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COME PAIN, WE SHINE:" STORIVIWATE�^ <br />AfANAQEMENT INC. <br />18th Ave West- Stormwater Treatment System <br />Size and Cost Estimate <br />Everett, WA <br />Information provided: <br />• Total contributing area = 0.67 acres <br />• Impervious area = 0.29 acres � <br />• Volume of the seuling basin = 402 cubic feet �� {2 <br />• Volume of runoff = 1,031 cubic feet r <br />• Depth of water in basin = 0.96 ft �` <br />• Detention release rate = OA1 c(s ��` l� �( <br />• Flow Rate per Cartridge = 7.5 gpm • � v `� <br />• Presiding agency = City of Everett � ` <br />� ���''/ '�� �,�5 �� <br />Assum ti�� ons: � V Y � f <br />• Media = Perlite cartridges �� C' G'� <br />• Event Mean Concentretion 60 m <br />• Drop required from inlet to outlet = 2.3' minimum <br />Size and cost estimates: <br />The StormFilter is a flow-based system, and therefore, is sized by calculating the peak water <br />quality flow rate associated with the design storm. However, when the StormFilter is placed <br />downstream of delention the flow rate generated at the water qualiry storm is not always <br />representative of the total volume of water th�i �Niil go through the syscem or type of <br />pollutant-loading the system may ex�erience in c,nE year. <br />Stormwater Management recommends using a precast manhole StormFilter with 3 <br />carlridges. The estimated cost of this unit is $10,800, complete and delivered to the job <br />site. This estimale assumes that tl�e manliole is less than 10' feet deep. The final system <br />cost will depend on lhe actual depth of the units. The contractor is responsible for setting <br />the StormFilter manhola and all exlemal plumbing. <br />Typically, we recommend annual maintenance for the StormFilter ireatment system, but the <br />maintenance cycle will ultimately depend on the rainfall conditions and actual pollutant <br />loading. If contracted with Stormwater Management Inc., the estimate maintenance cost for <br />the system is $220 per cartridge per cycle. <br />,�S\ <br />SMI ENGR: JOER 12/30/04 <br />