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� <br /> . <br /> �� P�.e%-�„ // <br /> � <br /> consuRinp engineers <br /> STORM DRAIN STORAGE REQUIREMENTS <br /> Drainage Basin <br /> A = .?. 3 6 acres Area of Basin <br /> Ce = o, iD _ � . Existing coefficient of imperviousness of <br /> Basin ground <br /> Cd = o, S�/ Developed coefficient of imperviousness of <br /> Basin as planned. Calculated Page 18. <br /> L = �bs, feet Length (maximum) of overland travel to <br /> yBo • Design point. <br /> S = 5 6 % Slope ;average, from Basin high point to <br /> 9' ' low point (on watercourse) <br /> o. i <br /> Vr = •�S ft./sec. Runoff rate Chart 1, page 25. <br /> i. o <br /> T� _ ` 3 D "minutes Time of concentration from formula: <br /> !; 10 + (L�V (60) = T <br /> I = o, � in./hr. Rainfall intensity frnm Chart <br /> rainfall curve ( d Year storm} � L r z s y� <br /> Qe . = o , a � cfs Existing outflow off of site frvm equation: <br /> � �el � - 4e <br /> Qo = o . �� Scfs Maximum outflow permitted per acre <br /> imperviousness from formula: Qo = Qe/ACd <br /> T = io 3./ minutes Storage time (to ca acity) from formula: z s y r <br /> T = -1 S r 7 z7oc <br /> •�S <br /> VS = �. ,g o 3.7 cf/A/Cd Required volume of storage per acre in Basin —=�•ir <br /> from eGuation: VS = ia�r y ou �? ,- <br /> T-2s <br /> Vt = 3 �7 3 cubic feet Required volume of storage for this Basin from <br /> equation: 1't = VS ACd <br /> Ref: "Storm drainage control , �equirements and guidelines" ,� <br /> King County Public Works Department; t�ay, 1979. <br /> 700 Iloyd bldg., seottle, wa 98101 (206) 622-5822 <br /> onchoroge los angeles portland seattle <br />