Healthy Recreational Water

Beaches are posted if levels of bacteria exceed safe levels

Beaches are posted if levels of bacteria exceed safe levels

By Kate Elgin, Environmental Health Specialist, San Mateo County Environmental Health

We are lucky in San Mateo County to be located between the majestic San Francisco Bay and the beautiful Pacific Ocean, but how do you know if the ocean, lagoon and creek water your family plays in is safe? San Mateo County Environmental Health samples 43 beach, bay and creek mouth sites weekly. We submit our samples to the County Public Health Lab, where they are analyzed for bacteria (total coliform, E. coli and enterococci). These bacteria are good indicators of contamination in the water. Any sites exceeding a safe threshold are then posted with signs that read, “Warning, these waters are contaminated.” Weekly results are available on our website or over a hotline (650) 599-1266. Waters may become contaminated for various reasons. Some of the most common are runoff contaminated with domestic and wild animal waste, discharge from storm drains, leaking sewers or septic leach fields.

What can you do to minimize your chances of coming into contact with contaminated water? Check the postings on our website or call our hotline to see which beaches, bays and creek mouths to avoid. We have a great new beach map on our website, updated weekly, which allows users to see which waters may not be safe to swim in. Also, use your common sense! Avoid stagnant waters, those with high algae growth, a strong smell, or waters with a lot of bird or animal activity. Young children, the elderly and those with compromised immune systems may be more susceptible to illness.

Symptoms of exposure to contaminated water can range from an upset stomach, flu-like symptoms, to earaches and rashes. If you think that you may have gotten sick from swimming in contaminated water, we encourage you to go see your primary care physician, as well as call our office at (650) 372-6200 to report the incident.

We utilize county staff as well as trained volunteers to help us collect our samples from all over the County every Monday morning. If you’re interested in volunteering, we can always use an extra pair of hands. It is a beautiful and rewarding way to start the week! We will train you and provide you with all the equipment necessary (with the exception of a car…you’ll need to provide that yourself). Please contact Kate Elgin at for more information.

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