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As stated in section 7 of this report, a bioretention area was sized using the 2012 WVVHM <br /> to infiltrate all roof runoff proposed with this project. This was done in order to not increase <br /> the amount of off-site runoff from the existing conditions. The model was run to determine <br /> the effect of this project's proposals increase the site runoff in any way. The results from <br /> the model are shown below. <br /> Existing Site Hydrology <br /> Total Site Area: 0.13 ac(Area of disturbance only) <br /> Hydrologic Soils Group C (Sandy loarns) <br /> Impervious Area: 0.00 ac <br /> Pervious Area 0.13 ac(lawn) <br /> Existing Condition Event Output: WWHM <br /> Peak Flow (cfs) Area (ac) <br /> 2-yr current 0.011 0.13 <br /> 10-yr current 0.031 0.13 <br /> 100-yr current 0.076 0.13 <br /> Developed Site Hydrology <br /> Developed Area: 0.13 ac <br /> Hydrologic Soils Group C (Sandy loams) <br /> Impervious Area: 0.04 ac(roof to bioretention area) <br /> Pervious Area 0.09 ac (lawn) <br /> Developed Condition Event Output: WWHM3 <br /> Peak Flow (cfs) Area (ac) <br /> 2-yr mitigated 0.007 0.13 <br /> 10-yr mitigated 0.021 0.13 <br /> 100-yr mitigated 0.053 0.13 <br /> As shown in the tables above, this project proposes matching, or a net decrease in site <br /> runoff in the 2 through 100-year storm events. Therefore, the flow control performance <br /> standard has been met. <br /> Diedrich Addition 21-0224 <br /> Sept 2021 Page 12 <br />