Water Grades For Bay Area Beaches Released

MARIN COUNTY, CA — Water quality at Marin County beaches showed some mixed results last year, according to an annual report on U.S. West Coast beaches.

According to the 35th annual report from Heal the Bay, 86 percent of Marin County beaches received strong A and B grades during summer and dry weather. Statewide, 91 percent of California beaches earned A and B grades in summer dry conditions, 89 percent in winter dry conditions and 76 percent during wet weather.

However, Chicken Ranch Ditch at Channel B near Inverness was named the state's No. 4 “Beach Bummer” due to high bacterial levels from stormwater runoff. A proposed project, led by the Tomales Bay Watershed Council Foundation with support from the U.S Fish and Wildlife Service, California Coastal Conservancy and Marin County Parks, aims to restore water quality and wetlands.

About 230 feet of Channel B, a man-made ditch carrying bacteria into Tomales Bay, will be filled. Water will be redirected through a meandering wetland with shallow pools to naturally filter it before it flows into Third Valley Creek. Construction started in August and will last about two months.

Marin County's Environmental Health Services Division monitored water quality at 31 bay and ocean sites for 31 weeks, from April to October 2024, to assign grades. This included 26 marine beaches, 12 federal, eight county, six local or private and five state, and five freshwater recreational sites.

Marin County beaches consistently received high grades for water quality during summer dry periods over five years. During wet weather, 82 percent of beaches averaged A and B grades, with only four sites receiving C and F grades.

While California experienced 9 percent less rain than its 10-year average, Marin saw a 7 percent increase, 24 inches, in rainfall between April 2024 and March 2025. The impact of decreased winter rainfall on beach water quality is unclear as most local beaches are not monitored then.

Rainfall, while alleviating drought, also flushes pollutants like bacteria, trash, fertilizer, pet waste, metals and automotive fluids into waterways, officials said.

Marin reported 25 sewage spills between 2024-2025, releasing approximately 55,000 gallons of wastewater, with 15,000 gallons entering Marin waterways. These spills were promptly addressed by sanitation districts and did not affect monitored recreational beaches.

Heal the Bay, based in Santa Monica, has analyzed water quality data in California beaches each year since 1991.

Marin EHS has monitored ocean, bay, and freshwater sites since 2003, posting weekly sample results. The Napa-Solano-Yolo-Marin County Public Health Lab processes samples, quantifying total coliform, E. coli and enterococcus bacteria.

Avoid water where signs are posted or within 100 yards of a storm drain, creek, or river, especially during or for three days after a storm, according to Heal the Bay. Elevated bacteria can cause illness.