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Storm drains are specialized drainage systems which are designed to handle an excess of water as a result of flooding or heavy rainfall. They are frequently found in major cities, especially in flood prone areas. A number of systems are used for the collection and ultimate discharge of water from these drains, and if there are drains of this kind in your area, it may be interesting for you to learn about how the water is processed before it is discharged.

When rainfall is heavy, the streets, parking lots, and other flat areas of a city can flood. In addition to the water falling directly on these surfaces, gutters also discharge large amounts of water into the street. The flooding can pose a hazard, which is why storm strains are installed.

The storm drains are frequently located on either side of a street, at a low point in the roadway where water would naturally collect. Typically, a large grate covers the drain, which takes the form of a giant pipe.

 In some parts of the world, storm drains are known as stormwater drains or a surface water system. Water flows down the pipes and meets up with other pipes, creating an ever-larger central pipe. In many areas, the storm drain system is kept entirely separate from the sewer system. The outlet for the pipe is found by a lake, ocean, or other major body of water. In other cases, these drains are connected with the sewer system, and the water from the drains is processed before it is disposed of.

 When water from the storm drains flows into a body of water, it can potentially distribute flooding to locations downstream, in the case of a river. It also poses a major pollution risk, because spills in the streets will be carried through the unfiltered storm drain system. For this reason, people are warned to stay away from storm drains and outlets for their health. Many such drains also have signs above them which say “No dumping, drains to lake” to remind people to protect their waterways by disposing of pollutants responsibly.

 When a storm drain is linked with the sewage system and the water level is controllable, the processing offered by the sewage treatment plant is beneficial. However, if water levels start to rise beyond the capacity of the system, backups can cause the discharge of raw sewage into streets and waterways. For this reason, cities which chose to interconnect the storm drain and sewage systems must have protections in place to ensure the safety of the water supply.

 As authorized by the Clean Water Act, the National Pollutant Discharge Elimination System (NPDES) permit program controls water pollution by regulating point sources that discharge pollutants into waters of the United States.  Industrial, municipal, and other facilities must obtain permits if their discharges go directly to surface waters.

When it rains, storm water flows over driveways, lawns, sidewalks, roads and parking lots on its way to the nearest entrance into the storm drain system.  In most cases the stormwater system discharges this polluted runoff to the nearest lake, creek, stream or ultimately a river with NO treatment.  This is unlike the water that goes down the toilet or sink in your home which discharges to the wastewater system for treatment. 

According to the United States Environmental Protection Agency, polluted storm water runoff is the nation’s greatest threat to clean water.  Stormwater pollution is toxic to fish and wetland wildlife.  It threatens all of us who use and enjoy our most valuable resource – WATER