Sewage systems are constructed through a series of carefully planned and executed steps. First, engineers design the layout, taking into account the topography, population density, and existing infrastructure. Next, excavation crews dig trenches to the required depth, ensuring proper slope for efficient wastewater flow. Specialized contractors then install the pipes, manholes, and other components, followed by backfilling and compacting the soil. Finally, the system is tested and inspected to ensure it meets all regulatory standards before being put into operation.