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The developed storm water runoff rates and the allowable release rates can be found in <br />Table 3 — Developed Storm Water Flows, and the Waterworks calculations can be <br />found in Appendix A — Basin Summaries. <br />Table 3. Developed Storm Water Flows <br />Storm <br />Interval <br />Historical/ <br />Existing Basin <br />Runoff <br />Developed Runoff <br />Rate (cfs) <br />Routed to system) <br />Discharge <br />Rate (cfs) <br />'/2 2-Year <br />0.032 h d #1 <br />0.624 h d #4 <br />0.033 h d #10 <br />10-Year <br />0.225 h d #2 <br />0.968 h d #5 <br />0.201 h d #11 <br />100-Year <br />0.534 h d #3 <br />1.466 h d #6 <br />0.532 h d # 12 <br />'hyd refers to the Hydrograph number which can be reviewed in Appendix A. <br />The proposed detention system must offer a minimum volume of 13,279 cf of live <br />storage per D.O.E.'s Stormwater Management Manual. The design vaults and pipes <br />offer 13,959 cf of live storage. <br />The existing control structure and catch basin will be removed. The new discharge <br />structure will consist of a baffle type flow restrictor-oil separator installed in a Type II <br />catch basin, designed to release the allowable discharge rates found in Table 3, with <br />the following orifice sizes and elevations: <br />Orifice #1 Elevation: 606.30 Diameter: 0.78" <br />Orifice #2 Elevation: 612.50 Diameter: 5.25" <br />Waterworks calculations can be found in Appendix A. <br />The baffle wall in the type II control manhole will serve as an emergency overflow for <br />the pond and vault. <br />The 100-year flow for developed conditions is 1.47 cfs and should be easily conveyed <br />through the riser should the contro:ling orifices become plugged. <br />Flows from the system will be routed to the existing public drainage system in 80TH <br />Street S.W. The existing outfall pipe will be utilized in order to avoid unnecessary work <br />within the public right of way. <br />IM.%SDG9001V7-SDG-011docs%Dralnage Anslysis77.doc 6 C%� <br />