This is a type of pit that forms the part of sewer system. It commonly square in shape with specific strainers that prevent the garbage entering in to the sewer lines. This can be taken as similar as traps used in residential plumbing. These are mostly used by city authorities to prevent clogging of the drains.These are positioned in a way that they are having slopes from all directions that allow the remains to get into it. This is connected to the main sewer line with grating inside the pipe that traps the garbage from entering the main pipeline. This helps in making the sediment free water to flow into main sewer.