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1 ' SURFACE IJATER MONITORING ~-°d~ W`~ t / There are two rivers in the vicinity of the Empi' re Energy (Imine site. The major river, the Vampa, flows in a southeasterly direcxion across ' the mine site. The Yampa River drains most of the north~SL corner of Colorado and part of south-central Wyoming. The second river is the 4lilliams Fork which is a major tributary of the Yampa River. The ' Williams Fork P,iver joins the Yampa River on the mine property. SURFACE !~JATER QUANTITY ' Flow data is collected by Empire Energy at one continuous gaging station and cne staff gage on the Williams Fork River and two staff gages on the Yampa River. The staff gages have been read monthly or ' weekly depending on the time of year. Due to the very high flows in the spring and early summer of 1983 the staff gages on the Yampa River were washed out. They were replaced in October, 1983. Also, the recorder on the 4lilliams Fork station broke in October, 1983. Empire ' Energy has entered into an agreement with the U. S. Geologic Survey to take over the operation of all the surface water gaging stations. They began their monitoring in February, 1984 at which time a new recorder ' was to be installed at the Williams Fork Station and the three staff pages again replaced. A summary of the staff gage readings are presented on Table 33. A plot ' of flow versus time for the Williams Fork River for 1983 is presented on Figure 21. This plot includes the mean monthly flows for the Williams ' Fork at Hamilton (a discontinued USGS gaging station). The plot is slightly different than that presented in the permit application. Anew rating curve was developed following discharge measurements performed in the summer of 1983. The figure may have to be adjusted again following t further discharge measurements by the USGS in 1984 and 1985. The flows in the Williams Fork and Yampa Rivers measured to date by Empire Energy do not show any significant variation from expected ' values. SURFACE WATER QUALITY ' Summaries of the water quality data are presented on Table 34 to Tabl 42. Plots of upstream and downstream electrical con uctivity measurements for each river are presented on ,F' 22 and Figure 2 ' The data indicates that the surface water quality does not sow any significant variation from expected values. The higher conductivity (field measurements) for the Yampa River downstream station during the ' summer appear to be due to the _i~,o n ad solids added to the Vampa by _ the Williams Fork River. The full suite of water quality measurements \ made in June and September show that the upstream water and the downstream water are of essentially the same quality except for elevated ~ ' suspended solids in the downstream sample. ' Cam.-. s tt~ Sc ~6s w~G^i^-ti G~M~w 77 -5 /