Orange County NC Website
Hillsborough State Employees Credit Union 033 <br />Stormwater Report <br />project # 70994252 <br />computer Model input for Watershed Areas <br />Through the use of HydroCAD, many aspects of the effluent flow were analyzed. The program requires <br />certain input regarding the characteristics of the land. The input required is: <br />L Design Storm Information <br />a. Length of storm <br />V Depth of rainfall <br />c, Time increment for analysis (dt) <br />2. Time of Concentration <br />1 Composite Areas with Corresponding SCS Runoff Curve Numbers <br />An SCS Type 11 24 Hour rainfall distribution was assumed for the storm analysis, with 0.01 -hour <br />increments.. A rainfall of 3.00 inches was used for the one -year storm analysis. For the 10 -year storm, 5.38 <br />inches of rainfall was used. <br />Time of Concentration <br />The time of concentration route was identified as the longest path that water would flow to reach the pond <br />Each route was broken into two segments: sheet flow and shallow concentrated flow. TR55 methods were <br />used to calculate the sheet and shallow concentrated flow times, through the HydroCAD PrOgrarn- <br />Comvosite Areas and Corresponding SCS Runoff Curve Numbers <br />The composite areas were entered into HydroCAD using measurements taken from the design drawings - <br />The corresponding SCS curve numbers were selected based on the surface composition, and can be seen in <br />the HydroCAD reports included in Appendix A. <br />Summary <br />After careful consideration of the pre and post development conditions Department Landscape <br />Employees Credit Union, discussions with the Orange concerns for surrounding watershed into <br />Architects from O'Brien Atkins, and after taking <br />consideration, the proposed stormwater plan was developed. This plan incorporates the existing <br />stormwater structures and the addition of a new underground detention system <br />page 2 <br />08/08/03 <br />