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What is Stormwater runoff?

Stormwater runoff is water from a precipitation event that “runs off” of the land rather than seeping into the ground. Paved, impervious surfaces don’t allow stormwater to soak in, which leads to higher flow volumes and no natural treatment for pollutants. Stormwater runoff enters the catch basins where it is conveyed by the storm sewer system to the Los Angeles River.


What are non-stormwater discharges?

Even when not raining, we produce tens of millions of gallons of runoff from car washing, watering our landscaping and cleaning. If it is not raining but there is runoff occurring, this is called a non-stormwater discharge. Polluted runoff leads straight to the ocean. Non-stormwater discharges are generally man-made and preventable. Non-stormwater discharges are regulated by the MS4 Permit as well as the City’s Water Conservation Ordinance. It is important to check that a non-stormwater discharge is permitted and to use required Best Management Practices (BMPs) to prevent contamination before discharging water to the storm drain.


How does stormwater pollution occur?

Everything that we put on the ground or in the storm drain has the potential to end up as a stormwater pollutant. Stormwater pollution is the untreated contaminated water that drains from the streets of Commerce through the municipal storm drain system. The largest source of stormwater pollution in Los Angeles is the general public, polluting as a non-point source.


The most common pollutants are:

  • Trash (fast-food wrappers, cigarette butts and Styrofoam cups); and
  • Toxins (used motor oil, antifreeze, pesticides, sewage overflow and pet waste).


How to prevent stormwater pollution? What are Best Management Practices?

To protect stormwater quality, stormwater controls, known as best management practices (BMPs) should be used. Best management practices (BMPs) is a term for practices, physical devices or systems used to prevent or reduce pollutant loading or reduce the volume of water discharged to the receiving water.  BMPs for residents can be found on the Pollution Prevention for Residents webpage. Businesses and construction sites may be required to obtain coverage under an NPDES permit, as discussed in Stormwater Regulations/Discharge Permits.


Is water from the storm sewer system treated?

No! Unlike wastewater from inside homes and businesses that flows to the sanitary sewer for treatment, exterior runoff generated from rain, garden hoses, and sprinklers flows through storm drains to the Los Angeles River and the ocean untreated carrying pollutants such as trash, pesticides, fertilizers, pet waste, and automotive fluids with it.