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State Reg. <br />• As mentioned earlier, the two unnamed tributaries to Fish Creek drain <br />less than 1.22 square miles within the Seneca II permit. Both streams are <br />first order ephemeral streams which flow in response to precipitation <br />events and snowmelt. As described in Appendix 7-7 (Alluvial Valley <br />Floors), portions along the southern mast stream appear to be subirri- <br />gated. A surface water gaging station (SW-52=6) has been established <br />directly downstreom from mining (see Exhibit 7-3) on the southernmost <br />tributary and will be sampled for quality and quantity in accordance to <br />CMLR guidelines. On the northern tributary a station was not estab- <br />lished due to difficulty of accessibility, lack of a defined channel, and <br />smallness of drainage area. However, visual observations will be made <br />monthly and if a flow does occur, the quantity and quality of the water <br />will be measured It should be noted that there has been no flow in <br />either tributary from January through May of 1981. <br />Finally, like the Yampa River, the impacts of mining Seneca II upon Fish <br />• Creek hydrologic regime would be extremely difficult to determine. <br />First of all, because only I.5% of the entire Fish Creek Basin will be <br />disturbed, only a small portion of Fish Creek's flow will be attributed to <br />mine effluent. Secondly, the the main stem of Fish Creek is over 4 miles <br />from the Seneca II Mine and meanders through land used for various <br />purposes. Fish Creek flow and quality are altered by these various uses. <br />It would be difficult to distinguish mining-related impacts from other use <br />impacts downstream of the tributaries directly affected by mining. <br />C. Grassy Creek Basin <br />As illustrated in Exhibit 7-3, approximately 72% (3.07 square miles) of <br />the Seneca II permit lies within the Grassy Creek Basin. This is about <br />12.5% of the entire Grassy Creek Bosin. Grassy Creek and its tributary, <br />Little Grassy Creek, are impacted by the Seneca II mining operation. <br />Grassy Creek receives effluent from NPDES 002 and 003. Little Grassy <br />Creek flows through the mine permit area and is diverted into the Wadge <br />• Impoundment before it discharges at NPDES 002 into the main stem of <br />Grassy Creek. As illustrated in Figure 7-24, the basic chemical proper- <br />ties of the effluent and Grassy Creek are very similar and of the <br />7-63 Revised 5/27/81 <br />