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ISca�ca}' I�ract I — Lot ? <br /> Slorm Drainaga Rcpnn _ <br /> The total runoff volume of the developed 6 month, 24-hour storm event is 0.0967 <br /> acre-feet, or 4,2U0 cubic feet. <br /> I <br /> Vegetated Treatment Cell <br /> The vegetated treatment cell is designed per section 3-3.5.1 of the City nf Everett <br /> Stormwater Design Manual. As a stated requirei��c�t, the treatment cell must be <br /> preceded by an open water cell andlor by a wetvaulUtank. The vegetated <br /> treatment cell must contain a minimum of 15% of the total permanent pool <br /> volume. The total depth is not to exceed 2.5-feet and should be planted <br /> appropriately. <br /> IMinimum Volume Calculation <br /> I4,200 cf x 15% = 630 cf (actual volurne = 1,460 c� <br /> Presettlinc Tank <br /> IThe presettling tank is designed to have a storage volume equal to the total <br /> volume ot runoff from the 6 month, 24-hour storm (4,200 cf) minus the volume <br /> Icontained in the vegetated treatment cell (1,460 cf). Therefore, the required tank <br /> volume is 2,740 cf. According to section 3-3.6.1 of the City of Everett <br /> IStormwater R�anagement Manual, lhe tank shall have a minimum permanent <br /> i pool volume as follows: <br /> � <br /> Minimum Permanent Pool Volume <br /> I V = 1,676.5QoH <br /> where: Qo = average (low during the 6 month, 24-hour event <br /> � Qo = 6 month storm volume / 86,400 seconds <br /> � <br /> = 4,200 cf/ 86,400 seconds <br /> = 0.05 cfs <br /> H = depth of permanent pool <br /> V = 1,G76.5 x 0.05 cfs x 6 feet <br /> V = 503 cf <br /> The minimum permanent pool volume requirement has been met since the tank <br /> Iwill have a permanent pool volume of 2,894 cf. <br /> _- - - - - - -- - - <br /> I�.�hi�i.u� '.. .�in.l � P;icc�l <br /> I �I'Rl;\D <br /> i � . , <br />