|
|
|
|
|
|
|
10.3.7
Average Number of Occupants Per House. |
|
|
|
|
|
|
|
|
This is the basic parameter for determining the capacity for sludge and scum accumulation in the interceptor tanks. It is calculated by dividing the population of the area by the total number of houses. In most cases the figure should correspond to the most frequent house-to-occupant ratio. The size of the population and number of houses can be established by a census or, more easily but less accurately, by a survey. For Cartagena the average number of occupants per house was 6.8 and for Granada and San Zenon it was 5.76 and 5.78, respectively, rounded up to 5.8. |
|
|
|
|
|
|
|
|
10.3.8
Location of Sewers and Interceptor Tanks |
|
|
|
|
|
|
|
|
As shown in Figure 10.2, sewers are typically located on each side of the street in the sidewalk area. House connection boxes, which serve for inspection purposes, are linked by the sewers, so the length is similar to the frontage length of the properties. In narrow streets, sewers can be located more centrally. |
|
|
|
|
|
|
|
|
Interceptor tanks must be located according to the householders' preference, but must have easy access for inspection and desludging and the shortest possible length for the outlet pipepreferably without change of direction, as shown in Figure 10.2. |
|
|
|
|
|
|
|
|
In low-income communities traffic loads are low, so at street crossings the sewers can be laid at a depth of only 10 cm below the gutter, embedded in concrete. The same applies to the entrance of garages. If properly laid in this way, vitrified clay or plastic pipes of up to 100 mm diameter will not be damaged by heavy vehicles. For pipes of larger diameter, the minimum depth is 20 cm. At 50 cm depth, if pipes are properly laid and the fill is well compacted, concrete embedding is not required. |
|
|
|
|
|
|
|
|
Sewers are designed with the aid of charts as for conventional sewers, also taking into account the number of houses and computing the correct design load using the simultaneity system. |
|
|
|
|
|