Beach Water Quality


From April 1-October 31st each year, the County of Marin Environmental Health Services conducts weekly monitoring of bacteria levels at selected sites (see map at right) where water-contact recreation is common. This "beach" monitoring program provides advisories to the public when the results of bacteria testing indicate levels do not meet Contact Recreation Standards. There are signs posted at sampling locations, and advisory signs are posted when warranted.


In an effort to provide this information to the public in a convenient and timely manner, the Tomales Bay Watershed Council will be maintaining this web-page to provide weekly notification of advisory conditions at local beaches throughout each monitoring season. The Advisory Table below shows the weekly advisory condition of each site during the season. Conditions will be updated weekly from April 1-October 31 when lab results become available.


To see past monitoring seasons complete advisory tables, click here.

Please check back for the most current advisory conditions, or call the County of Marin Beach WQ Hotline at 415-473-2335.


Advisory categories will follow the County of Marin Environmental Health Services, Beach Monitoring Program Bacteria Limits for Contact Recreation (See table below.)

Samples are collected by the County of Marin EHS staff.


All samples are analyzed by the Regional Public Health Lab. Samples from all sites are analyzed using IDEXX Quanti-Tray (SM9223B). The test quantifies the most-probable number of Total Coliform bacteria and E. coli in the sample. All samples are also analyzed for Enterococcus bacteria which is a better indicator for marine waters. All of these bacteria are used as indicators of the potential presence of other pathogenic bacteria that are linked to human illness. These advisories are provided for information purposes only, based on one sample per week, and so, do not imply up-to-the-minute conditions.

Bacteria Limits for Contact Recreational Use

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