​Nationally, one-fourth of the pollutants found in rivers and streams originate from residential use of pesticides, herbicides, and fertilizers. These materials can enter the storm drain system through illegal dumping, runoff from excessive lawn irrigation and heavy rains, and, from there, be discharged directly into our waterways.

Herbicides are defined as a chemical substance designed to kill plants, especially weeds, or to inhibit their growth..

​A pesticide is any substance or mixture of substances intended for:

• preventing,
• destroying,
• repelling, or
• mitigating any pest

Fertilizer is defined as "any substance containing one or more recognized plant nutrient(s) which is used for its plant nutrient content and which is designed, used or claimed to have value in promoting plant growth."​​