Housing areas A3.0 acres Aso aeres Intel MH3 net A-40 neres Cemetery iet MHT Ditancs between M MHA-MHE 0o MH2-MHI soo fe Outat sewer
The drainage area shown below comprises two housing areas served by inlets at MHS 3 and 2, and a 4- acre cemetery served by an inlet at MH 1. A circular concrete outfall sewer exits MH 1. Assume the following: Average runoff coefficient is 0.45 for the housing areas (3 acres to MH 3; 5 acres to MH 2) and 0.2 for the cemetery (4 acres to MH 1) Manning's n=0.013 Overland travel (inlet) times are 10 minutes for MH 2 & 3, and 8 minutes for MH 1 Flow velocity in all sewers upstream of MH 1 is 3.5 ft/sec Calculate the required diameter of the pipe from MH 1 to the outfall, if the minimum full-pipe velocity must be 3.5 ft/s. What is the minimum slope of the concrete outfall sewer (MH 1-Outfall)? Use the rational formula (Q=ciA) and the 10-year IDF curve in Figure 7.7 of your book. Manhole-to-manhole spacing is given in the figure below. For the pipe size and slope selected in part a, what is the actual full-pipe flow capacity? If the pipe is flowing at a depth of 40% diameter, what are the velocity and flow rate? Use Figure 6.2 and/or Table 7.2. a. b. C. Housing areas A30 Acres AWS ced Thiel MH3 u no MH2 A=0 acres *-Cemetery net MH1 Distances between MHS MH-MHZ 600 Ft M2-MH oft Outfalower Nominal Sewer Size 8 inch (200 mm) 10 inch (250 mm) 12 inch (300 mm) 15 inch (375 mm) 18 inch (450 mm) 21 inch (525 mm) 24 inch (600 min) 27 inch (675 mm) 30 inch (750 mm) 33 inch (825 mm) 36 inch (900 mm) 39 inch (975 mm) 42 inch (1050 mm) Minimum Slope in Feet Per 100 Feet (m 100m) 0.40 0.28 0.22 0.15 0.12 0.10 0.08 0.067 0.058 0.052 0.046 0041 0.037
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