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| Table 11.2 Comparison of design methodsa |
| | Design method | | | | | | Minimum flow velocity | | | | | | Brazilian tractive tension | | | | | | aBased on initial flow 45 1/s and a final flow of 60 1/s. | | | |
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0.56 m/s. Using the Brazilian procedure for the tractive tension method, Imin is 0.0009 and Qf/I0.5min = 2.0. From Table 11.1, a pipe diameter of 450 mm is selected at a d/D of 0.625. The corresponding V/I0.5 is 19.48, which translates to Vf = 0.58 m/s. Checking the initial conditions, Qi/I0.5 = 1.5 which is equivalent to a d/D of about 0.5, corresponding to an initial velocity of 0.54 m/s. These results are compared in Table 11.2. |
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Project areas are typically defined by individual drainage basins. Each basin may have its own collectors and treatment plant. As funds become available, the individual drainage basins may be connected to a common interceptor for conveyance to a regional treatment plant. |
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As the sewers are usually constructed in existing developed areas, they are commonly installed under sidewalks on both sides of the street, rather than in the street, to minimize the depth of excavation and the cost of pavement restoration. Also, the sewers are extended only to the last connection, rather than to the end of the block, to save pipe and excavation costs. |
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11.4.2
Design Period and Flow |
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The concept of a design period to project design flows is not used in developed urban areas. Instead, the saturation population for |
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