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bedrocks. The hydraulic gradient within the alluvium is expected to be about equal to the slope of the <br />channel (dh/dl = 0.005). The permeability (K) was assumed to be approximately the same as the highest <br />• permeability measured within the White River alluvium (24,970 gpd/ft2 at Qal-3 from Ford, Bacon, and <br />Davis, 1981). An average cross sectional area was estimated by assuming an average alluvial valley <br />width of 500 feet and east and west sideslopes of approximately 20 and 10 percent respectively. <br />Assuming that this entire alluvial valley was saturated (which it is not) the area would be 8750 feet 2 and <br />the resulting flow estimate would be 759 gpm. Of course this estimate is only approximate at best. The <br />permeability of the Red Wash alluvium is probably higher than that in the White River alluvium, but the <br />Red Wash alluvium is obviously not totally saturated. However, this estimate should be useful in indicating <br />the general order of magnitude of flows that may possibly move down the Red Wash alluvium when water <br />is available. <br />Scullion Gulch is very narrow and located above the general water table. It is felt that the alluvium <br />transports water only during and for a short while after runoff events occur. Figure II.C-31 is a generalized <br />map showing the location of recharge and discharge of groundwater in the differing facies. <br />II.C.3.e Aquifer Characteristics Aquifer testing was attempted on the three test wells and on selected <br />observation wells as well as on a well completed during late 1980 in the White River alluvium. Tabulation <br />of data and semilog plots are contained in Attachment C with the well location and log information. <br />Results of the aquifer testing program are summarized Table II.C-11. <br />• Data were analyzed for the determination of transmissivity and storativity using the common Jacobs <br />straight-line approximation from a semilog plot of depth to water (drawdown) versus time (Cooper and <br />Jacob, 1946). Specific capacities were determined as the ratio of the pumping rate and the total <br />drawdown (Walton, 1970). <br />The only true aquifer identified in the area is the White River alluvium. Pump tests and water level <br />measurements conducted during the baseline study period indicated that quantity (based on annual water <br />level fluctuations of about four feet) did not vary much seasonally and quality remained poor throughout <br />the year. <br />It is significant to note the large drawdown obtained with very low pumping rates, in most cases. Also, <br />only one test, Qal-3, gave a specific capacity greater than 1 gpm/ft. The production capacity of a well is <br />• Permit Revision #6 (3/2008) II.C-65 <br />