How Does Rain Cause Pollution?

Sources of pollution are many: pesticides and fertilizers we spread on our lawns, petroleum and antifreeze that spill from our cars, leaks from failing septic systems and broken sewer pipes, waste from our pets, soap from washing our cars, road salt we spread on our driveways and sidewalks, to name a few.

When it rains, this witches brew of pollutants washes over our lawns, driveways, parking lots and streets as “polluted stormwater runoff.” In most cases, the polluted stormwater runoff flows into storm drains, then through a series of subterranean pipes that carry the runoff directly to the local streams. For most of us, these polluted streams are a source of our drinking water.

The problem is being exacerbated by the steady march of black top, concrete, roof tops and other hard surfaces that are impervious to water. With fewer unpaved areas to filter the polluted runoff and allow it to soak into the ground, there is more polluted runoff rushing into our streams (and also more flooding).

Fortunately, there are strategies known as “Green Stormwater Infrastructure” that can capture, store and release polluted runoff into natural systems that can cleanse the water before it is released into streams or groundwater. Our science staff is designing and implementing such measures to address the problem and our policy staff work with state and local governments to require that developers implement those measures.

Diagram of Rain Garden (Rutgers University)