Page 594 - Fair, Geyer, and Okun's Water and wastewater engineering : water supply and wastewater removal

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550 Chapter 14 Design of Sewer Systems
50 m 2
A B Area Area, m c Overland Flow Time, min
30 m I 5,000 0.5 7
E II 10,000 0.4 5
F
III 16,000 0.7 5
15 m
100 m
H
G
Area | Area || Area |||
A B C D
Inlet 1 a b c
Sewer 1 D C
t 2 min
Inlet 2
Flow time Sewer 2
H to Inlet 1 2 min t 1 min H G F E Stream
E to Inlet 1 5 min
F to Inlet 1 6 min MH Figure 14.36 Layout of Storm Drainage for Problem 14.19.
C to Inlet 2 3 min
A to Inlet 2 10 min Sewer 3
B to Inlet 2 9 min The rainfall intensity i (mm/h) as a function of rainfall duration
t (min) is:
Figure 14.34 Layout of Storm Drainage for Problem 14.17.
3,360
i =
t + 17
14.18 The drainage system shown in Fig. 14.35 is designed to
collect the stormwater from three areas. The areas’ runoff coef- The average velocity in sewers 0.90 m/s. The length of each
ficients and overland flow times are as follows: of the sewers a-b and b-c 150 m.
Calculate the total stormwater discharge (L/s) into the
Area Area, ha c Overland Flow Time, min stream from the three areas combined.
14.20 Determine the size of storm sewers 1, 2, 3, and 4 needed
I 5 0.6 5
to serve the drainage areas shown in Fig. 14.37. The following
II 15 0.5 10
data are given:
III 10 0.8 8
Overland Flow Runoff
Inlet 1 Inlet 2 Drainage Area Area, ha Time, min Coefficient
Inlet 3 A1 2.8 20 0.60
MH A2 2.0 15 0.50
A3 1.5 10 0.40
Park 1.0 15 0.20

Area | Area || Area |||
Park
Figure 14.35 Layout of Storm Drainage for Problem 14.18.
A1 A2
The rainfall intensity i (mm/h) as a function of rainfall duration 1 2
t (min) is:
1,120 A3 3 Overland flow
i = 2 Sewer number
t + 110
Storm sewer
Inlet
The flow time in sewer 1-2 is 2 min and in sewer 2-3 is 2.5 min. MH
3
Determine the design flows (m /min) for the three sewers: A Housing area
1-2, 2-3, and 3-4. 4
14.19 The drainage system shown in Fig. 14.36 is designed to
collect the stormwater from three areas. The areas, runoff coef-
ficients and overland flow times are as follows: Figure 14.37 Layout of Storm Drainage for Problem 14.20.