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� � � , SOUTHWEST FLORIDA WATER MANAGEMENT DISTRICT , , � . - WATER QUALITY DESIGN � For thi� project, the Southwest Florida Water Management District requires the faccommodation of the first half inch of rainfall with recovery in less than or equal to 36 hours.; The following information shows that the proposed stormwater system detailed in � the site construction plans will comply with these requirements. � � ihe proposed stormwater facility will have a top of bank at elevation 91.5 feet with 4:1 side sli pes to the bottom of the facility at elevation 84.5 feet. The following calculations ` show that the half inch volume is stored in the proposed stormwater facility below an I elevation of 86.0 feet: ' Project Drainage Area = 140,992' sf I 140,992 sf x 0.5 inch x 12 inches = 5,875 cf ' '� foot St i rmwater Facility Area at 84.5 ft = 3,909 sf � Stormwater Facility Area at 86.0 ft = 5,563 sf Stormwater Facility Volume between EI. 84.5 and 86.0: � Volume = �3,909 sf + 5,563 sf1 x (86.0-84.5)= 7,104 cf ' 2 The half inch volume is recovered by percolation in less than 36 hours as can be seen in , � the m�I unding analysis in Appendix A. For example, the mounding analysis shows that after ine hour 22,139 cubic feet of runoff have been recovered by percolation, which is ' ' great i r than required15,875 cubic feet. The routing and mounding calculations were performed using the Basin Runoff Networking computer program developed by Mr. , James J. Boyd. (Hydrographs are included in Appendix B and the routing analysis is in i Appendix C). � i � , '�'The offsite drainage area's runoff will be conveyed via swales and/or on-site conveyance pipes to the existing FDOT basin/outfall (see Figure 3, Pre-Development Plan). I � CadM/tlata/99/6001-99/6001-99drainage � � i i I