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Swim at your own risk—bacteria contaminates local beaches

South End Rowing Club President Fran Hegeler, 58, looks out over the water outside the club in San Francisco on Aug. 30, 2022. | Kori Suzuki for The Standard

Biohazard signs line the beach at Aquatic Park after recent rain could have introduced bacteria containing E. coli into the ocean—the origin of the bacteria is unknown, but many suspect it is rain-related.

San Francisco’s beach quality hotline noted “elevated bacteria counts” at Aquatic Park and Sunnydale Cove at Candlestick Recreation Area from samples collected Tuesday that meant any “contact recreation” would be unsafe.

Ocean contamination is of particular concern in San Francisco given its unique dual sewage system, which makes it the only coastal city in California to have the same pipes treating both wastewater and stormwater. 

A biohazard sign was spotted at Aquatic Park on Wednesday, Nov. 9, 2022. | Annie Gaus/The Standard

It’s particularly dangerous when the early rains of the year clean off the streets, according to Dolphin Club member Michael Barber, who has been swimming in the ocean since 2014. 

“You can imagine what’s on the streets,” Barber said. “The cats do their thing, the birds do their thing, the San Francisco humans do their thing.” 

The California National Park Service, which operates Aquatic Park, is responsible for testing the water and putting up the yellow biohazard signs. 

“They’re good about coming out and testing,” Barber said. “But by the time the signs are there, you should have stopped swimming yesterday.” 

According to Barber, there’s a whole range of reactions among swimmers in the Dolphin Club, from very concerned to neutral to not concerned at all. 

“Some of the old timers, they could literally be swimming in shit and don’t care.” 

Barber noted that swimming in contaminated water has gotten him sick in the past, and he knows of others who’ve had similar experiences. 

An SFPUC alert that water at Aquatic Park contains elevated concentrations of bacteria is listed online on Nov. 9, 2022. | Courtesy SFPUC

“But after one or two ebb tides, it shouldn’t be a problem anymore,” Barber said. 

San Francisco’s Public Utilities Commission provides a map that tracks water quality across its beaches on a weekly basis.

Editor’s Note: A previous version of this story attributed the bacteria rise to sewage pushed into the ocean by rain. In fact, the source of the bacteria is unknown; bacteria levels can be caused by marine life, environmental events, or other factors, according to the city’s Public Utilities Commission.

Julie Zigoris can be reached at