Humboldt Baykeeper: Clam Beach Named Most Polluted in State

August, 2017



Last month, Heal the Bay’s annual Beach Report Card named Clam Beach the most polluted beach in California due to bacteria levels measured at the mouth of Strawberry Creek. Clam Beach has made the Top Ten “Beach Bummers” list for four years running, but this is the first time it’s been Number One.  And this year, Luffenholtz Beach in Trinidad was the eighth most polluted in the state.

Heal the Bay gathers data on bacteria levels and assigns letter grades to 416 beaches in California. In 2016-17, 96 percent of beaches received A or B grades during the summer. However, during rainy weather, nearly 50 percent of beaches received C to F grades.

Swim Guide for Clam Beach

People often ask, “How can Clam Beach be more polluted than beaches in urban areas in Southern California?” The short answer is that more rain means more bacteria in runoff. Humboldt County certainly gets more rain, particularly between April 1 and October 31, when bacteria levels are monitored. 

A good rule is to avoid contact with water for 72 hours after a major rain. Though parents typically attribute children’s stomach upsets to the flu, exposure to bacteria polluted waterways can cause flu-like symptoms. A pediatric study in Wisconsin found that emergency room visits for gastrointestinal illnesses were correlated with rainfall. And a three-year study of 650 surfers in San Diego found increases in illness after surfing during rainy weather.

Clam Beach water quality has been getting worse during both dry and wet weather. The reasons for this increase in bacteria levels remains a mystery, although there’s no shortage of hypotheses. Some point to septic systems, while others suggest livestock or pets. The only way to pinpoint the sources is to do more intensive sampling. 

In 2014, Baykeeper embarked on a study to identify the sources, whether human, cattle, dog, bird, or none of the above. In 2015, we formed a partnership with the Regional Water Board and Humboldt County Public Health Lab to identify the sources using a genetic analysis that will identify the primary sources of bacteria in our waterways. 

Starting with Little River, which drains to Moonstone Beach, and Janes Creek, which drains to Humboldt Bay near commercial oyster beds, we sampled during wet and dry weather throughout 2016. Later this month, we expect to have the first results showing how much of the bacteria are from human sources.

The oyster industry has known about the problem for decades, since regular testing is required for food safety. A lot more is known about bacteria levels in the bay than in its tributaries. Only one in 1,500 samples taken during dry weather were above the levels allowed for shellfish consumption. 

When the U.S. Environmental Protection Agency designated six local streams and five local beaches as “impaired” by bacteria, Humboldt Bay was not given that designation. From the oyster studies, it is known that the problems lie in the bay’s tributaries, which flush polluted runoff into the bay with every rainstorm. The problem appears to be worse in streams with lots of pavement and smaller riparian buffer zones. 

To check the latest bacteria levels at Clam Beach, Luffenholtz Beach, Trinidad State Beach, and Moonstone Beach, visit the Waterkeeper Swim Guide ( To read more about water quality at beaches in California, download the Beach Report Card 2017 at  

In Other Bay-related News:

• After being told (again) that the U.S. Environmental Protection Agency (EPA) would reject the plan to dump marina spoils onto Samoa Beach, the City of Eureka announced its intent to take the spoils to the already-permitted disposal site three miles offshore. The City hopes to dredge its marina in September.

• The California Transportation Commission ordered the North Coast Rail Authority to prepare a shutdown plan for the Humboldt and Mendocino sections of the rail line by October due to financial insolvency.

• The U.S. EPA awarded two Brownsfield grants to local agencies. The City of Arcata was awarded $300,000, some of which will be used for testing the dioxin site at Little Lake Industries on South I Street. Another $200,000 went to the Humboldt Bay Harbor, Recreation and Conservation District for debris cleanup at the former pulp mill in Samoa.

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