What happens to stormwater as it runs off?
When stormwater flows over the land – over rooftops, lawns, driveways and streets – it picks up nonpoint source pollution and debris. These pollutants include pesticides and fertilizers from yards and agricultural lands, oil and heavy metals deposited on pavement by our cars, sediment from eroding land or construction sites, debris and litter from various places, bacteria from pet waste, and others. Even nutrients from decomposing leaves and grass clippings can pollute water. In natural areas, a lot of these pollutants are cleaned out of the water as it soaks into the ground and is filtered by soil and vegetation. In developed areas, where much of the land surface is covered by buildings, pavement and other impervious surfaces, water cannot soak into the ground. Rather, it carries those pollutants with it into the storm drains and into our local waterways. It is important to recognize that stormwater is not necessarily polluted. Stormwater runoff is a natural process. It only becomes p
