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Signs warn the public to stay out of the water in an area harboring high bacteria levels near a drain at Will Rogers State Beach in August 2007 in Pacific Palisades.
The Natural Resources Defense Council has released its annual report on the state of the nation's beaches, and among the 30 states with coasts, California ranked 20th.
"So there are 19 states that are doing a better job in terms of water quality than California," said NRDC staff attorney Noah Garrison.
The pollution comes from grime swept up by stormwater and washed out to sea, said Garrison. That can include bacteria, trash, animal waste, metals oils and car materials.
Statewide, California had 5,515 beach closing and advisory days in 2012, a five percent decrease from the previous year. Garrison says the decrease is most likely due to natural variation and that overall the trend has been for beaches to become more polluted over time.
Some of the worst waters in California were found in Avalon Beach off of Catalina Island in L.A. County, and Doheny State Beach and Poche County Beach in Orange County.
On the up side, Bolsa Chica Beach, Newport Beach and San Clemente State Beach in Orange County were all singled out as "Superstar" beaches.
Garrison says the best way to keep our waters clean is to capture runoff before it reaches the ocean. He says people can set up rain barrels, create gardens and use pavement that absorbs rather than deflects water.