by Photo courtesy of San Diego County

San Diego County announced it is the first coastal county in the nation to use DNA-based ocean water testing technology that will rapidly deliver results on bacteria levels. 

The DNA-based droplet-digital polymerase chain reaction testing technology — ddPCR —will produce faster results and warnings of bacteria levels throughout the shoreline. According to County Board of Supervisors Vice Chair Nora Vargas, there are plans to expand the technology to more than 70 miles of shoreline for regular testing. 

“Faster results,” she said, “are going to allow the County to issue or lift beach advisories on the same day samples were collected. And it reduces the time the public could unknowingly be at risk and … when the water is contaminated.”

According to county officials, the new system will let the County sample beach water in the morning, get results, and warn the public by the afternoon instead of the next day. The previous method required growing bacteria cultures through Petri dishes. 

A side-by-side study was conducted by the County’s Public Health Laboratory in 2019 which compared both methods. The new system received final approval in February by the California Department of Public Health, allowing for its expansion. 

Vice-Chair Vargas, County Public Health Officer Dr. Wilma Wooten, and Heather Buonomo, director of the county's Department of Environmental Health & Quality gathered to announce the new technology Wednesday morning near Imperial Beach. 

Last month, a settlement was reached with the U.S. Section of the International Boundary and Water Commission (USIBWC), which allegedly violated the Clean water act for several years, and allegedly allowed polluted water, trash, and sediment to flow into the United States.  

The long-running cross sewage litigation valley was filed by several agencies and municipalities across the San Diego region to mitigate raw sewage and toxic chemicals from the Tijuana River Valley. USIBWC was the sole defendant in three separate lawsuits whose plaintiffs included the cities of San Diego, Imperial Beach, and Chula Vista, as well as the Port of San Diego, California San Diego Regional Water Quality Control Board, California State Lands Commission, and Surfrider Foundation.

The Tijuana River carries untreated wastewater, trash, and sediment from Mexico across the border into the United States. The polluted discharge into the Pacific Ocean from Tijuana’s wastewater treatment plant is carried northward during the summer, impacting beaches in southern San Diego County. 

“This litigation was a critical jumpstart, and we’re looking forward to cooperating with local, state, and federal officials, to further address a challenging environmental problem that crosses international boundaries. In addition to political will, we needed funding, and I appreciate the leadership at the federal level to provide $300 million to address the water pollution in our Tijuana River Watershed. With the case behind us, our focus now turns to work with our partners to ensure that federal pollution control infrastructure is constructed with the utmost expedience,” Chula Vista Mayor Mary Casillas Salas said. 

Under the settlement, the USIBWC, which owns and supervises the operation and maintenance of the South Bay International Wastewater Treatment Plant in the Tijuana River Valley, agreed to “diligently mitigate” water that flows across the border and regularly share information with stakeholders on its progress for seven years. 

Any violation of the terms means the entities can revive their lawsuits and file new lawsuits for any new alleged violations.

Visit for more information about the County’s beach water quality testing program and local conditions. 

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