We, Brian McNeece of the International Boundary and Water Commission (IBWC) Citizens Forum and Richard Gersberg, professor emeritus at San Diego State University, are writing to address significant inaccuracies in the Sept. 9 Op-Ed article, “Ocean Sewage Primer” by Leon Benham. While Mr. Benham (also a member of the IBWC Citizens Forum) raises concerns regarding coastal water pollution, his piece misrepresents several critical aspects of the current situation and efforts to manage sewage flow and water quality in our region. We believe it is important to correct the record to ensure the public has accurate information on this urgent issue.
The outfall is a 3.5 mile long pipe 90 feet underwater off the coast near the border. This pipe expels the combined effluents from the IBWC International Wastewater Treatment Plant and the City of San Diego South Bay Water Reclamation Plant into the ocean.
We all recognize that when untreated sewage in the Tijuana River flows across the border in sufficient quantities, the beaches become contaminated and get closed. We need to exercise all of our powers to ensure that Tijuana keeps its sewage collection system in good repair to pump excess flows out of the Tijuana River away from the border. Much progress is underway on that score.
But Mr. Benham makes inaccurate claims about the South Bay Ocean Outfall (SBOO) that are entirely counterproductive to our efforts to remediate the problem. He says:
“The second source of ocean water pollution is the 12-foot diameter sewage discharge pipe 90 feet deep below the ocean surface and 3 miles off the coast of Imperial Beach known as City of San Diego Ocean Outfall (SBOO). Scripps Institute studies from 1976 and water quality testing over the last 20 years conclusively prove this treated sewage water travels to the coastline of Imperial Beach and up to Coronado between 88% to 100% of the time. Monitoring water testing results show that this treated water flow from the SBOO is a major factor in beach closures.”
Not true at all. Mr. Benham mentions a source from 1976, but he doesn’t supply a link. He refers to currents that carry the effluent to shore but again cites no study. We have much better data now, and we know that the very complex current patterns along the South Bay beaches do not carry the effluents back to shore.
Indeed, every two years, the City of San Diego Ocean Monitoring Program compiles a study of the waters of the Point Loma Outfall and the South Bay Ocean Outfall. This is a well-respected program run by full-time environmental scientists. The Executive Summary in the most recent report for the years 2022-2023 concludes that the SBOO does not contribute to beach closures. Interested readers can access the full, nearly 800-page report by clicking here or by searching: Biennial Receiving Waters Monitoring and Assessment Report for the Point Loma and South Bay Ocean Outfalls.
Moreover, research done by Dr. Gersberg, an environmental microbiologist who has been studying this cross-border pollution problem for nearly 40 years, agrees with this assessment. In 2022, he co-authored a paper in the peer reviewed “Journal of Marine Pollution” evaluating the effect of the SBOO before and after the IBWC treatment plant was upgraded from primary to secondary treatment in 2011. His results were unequivocal: The SBOO is not polluting South Bay beaches. You can access Professor Gersberg’s article here:
The paper includes several maps that tell the story. Below are the most illustrative ones. They show surface waters—where people would be bathing or surfing during the rainy season between October and April. Map (a) shows integrated profiles of concentrations of enterococci (fecal) bacteria prior to 2011, when the IBWC plant treated wastewater only to primary levels. Map (b) is for water quality data between 2012 and 2019 after secondary treatment was added to the plant.
The colors yellow, orange, and red indicate worsening levels, with yellow meaning the water is unfit for human contact.
In map (a), the center of the offshore orange oval is the end of the SBOO. At that time there were levels of bacteria too high for human contact—in the region around the end of the outfall pipe. But in map (b), after secondary treatment was implemented, water levels around the end of the outfall are safe.
Moreover, there is no indication in either map that pollution reached the shore from the outfall (i.e. that there is a gradient of contamination from the outfall to the shore).
On the other hand, both maps show considerable pollution from the mouth of the Tijuana River and from the Punta Bandera Wastewater Treatment plant’s beach outfall (at San Antonio de los Buenos) ten miles south of the border in Mexico.
Therefore, Mr. Benham is not correct about the outfall causing beach closures. In fact, the outfall prevents beach closures because it treats Mexican sewage water that could otherwise end up in the Tijuana River.
Recent agreements with Mexico call for the IBWC plant (on our side of the border) to be doubled in capacity. Although money is budgeted for this expansion, Mr. Benham opposes it on grounds that the South Bay Ocean Outfall pollutes the beaches. This is not the case.
Brian McNeece is the co-chair of the International Boundary and Water Commission Citizens Forum and Richard Gersberg is a Professor Emeritus at San Diego State University.
