Los Angeles' beaches can be a dirty bunch, being next to a megalopolis filled with smog, trash and pollutants. 

The worst time of the year for coastal water quality is when it rains. Precipitation washes oil, chemicals and trash into the sea. But, as you well know, there haven't been too many storms in L.A. for a while. In fact, 2013 was the driest calender year ever for the city.

As a result, our beloved beach spots are relatively clean, and they're getting good grades, according to Heal the Bay's 24th annual Beach Report Card:
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A whopping 90 percent of Los Angeles' beaches got a B or higher grade, the group says. That's 6 percent better than last year and 9 percent better than the 5-year summer average, says Heal the Bay.

However, L.A. County could still be cleaner.

We lead the state in the number of poor-water-quality beaches, the organization says in a statement:

Overall, one in 10 L.A. County beaches received grades of C or lower during the busy summer season. The news is worse during wet weather, when half of the beaches received grades of C or lower.

Three of the state's 10 worst “Beach Bummer” locales are in L.A. County: Santa Monica Pier, near a storm drain, was number 7, Cabrillo Beach in San Pedro was number 4, and Mothers Beach in Marina del Rey came in at number 3, according to Heal the Bay.

Credit: Jeff Diffner/LA Weekly

Credit: Jeff Diffner/LA Weekly

What happens when you're exposed to some of that dirty water? Ask any surfer who has gotten sick surfing Malibu after a storm: flu, ear infections, upper respiratory infections, rashes, all that good stuff.

In fact, Heal the Bay says $21 million in annual health care costs result from dirty beach illnesses.

On top of that, Heal the Bay is preparing for the worst as another El Nino year is predicted for fall. It could bring heavy rainfall, which would be good for farmers and water supplies but not so good for beach-goers.

Kirsten James, science and policy director for water quality at Heal the Bay:

We've seen marked improvements in California's beach water quality this year due to the historically dry conditions. However the rains will return, and when they do, we need to capture this valuable resource to maximize our local water supplies and keep polluted water out of our ocean.

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