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• Suspended solids concentrations in the general area tend to vary <br />proportionately with flow rate. In Red Wash suspended solids <br />concentrations at the mouth have ranged from 133 to 254,600 milli- <br />grams per liter. Investigations indicated that a major portion of <br />this suspended sediment originated as channel erosion, which has <br />a large effect on sediment yield because of the proximity of the <br />sediment source to the transport media (see Renfro, 1975). <br />Hydrogen ion activity (p H) of surface water in the lease and <br />adjacent areas, tends to be rather constant, varying normally <br />between 6.5 and 8.5 with no significant difference being noted. <br />Sediment Yield <br />• An estimate of the average annual sediment yield to be expected <br />was made using a methodology developed by the Pacific Southwest <br />Inter-Agency Committee (1968). Estimated average annual yield <br />of 0.60 acre-foot per square mile compares favorably with estimates <br />made by the Colorado Land Use Commission (1974). Based on guidelines <br />given by Strand (1975) for streams with sand and clay bottoms and <br />flow events resulting in high suspended sediment concentrations, <br />it is estimated that approximately 10 percent of the sediment yielded <br />from the mine permit and adjacent ephemeral areas occurs as bedload. <br />The remaining 90 percent presumably occurs as suspended sediment <br />load. For Red Wash this would yia.ld approximately 73.5 acre-feet <br />per square mile per year. <br />• <br />4/81 II.D-9 <br />