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RAG. Empire Corporation 2000 AHR SURFACE WATER MONITORING RIVERS There are two rivers in the vicinity of the mine site. The Yampa, flows in a southeasterly direction across the mine site. The Yampa River drains most of the northeast comer 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. Monitoring data is collected for the Williams Fork River. Monitoring data is also collected from one spring, the #] Strip Pit (NPDES site 022). FLOW S The U.S. Geologic Survey at one continuous gaging station and one staff gage collects the Williams Fork River flow data. The Wiliiams Fork River continuous gaging station (w%F-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 points. The flow data for Station WF-2 for 2000 was provided by the USGS. A plot of daily mean flow versus time for the Williams Fork River for 2000 is presented in Figure 22. For the Williams Fork River at RAG Empire Corporation, flows measured by the USGS during calendar year 1996 showed a maximum mean daily flow of 1230 cfs and a minimum mean daily flow of 15 cfs. Monthly minimum, maximum and mean flows are plotted for each month of record in Figure 23. The flows in the Williams Fork River during 2000 appear to be about average for the period of record. These flows including comparison between up gradient, WF-l, and down gradient, WF-2, measured to date, do not show any stream depletion impacts from mine dewatering. WATER QUALITY Summaries of the water quality data are presented in Tables 27 through 30. A plot of upstream and downstreant dissolved solids measurements for the river is presented in Figure 24. The data indicates that the surface water quality does not show any significant variation from expected values. The comparisons of data from the upstream and downstream station on [he Williams Fork River indicate that there is no detectable effect of mining on river water quality. As expected, dissolved solids decrease with increasing flow rate in the rivers, due to dilution from runoff. SPRINGS FLOW S • One spring on the mine site area is being monitored. The spring is [he #1 Strip Pit Discharge. The #1 Strip Pit Discharge is an NPDES monitoring point (Outfall 022). There are a few other 1~\Environmental\EMPIRE\A}1R\2000\Text\Empire2000AHR.doc Page 6