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Sepetember 13,2019 CCf <br /> Page 2 of 2 c i V i i k r 5.,t k c r s <br /> ➢ An inflow spillway was placed on the south side of Reservoir 3. This spillway will allow water to flow into and the <br /> reservoir as the invert elevation will be set in the natural low spot of the reservoir grade and is a minimum of one foot <br /> below the base flood elevation. <br /> ➢ The reservoir is 307 acre-feet in volume and the spillway has 1096 cubic feet per second (cfs) capacity at 2 foot of <br /> overtopping depth. Each spillway was designed to be able to fill the reservoir so the banks are less susceptible to <br /> major washouts. A one-inch per hour rise in flood water would fill the reservoir in approximately 4.5 hours. This is <br /> adequate to protect the non-reinforced banks from severe erosion as the reservoir would be full by the time the banks <br /> would overtop and potentially erode. <br /> ➢ The reservoir was also equipped with a discharge spillway at the downstream low point. The discharge spillway will <br /> help direct flow as flood waters recede and limit erosion to localized areas. The outflow spillway will potentially serve <br /> as an inflow point in conjunction with the upstream spillway depending on how the flood waters rise in the vicinity of <br /> these pits. <br /> Conclusion <br /> The analysis was completed based on general hydraulic characteristics of the Big Thompson as a flooding source. The pattern <br /> of storms is largely unpredictable and therefore the recommended improvements cannot guarantee that the facilities will not be <br /> damaged during large-scale storm events. <br /> J:1Bestway-2131voglldrrnslfloodcontrol-9-11-19.docx <br />