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d . <br /> � (a) ta size orifice, <br /> D = 6.12 ` aflow <br /> v (h� <br /> the value of "h" is depa:•,dent upon site conditions, such as existing <br /> and proposed topography and thr_ location of other existing and proposed <br /> utilities. For �;urposes of this example, assume that "h" = 2.0 feet, therefore: <br /> D = 6.12 i53 <br /> (2 S4 <br /> D = 2.01 <br /> �1 � <br /> L <br /> (S) From Figure 1, Tc in the developed state= 630 = 13 min. <br /> � , 4 60 <br /> \'l_r``/ <br /> Q25 yr - 0.865 (1.95) (3) = 5.06 ' <br /> Filling time = 8763 Ft3 = 1732 secs (assuming orifice is clogged) <br /> 5.06 FT3/sec <br /> or 29 min <br /> ( <br /> therefore, design Tc = 29 + 13 = 42 min <br /> so, Q = (0.865)(1,05)(3) = 2.72 c.f.s. <br /> qssuming the grate elevatior� of the restrictor catch basin is 2 <br /> feet above the top of the siser and an underground detention <br /> system, from Fig�re 5, by extrapolatior�a 10" riser will be required. <br /> . (c) Assuming a concrete outlet pipe at 2% slope, from Figure G <br /> it can he seen that a !0" outlet pipe has a capacity of 3.4 cfs� 2.72 <br /> .�. !0" outlet pipe is o.k. <br /> � <br />