Science & Technology



Surfers were right: Imperial Beach is polluted with Tijuana sewage even in summer

Joshua Emerson Smith, The San Diego Union-Tribune on

Published in Science & Technology News

SAN DIEGO — Imperial Beach surfers and swimmers have long complained about foul smells along the city's shoreline during summer months. For years, those concerns were swept aside as the Mexican sewage plaguing the town rarely spills over the border through the Tijuana River unless it's raining.

A new report out of UC San Diego's Scripps Institution of Oceanography, Stanford University and the U.S. Environmental Protection Agency now confirms what many have suspected: A crumbling wastewater plant south of the border is daily discharging millions of gallons of raw sewage into the ocean that routinely carry pathogens up the coast.

"I'm embarrassed to admit, but we used to get complaints from surfers along Imperial Beach when there would be these strong norward currents," said Doug Liden, EPA environmental engineer and co-author on the paper. "We'd think, 'Six miles south of the border, that's a long way for wastewater to travel.'"

The study, published in the American Geophysical Union journal GeoHealth, found that thousands of beachgoers in the city, particularly in the summer, are likely contracting norovirus through untreated wastewater. Symptoms include nausea, vomiting, headache and diarrhea.

While some of those pathogens come through the Tijuana River — especially when rain and sewage spills overwhelm a diversion system that otherwise sucks flows out of the concrete channel — the lion's share of illness during summer months can be traced back to discharges from the San Antonio de los Buenos Wastewater Treatment Plant at Punta Bandera, according to the study.

"We saw with our own eyes: you pump in dye, and it's rapidly transported along the coast," said Falk Feddersen, the study's lead author and hydrodynamics expert at Scripps Institution of Oceanography. "They're putting in 35 million gallons a day of essentially raw sewage."


Baja California's top water officials have acknowledged that the more than 30-year-old plant is in disrepair and spewing untreated wastewater into the ocean. They've said a rehabilitation project is going out to bid this year.

However, U.S. officials aren't waiting for Mexico to replace the facility. The UCSD study was undertaken specifically to inform a major EPA initiative aimed at overhauling wastewater infrastructure along the border.

Congressional leaders secured $300 million in late 2019 to help address the issue, under the United States-Mexico-Canada trade agreement. Since then, EPA has workshopped several concepts for spending the funding, with the overall goal of reducing beach-closure days in San Diego's South Bay.

After reviewing the recent study, federal and local officials prioritized efforts to reroute much of the wastewater currently pumped to Punta Bandera. Instead, that sewage would be sent to the South Bay International Wastewater Treatment Plant along the border in San Diego. The facility uses a more modern treatment technology compared to the plant at Punta Bandera, which relies on a system of outdated lagoons.


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