Stormwater Information

Stormwater Runoff

What is Stormwater Runoff?
Stormwater runoff occurs when precipitation from rain or snowmelt flows over the ground. Impervious surfaces like driveways, sidewalks, and streets prevent stormwater from naturally soaking into the ground

Why is Stormwater Runoff a Problem?
Stormwater can pick up debris, chemicals, dirt, and other pollutants and flow into a storm sewer system or directly to a lake, stream, river, wetland, or coastal water. Anything that enters a storm sewer system is discharged untreated into the waterbodies we use for swimming, fishing, and providing drinking water.

The Effects of Pollution
Polluted stormwater runoff can have many adverse effects on plants, fish, animals, and people. Sediment can cloud the water and make it difficult or impossible for aquatic plants to grow. Sediment also can destroy aquatic habitats Excess nutrients can cause algae blooms. When algae die, they sink to the bottom and decompose in a process that removes oxygen from the water. Fish and other aquatic organisms can’t exist in water with low dissolved oxygen levels. Bacteria and other pathogens can wash into swimming areas and create health hazards, often making beach closures necessary. Debris—plastic bags, six-pack rings, bottles, and cigarette butts—washed into waterbodies can choke, suffocate, or disable aquatic life like ducks, fish, turtles, and birds. Household hazardous wastes like insecticides, pesticides, paint, solvents, used motor oil, and other auto fluids can poison aquatic life. Land animals and people can become sick or die from eating diseased fish and shellfish or ingesting polluted water. Polluted stormwater often affects drinking water sources. This, in turn, can affect human health and increase drinking water treatment costs.

Solutions to Stormwater Runoff
• Don’t overwater your lawn. Consider using a soaker hose instead of a sprinkler. Use pesticides and fertilizers sparingly. When use is necessary, use these chemicals in the recommended amounts. Use organic mulch or safer pest control methods whenever possible. Compost or mulch yard waste. Don’t leave it in the street or sweep it into storm drains or streams. Cover piles of dirt or mulch being used in landscaping projects.
• Inspect your septic system every 3 years and pump your tank as necessary (every 3 to 5 years). Don’t dispose of household hazardous waste in sinks or toilets.
• Use a commercial car wash that treats or recycles its wastewater, or wash your car on your yard so the water infiltrates into the ground. Repair leaks and dispose of used auto fluids and batteries at designated drop-off or recycling locations.
• When walking your pet, remember to pick up the waste and dispose of it properly. Flushing pet waste is the best disposal method. Leaving pet waste on the ground increases public health risks by allowing harmful bacteria and nutrients to wash into the storm drain and eventually into local waterbodies.

• Sweep up litter and debris from sidewalks, driveways and parking lots, especially around storm drains.
• Cover grease storage and dumpsters and keep them clean to avoid leaks.
• Report any chemical spill to the local hazardous waste cleanup team. They’ll know the best way to keep spills from harming the environment.

• Divert stormwater away from disturbed or exposed areas of the construction site.
• Install silt fences, vehicle mud removal areas, vegetative cover, and other sediment and erosion controls and properly maintain them, especially after rainstorms.
• Prevent soil erosion by minimizing disturbed areas during construction projects, and seed and mulch bare areas as soon as possible.


• Keep livestock away from streambanks and provide them a water source away from waterbodies.
• Store and apply manure away from waterbodies and in accordance with a nutrient management plan.
• Vegetate riparian areas along waterways. Rotate animal grazing to prevent soil erosion in fields.
• Apply fertilizers and pesticides according to label instructions to save money and minimize pollution.

Reducing Flood Risk
The Maricopa County Flood Control District has produced a helpful document to help address commonly asked questions regarding flood hazards and floodplain management.

Reducing Flood Risk: A Resource Guide (PDF)