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The vault has been sized using WWHM4. Based on the system sizing, a <br /> detention vault providing 40,850 cf of detention will be required. The <br /> proposed vault will provide a total of 46,648 cf with 7' of live storage, which <br /> exceeds the required detention. <br /> Based on Chapter 13, Volume III of the City of Everett Stormwater Management <br /> Manual, any BMP which has a General Use Level Designation from the <br /> Washington State Department of Ecology may be used to meet water quality <br /> requirements. This project proposes to use a Stormfilter system to address <br /> water quality needs. Individual Stormfilters will be provided for catch basins <br /> 14A, 15, 17A, and 18 to treat the inflow into these basins. The required flows <br /> and cartridges are noted below: <br /> Structure ID Water Cartridge No. of Structure Vault WQ <br /> Quality Height Cartridges Outlet IE Stage <br /> Flow (CFS) ELEV <br /> CB-14A 0.03 18" 2 441.77 435.35 <br /> CB-15 0.08 27" 3 438.79 435.35 <br /> CB-17A 0.05 18" 3 438.60 435.35 <br /> CB-18 0.09 27" 4 438.79 435.35 <br /> CB-20 0.14 12" 13 437.47 435.35 <br /> According to the table above, all water quality StormFilter outlet invert <br /> elevations are vertically above the water quality flow rate stage storage <br /> elevation in the vault. Therefore the StormFilter cartridges will not be <br /> submerged in backwater conditions resulting by the vault tailwater elevation <br /> generated by the storm event as identified by the WWHM WQ flow rate in the <br /> vault B output. <br /> For additional detail, see the project calculations included in Appendix 4-B. <br /> July 2014 4-3 LDC Job No. 13-144 <br />