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• or could be alluvial valley floors. However, based upon this same <br />information, areas adjacent to the Edna Mine in the Trout Creek Valley are <br />likely to be classified as alluvial valley floors. Since mining will not <br />disturb the valley itself it is clear that the Edna Mine will not affect the <br />valley's characteristics in supporting the collection of water, storing water, <br />regulating the flow of water or making water available. As described in <br />Section 2.5.3.4 and 2.5.3.2, mining will have no appreciable affect on the <br />quantity of water reaching the alluvial floor. The existing West Ridge and <br />Center Ridge sediment ponds do not affect the flow regime since their <br />permanent pools remain full causing them to discharge a volume equal to their <br />ephemeral flow. The new Moffat Area pond will most frequently discharge its <br />flow to Trout Creek through the shallow groundwater system. The quality of <br />the water will change after mining. In particular the total dissolved solids <br />concentration in the water reaching the alluvial valley floor from the Moffat <br />Area and from West Ridge will increase. As described in Section 2.5.3.5, <br />total dissolved solids concentrations will increase roughly 33 percent from <br />2122 milligrams per liter to 2828 milligrams per liter. In the Moffat Area <br />the change will be more appreciable since the present total level of dissolved <br />• solids is roughly 541 milligrams per liter and after mining will be 2290 <br />milligrams per liter. However, since the amount of flow contributed to Trout <br />Creek from both the Moffat Area and West Ridge are such a small percentage of <br />the overall flow in the stream, the increase in total dissolved solids in <br />Trout Creek will be only 12 milligrams per liter with the postmining levels of <br />total dissolved solids in Trout Creek estimated to be an annual average of 196 <br />milligrams per liter. Thus, there will be no appreciable change in the <br />quantity or quality of water in Trout Creek and the predicted postmining <br />quality is well within accepted standards for irrigated use and will not <br />result in crop yield decrease. <br />For Oak Creek, the valley floor in the vicinity of the Edna Mine should <br />not be considered an alluvial valley floor. The U.S. Department of the <br />Interior, Office of Surface Mining Reclamation and Enforcement, Alluvial <br />Valley Floor identification and Study Guidelines. (1983), Chapter II, <br />Identifying the Occurrence of Alluvial Valley Floors, states: <br />• 4.6-61 (a) April 21, 1994 <br />