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• <br /> Determining Number of <br /> CONTECH Cartridges for Systems <br /> ENGINEERED SOLUTIONS Downstream of Detention <br /> CONTECH Stormwater Solutions Inc. Engineer: CRH <br /> Date 7l11 f2014 <br /> Site Information <br /> Project Name Silver Lake Center <br /> Project State Washington <br /> Project Location Everett <br /> Basin ID A <br /> Drainage Area, Ad 1.83 ac <br /> Impervious Area, Ai 0.90 ac <br /> Pervious Area,Ap 0.93 <br /> % Impervious 49% <br /> Runoff Coefficient, Rc 0.49 <br /> Upstream Detention System <br /> Peak release rate from detention, —release peak 0.77 cfs <br /> Treatment release rate from detention,Q release treat 0.03 cfs <br /> Detention pretreatment credit 50% <br /> (from removal efficiency calcs) <br /> Mass loading calculations <br /> Mean Annual Rainfall, P 36 in <br /> Agency required % removal 80% <br /> Percent Runoff Capture 90% <br /> Mean Annual Runoff,Vt 105,678 fte <br /> Event Mean Concentration of Pollutant, EMC 60 mg/I <br /> Annual Mass Load, Mtotai 395.60 lbs <br /> Filter System <br /> Filtration brand Storm Filter <br /> Cartridge height 18 in <br /> Specific Flow Rate 1.00 gpm/ft2 <br /> Number of cartridges -mass loading <br /> Mass removed by pretreatment system, More 197.80 lbs <br /> Mass load to filters after pretreatment, Mpassl 197.80 lbs <br /> Estimate the required filter efficiency, Efilter 0.60 <br /> Mass to be captured by filters, Mfiitar 118.68 lbs <br /> Allowable Cartridge Flow rate, Qcart 7.50 <br /> Mass load per cartridge, Mcart(Ibs) 36.00 lbs <br /> Number of Cartridges required, Nmass 4 <br /> Treatment Capacity 0.07 cfs <br /> Determine Critical Sizing Value <br /> Number of Cartridges using Qreleasetreat, Nriow <br /> Method to Use: MASS-LOADING <br /> SUMMARY <br /> Treatment Flow Rate, cfs 0.07 <br /> Cartridge Flow Rate, gpm 7.5 <br /> Number of Cartridges 4 <br /> 1 of 1 <br />