Stormwater Pollution Prevention Methods

Storm Drain graphic

As water flows over yards, farmland parking lots, roads, sidewalks and other surfaces, it can pick up pollutants from the ground and carry them, through both natural and man-made drainages, to our local streams and rivers and eventually to the Pacific Ocean. Some of these pollutants can be very harmful to the environment.

The water that goes down a sink, toilet or floor drain in a home or business travels through the sanitary sewer system and ends up at a wastewater treatment plant, where most pollutants are removed with filters and treatment. The water is then discharged, under a permit, to a waterway or used as recycled water.

On the other hand, the water that flows into the storm drain system from parking lots, roads, agricultural fields or other surfaces is not treated. It flows directly to local waterways and eventually, to the Pacific Ocean.

Common pollutants that end up in runoff include motor oil, pesticides and herbicides, brake dust, pet waste, household chemicals, trash and more. The 2005 California Water Plan reports that In the San Joaquin River watershed, water quality problems are the result of many factors, including:

  • Reduced freshwater flows into the river
  • Permitted and unpermitted municipal and industrial wastewater discharges
  • Runoff from urban areas such as parking lots and roads
  • Natural and imported salt loads from agricultural drainage higher up in the watershed
  • Runoff and other pollutants associated with long-term agricultural irrigation and production, including nutrients, selenium, boron and organophosphate pesticides

These pollutants can have harmful effects on aquatic wildlife, recreation and our drinking water supplies. Runoff in California is regulated by the State Water Resources Control Board and, in our area, by the Central Valley Regional Water Quality Control Board.

Summer means fun in the sun and the swimming pool! It also means lots of pool cleaning time. In an effort to keep our storm drains clean and free flowing, Stanislaus County prohibits discharge of pool water into the storm drain system including filter backwash water.

Pool water should only be discharged into the sanitary sewer clean-out.. For assistance in locating a clean-out, residents should contact their Sanitary Sewer Service Agency.

Please note that when cleaning your pool, it is illegal to dump pool water into the gutter where it can flow into the County’s storm drain system. Your pool water must be disposed through the sanitary sewer system.

Control algae with chlorine or other alternatives, instead of copper based algaecides, which could be harmful to drinking water and aquatic life.


Only Rain Down the Drain!

Many public agencies and associations offer free, bilingual units of study that are aligned to California Content Standards, and support the Education and the Environment Initiative.

Grades 4, 5 and 6
Free, ready-to-use English and Spanish lesson plans

Education Associations (resources for all grades)

Awards, grants and scholarship programs

Games and activities

Vehicle Maintenance:

  • Service vehicles regularly to help prevent leaks and reduce emissions.
  • Use a commercial car wash whenever possible.
  • When washing cars at your residence, park on grass or gravel to allow the soapy runoff to filter through vegetation or soil and not into gutters and storm drains. Use water efficient shut-off devices on garden hoses while washing cars. Empty the soap bucket into the toilet or sink instead of streets and gutters.
  • Baking soda paste is a non-toxic substance which can be used to clean battery heads, cable clamps, and chrome. Add a mild, biodegradable dish washing soap to the paste to clean wheels and tires. White vinegar or lemon juice mixed with water works well for cleaning windows.
  • Have your car tuned-up regularly to make sure it is operating as efficiently as possible with no leaks of oil or other fluids.
  • Find a location near you to recycle motor oil, antifreeze and other automotive fluids.

Disposal of Automotive Products:

  • Never dispose of gasoline, used oil, or other automotive products in the gutters, storm drains, sinks or toilets. Take these products to the Stanislaus County Hazardous Waste Facility. This facility is located at 1710 Morgan Road, Modesto. Please visit the Stanislaus County Household Hazardous Waste Program webpage for drop off times, locations, or for more information.
  • Absorb any spills of automotive fluids in the garage with kitty litter, sawdust or corn meal. Dispose of the cleanup materials from a small spill by placing them in a plastic bag in the trash.
  • When buying a new car battery, take the old one to the retailer. California law requires retailers to accept them. Any local hazardous waste collection events will also take them.
  • Car wax and automotive fluids have long shelf lives. Store them in airtight containers and use them completely instead of disposing of them.

Household Maintenance:

  • Always read labels carefully before buying household cleaning and maintenance products. Know that ingredients range in levels of toxicity from CAUTION, which means least toxic, to WARNING and finally, to DANGER or POISON. A symbol of a skull and cross-bones also refers to high toxicity. Avoid buying products that contain extremely toxic ingredients.
  • Use safe, less toxic alternative cleaners such as baking soda, salt, borax, vinegaror plain water..
  • Choose water-based paints instead of oil-based paints. Don't use any paint over 15 years old since it may contain lead. Take old or unwanted paint to the Stanislaus County Hazardous Waste Facility. This facility is located at 1710 Morgan Road, Modesto. Please visit the Stanislaus County Household Hazardous Waste Program webpage for drop off times, locations, or for more information.
  • To minimize waste and spills, use products carefully and store them in sealed, heavy duty, air-tight containers.
  • Flush drains with boiling water instead of using potentially hazardous chemical drain cleaners.
  • Buy products made from renewable resources and recycle all substances that are non-biodegradable.

Disposal of Household Products:

  • Never pour toxic paints, preservatives, brush cleaners, paint thinners, solvents or anything else into gutters or down the storm drains, sinks or toilets. Take them to the Stanislaus County Hazardous Waste Facility. This facility is located at 1710 Morgan Road, Modesto. Please visit the Stanislaus County Household Hazardous Waste Program webpage for drop off times, locations, or for more information.
  • Only buy the amount needed and use the entire product.

Although the amount of polluted runoff from one home may be small, the cumulative effects of runoff from neighborhoods, towns and cities can be significant for local creeks and rivers. Any steps you take to decrease polluted runoff from your home and landscaping make a big difference!

Do this today:

  • Check the area where you store your home and garden chemicals. Are the containers properly sealed and free from leaks? Are the chemicals stored in a clean, dry place?
  • Read the labels on each of your fertilizer, pesticide and cleaning products. Are you using the right chemicals, in the proper concentrations? Are you disposing of the empty containers properly?
  • If you haven’t used all of a product, dispose of it at a Household Hazardous Waste collection day, not in the garbage. NEVER pour chemicals in the toilet, on the ground or down any storm drain.
  • At the store, consider all of the products available, and choose the one that will do the job with the least amount of pollutants or toxic chemicals. For safer products for specific pests, visit UC Integrated Pest Management, the California Environmental Protection Agency, the State Water Resource Board's Homeowner's Outreach or your city.
  • If you use automatic sprinklers, check to be sure you are not overwatering. Overwatering leads to runoff. Visit H20House for all you need to know about indoor and outdoor water efficiency!
  • Where possible, choose alternatives to pesticides, such as resistant plants, biological controls (like ladybugs to control aphids) or physical controls (like traps or barriers). These options have the added advantage of being child- and pet-friendly, as well. Find out more at the UC Davis Integrated Pest Management Web site or the Our Water, Our World Web site.
  • Visit your University of California Cooperative Extension office or your local nursery to get answers to your specific home or landscape questions.

Do this over time:

  • When planning new landscaping, consider the amount and placement of impermeable services (such as decks, patios, driveways, etc.). If you can surround impermeable surfaces with native grasses or rock beds, you can reduce the amount of pollutants flowing to the street from your property.
  • Always choose plants that are native to the area and appropriate for the spot in your landscape. They have a better chance of survival without chemicals, and are more resistant to pests and disease. For more on choosing plants, visit your county’s University of California Cooperative Extension office or your local nursery.

General Practices:

  • Use up pesticides and herbicides completely. Always read the label and follow the directions for proper use. Rinse the containers and use the rinse water as a diluted product. Recycle clean containers if possible.
  • Use safer, more organic products.
  • Dispose of unused pesticides and herbicides at the Stanislaus County Hazardous Waste Facility. This facility is located at 1710 Morgan Road, Modesto. Please visit the Stanislaus County Household Hazardous Waste Program webpage for drop off times, locations, or for more information.
  • Store pesticides, fertilizers, chlorine and other chemicals indoors or in a shed or storage cabinet.
  • Schedule grading and soil excavation projects during dry weather. Prevent dirt from going into streets and storm drains.

Landscaping Practices:

  • Do not blow or rake leaves, grass or dirt into streets. Keep all garden waste out of storm drains.
  • Collect lawn and garden clippings, pruning waste and tree trimmings. Chip if necessary and compost.
  • Protect stockpiles and landscaping materials from wind and rain by storing them under tarps or secured plastic sheeting.
  • Practice "grasscycling", or composting grass clippings.

In Your Garden

  • Purchase household and garden products that are "least toxic" to the environment.
  • Sweep sidewalks and patios rather than hosing debris into gutters.
  • Garden organically, or use alternatives to chemical pesticides and herbicides whenever possible.
  • Do not over-water lawns and gardens. Over-watering can flush large quantities of pesticides and fertilizer directly into storm drains.
  • Take care of your lawn in an environmentally friendly way.
  • Download the EPA booklet Healthy Lawn, Healthy Environment [PDF - 6MB]

Water that flows off our yards, streets, parking lots and driveways into storm drains eventually ends up in local creeks, streams, and rivers.

The storm drain system and sanitary sewer system are completely separate. Our storm drains transport runoff untreated to local streams and riversr.

As water makes its way to storm catch basins it picks up and carries pollutants found on streets, sidewalks, gutters, driveways, yards and parking lots.

Did you know that dumping just one quart of motor oil down a storm drain could pollute 250,000 gallons of water?

Help us reduce pollution in our local creeks, streams, and rivers by doing the following:

  • Comply with the City/County landscape watering schedule
  • Don’t overuse fertilizers or pesticides
  • Pick up your pet’s waste
  • Sweep up yard debris into green container
  • Call 209-525-4130 to report any illegal dumping

General Practices:

  • Place an oil absorbing sponge in the bilge to remove oil.
  • Use non-toxic detergent, elbow grease, and a scrub brush to clean the hull. Products that remove stains or make the boat shine can be toxic.
  • For live-aboards, hook up to a community sewage collection system.
  • Reduce shore erosion in streams, rivers, and inlets by slowing down and decreasing the boat's wake.

Disposal of Boating Materials:

  • Vacuum boat scrapings and take the bag to the Stanislaus County Hazardous Waste Facility. This facility is located at 1710 Morgan Road, Modesto. Please visit the Stanislaus County Household Hazardous Waste Program webpage for drop off times, locations, or for more information.
  • Go to a pump-out station to discharge holding tank wastes.
  • Bring all packaging, containers and fishing gear back to the dock and pick up any litter floating in the water.
  • Reusable cups, plates and other utensils are preferable to disposable, non-biodegradable supplies.
  • A certified used oil recycling center will reimburse for each gallon that is recycled. Up to 20 gallons a day may be recycled in containers no larger than 5 gallons.


Only Rain Down the Drain!

The nature of agricultural activities, including applying water to crops that have been previously treated with pesticides and fertilizers, means that growers have opportunities and responsibilities to carefully manage their operations to reduce polluted runoff to local waterways. In the Central Valley, the Regional Water Quality Control Board administers the Ag Waiver program, allowing growers to work together to monitor water quality and manage runoff.

Do this today:

  • Become familiar with the Ag Waiver program and decide if and how you’d like to participate. Visit the Regional Water Quality Control Board for information on the overall program, and the local Water Quality Coalitions for information about your specific area.
  • Keep your irrigation water on your property. Techniques such as infiltration drains or holding ponds work well. Find out more from your county Agricultural Commissioner, local Resource Conservation District or UCCE specialist.
  • If you use pesticides or fertilizers, read the label carefully and always apply according to the label directions. Be certain that your workers are trained in how to apply chemicals properly.
  • Store all petroleum-based products, lubricants, solvents, pesticides and fertilizers in a dry and secure location.
  • Perform equipment maintenance activities on an impermeable surface, such as asphalt or concrete, and control runoff from this surface so that it does not get into surface water.

Do this over time:

  • Consider a tail water return system, which recycles water from the bottom to the top of the field.
  • Contact your local Resource Conservation District or Cooperative Extension office to schedule an irrigation efficiency evaluation. You can save water and help to improve water quality.
  • Stay on top of innovations in growing practices by participating in continuing education programs, grower cooperatives and commodity groups.
  • Consider planting cover crops to prevent erosion and runoff.
  • Consider where and when you can use Integrated Pest Management Practices on your farm to reduce your overall use of chemicals.

Hazardous Wastes:

  • Chemical paint stripping residue is a hazardous waste.
  • Chips and dust from marine paints or paints containing lead or tributyl tin are hazardous wastes.
  • Liquid residues from paints, thinners, solvents, glues and cleaning fluids are hazardous wastes.

Disposal of Paints:

  • Keep all liquid paint products and wastes away from the gutter, street and storm drains. If they are thoroughly dried, empty paint cans, spent brushes, rags and drop cloths may be disposed of as trash.
  • Paint chips and dust from non-hazardous dry stripping and sand blasting may be swept up and disposed of as trash.
  • When stripping or cleaning building exteriors with high pressure water, block the storm drains. Wash water onto a dirt or landscape area, or vacuum up and dispose in the sanitary sewer system.
  • Never clean paint brushes or containers into a street gutter, storm drain or waterway. Use water-based paints when possible.
  • For water-based paints, paint out brushes to the extent possible, and rinse into the sanitary sewer system.
  • For oil-based paints, paint out brushes to the extent possible and filter and reuse thinners and solvents. Dispose of excess liquids and residue as hazardous waste.
  • Recycle excess water-based paint, or use completely. Dispose of excess liquid, including sludges, as hazardous waste.
  • Re-use leftover oil-based paint. Dispose of excess liquid, including sludges, as hazardous waste.
  • You can dispose of paints & solvents at the Stanislaus County Hazardous Waste Facility. This facility is located at 1710 Morgan Road, Modesto. Please visit the Stanislaus County Household Hazardous Waste Program webpage for drop off times, locations, or for more information.


Only Rain Down the Drain!

General Outdoor Practices:

  • Runoff from roof gutters, basements and sidewalks should be directed onto grass or gravel to slow the velocity of water running into the storm drain system. This practice will naturally filter and clean the runoff.
  • Increase the amount of permeable surfaces around your home. Use wooden decking, bricks or stones for driveways, walkways and other outdoor areas, instead of solid paving.
  • To eliminate the need for chemical control of termites, store wood away from the house.
  • Do not build, pave, park or drive over a septic system drainage field. Plant trees and shrubs away from drain tiles.

Disposal Practices:

  • Don't pour solvents, toxic chemicals or grease down the drain. They can inhibit the system's ability to break down waste. Instead, take them to Stanislaus County Hazardous Waste Facility. This facility is located at 1710 Morgan Road, Modesto. Please visit the Stanislaus County Household Hazardous Waste Program webpage for drop off times, locations, or for more information.
  • Have septic tanks inspected every year and pumped out every 3-5 years.
  • Septic system cleaning products which contain methylene chloride or 1,1,1-trichloroethane should not be used.
  • Do not dispose of pet waste in the storm drain. Pick up after pets and dispose of wastes in the toilet or garbage.


Only Rain Down the Drain!

Invite "Good Bugs" to Your Garden:

Spring and summer bring warm sunshine, fields of flowers, vines bursting with tomatoes and, of course, those destructive little pests and bugs! But did you know some are actually "Good Guys" in the garden? For example, ant lions really do feast on ants, and lacewings have a voracious appetite for aphids. Studies have shown that the use of chemical pesticides can actually cause outbreaks of pests by eliminating these natural predators.

Consider alternative pest management practices such as biological controls. Many nurseries sell beneficial insects like ladybugs. Ladybugs, both adults and larvae, are known primarily as predators of aphids. But they also prey on many other pests such as soft-scale insects, mealy bugs and spider mites; and they devour the eggs of beetles and borers.

One of the best ways to promote biological control of pests is to encourage beneficial insects by choosing plants that provide them with pollen, nectar and shelter. Fennel, coriander and dill provide the tiny flowers savored by parasitoid wasps. These tiny wasps are aggressive beyond their size when it comes to pursuing aphids and caterpillars.

And rather than pulling out all of your "wild weeds" such as dandelions, goldenrod and mustard, leave a few in the back yard. They're all good sources of food for many predatory insects.

Stewards of Our Waterways

By saying "NO" to chemicals, you're also protecting our creeks and streams. Unintentional rinsing of chemical pesticides into storm drains pollutes our creeks and streams because storm drains are direct paths to our waterways.

If your pest problem cannot be controlled biologically, consider using less-toxic pesticides like and insecticidal soaps, dusts and horticultural oils. Apply pesticides sparingly, follow label instructions, and apply only to problem areas. Some don'ts to remember:

  • Don't let water run-off your yard right after applying pesticides.
  • Don't apply pesticides if rain is forecast.

Proper Pesticide Disposal

Proper disposal of pesticides, is just as important as proper use. Never dispose of chemical pesticides, or any other toxic waste, by dumping down storm drains or sinks. Take your unused toxic chemicals to the Stanislaus County Hazardous Waste Facility. This facility is located at 1710 Morgan Road, Modesto. Please visit the Stanislaus County Household Hazardous Waste Program webpage for drop off times, locations, or for more information.

Visit these sites for more information on Alternative Pest Management:

  • Use care in controlling pests around your home and in the garden. Check out the UC Davis Integrated Pest Management site for information about pest management and identification.
  • To solve pest problems with less toxic products, check out the fact sheets at Our Water Our World.
  • "Pest Notes" from the UC Davis Integrated Pest Management (IPM) Project provide in-depth information on insect pests and alternative control measures.
  • The Bio-Integral Resource Center (BIRC) in Berkeley provides consultation, literature, and periodicals on non-toxic pest control to individuals, businesses, public agencies.