ANS:A - a trunk sewer

A trunk sewer is a large underground pipe or conduit that serves as a major artery in a sewer system, transporting wastewater from smaller sewer lines or lateral sewers to the treatment plant or disposal point. Trunk sewers are typically designed to handle significant volumes of wastewater from various sources within a city or urban area. Here are some key characteristics and features of trunk sewers:

1. Large Diameter: Trunk sewers have a much larger diameter compared to local or branch sewers. This larger size allows them to accommodate higher flows of wastewater from multiple smaller sewers.
2. High Capacity: Trunk sewers are designed to have a high capacity to handle the combined wastewater flow from numerous smaller sewer lines. They are built to withstand heavy flows during peak usage periods and during storm events.
3. Long Distance: Trunk sewers often extend over long distances, traversing through multiple neighborhoods or districts within a city. They may also connect different municipalities or regions to centralized treatment facilities.
4. Gravity Flow or Pumping: Depending on the topography and layout of the sewer system, trunk sewers may rely on gravity flow to transport wastewater downhill towards the treatment plant. In some cases, especially when dealing with challenging terrain or long distances, pumping stations may be installed along the trunk sewer route to lift the wastewater to higher elevations.
5. Structural Integrity: Trunk sewers are built with robust materials and construction techniques to ensure structural integrity and prevent leakage or collapse. They are often made of concrete, brick, or reinforced plastic to withstand the pressure and flow of wastewater.
6. Maintenance Access: Access points such as manholes are strategically placed along the trunk sewer route to allow for inspection, maintenance, and cleaning activities. These access points also facilitate the removal of debris or blockages within the sewer system.