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HomeMy WebLinkAboutApplication Files_89666_pg0020 4�mou�j Ple�� July 17,2013 Vat" Cj Water Quality Volume Calculations Reference:2004 Connecticut Storm Water Quality Manual WQV=(I'1(R)(A) WQV=volume in ac-ft 12 R=0.05+0.009I I—%impervious coverage REEC—A=site area in acDEVELOPED NORTH-EAST:WQV=(1")(0.05+0.009*42.4)(1.18)=0.0424 ac-ft=1,848 cf cvON 12 Provided: 814 cf (0;2 inch of total area nmoff; approx.44%of total WQV; approx. 100%of WQV required for improvements alone) DEVELOPED SOUTH-EAST: WQV drainage area=(1")(0.05+0.009*82.3)(0.5lac)—0.0336 ac-ft=1,464 cf- 12 WQV improvements only entire drainage area=(1")(0.05+0.009*100)(0.127ac)—0.01 ac-ft—4 cf y.a '_ 12 f WQV area bypass stormceptor—(1'1(0.05+0.009*76.2)(0.21ac)—0.0128 ac-ft,=561 of 1 12 - WQV improvements only bypass stormceptor =(1")(0.05+0.009*100)(0.08ac)=0.0063 ac-ft—276 cf 12 WQV to stormceptor 450i=(I")(0.05+0.009*86.6)(0.30ac)=0.0207 ac-ft=902 cf 12 Provided:418 cf(225 inch of total area runoff, approx.29%of total WQV; 96%of 435 cf WQV required for improvements alone 150%of 276 of WQV required for improvements alone bypassing stormtech 450i Water Quality Flow(WQF)to stormceptor 450i: CN — 1000 _ - [10+5P+I OQ— 10(Q�+1.25QP)I/fl CN=Curve number P=water quality storm=I" Q=Runoff depth in watershed.inches.=(0.0207 ac-ft/0.30 ac)*12in/ft=0.928 inches CN— 1000/[10+5(1)+10(0.828)-10((.82s)'+1.25*0.828*1)Y,] f CN=98.4 Ia—0.041 (for CN—98) la/P=0.041/1"=0.041 qu=450 csm/in(for la/P=0.041; Tc—.11 hrs) WQF—(qu)*(A)*(Q) A=area(sq.miles)=.30 ac=0.0004688 sq.miles WQF=(450)*(0.0004688)*(0.828) WQF=0.175 cfs Stormceptor 450i treatment flow=0.4 cfs DEVELOPED SOUTH-BUILDING: WQV=(1")(0.05+0.009*46.7)(.03)=000118 ac-ft=51.2 of 12 Provided: 55 of (100%of total WQV)