San Mateo County Health is warning swimmers and beachgoers to stay out of the water at seven coastal sites where bacteria levels exceed state safety standards.

The agency posted warnings at five ocean beaches and two creek mouths based on water samples collected Monday, July 6, according to its beach monitoring page updated Wednesday, July 8. No bay beaches are affected.

The posted ocean sites are Linda Mar #5 (at San Pedro Creek in Pacifica), Pillar Point #7 (Surf-West Point Ave), Pillar Point #5 (Capistrano Beach), Pillar Point #9 (Outer Harbor), and Dunes Beach in Half Moon Bay. Two creek crossings also tested high: San Vicente Creek at Fitzgerald and Pilarcitos Creek at Venice-South.

Warning signs at each location read that the waters "are contaminated and are not suitable for swimming or other water contact activities."

The warnings mean bacterial samples exceeded at least one of three state thresholds tested by the San Mateo County Public Health Laboratory: total coliform, E. coli, or Enterococcus. A warning differs from a closure. Closures happen only when a confirmed sewage spill is directly affecting a beach. In this case, no confirmed contamination source has been identified.

Testing schedule and safety advice

San Mateo County Environmental Health Services tests 43 sites every Monday morning using a mix of county staff and volunteers. Results are typically posted by Wednesday. The county samples on a weekly Monday cycle, meaning the next round would fall on July 13, with results expected by Wednesday, July 15.

Signs will stay up until bacteria counts drop below state limits and a re-test confirms the improvement.

The county advises swimmers to avoid ocean water within 300 feet of a flowing storm drain or creek mouth. Creek water where it crosses the beach often carries higher bacteria than the adjacent surf, even when it looks calmer.

People who develop skin rashes, ear or eye infections, gastrointestinal symptoms, or persistent headaches after water contact should call County Environmental Health Services at (650) 372-6200 to file a report.

For the latest posting status, residents can call the Beach/Creek Posting Hotline at (650) 599-1266 or visit smchealth.org/beaches.