What Is Stormwater?
Stormwater is runoff generated by rain or snowmelt from impervious areas or surfaces such as paved streets, parking areas, and building rooftops, or from pervious surfaces when more rain is falling than can soak into the ground. Impervious surfaces do not allow the rainfall to soak into the soil surface, causing the rainfall to become runoff. This runoff can enter a storm sewer system, which ends up in local streams, creeks, rivers, lakes, and coastal waters.
Why Worry about It?
Stormwater runoff can pick up pollutants such as oil and grease, chemicals, nutrients, metals, and bacteria as it travels across land.
The United States Environmental Protection Agency (U.S. EPA) has stated that in some instances the first inch of rainfall is responsible for a large amount of the pollutants in stormwater runoff.
Polluted stormwater often affects drinking water sources, and can affect human health and increase drinking water treatment costs.
Most cities have a system to collect stormwater and direct it into local waterways.
These systems are totally separate from sanitary sewer systems, which are designed to treat sanitary waste.
Stormwater runoff that enters a storm sewer system is discharged UNTREATED into the water bodies we use for swimming, fishing, and drinking water.
In some instances, heavy precipitation or snowmelt can also cause sewer overflows that may contaminate water sources with untreated human and industrial waste, toxic materials, and other debris.
After a dry season, the first flush of stormwater can have the same pollutant load as raw sewage.
There is a major difference between what is beneath each of these manhole covers.
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