Have you ever wondered what happens to rain when it goes down a storm drain? It’s carried by the storm sewer and discharged into nearby waterways. This water, called stormwater runoff, is not treated. It carries everything it has picked up from streets, lawns, rooftops, and other surfaces, including trash, chemicals, bacteria, and other pollutants. However, runoff isn’t just caused by rain; human activities also create it. For example, we can create runoff simply by hosing off our driveways.