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New pollution tests wreaking havoc on South San Diego County beaches

Pollution warning sign in Imperial Beach in this undated photo
Erik Anderson / KPBS
Pollution warning sign in Imperial Beach in this undated photo

The tests are finding more pollution, which is leading to more beach closures that are threatening tourist economies in Coronado and Imperial Beach.

The prospect of more summertime beach closures in San Diego’s South County has beach communities and county officials at odds over pollution warning signs.

Imperial Beach and Coronado have endured a steady diet of closings since May.

The new testing protocol being used by San Diego County Department of Environmental Health officials promises faster and more accurate results. Imperial Beach Mayor Serge Dedina, however, is worried that beaches could be unnecessarily closed because the tests detect pollution levels that aren’t harmful to humans.


The testing switch was heralded by San Diego County Supervisor Nora Vargas when it was introduced on May 4.

“The Tijuana River Valley pollution directly impacts the families of not only Imperial Beach but the community and the region as a whole,” Vargas said. “This advancement in water testing today is going to allow us to better monitor quality and provide us and the community with faster and more accurate information.”

The county is the first local government to get U.S. Environmental Protection Agency approval to use the new, more sophisticated tests.

The new method, called the Digital Drop Polymer Chain Reaction (DDPCR) test, searches for bacterial DNA in water samples. If it detects that genetic material, officials deem the water unsafe. The test can be performed in four to six hours.

The old tests relied on culturing water samples in a county lab for 18 to 24 hours. If bacteria grew in those cultures, local officials would know the water was not safe for humans.


A major consequence of the new testing regime is pollution warning signs have been up for the past several weeks in Imperial Beach and Coronado. This is not typical for the summer when there is little or no rain.

“The county rolled out a new testing methodology,” said Serge Dedina, the mayor of Imperial Beach. “We’re closing beaches when the city of San Diego testing, the old testing, shows that the beaches are clean.”

Dedina does not want the new tests to be dumped, but he suggested interpreting the testing results might benefit from the inclusion of additional factors such as ocean currents.

He said the county has not been receptive.

“We should’ve been meeting with the county weeks ago, a meeting that we requested, and we still have not met with the county of San Diego to have that discussion,” Dedina said. “Frankly I have never been more disrespected as a city and as some who does environmental work and who’s worked with the county for 35 years I’ve never seen them avoid having stakeholders in the room to talk about this.”

Officials with the San Diego County Department of Environmental Health (DEH) said that is not the case. They say they’ve been working with Dedina and other stakeholders for the past nine years to prepare for the DDPCR test, which is being used along San Diego’s entire 70-mile coastline.

Even though they expected more positive tests, DEH chief Heather Buonomo, however, said she and her colleagues are surprised at the number of positive tests and beach closures in South County.

“These are the only beaches where we’re experiencing these increased closures,” Buonomo said.

The county stands behind the quality of the testing and said the pollution postings are warranted.

“There is sewage contamination in the water and we really need to focus on the root cause of this issue, which is the sewage contamination. That’s where we need to focus our efforts,” Buonomo said.