What is Nonpoint Source Pollution?
Nonpoint source (NPS) pollution is caused when rainfall carries pollutants from a wide variety of sources into surface water or ground water. The term distinguishes pollution that is diffuse in its origins from pollution that is traceable to a single "point source", like a factory or wastewater treatment plant. Many products and materials we use in daily life become nonpoint source pollutants when they reach a body of water. NPS pollutants can be chemicals, like pesticides and fertilizers. They can be automotive products like gasoline, motor oil, antifreeze, or common household items like paint and solvents. They can even be natural materials like soil, animal wastes, grass clippings, and fallen leaves.
Sometime NPS pollutants wash directly into a creek, river, or lake. Construction activity can send soil and debris directly into nearby creeks and streams. In the City of Coppell, the most common route for NPS pollutants is the network of storm drains that carry excess rainwater away from streets and directly into waterways. NPS pollutants can be washed by rainfall from lawns and streets into the storm drains, or they can be dumped there by people who mistakenly think the storm drains flow to a water treatment plant. This dumping greatly increases the level of NPS pollutants already present in urban storm water runoff and can contribute substantially to a decline in water quality.
Pollution affects drinking water quality
Just as the nature of NPS pollutants varies widely, so do their effects on water quality. Pesticides, antifreeze and motor oil contain toxic chemicals that are harmful to humans, animals and plants. Just one quart of motor oil can ruin the quality of 250,000 gallons of water. The phosphorus and nitrogen in fertilizers, pet and livestock wastes and decomposing leaves and grass can cause large amounts of algae to grow, which depletes the oxygen level in the water and can lead to fish kills. Animal wastes also introduce harmful bacteria and other pathogens into water supplies. Sediment from soil erosion or construction activity can reduce the clarity of water and block sunlight needed by aquatic plants and fish. Litter and debris, particularly plastic items that float, spoil the beauty of streams, lakes and rivers and can be harmful to fish and birds who mistake them for food.
Storm drain labels discourage polluters
The City is working to reduce nonpoint source pollution by labeling storm drain inlets with plastic, UV resistant curb markers warning citizens not to dump polluting materials. The labeled storm drains themselves become public education tools, reminding potential polluters, motorists, pedestrians, and area residents that storm water runoff flows to area water bodies. The knowledge that whatever enters a storm drain enters the nearby creek, river, or lake makes people more conscientious about littering, over fertilizing, sweeping grass clippings into the gutter, and other practices that aggravate NPS pollution. By raising public awareness of NPS pollution through storm drain labeling, the City hopes to discourage practices that generate NPS pollutants.