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• 50 from the disturbed areas which do not drain into Sediment Pond "C". The con- tributing drainage areas for the proposed relocation of Sediment Pond "E" is 18.5 acres. Because most of the runoff will enter the diversion and then flow to the sediment pond, it is deemed adequate to design the sediment pond and the diversion for the 10-year, 24-hour event. The drainage area being intercepted by the diversion is 16.6 acres. Design of the diversion is addressed in section 6.4. The proposed relocation of Sediment Pond "E' and location of the diversion are shown on Hydrology Map 2, Appendix A. The 10-year, 24-hour runoff volumes and 25-year, 24-hour peak discharges for existing sediment Ponds "A', "8', 'C", and "T' and proposed sediment Pands "D", 'F", and 'G' are based on MULTSED results. For the proposed relocation of ~. Sediment Pond "E', the 10-year, 24-hour runoff and 25-year, 24-hour peak discharge were estimated using the same method and parameters as presented in Section 6.1 f for internal drainage areas. The 10-year, 24-hour runoff volumes and 25-year, 24-hour peak discharges for existing and proposed sediment pond structures are given in Table 13. • 6.3.3 Sediment Storage Volume The required sediment storage volume is three times the estimated annual sediment yield. The annual sediment yield was estimated by extrapolatior_ from the 10-year storm results. The proportion of sediment yield to rainfall volvme of the 10-year storm vas assumed to be representative of annual conditions. This is conservative since the l0~year storm is longer than the average type storm and produces a higher proportion of sediment. The average annual precip- itation vas taken as 12.6 inches. This amount was reduced to 9.93 inches to represent tie orecipitation that will occur as rainfall (April through October). These precipitation values are based on the climatological data for Canon City, Colorado. 'The portion of the precipitation occurring from November through March does not result from thunderstorms and will not produce significant runoff. Frog this methodology, the annual sediment yields were computed as 3.2 times the 10-year storm sediment yields. The three-year sediment yields were ob- tained by multiplying the estimated annual sediment yields by three. A volume of deposited sediment was determined by using the methodology • given in Design of Small Dams (1977) for determining the unit weight of deposited sedirtint. Cling a distribution of 97 percent sand, 2.5 percent silt, and 0.5 percent clay, results in ,a unit weight of approximately 96 pounds per cubic foot. The resulting three-year sediment volumes are also presented in Table 13.