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<br /> <br /> <br />1 <br />1 <br /> <br /> <br />1 <br />1 <br /> <br />WATER LEVELS <br />Ground water levels in the alluvium have remained fairly regular, <br />with normal seasonal fluctuations, apparently related to changes <br />in river levels. Ground water levels in the alluvium are plotted <br />in Figure 22. A piezometric map for the Williams Fork Alluvium <br />(December, 1990) is presented in Figure 23. <br />WATER QUALITY <br />Summaries of the water quality data for the alluvial wells are <br />presented in Tables 23 through 28. A plot of field electrical <br />conductivity versus time is presented in Figure 24. <br />There is no conclusive evidence of seasonal variation of water <br />quality in the alluvium. The field conductivity of Well AVF-5 was <br />above normal in late 1983 and early 1984. The laboratory <br />measurements did not show the same high levels during that period. <br />Only Well AVF-3 is showing an upward trend in dissolved solids. <br />There is also a correlative increase in calcium, magnesium, <br />sulphate and chlorides. The source of this change is unknown. <br />However, it is probably not from the mine discharge because the <br />mine discharge is sodium bicarbonate water. <br />SURFACE WATER MONITORING <br /> <br />1 <br /> <br /> <br />There are two rivers in the vicinity of the mine site. The major <br />river, the Yampa, flows in a southeasterly direction across the <br />mine site. The Yampa River drains most of the northeast corner of <br />Colorado and part of south-central Wyoming. The second river is <br />the Williams Fork, which is a major tributary of the Yampa River. <br />The Williams Fork River joins the Yampa River on the mine property. <br />Data is collected for the Williams Fork River. Data is collected <br />from one spring, the A'1 Strip Pit (NPDES site 022). In 1990 there <br />was also a small amount of discharge from two sediment ponds. <br />' RIVERS <br />FLOWS <br />1 <br />1 <br />1 <br /> <br />The Williams Fork River flow data is collected by the U.S. Geologic <br />Survey at one continuous gaging station and one staff gage. The <br />Williams Fork River continuous gaging station (WF-2) is near the <br />confluence with the Yampa River, downstream of the //5 Mine <br />discharge. The staff gage (WF-1) is located upstream of the mine <br />discharge points. <br />-3- <br />