F11_hw08 - Use the Christensen experimental method for the...

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ENV 4561 Fall 2011 Homework # 8 Assigned: October 20, 2011 Due: October 27, 2011 1. 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 150 gal/capita/day. The number of house connections to the sewer is presented in Table 1. Assume an average of 2.5 people/house. a. Determine the size of the pipes that will carry the flow in the sewer system shown below, assuming a safety factor of 3.5. 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. Determine the number of manholes in each section and the number and location of lift stations in the system. Assume a maximum pipe length of 400 ft, with 20 ft pipe sections. Also assume that the maximum depth you can go below the ground surface is 14’, and the sewer pipes should be at least 3’ below ground (i.e. 3 ft of cover soil) c. Find the actual depth of the water traveling between manholes for each section.
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Unformatted text preview: Use the Christensen experimental method for the depth. The graph for Christensens method can be approximated by the equation below. 0916 . 5003 . 1 6336 . 1 * 9655 . 2 3 + + - = Qfull Qactual Qfull Qactual Qfull Qactual Dfull Dactual Note: Remember that the minimum pipe diameter to be used in the sewers is 8 and the minimum velocity of the water in the pipes when flowing full is 2fps. If you work this problem in Excel, you can email me your spreadsheet but make sure the equations used are written somewhere in the spreadsheet and your work is very organized. 1 2 4 3 A B EL=130' EL= 110' EL= 150' EL= 130' EL= 122' EL= 86' EL = Elevation Figure 1. Sewer System Plan View Table 1. # of house connections to sewer system. Sewer Section Length of Section ft # of house connections per section 1 to A 11,000 600 2 to A 6,900 340 A to B 4,500 270 3 to B 8,000 310 B to 4 2,500 415...
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F11_hw08 - Use the Christensen experimental method for the...

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