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purposes, Also of concern is the recharge high in total dissolved solids (TDS). This further in assessing the impact of the Edna of the alluvial aquifer by water condition will be evaluated Mine on surface water quality. Water quality conditions upstream of the mine indicate that dissolved iron, manganese and other trace metals all have occasionally exceeded receiving stream standards. Baseline data indicate minor changes in water quality occur between upstream and downstream stations on both Trout and Oak Creeks. This is probably due to the impacts of past mining activities. The baseline quality of the water in Oak Creek is generally poorer than that in Trout Creek above the permit area, due to more extensive mining that has occurred in the Oak Creek drainage during the past century. The majority of runoff from disturbed areas at the mine site is routed through sedimentation ponds in order to reduce degradation of water quality in Trout Creek and Oak Creek. Certain small areas are exempted from this requirement. These are areas of minor disturbance on the fringes of mining activity or adjacent to buildings at the mine site that comprise small acreages and/or are located on drainage divides. Alternative sediment control is provided by contour furrowing, revegetation and straw bale filters. The Division granted, during the previous permit term, an exemption from the requirements of 4.05.2(1) for the following areas: Area Acreage Location Map West Ridge 14.5 Ex. 4.6-17 West Ridge 9.5 Ex. 4.6-]7 Center Ridge 2.1 Ex. 4.6-23 Tipple Area 0.8 Ex. 4.6-22 Moffat Area 25 Ex. 4.6-2 The exemption has been granted in accordance with Section 4.05.2(3) based on the finding that: 1) the construction of sediment ponds is either impractical or unfeasible; or, 2) the area of disturbance is sufficiently small such that alternative sediment control measures are adequate to meet effluent limitations. Peak flows for all water control structures were reviewed. Flow routing calculations for the West Ridge and Center Ridge ponds were analyzed and found to provide adequate detention times, storage, and spillway capacities. In addition, NPDES discharge data at the outlet of both ponds indicate that the outflow has historically met effluent limitations. The Moffat and Tipple area pond calculations indicate that detention times are less than the twenty-four hours recommended by the Colorado Mined Land Reclamation Division for achieving effluent limitations. The tipple ponds have historically met all NPDES effluent limitations, and receive maintenance to ensure adequate storage. The Moffat Area pond designs have not been approved by the Division at this time. Disturbance of the Moffat Area by surface mining activities has -14-