ENV 4561
Fall 2011
Homework # 8
Assigned: October 20, 2011
Due: October 27, 2011
1.
(100 points)
The plan view of the sewer system you have to design is shown in Figure 1. The
annual average daily flow you are designing for is 130 gal/capita/day. The number of house
connections to the sewer is presented in Table 1. Assume an average of 2.3 people/house.
a.
(40 points)
Determine the
size of the pipes
that will carry the flow in the sewer system
shown below,
assuming a safety factor of 3. Use the table 38 on the next page to determine
the ID
of the pipes for your calculations. Use Manning’s eq. for full flow conditions. Assume
n = 0.013
b.
(40 points)
Determine the number of manholes in each section and the number and location
of lift stations in the system. Assume a maximum pipe length between manholes of 500 ft, with
30 ft pipe sections. Also assume that the maximum depth you can go below the ground surface
is 12’, and the sewer pipes should be at least 2’ below ground (i.e. 2 ft of cover soil)
c.
(20 points)
Find the actual depth of the water traveling between manholes for each section.
Use the Christensen experimental method for the depth.
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 Fall '08
 Zoltek
 Sanitary sewer, 30 ft, 2 ft, Lift Station Placement

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