For the first time in its history, Bolinas Beach was abruptly closed by Marin County officials on Friday after alarming levels of wastewater contamination were discovered near its shores. The discovery cast doubt on the viability of the town’s aging septic systems and prompted fears about the pace of bluff erosion.
Marin County Environmental Health Services conducts weekly water quality tests from April through October at various sites along the coast, but sewage seeps were discovered unexpectedly during a routine building permit inspection on Sept. 5.
County staff observed effluent draining down the Big Mesa’s cliff face along the Pacific Ocean, uncovering a far-reaching problem stretching from Brighton Avenue to Agate Beach—a mile and a half of compromised coastline.
“You don’t see something like that from just one property,” said Sarah Jones, director of the Marin County Community Development Agency. She recalled receiving a blunt assessment from an environmental health officer: “There’s a lot of shit running downhill.”
Initial tests on five of the more than 30 bluff-side seepages, some of which reach the sand, confirmed the contamination. An ammonia-detecting strip used by E.H.S. staff showed positive results, prompting further testing of samples for total coliform, E. coli and enterococcus bacteria.
The results were alarming: Total coliform levels were exceptionally high, signaling the potential presence of more harmful pathogens. One sample recorded a total coliform count exceeding 24,196 per 100 ml, far beyond the lab’s measurement capabilities. Enterococcus bacteria, a key indicator of fecal contamination, were detected at levels of 1,130 per 100 ml—10 times above the recreational safety threshold. Plans are underway to test seawater later this week.
The testing process was not without complications. The sample bottles, though sealed and unopened, were expired, according to Becky Gondola, a senior environmental health specialist with the county. Still, E.H.S. staff instructed the lab to proceed, believing the expiration would not cause false positives for fecal bacteria. Additionally, two samples were too dark to reliably detect the color change that indicates contamination.
Despite the closure, the crowd of swimmers, surfers and sunbathers remained undeterred over the weekend. Red and yellow signs stretched from Brighton Avenue to Duxbury Reef, urging visitors to steer clear of the ocean, yet for many locals, it was business as usual.
“I saw the notice last night and immediately went surfing,” said Tobi Earnheart-Gold, a Bolinas native who, like many, seemed unfazed by the warnings. He’s mostly kept to the section of the ocean toward Seadrift.
The beach closure sparked frustration among other residents, many of whom felt left in the dark. “Closing Bolinas Beach because of sewage runoff is actually a big deal,” said Will Bartlett, a frequent surfer and a Bolinas resident. “Even if you’re being cautious, you need to back up that decision with empirical data.”
Officials have not said when they will reopen the beach.
Septic tanks are underground containers that hold whatever is flushed down a toilet. Solids settle at the bottom and require periodic pumping, while liquid waste filters through a series of perforated pipes that disperse discharge from the tank into a leach field, where it percolates into the soil and is stripped of harmful bacteria before it reaches the water table.
Yet rising sea levels are pushing groundwater levels higher, reducing the soil buffer that protects local waterways and underground aquifers. In Bolinas, the erosion of the Monterey shale that makes up the bluffs exacerbates the problem.
County officials remain uncertain whether the contamination is due to failed septic systems, cliff erosion, or a combination of both. “With the conditions on the Mesa—the geologic conditions there and the rising groundwater—I don’t think that people who understand this area would be entirely surprised by it,” Ms. Jones said.
Some surfers remarked that it is not atypical to be hit with an unmistakable odor while you’re catching a wave, with one noting, “There are times when you’re at the Patch, and it just smells like shit!”
County officials suspect the wastewater leakage has been ongoing for some time, but the full extent and precise sources remain unclear. Unlike typical runoff that affects seawater quality from a distinct source like a creek, this contamination appears more diffused. The possibility that contamination is affecting local wells prompted officials to advise against drinking well water.
In response, the county declared a level-three emergency, coordinating with the San Francisco Bay Regional Water Quality Control Board to conduct further testing along the beach and in the ocean this week with appropriate sampling equipment.
“This is very much a situation that is still unfolding,” Ms. Jones said.
As the investigation continues, Bolinas residents are left to grapple with the risks, weighing the allure of the waves against the unmistakable warnings of contamination.