County of Marin - News Releases - Beach Water Quality

For Immediate Release
June 07, 2018

Banner Year for Beach Water Quality in Marin

All 23 locations tested during wet weather received A grades

San Rafael, CAHeal The Bay, which annually rates water quality at beaches along the U.S. West Coast, just gave Marin County a near perfect score from 31 weekly samples taken last year.

A man and woman walk their dog on Rodeo Beach in the Marin Headlands.Rodeo Beach, on the west side of the Marin Headlands, scored well in Heal the Bay's water quality ratings.
Marin’s water quality monitoring program, overseen by the Marin County Community Development Agency’s Environmental Health Services Division (EHS), gathered data from April through October 2017 from 23 bayside and oceanside monitoring locations. Nineteen of the locations received A-plus wet-weather ratings year-round and the remaining four were graded A. There were only three B ratings during the summer dry months (April through October).

The Marin locations tested regularly are Stinson Beach, Muir Beach, Bolinas Beach, Baker Beach, Rodeo Beach, Schoonmaker Beach, McNears Beach, China Camp State Park, and seven beaches on Tomales Bay.

According to the report, Marin experienced 17 sewage spills that reached a body of water in 2017, half the total from 2016. Four health warnings were issued and one beach closure took place. Two Marin spills were considered major (more than 10,000 gallons), three were minor (1,000 to 10,000 gallons), and 12 were small (less than 1,000 gallons).

Rain greatly impacts the water quality ratings by flushing contaminants and bacteria sources from streets, including trash, fertilizer, pet waste, metals, and automotive fluids, into urban waterways. The untreated runoff drains directly into the ocean and results in elevated bacteria levels. In the wettest months (November through March), 28 percent of beaches statewide received D or F grades on water quality, matching the state’s five-year average. In Northern California, only 17 percent of water quality samples received D or F grades, much better than the 35 percent figure in Southern California.

California had excellent water quality during the summer dry season, with 96 percent of beaches receiving an A or B grade. Higher grades are indicative of better water quality and a lower health risk for people in the water. Winter dry grades were worse this year, with only 77 percent receiving an A grade compared with the five-year average of 81 percent.

Heal the Bay, based in Santa Monica, has analyzed water quality data at California beaches each year since 1991. It also rates beaches in Oregon and Washington. 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 between April and October since 2003 and posts sample results weekly. The samples are processed by the Napa-Solano-Yolo-Marin County Public Health Lab. These tests quantify the most-probable number of Total Coliform, E. coli, and Enterococcus bacteria present in the water sample.

If lab results indicate water samples exceed State of California standards for recreational waters, a warning sign is posted to alert the public that bacterial standards were not met. 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.

Learn more about the testing program on the webpage.


Lorene Jackson
Project Manager, Environmental Health Services
Community Development Agency

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