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map for the Williams Fork Alluvium (October, 1991) is presented in Figure 23. The data indicates no impact <br />• on alluvial water levels related to mining. <br />WATER OUAIJTY <br />Summaries of the water quality data for the alluvial wells are presented in Tables 23 and 28. A plot of field <br />electric conductivity versus time is presented in Figure 24. <br />There is no conclusive evidence of seasonal variation of water quality in the alluvium. The field conductivity <br />of Well AVF-5 was above normal in late 7983 and early 1984. The laboratory measurements did not show <br />the same high levels during that period. Only Well AVF-3 is showing an upward trend in dissolved solids. <br />There is also a correlative increase in calcium, magnesium, sulfate and chlorides. The source of this change <br />is not known. However, it is unlikely due to mine discharge because its location and the dissimilar chemical <br />composition of mine discharge. Also, it is unlikely due to the waste water lagoon because the conductivities <br />in the well exceed the levels measured in waste water. <br /> <br />SURFACE WATER MONITORING <br />There are two rivers in the vicinity of the mine site. The major river, the Yampa, flows in a southeasterly <br />direction across the mine site. The Yampa River drains most of the northeast corner of Colorado and part <br />of south-central Wyoming. The second river is the Williams Fork, which is a major tributary of the Yampa <br />River. The Williams Fork River joins the Yampa River on the mine property. Monitoring data is collected <br />for the Williams Fork River. Monitoring data is also collected from one spring, the #1 Strip Pit (NPDES site <br />022). In 1991 there was no discharge from the sediment ponds. <br />• 7 <br />