Stormwater Pollution Prevention
San Francisco is the only coastal city in California with a combined sewer system that treats both wastewater (from our toilets, sinks, and showers) and stormwater (from the rain that falls on our rooftops, driveways, and parking lots) before discharging them into the bay or ocean. Treating stormwater removes any pollutants picked up from our city surfaces, but treating wastewater is far more important.
Combined sewer systems are a feature of older cities like San Francisco, whereas newer cities have municipal separate storm sewer systems (MS4) that discharge stormwater directly to receiving waters with minimal treatment. Newer parts of San Francisco also have MS4 storm drains that flow directly to the bay or ocean. In MS4 areas, we should be extra careful to prevent stormwater pollution. MS4 areas include: Aquatic Park, Candlestick Point, Embarcadero, India Basin, Mission Bay, Lake Merced, Ocean Beach, Sea Cliff, and Treasure Island.
| Sources of Stormwater Pollution | How You Can Prevent It |
| Cleaning products, paints and solvents, pharmaceuticals, garbage and recycling. | Don’t dump anything down the storm drain. Report any illegal dumping at sf311.org or by calling 3-1-1. Visit a hazardous waste disposal center to properly dispose of any household chemicals. Find one near you: sfrecycles.org/. |
| Trash and organic debris that accumulates around storm drains. | Go to sf311.org or call 3-1-1 to report a clogged drain. Visit adoptadrain.sfwater.org to join the Adopt a Drain program, adopt a drain in your neighborhood, and pledge to keep it clear of trash and debris. |
| Motor oil, gasoline, antifreeze, car batteries, automotive fluid leaks, carwash water, vehicle emissions. | Whenever possible, use public transit, bicycle, or walk. If you own a car, keep it well maintained. Fix any leaks and clean up any spills. Use a drip pan underneath any existing leaks to prevent motor oil and other hazardous chemicals ending up in stormwater. Wash your car at a commercial carwash (they are required to treat their wastewater before discharging it to our sewer system and have special equipment that reduces water waste). If you do wash your car at home, remember to use less-toxic products and biodegradable soaps that are phosphate-free. Use a hose with a shut-off valve to control water waste. If you can, park your car on a surface that will help reduce runoff, like a lawn or gravel. |
| Yard clippings, bare and eroded soil, leaves, pesticides, herbicides, fungicides, insecticides, fertilizer. | Use less-toxic products when gardening. Spot treat your weeds and avoid applying pesticides and herbicides right before it rains. Visit ourwaterourworld.org to learn more about chemical alternatives and how to conserve water while gardening. |
| Animal waste left on the street, flea and tick medicine. | Always pick up after your pet! If possible, use biodegradable bags. Pet waste that gets into stormwater is a big contributor to bacterial contamination in our waterways. Some flea and tick medications contain chemicals that cause water toxicity. Visit baywise.org to learn more. |
| Want to go above and beyond? | Plant a garden of native plants that are drought tolerant. Drought-tolerant plants are specifically adapted to low-water environments. This means you’ll be conserving water and preventing runoff from entering storm drains! For plant recommendations go to sfplantfinder.org. |