What Is the Largest Source of Stormwater Pollution?

When it rains, water quickly flows over our roads, parking lots, and rooftops, picking up everything in its path and carrying it to nearby storm drains. Most of us know stormwater plays a big role in our community’s water cycle—but have you ever wondered what the biggest source of stormwater pollution actually is? At Accena SWPPP Services, helping businesses and organizations manage and reduce stormwater pollution is our mission. Let’s dive into the answer.

The Largest Source: Nonpoint Source Pollution

The biggest contributor to stormwater pollution is something called nonpoint source pollution. Unlike industrial facilities or sewage treatment plants, which release pollutants from specific, identifiable locations (“point sources”), nonpoint source pollution comes from many diffuse sources throughout our landscape.

This means that instead of one obvious source, stormwater pollution mostly comes from everyday activities all over town—and that can make it more challenging to control.

What Is Nonpoint Source Pollution?

As rain or melting snow runs across streets, lawns, farms, construction sites, and parking lots, it picks up a cocktail of contaminants. The most common culprits include:

• Oil, grease, antifreeze, and other vehicle fluids from driveways, streets, and parking lots

• Fertilizers, pesticides, and herbicides from lawns, gardens, parks, and golf courses

• Sediment and soil from construction sites and bare ground

• Trash, plastics, and litter from sidewalks, gutters, and open areas

• Pet waste from yards and parks

• Heavy metals and chemicals from rooftops and industrial sites

Once carried into the storm drain system, these pollutants can flow directly into our local rivers, streams, and lakes—often without any treatment. The environmental impacts can be serious, ranging from algae blooms and fish kills to contaminated drinking water and harm to wildlife.

Why Nonpoint Source Pollution Matters

It’s estimated that up to 70% of all water pollution in the U.S. comes from nonpoint sources. Because it’s generated by normal, everyday activities, every business, household, and driver can play a role in both causing—and preventing—this pollution.

How Can You Help Prevent Stormwater Pollution?

Reducing nonpoint source pollution starts with small changes and sound management practices, such as:

• Properly disposing of oil and chemicals—never pouring them down storm drains

• Using fertilizers and pesticides sparingly and following label instructions

• Picking up pet waste and disposing of it correctly

• Keeping construction sites covered and controlling erosion

• Cleaning up litter and sweeping sidewalks, driveways, and parking lots regularly

• Implementing green infrastructure, such as rain gardens, vegetated swales, and permeable pavement

For commercial and industrial properties, implementing and maintaining a Stormwater Pollution Prevention Plan (SWPPP) is essential for compliance and good stewardship.

How Accena SWPPP Services Can Help

Managing stormwater pollution might seem daunting, but you don’t have to do it alone. At Accena SWPPP Services, we specialize in helping businesses and property owners develop, implement, and maintain effective SWPPP programs designed to reduce nonpoint source pollution and keep you compliant with local, state, and federal regulations.

From site assessments and inspections to training and catch basin cleaning, we’re here to protect your property and your community’s waterways.

Conclusion

The largest source of stormwater pollution isn’t a single factory or dumping ground—it’s the sum of many small actions across our cities and towns. By staying informed and taking everyday steps to reduce runoff and pollution, we can all make a meaningful difference.

Contact Accena SWPPP Services today to learn more about stormwater best practices and how we can help you safeguard our environment, one drop at a time.