What is Stormwater Pollution?
Stormwater pollution is the untreated contaminated water that drains from the streets of Los Angeles, through the municipal storm drain system and into the Santa Monica and San Pedro Bays.

The largest source of stormwater pollution in Los Angeles is the general public. The most common pollutants are:

  • trash (fast-food wrappers, cigarette butts and Styrofoam cups)
  • toxins (like used motor oil, antifreeze, fertilizer, pesticides, sewage overflow and pet droppings)

These pollutants are picked up as water (from rain, hoses, sprinklers, etc.) drains from streets, parking lots, and lawns and enters the 66,000 catch basins throughout the City of Los Angeles. From there, this "toxic soup" flows through a massive system of pipes and open channels – straight to the ocean untreated.

Basically, anything dumped or dropped on the ground or in the gutter contributes to stormwater pollution.


Is Stormwater Pollution a Big Problem in Los Angeles?

Yes. In Los Angeles County, approximately 100 million gallons of contaminated water and debris drain through the storm drain system each dry day. One hundred million gallons would fill the Rose Bowl 1.2 times. On rainy days, the daily flow can increase to 10 billion gallons.


Is Stormwater Treated Before Entering the Ocean?

No. The Los Angeles storm drain system flows directly to the ocean. Contaminated stormwater receives no treatment because of the sheer volume of runoff from an area encompassing 1,060 square miles. The cost of treating Los Angeles’ County’s stormwater would be so high that it would exceed available resources.

On the other hand, the Los Angeles sewer system is separate and only treats wastewater from sewage lines. See next question.


Is There a Difference Between a Storm Drain and a Sewer Drain?

Yes. The sewer system and the storm drain system are two completely separate drainage systems.

The sewer system, or sanitary wastewater system, takes all household wastewater from toilets, showers and sinks, and routes it through your plumbing system into the City of Los Angeles’ Hyperion Treatment Plant. Once there, it receives 3 levels of filtration treatment before being discharged 5 miles out into the ocean.

The stormwater system, on the other hand, was intended to route rainwater quickly off the streets during a heavy storm, but unfortunately takes all urban runoff along with it. Chemicals, trash and debris from lawns, parking lots and streets, either intentionally or accidentally spilled, goes straight into the ocean.


What Are the Effects of Stormwater Pollution?

Health: Stormwater pollution poses a serious health risk to people swimming or fishing in the Santa Monica and San Pedro Bays, particularly within 400 yards of storm drain outlets in the bays.

Economy: Beach attendance has dropped by 56% since 1983.

Environment: Countless marine plants and animals living in the Santa Monica and San Pedro Bays become sick or die from contact with stormwater pollution.

Neighborhoods: Clogged catch basins significantly decrease the quality of life in many neighborhoods throughout the City of Los Angeles. These "nests" of trash and debris can attract rats and cockroaches, create foul odors, and clog the storm drain system – affecting neighborhood aesthetics and property values, and causing local flooding.


For more questions and answers on storm water, refer to the FAQ’s page.

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