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ICOME RAIN, WE SHINE:" STORMWA�• <br />I MANAOEMEMi /NC. <br />L <br />Mountaln View Plaza - Stormwater Treatment Svstem <br />Size and Cost Estimate <br />Everett, WA <br />Information orovided: <br />• Total contributing area = 2.5 acres <br />• Impervious area = 1.8 acres <br />• Peak Flow Rate = 0.42 cfs <br />g,s�um�tions: <br />• Presiding agency = City of Everett, WA <br />• Media = Perlite/Zeoiite/GAC cartridges <br />. Drop required from inlet to outlet = 2.3' minimum <br />�a <br />C �� e d <br />}��soq-czy <br />� <br />, �.,��; �'`'9 <br />CP <br />����r1 � <br />V <br />� <br />�� <br />��I <br />Size and cost estimates: <br />The StormFilter is a flow-based system, and therefore, is sized by calculating the peak water <br />quality (low rate associated with lhe design slorm. However, when the StormFilter is placed <br />downstream of detention the flow rate generated at the water quality storm is not always <br />representative o( the �otal volume of water that will go through the system or type of <br />pollutant-loading the ;ystem may experience in one year. <br />The StormFilter for this site was sized based on � treatment flow rate of 0.03 cfs. To <br />accommodate this flow rate, Stormwater Management recommends using a 6'x12' precast <br />StormFilter with 11 cartridges (see attached detail). The estimated cost of this system is <br />8 00, complete and deiivered to the job site. This estimate assumes that the vault is <br />less than 9 feet deep. The final system cost will depend on the actual depth of the units and <br />whether extras like doors rather than castings are specified. The contractor is responsible <br />for setting tlie StomiFilter vault and all externai plumbing. <br />The precast StormFilter has an intemal bypass capacity of 1.8 cfs. If the peak discharge off <br />the site is expected to exceed that rale, we reconunend placing a high-flow bypass upstream <br />of the StonnFilter system. Stonnwater Managemenl could provide our high-flow bypass, the <br />StomiGate, which provides a combination weir-orifice control structure to limit tlie tlow to the <br />StormFilter, for approximately 33,900. The final cost would depend on the actual depth and <br />size of the unit. <br />SMIENGR::CL 6/27/05 <br />/� <br />