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Basin B <br /> As previously mentioned, all future roof and driveways will be 100% infiltrated on-site and <br /> will not generate any runoff, therefore these surfaces were not modeled when determining <br /> the difference in the 100-year storm for the existing and developed basin areas. <br /> Existing Site <br /> Predeveloped Area: 0.55 ac (disturbed area only) <br /> Hydrologic Soils Group C (Till) <br /> Impervious Area: 0.00 ac <br /> Pervious Area 0.55 ac (Forest, Type C Soils, Moderate Slope) <br /> Existing Condition Event Output: WWHM12 <br /> Peak Flow (cfs) Area (ac) <br /> 2-yr 0.01 0.55 <br /> 10-yr 0.02 0.55 <br /> 50-yr 0.03 0.55 <br /> 100-yr 0.04 0.55 <br /> Developed Site <br /> Developed Area: 0.55 ac <br /> Hydrologic Soils Group C (Till) <br /> Impervious Area: 0.05 ac (Effective Only—Sidewalks, Mod) <br /> Pervious Area 0.21 ac (Lawn, Type C Soils, Moderate Slope) <br /> Developed Condition Event Output: WWHM12 <br /> Peak Flow (cfs) Area (ac) <br /> 2-yr 0.04 0.26 <br /> 10-yr 0.09 0.26 <br /> 50-yr 0.15 0.26 <br /> 100-yr 0.17 0.26 <br /> The output from the WWHM for the 100-year flow frequency for the existing and <br /> developed basins area as follows: <br /> Peak 100-year flow rate for Existing Condition: 0.04 cfs <br /> Peak 100-year flow rate for Developed Condition: 0.17 cfs <br /> Change in 100-year flow rate: 0.13 cfs <br /> Seahurst SP 18-0727 <br /> September 2019 Page 14 <br />