle Draw as shown on Exhibit 1. This <br />site was dry three of the four times that it was monitored in 1980; <br />the data are presented in Appendix B. Monitoring at this site was <br />abandoned in the fall of 1980 because upstream monitoring at NPDES <br />006 and downstream monitoring at SW-N3 precluded the need for this <br />site. Consequently, considering the limited data, no further <br />discussion is hereby provided. <br /> <br />66 <br />