Runoff from urban and suburban areas is a major origin of nonpoint source pollution. Much of the urban environment is paved with asphalt or concrete, or covered with buildings. These surfaces are usually impervious, meaning that water runs off of them without being absorbed into the soil. These hard, impervious surfaces make it easier for stormwater to pick up, absorb, and carry pollutants.
Other environments in urban and suburban areas also add to nonpoint source pollution. At construction sites, soil that has been disturbed or piled up without being contained can easily erode. Discarded construction materials (plastics, wood, oils, trash) can also be carried away from these sites by runoff waters.
In suburban areas, the chemicals used in lawn care, and even pet wastes, often end up in runoff and contribute to nonpoint source pollution. In many towns and cities the water flowing into storm drains is not treated before emptying into nearby waterbodies. That's why many municipalities, like those in suburban Maryland and Virginia that border the Potomac River and Chesapeake Bay, are painting words like "It Ends Up In The Bay" in large bright letters across their storm drains. This reminds residents in towns more than two hours away from the Chesapeake Bay that their very own nonpoint wastes, no matter how small, eventually contribute to polluting the great bay.