Less sewage spills and less runoff caused by drier weather likely aided Marin County beaches in having cleaner water, county health officials said.
Marin County beaches continued to receive high marks for their water quality with only Stinson Beach receiving a failing grade during wet weather.
All 24 testing sites in the county received “outstanding” marks during dry weather in 2019-2020, according to the latest “Beach Report Card” by environmental organization Heal the Bay. The annual report grades beaches throughout the West Coast based on levels of bacterial contamination in the water.
One of the main reasons for this year’s high marks was the lack of rainfall the county received, according to Marin County Environmental Health Service Division project manager Arti Kundu.
“We know that if it rains it’s going to bring back a lot of pollutants and runoff that will get into the beaches and make it much more polluted,” Kundu said, “but the dry weather helped contribute to the much cleaner beaches for 2019 to 2020.”
Marin recorded about 14 inches of rain, which is about 34% lower than the average of 22 inches, according to the report.
The county also saw a significant reduction in the amount of sewage spilled in the 2019-2020 monitoring period compared to 2018-2019. About 20 sewage spills occurred in the county, of which nearly 11,750 gallons of sewage reached the surface water, according to the report. Health warnings were issued for San Rafael Creek and Richardson Bay as a result of these spills in 2019. This is down from 41 spills that occurred during the last testing period during which 248,000 gallons reached the ocean.
Bill Johnson, wastewater and enforcement chief with the San Francisco Bay Regional Water Quality Control Board, puts the amount closer to 12,300 gallons for Marin County. The largest spill of about 4,200 gallons was reported in August 2019 by the San Rafael Sanitation on Miramar Road, which entered San Rafael Creek. The next largest spill of about 1,500 gallons was reported by Mill Valley on March 29, 2020.
The county Environmental Health Services Division routinely tests 27 beach sites throughout the county as well as local streams and waters for fecal coliform, E. coli and Enterococcus bacteria. These tests only occur from April through October due to state funding availability, Kundu said.
The Beach Report Card provides separate water quality grades for counties based on the time of year and whether or not the tests were conducted during dry or wet weather.
For the dry “summer” months of April through October 2019, 23 of the 24 beach sites in Marin County received A grades, many with A+ grades. McNears Beach received a B grade.
For the wet testing days between April through October 2019, 16 of the 24 beaches received perfect grades but there were some outliers. Stinson Beach’s northern and central testing areas received F grades for high bacteria. The southern testing site received a C grade.
Kundu attributes this to the Sept. 18 storm, which led to a “surge in the number of fecal bacteria” at those sites.
“Whenever there is a big storm even that happens the rain brings in a lot more pollutants,” Kundu said.
After the results came back, the county posted health advisories which can only be lifted if bacteria levels drop below state-mandated thresholds.
No other bacteria advisories have had to be implemented at Stinson Beach since then, Kundu said. The beach received A grades during dry months as well.
Other less than satisfactory wet weather grades were given to Chicken Ranch Beach, which received a D, and Muir Beach’s northern and southern sites which received C grades.
The county did not receive grades for the dry “winter” months of November 2019 through March 2020 because it does not test during that period.
While not included in the report card, Marin County also tests freshwater sites along Lagunitas and San Geronimo creeks. In its self-assessment, the county states it would have received poor grades at these sites.
“Bacteria exceeded recreational standards at the Inkwells in Lagunitas (81% of the time), Green Bridge near Point Reyes Station (74%), and Samuel P. Taylor State Park (14%),” the county stated in a summary, noting that monitoring at Samuel P. Taylor was suspended in May 2019 due to limited resources.
Todd Steiner of the Salmon Protection and Watershed Network, or SPAWN, which has been working to survey and restore the San Geronimo Creek watershed, said the higher bacteria levels are likely caused by failed septic systems, livestock and recreational horse ranches to close to creeks.
“Solutions are simple: require septic testing and needed upgrades at time of property sale, and regular septic system testing; strong protective regulations and enforcement of streamside habitat and vegetation; and adequate fencing and restoration along streams to keep cattle and horses out of waterways,” Steiner wrote in an email.