http://articles.latimes.com/2011/jul/10/local/la-me-avalon-water-20110710

Even though the city of 4,000 has spent $3.5 million testing and rehabilitating sewer lines, the water is no cleaner. A report last month by the Natural Resources Defense Council listed Avalon as one of the 10 most chronically polluted beaches in the nation for failing state health tests as much as 73% of the time.

Researchers years ago zeroed in on the cause: the city's rickety sewer system, made of century-old clay and metal pipes. Because half the lines are flushed with corrosive salt water, some have deteriorated so much they have simply vanished. So human waste flows unchecked into the earth, trickling into the city's groundwater and filtering through the sand into Avalon Bay.

Avalon's water woes surfaced in 1999, when a new state law required weekly health testing of California beaches from April to October.

Faced with poor results, city officials at first suspected boaters who drop anchor in the marina. That was ruled out because of the city's strict dye tablet program that banishes any boater who releases sewage into the harbor.

Next, they pointed the finger at seabird droppings fouling the water, an idea underscored by a limited city-commissioned study that found no evidence of human waste. For a time, visitors getting off the ferry were handed a pamphlet from the island Chamber of Commerce blaming the pollution on "large populations of birds."

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Notice that they blamed boaters first... typical reaction, eh?