Water that flows into the sewers from the surface (streets, yards, etc.) is referred to as storm water. This includes rain and snow melt, but also excess water from watering your lawn. Storm water also means surface run-off water that is the result of natural precipitation. This can include surface water on ground or from the roof surfaces.
In almost all areas of the city, storm water drains into a separate sewer system that contains storm water only. Since it is not contaminated to begin with, storm water does not need to undergo the same treatment process as wastewater. Instead, it is channeled, via the storm water system.
Sometimes however, you may find a combined storm water and wastewater line that are joined together in the same system. This maybe found in older neighborhoods.
The main purpose of storm sewers is to drain surface water and prevent flooding. However, in some newer neighborhoods storm water management lakes also provide a secondary benefit – recreation.
In some Province or Cities , mechanical techniques or means must be utilized to control the rate of release of storm water from the lot of roof surfaces, and to store on the property the volume of storm water in excess of the rate of release as directed by the City’s bylaw. This is to minimize the amount of storm water entering/discharging into the City’s public sewage lines/pipes at the same time. Storage tanks, storage ponds, sumps, sump pumps, and control devices etc. are some of the techniques that can used for such purposes.
