What is Stormwater?
Stormwater runoff occurs when rain and snowmelt flows over land or impervious surfaces (such as streets, parking lots, sidewalks, and rooftops) and does not percolate into the ground. Increases in impervious surface area cause higher flow rates as runoff collects debris, chemicals, oils, sediment and other pollutants that could adversely affect water quality if discharged to the environment without first being treated.
Why Treat Stormwater?
Control and treatment of stormwater runoff in the United States was mandated by the Clean Water Act in 1972. The National Pollutant Discharge Elimination System (NPDES) program requires businesses, states, and municipalities to have programs, practices, and infrastructure in place to control the discharge of pollutants in stormwater. As a result, most sites constructed in the past 20 years include some form of stormwater treatment.
How is Stormwater Managed?
Controlling and treating runoff is known as stormwater management. While there are many different types of facilities used to control stormwater, two broad categories are Above Ground and Below Ground. Above Ground facilities include basins, dry ponds, wet ponds, sand filters, bioretention, swales, etc. Below Ground facilities are usually unseen and may be underground pipe storage systems, oil/water separators, sand filters, vaults, or they may be proprietary devices for separating, filtering, or storing stormwater.
Check out this great Stormwater 101 video: