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A total of 8.16 ac-ft. of storage is provided for sedimen~ storage in Pond <br />• 008. This will provide for approximately 4.5 years of sediment storage. <br />Peabody will restore adequate sediment storage to the pond when the <br />available sediment storage becomes 3.3 ac-ft. or less (40 percent <br />remaining sediment storage). Periodic sediment surveys v!ill be conducted <br />to determine available storage. <br />S iP 11waY <br />Sediment Pond 008 provides for a combination of principal-emergency <br />spillway to safely discharge the runoff from a 25-year, 24-hour storm. <br />The principal spillway inlet will also be used as the nonclogging <br />dewatering device and is located at an elevation higher than the maximum <br />sediment storage volume. The principal spillway inlet is located in a <br />position on the embankment so as to prevent short-circuiting as much as <br />possible. The stage-discharge relationship of the emergency spillway <br />inlet was calculated using SEDIMOT II, while the stage-discharge <br />relationship of the principal spillway inlet was calculated using the <br />• orifice flow equation. <br />Q = C Ao 2gH <br />where: C = 0.6 (coefficient of discharge) <br />Ao = 0.196 ft.2 (6" dia.) <br />g = 32.2 ft/sec.2 <br />H = 0 to 6.6 ft. (above the opening) <br />Elevation H (ft.) Q (cfs) <br />7011.4 0 0 <br />7014.0 2.6 1.52 <br />7015.0 3.6 1.79 <br />7016.0 4.6 2.02 <br />7018.0 6.6 2.42 <br />Table 3 is a summary of the spillway data. <br />n <br />U <br />5 <br />