Coronado’s tony seaside community and working-class Imperial Beach could be headed for a major reckoning with the sewage continuing to spill over the border from Tijuana.

Beach closures that were once thought of as largely a wintertime occurrence now appear poised to become a year-round phenomena in San Diego’s South Bay.

However, that’s not because the cross-border pollution from Baja California’s overtaxed and crumbling wastewater system has dramatically escalated, according to county officials.

It’s because the ocean is more polluted than previously thought. A spate of recently shuttered shorelines followed a May 5 rollout of a new DNA-based water-quality testing system nearly a decade in the making.

“This method is more accurate, more precise, so we’re able to get a better picture of what the water quality truly is,” said Heather Buonomo, director of the county’s Department of Environmental Health and Quality.

“Until the root cause of this issue is addressed, which is correcting the sewage contamination that’s flowing up to these beaches, this will continue,” she warned.

Coronado’s beaches have been shuttered for an eye-popping 17 days since the new testing started early last month. The Imperial Beach shoreline to the south, which historically has suffered much greater impacts from sewage pollution, was immediately closed and has yet to reopen.

“No one was expecting that this was going to result in these closures all the way up to Coronado,” Imperial Beach Mayor Serge Dedina said Tuesday. “Right now our beaches are going to be closed all summer.”

Coronado Mayor Richard Bailey questioned whether the tests were really indicating a fresh understanding of sea conditions.

“If these new tests are detecting new conditions that pose a real health risk, the beaches should be closed. But if the new tests are detecting the same conditions that always exist during the summer when people typically enjoy the beach without negative health consequences, the beaches should be open,” Bailey said in a statement late Tuesday. “I strongly suspect the conditions haven’t changed and the beaches should be open, but I’ll be meeting with county officials to better understand the new testing protocols.”

Dedina and others expressed concerns that the closures could have widespread economic and social impacts, potentially shuttering programs such as the junior lifeguards and YMCA surf camps and interfering with Navy training operations.

Reporter Joshua Emerson Smith discusses this story on the San Diego News Fix:

“The Hotel del (Coronado beachfront) is going to be closed all the time now,” said Chris Helmer, environmental and natural resources director for Imperial Beach. “That’s going to piss off a whole lot of powerful people.”

The Naval Special Warfare Command, whose base is located on the southern end of Coronado and is the training home of San Diego’s Navy SEALs, did not return requests for comment.

The closures are necessary to protect beachgoers from dangerously high levels of bacteria and viruses, according to county public health officials. Swimmers who ignore the restrictions could be at risk of diarrhea, fever, respiratory disease, meningitis and even paralysis.

San Diego is the first coastal county in the nation to institute a federally approved water-quality testing system that uses DNA technology, officials said. The effort involved the U.S. Environmental Protection Agency, California Department of Public Health and researchers at UC San Diego.

“We started this process nine years ago because we heard loud and clear from the community that they wanted to know what was going on with their water,” said Buonomo with the county. “They wanted faster results and more accurate information on if it could make them sick.”

The old testing regime relied on what’s known as taking a culture, where scientists examine water samples for bacterial growth in a lab. Officials said the new DNA-based method is not only more accurate but quicker, returning results within 10 hours, rather than 24. In either case, the presence of bacteria is considered an indicator for pathogens, such as E. coli, Vibrio and salmonella.

“When you have high increase of sewage in your sample, often the culture method might miss those, whereas the DNA test is not missing those,” said Jeremy Corrigan, director of operations at the San Diego County Public Health Laboratory.

For years, environmental regulators thought sewage pouring over the border from Mexico was largely the result of heavy winter rains that flushed polluted runoff and wastewater through the Tijuana River channel into the estuary in Imperial Beach.

However, recent studies out of UCSD’s Scripps Institution of Oceanography and Stanford University have identified a defunct wastewater facility in Tijuana as a major source of the pollution. San Antonio de los Buenos sewage treatment plant at Punta Bandera is estimated to be dumping as much as 35 million gallons of raw sewage a day into the Pacific Ocean.

When ocean currents move northward, referred to as a “south swell,” they can carry plumes of feces and other pollution as far north as Coronado. Such conditions are prevalent in the spring and summer, according to health officials.

The EPA has released a $630 million blueprint, nearly half of which has funding, to stem the cross-border pollution. A major part of the plan is an effort to reroute much of the wastewater currently pumped to Punta Bandera, which relies on a system of outdated lagoons. Instead, that sewage would be sent to the South Bay International Wastewater Treatment Plant along the border in San Diego.

Staff writer Andrew Dyer contributed to this report.

8:55 p.m. June 14, 2022: This story has been updated with comment from Coronado Mayor Richard Bailey.

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