County of Marin - News Releases - Beach Water Quality

For Immediate Release
June 28, 2023

Report: Marin’s Beach Water Excellent

All beach locations tested during summer months received A grades

San Rafael, CA – Water quality was excellent last summer at all Marin County beaches according to a new report from Heal The Bay. The annual report rates water quality at beaches along the U.S. West Coast.

The summer day grades at the Marin County beaches were exemplary for a fifth straight year, with 100% of beaches receiving A grades. The grades came from sampling 26 beach sites over 31 weeks.

A young boy plays in the sand at a local beach with other people sunbathing and playing in the backgroundMarin County beaches were exemplary for a fifth straight year, with 100% receiving A grades from summer sampling.

Marin’s water quality monitoring program, overseen by the Marin County Community Development Agency’s Environmental Health Services Division (EHS), gathered data from April 2022 through October 2022 from 26 bayside and oceanside monitoring locations. Twenty-four are marine beaches, and two are fresh water recreational sites. The beaches are managed by a variety of agencies.

When looking at the average grades of sites in a span of five years, 23 beach sites received A's, and only one location received a B. During the wet weather events from April through March, 15 sites received A and B grades and only five sites received either C, D, or F grades. The five-year wet weather beaches grade average is 77%.

Heal the Bay reports Marin received 37 inches of rain between April 1, 2022, and March 30, 2023, a 93% increase from the historical average of 19 inches. The full impact of the decreased rainfall in winter months is difficult to assess because most of the local beaches are not monitored during winter.

Rain alleviates drought conditions, but it also results in more pollutants, including bacteria, being flushed into streams, the bay, and the ocean. Pushed by rainwater, contaminants flow from streets in the form of trash, fertilizer, pet waste, metals, and automotive fluids.  

Marin County faced the challenge of sewage spills in the 2022-23 observation period, resulting in a total of 35,000 gallons of wastewater reaching a body of surface water. Among these incidents, two spills, totaling 8,025 gallons, were reported to have flowed into the Corte Madera Marsh Ecological Reserve.

The spills in question, falling under the jurisdiction of various sanitation districts, have been diligently addressed by the responsible authorities. The spills were promptly reported, and appropriate measures were taken to mitigate any potential impact on the environment and public health. It is important to note that these incidents did not affect any recreational beaches within the area.

Heal the Bay, based in Santa Monica, has analyzed water quality data at California beaches each year since 1991. The Beach Report Card is funded by grants from the Surf Industry Manufacturers Association and the Grousbeck Family Foundation. See the full report at

Marin EHS has monitored ocean, bay, and freshwater sites since 2003 and posts sample results weekly. The samples are processed by the Napa-Solano-Yolo-Marin County Public Health Lab. The tests quantify the most probable number (MPN) of total coliform, E. coli, and enterococcus bacteria present in each water sample.

A warning sign is posted to alert the public if lab results indicate water samples exceed the State of California standards for recreational waters. The California Department of Public Health advises beach users to avoid contact with recreational waters where warning signs are posted. People in contact with elevated bacteria levels in recreational waters may become ill.

Heal the Bay recommends beach users never swim within 100 yards on either side of a flowing storm drain, creek, or river in any coastal waters during a rainstorm, and to stay out of the water for at least three days after a storm has ended.

Learn more about the testing program on the Environmental Health Services webpage.


Arti Kundu
Project Manager, Environmental Health Services
Community Development Agency

3501 Civic Center Drive
Suite 236
San Rafael, CA 94903
(415) 473-7146
Email: Arti Kundu
Environmental Health Services