WESTMINSTER — More than half of Southern California’s shoreline – from Santa Barbara to San Diego – is unsafe for swimming after rainstorms because of bacteria carried to the ocean by urban runoff, according to a new study.
The report, released Tuesday by the Southern California Coastal Water Research Project, found that 56 percent of the shoreline has high bacteria readings after a major rainstorm.
That’s 10 times more than the violations found during a similar summertime survey.
The results indicate that more than half of all beaches may be unsafe for swimming or surfing after a storm that brings 1.1 to 3 inches of rain.
“Whereas in summer our beaches are generally safe to swim at, our beaches are uniformly unsafe to swim at following a rainstorm,” said Stephen Weisberg, executive director of the scientific group, which is based in Westminster and operated by local, state and federal agencies.
This is the first time scientists have been able to provide a complete, regionwide picture of the extent of beach pollution. They said they didn’t expect to find such high levels of bacteria at beaches far from storm drains as much as 36 hours after the rain had ended.
“I’m not surprised that we saw bacterial hits, but it’s the intensity of the hits, far from the drains, that is unusual,” Weisberg said. “Some of these places are pretty darn far.”
Many surfers and others mistakenly believe that the only contaminated waters are around river mouths and storm drains. Contrary to another popular perception, that runoff pollution is mostly a problem for Santa Monica Bay, beaches in all five coastal counties registered similar bacteria counts.
In the past, some local officials have suggested that a major cause of high bacteria levels at beaches is bird droppings or other animal wastes that do not pose much of a health risk.
But Noble said most of the beaches tested positive for fecal coliform, total coliform and enterococcus bacteria, which means human feces are likely to be present. Such sewage can cause diarrhea, ear infections and skin rashes, as well as more serious illnesses.
No one is certain how sewage winds up in urban runoff. The waste is supposed to remain in sewer pipes. But leaks, septic tanks built too close to the shore, overflows and illegal sewer connections apparently let sewage flow untreated into streets and curbside drains. The report is based on samplings of ankle-deep water from 254 sites in five counties – San Diego, Orange, Los Angeles, Ventura and Santa Barbara – taken on Feb. 20, a day and a half after a heavy rain.
sent all ocean waters accessible to swimmers along 690 miles of shoreline.