Laserfiche WebLink
(a) to size orifice, <br />D = 6.1V(hi <br />allow <br />thevalue of "h" is dependent upon site conditions, such as existing <br />and proposed topography and the location of other existing and proposed <br />utilities. For purposes of this example, assume that "h" = 2.0 feet, therefore: <br />D = 6.12 .1s3 <br />(2 Y, A <br />D = 2.01 <br />(b) From Figure 1, Tc in the developed state = 630 = 13 min. <br />4 60 <br />Q25 yr = 0.865 (1.95) (3) = 5.06 <br />Filling time = 8763 Ft! = 1732 secs (assuming orifice is clogged) ' <br />5.06 FT3/sec <br />or 29 min <br />therefore, design Tc = 29 + 13 = 42 min <br />so, Q = (o.865)(1.05)(3) = 2.72 c.f.s. <br />Assuming the grate elevation of the restrictor catch basin is 2 <br />feet above the top of the riser and an underground detention <br />system, from Figure by extrapolation a 10" riser will be required. <br />(c) Assuming a concrete outlet pipe at 2% slope, from Figure 6 <br />it can be seen that a 10" outlet pipe has a capacity of 3.4 cfs> 2.72 <br />.. 10" outlet pipe is o.k. <br />