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      Department of Public Works Bureau of Sanitation

Related Links

Biodegradation Timeline of Items Commonly Found on Beach
What the City of Los Angeles is Doing to Combat Pollution
Educational Materials
Health Risks for Swimmers
Stormwater pollution is the untreated contaminated water that drains from the streets of Los Angeles, and through the municipal storm drain system. The runoff eventually drains 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 (used motor oil, antifreeze, fertilizer, pesticides, sewage overflow and pet waste)

These pollutants are picked up as water (from rain storms, garden hoses, or sprinklers, etc.) drains from streets, parking lots, and lawns–and then enters the system through the 34,000 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, and unfortunately, much of this is not biodegradable and can be harmful to marine life.

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, 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 create the potential for local flooding during heavy rain events.

What is the City of Los Angeles Doing About Improving Water Quality in Our Receiving Waters?

The City of Los Angeles has four major education programs geared toward the General Public, Businesses, City Employees, and School Education. Free informational materials such as posters, videos, brochures, coloring books and other giveaway items are distributed throughout the City, or can be requested through the program’s hotline at (800) 974-9794.

In addition, the City is installing pollution control devices at key locations throughout Los Angeles.

The City is also encouraging developers and new construction projects to install structural BMPs and acting as technical advisors.

For more information on stormwater, refer to the FAQ’s page, the Glossary, or more information on the storm drain system.