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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 />Numberr I Upstream Area 10-year,24-hour' Design <br />(Acres) Inflow Capacity <br />Disturbedd i Undisturbed i (.Acre-feet) j(Acre-feet) <br />• <br />0.11 <br />.49 j 0.90 <br />.04 ~ <br />.30 .60 <br />.04 <br />.28 1.00 <br /> <br />1 ~ ,0.5 A-F <br />each pond) <br />_ I ~ <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 />11.0 <br />1 ( 12.3 j <br />2 i i 4.5 <br />7.5 <br />3 & 4 I i 4.5 <br />! 6.9 <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 />