Beach water monitoring

Weekly water quality monitoring at Marin County beaches ended on October 31, 2026, and will resume in April 2027. Results posted here reflect the last samples collected during the 2026 season and do not show current conditions.

Water quality can change at any time, especially after rain. To reduce your risk of illness:

• Avoid water contact for at least three days after rainfall.
• Stay away from storm drains, creeks and lagoon outlets that flow onto the beach.
• Avoid water that looks or smells unusual.

Historical results are available on the State Water Board’s BeachWatch website. For questions, contact Environmental Health Services at 415-473-6907.

To report elevated bacteria levels in local recreational waters, please email Marin County Environmental Health Services or call at 415-473-7146.

Contact our staff

The Marin County Beach Monitoring Program routinely analyzes water samples for indicator bacteria, including total coliform, E. coli, and enterococci, in accordance with State Water Resources Control Board requirements and the County's Quality Assurance Program Plan. These indicator organisms are used to assess potential fecal contamination and associated public health risks.

Beach advisories are issued when bacterial concentrations exceed the applicable State standards established to protect recreational water users. Weekly monitoring results, including locations with exceedances and advisories, are currently posted on the County website during the monitoring season.

Every week from April to the end of October each year, our team collects water samples from 31 locations across Marin. These locations include oceans, bays, and freshwater spots. We test these samples to make sure that they meet California's safety standards for:

• swimming
• wading
• other recreational activities

The Napa-Solano-Yolo-Marin-Mendocino Public Health laboratory does our testing.

Please note: These water samples provide a water quality snapshot. Conditions may change from each day.

If the sampled water exceeds the State standards, we post a warning sign to alert the public. The California Department of Public Health advises the public to avoid contact with these waters.  

Current results are available online and are updated April thru October each year.

• Beach water quality information shows 4 weeks of results by location.
• Current beach water samples map provides results on a map for just 1 week.
• For a recorded list of waters safety issues, call 415-473-2335.