ORD-2003-142 PD-1-03 State Employees Credit Union Addition Special use permit

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Hillsborough State Employees Credit Union Stormwater Report Project # 70994252 Computer Modei Lnput for Watershed Areas Through the use of HydroCAD, many aspects of the effluent flaw were analyzed. The program requires certain input regarding the characteristics of the land. The input required is: 1. Design Storm information a. Length of storm b. Depth of rainfall c. Time increment for analysis (dt) 2. Time of Concentration 3. Composite Areas with Corresponding SCS Runoff Curve Numbers esrgn torms An SCS Type II 24 Hour rainfall distribution was assumed for the storm analysis, with 0.01-hour increments. A rainfall of 3.00 inches was used for the one-year storm analysis. For the 10-year storm, 5.38 inches of rainfall was used. Time. of Concentration The time of concentration route was identified as the longest path that water would flow to reach the pond. Each route was broken into two segments: sheet flow and shallow concentrated flow.. TR55 methods were used to calculate the sheet and shallow concentrated flow times, through the HydroCAD program, Con~osite Areas and Corresponding- SCS Runoff Curve Numbers The composite areas were entered into HydroCAD using measurements taken from the design drawings. The corresponding SCS curve numbers were selected based on the surface composition, and can be seen in the HydroCAD reports included in Appendix A. Summary After careful consideration of the pre and post development conditions at the Hillsborough State Employees Credit Union, discussions with the Orange County Inspections Department, Landscape Architects from O'Brien Atkins, and after taking concerns for the surrounding watershed into consideration, the proposed stormwater plan was developed. This plan incorporates the existing stornrwater structures and the addition of a new underground detention system 08/08/03 Page 2