Stormwater Pollutants

Storm drains (like those found along curbs) do not go to wastewater treatment plants. Water entering storm drains flows untreated into streams, rivers, ponds, wetlands, lakes, sounds, bays, and oceans. The diagram below shows the difference between a municipal separate storm sewer system (MS4), which we have in North Carolina, and a combined sewer system (CSS) which are used in other parts of the country.

(image courtesy of the Chesepeake Quarterly)

Since stormwater is not treated, it can pick up and carry numerous pollutants into our waterways. Many of these pollutants can cause problems in very small amounts. Polluted stormwater runoff is often considered a non-point source pollutant, meaning that it comes from such varied and widespread sources across the landscape that it is difficult to identify where the pollution starts.

Sediment runs off into a road culvert (image courtesy of Mobile Baykeeper).

Did you know that sediment is the number-one pollutant in the country and in North Carolina? Sediment comes from anywhere soil is disturbed and is allowed to enter waterways. When it is suspended in the water, it clouds water and suffocates aquatic life. When it settles out of water, it deteriorates habitats for fish and plants by burying stream riffles, which add oxygen to water.

The “Big 6”

Flip through the image carousel to learn more about the “Big 6” common stormwater pollutants and how you can prevent them.

Pet Waste

Yard Waste

Household Hazardous Waste (HHWs)

Vehicle Maintenance


Pesticides, Herbicides, and Fertilizer

If you are interested in learning more about the different types of water pollution and why protecting our water sources is important, check out the Basement Guides to Water Pollution infographic site.