1990-04-09_REPORT - C1981044 - Laserfiche WebLink

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' WATER QUALITY ' Summaries of the water quality data for the alluvial wells are presented in Tables 22 through 27. A plot of field electrical conductivity versus time is presented in Figure 24. ' There is no evidence of seasonal variation of water quality in the alluvium. The field conductivity of Well AVF-5 was above normal in late 1983 and early 1984. The laboratory measurements did not ' show the same high levels during that period. The Williams Fork alluviam wells are showing a small upward trend in dissolved solids. This is most evident in Wells AVF-3 and AVF-6. There is ' also a correlative increase in calcium, magnesium, sulphate and chlorides. The source of this change is unknown. However, it is probably not from the mine discharge because the mine discharge is sodium bicarbonate water. SURFACE WATER MONITORING 1 There are two rivers in the vicinity of the mine site. The major river, the Yampa, flows in a southeasterly direction across the mine site. The Yampa River drains most of the northeast corner of Colorado and part of south-central Wyoming. The second river is the Williams Fork, which is a major tributary of the Yampa River. The Williams Fork River joins the Yampa River on the mine property. Data is collected for the Williams Fork River. In addition, data ' is collected from one spring, the #1 Strip Pit (NPDES site 022) . RIVERS ' FLOWS t The Williams Fork River flow data is collected by the U.S. Geologic Survey at one continuous gaging station and one staff gage. The Williams Fork River continuous gaging station (WF-2) is near the ' confluence with the Yampa River, downstream of the #5 Mine discharge. The staff gage (WF-1) is located upstream of the mine discharge point. ' The flow data for Station WF-2 for January through September, 1989, was taken from published USGS reports. The data for October through December was derived from unpublished, unchecked data, ' supplied to Cyprus by the USGS. The actual flow rates for this period will be slightly different than those used in this report. A summary of the staff gage readings for 1989 is presented in Table ' 28 . A plot of daily mean flow versus time for the Williams Fork River for 1989 is presented in Figure 25. The plot for the Williams Fork River includes the mean monthly flows for the ' Williams Fork at Hamilton (a discontinued USGS gaging station) .