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      Department of Public Works Bureau of Sanitation
The City of Los Angeles Stormwater Program receives many questions regarding stormwater pollution through the phone hotline and public events. These questions range from general stormwater related to specific topics such as area topography, types of pollutants found, and what the City is doing to combat stormwater pollution–as well as on the City’s Stormwater Program in general. The following are some of the most commonly asked questions:

About the System

Illegal Dumping

About the Program

General Environmental


Q: What is a catch basin?

A: A catch basin is a curbside, box-like receptacle that drains water from the street gutter to the underground storm drain pipe. There are approximately 35,000 of these structures within the City of Los Angeles (over 60, 000 countywide) and are the entry points to the storm drain system. This system was designed to prevent flooding on city streets.

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Q: Are sewers and storm drains the same thing?

A: No. They are two separate drainage systems. Wastewater from homes, industry, etc. travels through the sewer system where it is treated at sewage treatment plants before reuse or discharge into the ocean. Runoff from streets, parking lots, yards, etc. enters the storm drain system, receives no treatment, and flows directly to the ocean.

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Q: What is the frequency in which catch basins and storm drains get cleaned out?

A: The City’s Bureau of Sanitation, Wastewater Collections Division, cleans approximately 35,000 catch basins, 100 debris basins, and 140 open channels throughout the City. All catch basins are cleaned annually; those in areas receiving high loads of generated trash from illegal dumping are cleaned more frequently. Clogged catch basins are cleaned immediately when reported by the public prior to the rainy season.

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Q: Why doesn’t the City install filters or screens in front of catch basins?

A: The City has installed several types of pollutant abatement devices on catch basins throughout the city. One of those are screens over catch basins. The screens will be used only during the dry season. During the wet season, they will be removed to avoid flooding since the screens can become clogged with trash during a rain event.

Other methods of trash capture and containment are explained in detail here.

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Q: Why isn’t a net/fence/barrier installed at the end of the storm drain channel to catch all of the trash?

A: Los Angeles County manages the large, open flood channels and has placed a large net close to the mouth of Ballona Creek. This net mainly catches floating trash like Styrofoam cups, fast-food containers, etc. It has no effect on smaller items— bacteria from human and animal feces, or dissolved pollutants like oil, grease, pesticides, and various metals.

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Q: Why doesn’t the City build a stormwater treatment facility?

A: The City has determined that building stormwater treatment facilities is not a cost effective solution due to the large number of the facilities required to treat the stormwater flow generated on a seasonal basis. Instead, smaller multi-purpose regional projects placed in various strategic locations within the city have been recommended for implementation, such as those funded by Prop. O. These types of projects will mitigate many of the pollutant concerns in stormwater generated runoff.

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Q: What kind of pollutants are found in the storm drain system?

A: Paint thinner and paint products, motor oil, pesticides, Styrofoam cups, paper, human and animal feces, antifreeze, golf balls, dirty diapers and dead animals are but a few of the pollutants found in the system on a daily basis.

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Q: How much water passes through the system and into Santa Monica Bay?

A: On a typical dry summer day, an average of about 24 million gallons per day (mgd) flows through the storm drain system into Santa Monica Bay. The largest source is from Ballona Creek (13 mgd). This flow comes from natural ground water sources, over watered lawns, fire hydrant pressure releases, and car washes throughout the region, just to name a few.

In a heavy rainstorm, this flow can increase to billions of gallons per day.

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Q: When was the storm system built? Why?

A: Devastating floods in the early 1900’s caused numerous deaths and extensive property damage. In response, the U.S. Army Corp of Engineers designed and constructed an extensive flood control system throughout the Los Angeles River basin and region.

For a visual explanation, refer to the Storm Drain History and Construction sections.

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Q: Why do the channels have to be concreted? Can’t they be natural waterways?

A: Concrete channels are designed to convey large amounts of water without taking up a lot of space. Natural waterways can handle the same amount of water, but require a wider area to handle flood events. It has been estimated that the LA River, if unlined, would need to be at least several thousand feet wide to handle the flow during wet weather.

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Q: What makes stormwater runoff unique in the Los Angeles area?

A: The runoff area, or watershed, in Los Angeles begins at the 3,000 foot level in the San Gabriel Mountains and discharges into the Santa Monica and San Pedro Bays 51 miles downstream. What makes this problematic is that nearly most of the area in between is paved surface, not natural open space. Because there is no opportunity for this rain to infiltrate into the soil and be absorbed into the underground water table, this stormwater picks up every type of pollutant found on city streets and turns the flood control channels into raing torrents.

In comparison, the Mississippi River drops 1,463 feet over a distance of 2,348 miles!

Q: What is the City of Los Angeles doing about illegal dumping into storm drains?

A: An ordinance passed in 1999 (LAMC Sec 64.70) makes it illegal to dump or discharge trash, debris, chemicals, contaminated water, or any other liquid or solid material into the storm drain system. Violators are now subject to stiff fines and criminal prosecution. The Stormwater Program’s Enforcement Section receives many calls to its (800) 974-9794 hotline number from the public reporting illegal dumping violations and these calls are investigated.

In addition, the Stormwater Program has trained all 41,000 City employees on how to spot illegal discharge violations and encourages them to report these to the Stormwater Hotline.

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Q: How much does the City spend on illegal dumping?

A: The City spends over $1million per year responding to and cleaning up illegally dumped waste materials.

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Q: I see people dumping used oil into storm drains all the time. What can I do?

A: Dumping used oil is not only illegal but also severely impacts the environment. One gallon of motor oil can pollute 250,000 gallons of drinking water. To report violations, call the Stormwater Hotline at (800) 974-9794. Residents are strongly encouraged take their used motor oil to a recycling center, call (800) 98-TOXIC to locate the nearest collection center or click here for a listing of the City of Los Angeles’ permanent S.A.F.E. collection centers.

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Q: What happens if I see a neighbor, or know someone who’s throwing trash or other pollutants into a storm drain?

A: Storm drains are for the sole purpose of handling rainwater overflow. Dumping trash, pollutants and debris into the catch basins is illegal. Call the Stormwater Hotline to report the illegal dumping. If you know the person, you might explain to them how their actions negatively impacts the neighborhood as well as the environment, and that this behavior is highly illegal. Safe, legal alternatives to disposing of waste materials are available throughout the City.

If it is someone who you feel is knowingly violating and repeatedly dumping into storm drains, please call the Stormwater Hotline at 1-800-974-9794; or the Los Angeles County Department of Public Works at 1-800-303-0003.

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Q: I have some paint/thinners/chemicals/ at home that need to be disposed of. Where can I take these?

A: The County of Los Angeles conducts monthly Household Hazardous Waste roundups. Call (800) 98-TOXIC or (888) CLEAN-LA for the collection and drop-off location nearest you.

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Q: What is the fine/penalty for illegal dumping?

A: Under the Los Angeles Municipal Code 64.70, there are several penalties involving both civil and monetary fines.

Q: How much trash gets washed up on beaches?

A: Every year, roughly 40 tons of trash and debris is deposited onto our local beaches from stormwater runoff.

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Q: Where do funds for the storm water pollution control program come from?

A: Every taxpayer is assessed an average of $24 on their property tax. This tax forms the Stormwater Pollution Abatement Charge (SPAC) that funds the program. This fee is determined by the amount of runoff based on the the size of the property.

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Q: As an LAUSD teacher, what kind of educational programs or informational materials does the City offer for students?

A: There are a variety of programs for elementary school children on how to prevent stormwater pollution. WaterCycle is an interactive school assembly and EcoTours is an educational walk program coordinated by environmental educators. To receive more information, contact TreePeople, or call the City of Los Angeles Stormwater program at 1-800-974-9794 for educational materials.

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Q: I have often seen stencils over the catch basins. How do I get a stencil for a catch basin near me?

A: Call Heal the Bay at (800) HEALBAY for more information on the neighborhood stenciling program. The City of Los Angeles has nearly completed the installation of a newly designed catch basin marker.

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Q: I wash my own car. How can I be environmentally responsible?

A: The best place to wash your car is to pull it up on the lawn or gravel. Use biodegradable soaps to wash you vehicle, using as little water as possible. Shut off water while washing your car, then rinse. Remember not to leave your car on the lawn. We would highly recommend going to a full or self service car wash because the used water is recycled.

For a complete how-to on carwashing, refer to the Car Wash Fundraiser Guide.

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Q: Yard clippings leaves are natural, so they don’t cause problems if swept into storm drains, right?

A: Grass, leaves and yard clippings that are repeatedly swept into catch basins can clog the drain, causing flooding and the potential for becoming a breeding ground for rodents and insects. Additionally, grass and leaves decompose and once they enter the ocean, they contribute to new plant growth which deprives fish of their oxygen, and the fish die. For more information on home gardening tips, refer to the residential Good Housekeeping Practices.

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