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4. Impact Analysis <br />A. Impacts of Alternative 1 Approval without Conditions <br />The greatest potential to adversely impact surface water quality <br />comes from sediment eroded from the 7.7 acre disturbed area. A <br />sedimentation control system approved by the Colorado MLRD and in <br />compliance with the regulations will route undisturbed flow around <br />the disturbance and will conduct all flow from the disturbed area <br />through a properly sized sedimentation pond. The water contained in <br />the sedimentation pond will be released into the natural drainage <br />oaly after it is determined that the discharged water will meet all <br />applicable effluent standards. <br />The II.S. Fish and Wildlife service believes any depletion of flows <br />in the IIpper Colorado River Basin adversely effects endangered fish <br />species. OSMRE has conditioned the mining plan approval to include <br />a contribution by the company to the Colorado River conservation <br />fund. <br />Grouad Water Hydrology <br />The greatest impact to ground water hydrology will occur after <br />mining as the mine workings and the dewatered aquifer is recharged. <br />___~ T.__ Decades will be required to refill the aquifers, during which time <br />-,~, ----`less water-vilYflow in the adjacent stream.--The reduction in_flo~~ _ ' <br />+ ~ will be about 2.5 gpm, which is not considered. to be significant. <br />\ Subsidence may result in local perched aquifers and attendant <br />springs being drained. <br />Alluvial Valley Floors <br />No farming activities will be physically affected by the above <br />surface impacts. The land use type which will be directly affected <br />is wildlife and livestock grazing. The conclusion is that the <br />surface disturbance related to the operation is limited in extent <br />and will not directly affect any farming activities in the alluvial <br />valley floor. <br />Probable Hydrologic Consequences and Cumulative Impacts <br />The McClane Canyon mine will have very limited impact on the surface <br />and ground water hydrology of the hydrologically adjacent area. Any <br />impacts on surface water quantity and quality will be limited <br />because of the small area of drainage impacted by the operation. <br />Also because the operation may only exist for this permit term, and <br />impacts will be limited with respect to time. After the area is <br />reclaimed, the hydrologic characteristics of the alluvial system <br />will be restored. <br /> <br />-B- <br />