SAN FRANCISCO (CBS SF) — Three Northern California beaches have been ranked among the most polluted in the state with a Santa Clara beach topping the list, an environmental group reported Thursday.

The rating came out as part of the annual Heal the Bay report card.

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The group said it’s testing found that Cowell Beach at the wharf in Santa Cruz County was the most polluted beach in the state. Meanwhile,Pillar Point Harbor in San Mateo County and Sunnydale Cove near Candlestick Point in San Francisco made the top 10.

Heal the Bay said part of the problem at Cowell Beach — located at the wharf in Santa Cruz County — was from birds roosting. Work has started to install steel fencing to prevent the roosting.

Elsewhere, of the graded ocean-side beaches from Marin County to San Mateo County, 38 of 40 received an A grade for the high-traffic summer period of
April to October. That is percent higher than a five-year average for the beaches during the summer period.

The group test for harmful bacteria that can cause illnesses such as stomach flu, ear infections, upper respiratory infections, and skin rashes among people who go in the water.

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Heal the Bay officials said El Nino contributed to poor water quality grades at some beaches this past winter because high amounts of rainfall can cause older sewer systems to inadvertently release under-treated sewage into the Bay or ocean.

Beach water quality is graded each week and the grades can be found at

Beaches facing San Francisco Bay had lower grades overall than ocean-side beaches. Twenty-four of 28 Bayside beaches, or 85 percent, received A or B grades, according to the report card.

In Sonoma County, all seven monitored beaches received grades of A+.

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