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1 <br />1 <br /> <br /> <br />1 <br /> <br /> <br />1 <br /> <br />1 <br />~r <br />1 <br />There is no evidence of seasonal variation of water quality in either <br />alluvium. The field conductivity of Well AVF-5 was above normal in late <br />1983 and early 1984. The laboratory measurements did not show the same <br />high levels during that period. The Williams Fork alluvial wells are <br />~ showing an upward trend in dissolved solids. This is most evident in <br />Wells AVF-3 and AVF-6. There is also a correlative increase in calcium, <br />magnesium, sulphate and chlorides. The source of this change in unknown. <br />~~ However, it is not from the mine discharge because it is sodium <br />bicarbonate water. <br />SURFACE WATER MONITORING <br />There are two rivers in the vicinity of the mine site. The major river, <br />the Yampa, flows in a southeasterly direction across the mine site. The <br />Yampa River drains most of the northeast corner of Colorado and part of <br />south-central Wyoming. The second river is the Williams Fork which is a <br />major tributary of the Yampa River. The Williams Fork River joins the <br />Yampa River on the mine property. Data is collected for the Williams Fork <br />River. In addition, data is collected from three springs: 1) the No. 1 <br />Strip Pit (NPDES site), 2) Haxton Springs, and 3) North Spring. The North <br />Spring is not a true natural spring because it is at least partially fed <br />by seepage from a small dam. <br />RIVERS <br />River Flow <br />The Williams Fork River flow data is collected by the U.S. Geologic Survey <br />at one continuous gaging station and one staff gage. The Williams Fork <br />River continuous gaging station is near the confluence with the Yampa <br />River. <br /> A summary of the staff gage readings for 1987 is presented in Table 27. A <br />' plot of daily mean flow versus time for the Williams Fork River for 1986 <br /> is presented in Figure 23. The plot for the Williams Fork River includes <br /> the mean monthly flows for the Williams Fork at Hamilton (a discontinued <br />' U.S.G.S, gaging station). For the Williams Fork River, the maximum mean <br /> daily flow was 1,130 cfs, the minimum mean daily flow was 42 cfs and the <br /> mean flow was 172 cfs. A plot of minimum, mean monthly and maximum flows <br /> measured by the U.S.G.S. for the Williams Fork River at Empire Energy is <br />' presently on Figure 24. The flows in the Williams Fork River, were on the <br /> average, lower in 1987 than the previous three (3) years. <br />' The flows in the Williams Fork measured to date by Empire Energy do not <br /> show any significant variation from expected values. <br />' <br /> River Water Quality <br /> Summaries of the water quality data are presented in Tables 28 through 31. <br />' A plot of upstream and downstream field electrical conductivity <br />' 4 <br />