Introduction to Stormwater Pollution

Every time it rains, some of the water runs off of the land. This is known as stormwater runoff. As it flows off of rooftops and lawns, and down driveways and streets, stormwater picks up pollutants and debris. This can include such things as:

• Sediment (dirt)
• Fertilizer
• Pesticides
• Motor Oil
• Grease
• Heavy Metals (lead, copper, zinc, cadmium)
• Leaves and Grass Clippings
• Pet Waste
• Litter

All of these contaminants are carried by stormwater (now known as polluted stormwater runoff) to the nearest storm drain or drainage swale and are eventually delivered, untreated, into the nearest river, lake or stream. This type of water pollution is known as nonpoint source pollution because the sources of contamination come from many dispersed locations that, while each may be very small, cumulatively have a large impact. This is opposed to a sewage spill or industrial discharge, which is known as a point source of pollution.

A common misconception is that water that runs off streets and parking lots into a storm drain goes directly to a wastewater treatment plant. It doesn't. In fact, stormwater usually receives no treatment!

Stormwater pollution can make monitoring and treatment of our drinking water more difficult and costly. In addition, it can hinder the health of the aquatic ecosystem and result in the loss of our rivers, lakes and streams for recreational purposes.