San Rafael, CA – Marin County Parks received good news from a commissioned study that tested water quality at a popular West Marin beach, ending speculation that human bacteria could be causing a problem.
Routine bacteria tests of water at Chicken Ranch Beach on Tomales Bay occasionally showed levels that exceeded state limits for recreational water contact by humans, sparking concern from local residents, beachgoers and County Parks managers. One thought was that septic systems near the beach could be failing.
This week, the Nicasio-based Carbon Cycle Institute shared new test results that conclude it is “extremely unlikely” that the bacteria levels were from human sources. In addition, Marin County Public Health Officer Dr. Matt Willis said there have been no public health concerns in 2014 about contaminated water at the beach just north of Inverness.
“We are relieved and pleased,” said Linda Dahl, Director of Marin County Parks. “The results of this study underline the importance of data and research in determining actions that we should take.”
The County received requests to clean up the site but no real data to determine the presence, type, or source of contamination. The County contracted with the Carbon Cycle Institute to perform the microbial study at Chicken Ranch Beach before spending thousands of dollars on remediation actions.
The tests, from samples taken earlier this year on January 21, April 28 and July 18, were performed to determine the presence or absence of human-source bacteria. Samples were analyzed with a trusted and reliable tool developed by Lawrence Berkeley National Laboratory previously used in beach studies and the aftermaths of oil spills. Additional testing would be necessary to determine the sources of non-human bacteria, which could include wildlife.
Over the past 10 years, Marin County Parks has reported isolated instances of high bacteria levels at its waterfront beaches along the Pacific Ocean and San Francisco Bay. Marin County Environmental Health Services (EHS) monitors ocean, bay, and freshwater sites in Marin. Chicken Ranch Beach is one of 28 sites sampled once a week from April 1 through October 31 to determine if it meets California water quality standards for recreational water contact. Visit the EHS Water Quality Testing Program webpage for more information and results from weekly samples. Test results are available on the webpage, on the Heal the Bay website or by calling the EHS beach hotline at 415-473-2335.
The EHS works cooperatively with Marin County Parks to collect water samples and posts advisory signs as needed at the sampling sites. Signs of a potential health hazard are always posted if a single sample of high bacteria levels exceeds the state’s maximum safe threshold. The County works closely with regional and state water quality boards in monitoring water samples and will continue to make every effort to keep all County parks as clean and safe.