Must be of adequate size to avoid over flow
Must flow under gravity $$ rac{1}{2}$$ to $$ rac{3}{4}$$ full
Must be laid at least 2 to 3 m deep to collect /water from the basements
All the above
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Answer is Wrong!
The correct answer is D. All the above.
Sewers are designed to carry wastewater away from homes and businesses to treatment plants. They must be of adequate size to avoid overflow, and they must flow under gravity at a rate of $\frac{1}{2}$ to $\frac{3}{4}$ full. This ensures that the wastewater is not stagnant and that it does not back up into homes and businesses. Sewers must also be laid at least 2 to 3 m deep to collect water from the basements. This prevents basement flooding and helps to protect the health and safety of residents.
Here are some additional details about each of the requirements:
- Adequate size: Sewers must be of adequate size to avoid overflow. This means that the sewer must be able to carry the maximum amount of wastewater that is likely to be generated by the homes and businesses that it serves. If the sewer is too small, it will overflow during periods of heavy rainfall or when there is a large influx of wastewater from businesses.
- Flow under gravity: Sewers must flow under gravity. This means that the sewer must be sloped so that the wastewater flows downhill. If the sewer is not sloped properly, the wastewater will not flow and will instead back up into homes and businesses.
- $\frac{1}{2}$ to $\frac{3}{4}$ full: Sewers must flow under gravity at a rate of $\frac{1}{2}$ to $\frac{3}{4}$ full. This means that the sewer must not be too full or too empty. If the sewer is too full, the wastewater will not flow and will instead back up into homes and businesses. If the sewer is too empty, the wastewater will not be treated properly and may contaminate the environment.
- Laid at least 2 to 3 m deep: Sewers must be laid at least 2 to 3 m deep. This prevents basement flooding and helps to protect the health and safety of residents. If the sewer is not laid deep enough, it may be damaged by flooding or by heavy equipment.