Marin County Ocean and Bay Water Quality Testing Program

Marin County Environmental Health Services (EHS) has monitored ocean, bay and freshwater sites in Marin County since 2003. The 28 ocean, bay and freshwater sites, countywide are sampled once a week from April 1 through October 31 to determine if a beach meets the California water quality standards for recreational water contact. EHS works cooperatively with other agencies to collect water samples and post advisory signage as needed at the designated sampling sites.

Should the State water standards be exceeded at any time, a warning sign is posted to alert the public that the bacterial standards were not met. The California Department of Public Health advises beach users to avoid contact with the recreational waters where warning signs are posted. People in contact with the elevated bacteria levels in recreational waters may become ill.

The water samples are processed by the Marin County Public Health Laboratory. The tests utilized, quantify the most-probable number of Total Coliform, E. coli, and Enterococcus bacteria present in the water sample. The water samples represent a "snap shot" in time. The bacteria themselves are generally not pathogenic, but are used as indicators of the potential presence of other pathogenic bacteria that are linked to human illness.

Advisories are provided for informational purposes only and are based on one sample per week therefore they do not provide current conditions. Water sample processing requires 24 hours so the information is at least one day old when posted.

Results from the weekly samples are available on:

• the EHS beach hotline (415-473-2335);
• the EHS website;
• the Heal the Bay website