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2019 Municipal Plaza and Center Street Concept Stormwater Reuse <br /> 06/26/2019 <br /> Page: 4 <br /> Additional Considerations <br /> A simplified estimate of stormwater runoff expected from the street section was assembled to <br /> ensure the watershed can produce enough runoff to adequately fill the tanks. Table 1 is a summary <br /> expected runoff volumes for a variety of events. A rainfall event producing between 3.6 and 4.3 <br /> inches in 24 hours (5-year to 10-year return interval) can completely fill the tank. <br /> Table 1: Summary of expected runoffbolumes. <br /> s !41, <br /> 1" Event 1.00 5,500 140 <br /> 1-Year 2.46 14,700 ,956 <br /> 2-Year 2.86 17,600 131,648 <br /> 5-Year 3.58 22,700 169,796 <br /> 10-Year 4.26 27,500 205,700 <br /> During final design, additional hydraulic information will be provided to provide an effective high <br /> flow bypass system. In other words, if the tank is full and the City experiences a 100-year rainfall <br /> event, there will be adequate bypass capacity to reduce local flooding and protect the tank(s). Also, <br /> since the COR trunk storm sewer system is already designed to accommodate a 100-year rainfall <br /> event with discharge to regional flood storage areas, the bypass system will effectively mimic the <br /> originally designed scenario. In between events when irrigation is occurring, or the tanks is being <br /> filled, there will be hydraulic relief on the trunk system and volume control provided. <br /> Since the reuse water will pass through a filter and UV treatment system,the impact to groundwater <br /> resources through the infiltration of irrigation water is expected to be very minimal. Impacts to <br /> groundwater resources in the ERA are not anticipated. <br /> Sincerely, <br /> Bolton&. Menk, Inc, <br /> Timothy J.Olson,PE, CFM <br /> Water Resources Project Manager <br />