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.� ' Architecture <br /> Engineering An Employee-Owned Company <br /> Environ menta I Stormwater Management Report <br /> . Land Surveying <br /> Companies <br /> Based upon the above calculations, the volume reduction received by the bioretention basin is <br /> greater than the volume reduction required by the San Joaquin County SWQCCP. The completed <br /> San Joaquin County Calculation spreadsheets can be found in Appendix E. <br /> The bioretention system was sized to conform with the San Joaquin County requirements, <br /> including the Stormwater Quality Design Volume (SQDV). The bioretention basin has a <br /> designed drawdown of 12 hours. Based on Figure 6-1 from the SWQCCP, the Unit Basin <br /> Storage Volume is 0.20 inches for the single tributary area. A summary of the SQDV <br /> calculations can be found on Table 4. <br /> Table 4—Summary of Volume Reduction <br /> Tributary Area ft2 394,652 <br /> Tributary Impervious Area Credit ft2 0 <br /> Effective Tributary Area ft2 394,652 <br /> Design Drawdown hr 12 <br /> Weighted Runoff Coefficient 0.63 <br /> Unit Basin Storage Volume in 0.20 <br /> (Figure 6-1 from SWQCCP) <br /> Bioretention Basin Depth ft I <br /> Ponding Depth in 12 <br /> SQDV (Unit Basin Storage <br /> Volume * Effective Tributary ft 6,578 <br /> Area * 1 Win <br /> Planting Zone Area Provided ft2 32,566 <br /> Planting Zone Area Required ft2 6,578 <br /> Difference (PZ(req>d)—PZ) ft2 25,988 <br /> As noted in the above summary Table 4, the proposed bioretention basin's planting area is <br /> greater than the planting zone area required by San Joaquin County. A spreadsheet detailing the <br /> specific calculations can be found in Appendix E. <br /> For this stormwater system to function as designed, cleaning and maintenance is required. An <br /> operations and maintenance plan(O&M) detailing the upkeep necessary for the proposed <br /> stormwater system can be found in Appendix F. <br /> 220 Norwood Park South,Suite 201 • Norwood,MA 02062 • T(781)619-9500 • F(203)630-2615• www.blcompanies.com <br /> 7 <br />