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SECTION V—ANALYSIS AND DESIGN OF REQUIRED RUNOFF <br /> CONTROL BMPs <br /> Hydraflow Hydrographs Extension for AutoCAD Civil 3D 2009 software was used to <br /> calculate storm water detention facilities. DOE hyetograph(Table 1-5.2 of Everett <br /> Stormwater Management Manual)was used as a design storm hyetograph. Rational <br /> Method(Chapter 1-5.2.1) and Hydraflow Storm Sewer Extension for AutoCAD Civil 3D <br /> 2009 software was use to size conveyance system. <br /> Although overall site area is 1.092 Ac, storm water quality and quantity control has been <br /> designed using 0.54 Ac,which includes the roof,parking sidewalks, and landscaping <br /> adjacent to the building and parking areas. Rest of the site,being 0.552 Ac, is reserved <br /> for enhanced wetland buffer area. Since no grading or changing hydrologic <br /> characteristics will be done in this area, it is assumed that natural sheet flow to the <br /> adjacent wetland will be preserved. <br /> See also Developed Drainage Areas in Appendix D and Erosion and Sediment Control <br /> Plan in Appendix F. <br /> Existing Site Hydrology: <br /> Pre-Developed flow characteristics for Stream Bank Erosion Control analysis: <br /> Land Cover CN Tc Acreage <br /> Young Gr/Brush 81 32.3 0.54 <br /> Pre-Developed portion discharging to wetland(preserved buffer area) <br /> Land Cover CN Tc Acreage <br /> Young Gr/Brush 81 40.7 0.552 <br /> All characteristics were validated by site investigations including an engineering site <br /> visit. <br /> A Pre-developed Drainage Area Map is attached in Appendix D. <br /> Developed Site Hydrology: <br /> Developed flow characteristics for Stream Bank Erosion Control analysis: <br /> Land Cover CN Tc Acreage <br /> Roof/Parking/SW 98 0.477 <br /> Lawn 86 0.063 <br /> Weighted 97 17.6 0.54 <br /> 4 <br />