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BE�C <br /> ENGINEERS <br /> �l <br /> D• PROPOSED CONDITIONS <br /> DetenUon calculations contatned in thls report are for thc <br /> Japanese Gulch Basin. Th1s is where most of the work occurs <br /> for the Slte Dlsplacement, Track Relocatlon, and Building <br /> 'IYack Packages. The only calculations contained, herefn, for <br /> Powder Mill Gulch are for conveyance plpe slzing. Further <br /> plpe sizlnq calculatlons for the Powder Mlll Gulch Basin wlll be <br /> included at the time oC appltcatton for a bullding permlt for the <br /> Building Package portion of this pro)ect. <br /> A new detentlon pond in Japanese Gulch Basin is proposed for <br /> the low area west of West Perimeter Road. The pond wlll be a <br /> wet pond, alternate "B", with an open water cell and a wetland <br /> treatment cell separated by a batTle. <br /> Preliminary pond sizing parameters we�e provided to the City <br /> of Everett Publlc Works Department using thelr "Dralnage <br /> Calculatlon Submission Form ", see SECTION F of thls report. <br /> The parameters were based on a pre-develupment peak rate of <br /> runoff for a ten year design storm and a post-development <br /> � detention storage for a 25 year deslgn storm, <br /> After revfewing ihis form, the ctty has told us verbally that the <br /> total detentlon storage requlred 1s 23,960 cubic feet and <br /> allowable outflow rate is 6.10 cubic feet per second. <br /> Vegetated swales w(11 be provtded both immediately upstream <br /> and downstream of the pond. <br /> For a further descriptfon of the proposed or post-development <br /> condlUons, see the PROPOSED DRAINAGE PLAN in SECTION <br /> E of these calculaUons. <br /> . <br /> mJc:326-�1239-CALC-1 <br /> 12/10/91 <br />