Which collection system carries a combination of two or more types of wastewater and often has a basin where excess wastewater is collected?

• A. Sanitary
• B. Industrial
• C. Storm
• D. Combined

Answer: (D)

A system that carries both sanitary wastewater and stormwater in the same network is designed to handle two or more types of wastewater in one set of pipes, and it often includes a basin or storage area to hold excess flow during heavy rain. This storage helps prevent overflows by giving a place to hold the surge until water can be treated or discharged under control. That combination and the storage feature distinguish it from other sewer types. A sanitary system carries only domestic or industrial wastewater and doesn’t mix in stormwater; a storm system handles only rainfall runoff; and industrial isn't a standard separate sewer type and doesn’t inherently imply a basin for excess flow.