What kid (or adult) doesn’t enjoy splashing around in puddles of water left on the street after a heavy rainfall? But before long, the water flows away and the puddles are gone. Where does the water go??
Most suburbs and newer communities have separate sewer systems for stormwater, which are the underground conveyance systems designed to move water away from an area as quickly as possible. In urban areas, stormwater and snowmelt are directed towards storm drains. The water is collected and transported by the separate sewer system which releases the water, untreated, into nearby rivers or streams. These systems are owned and managed by a public entity, such as your village, county or state. Your tax dollars help pay to install and maintain these systems. These systems are regulated by the National Pollutant Discharge Elimination System (NPDES) Municipal Separate Storm Sewer System (MS4) Permit.
In some older cities, stormwater is managed by combined sewer systems. Combined sewer systems collect stormwater, domestic sewage, and industrial wastewater in the same pipe. Most of the time, combined sewer systems transport all of their wastewater to a wastewater treatment plant, where it is treated and then discharged to nearby river or stream. However, during periods of heavy rainfall or snowmelt, the rate and volume can exceed the capacity of the sewer system or treatment plant. When this occurs, combined sewer systems are designed to overflow and discharge excess wastewater directly to nearby streams, rivers, or other water bodies. These overflows, called combined sewer overflows (CSOs), contain not only stormwater but also untreated human and industrial waste, toxic materials, and debris. They are a major water pollution concern for approximately 772 cities in the U.S. Approximately 100 cities in Illinois have combined sewer systems.
One of the best ways to manage stormwater is to help catch and keep it where it falls. This can be a challenge in urban areas because there is so much impervious area. Impervious areas increase the amount of stormwater and that rate that stormwater must be managed.