Stormwater and wastewater (sewage) systems can be built as separate or combined facilities. The more modern houses and businesses now have separate piping systems for sewage and stormwater, while some cities are upgrading their present combined systems due to the occurrences of spillage of sewage into the environment following a rainstorm. This spillage can be from overflow at the wastewater plant or from regulators in the piping system, but both measures involve dumping raw sewage into the local environment.

This happens because of a combined plant