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shown in Figure 3. Table 3 summarizes drainage areas upstream from <br />• each pond, estimated 10-year, 24-hour inflow and required storage capacity. <br />Total storage capacity would be aoproximately 2.5 acre-feet. <br />Table 3. Upstream area, inflow, and capacity of Orchard Valley Mine <br />sediment retention ponds <br />Pond ~ Approximate Estimated <br />Number! I Upstream Area 10-year,24-hour' Design <br />(Acres) Inflow Capacity <br />Disturbed i Undisturbed i (.Acre-feet) j(Acre-feet) <br />12.3 <br />• <br />2 <br />3 & 4 <br />7.5 <br />11.0 ~ 0.11 <br />I <br />~ .49 <br />4.5 ~ .04 <br />4.5 <br />30 <br />04 <br />28 <br />j 0.90 <br />I <br />.60 <br />! 1.00 <br />(0.5 A-F <br />each pond) <br />i <br />6.9 <br /> <br />!Ponds are consecutively numbered in do~:rnstreain direction; <br />^Jo. 1 is the uppermost pond. <br />'Estimated direct runoff from 10-year, 24-hour precipitation event: <br />Disturbed watershed = 0.04 acre-feet/acre (Rc = 2.75"). <br />Undisturbed watershed = 0.01 acre-feet/acre (Rc = 4.75"). <br />The dams would help protect Stevens C,ulch and ultimately the North <br />Fork of the Sunnisen River from detrimental effects on water quality, <br />specifically sediment. Maintenance crevrs o-rill regularly clean the ponds <br />• <br />