After years of inadequate maintenance, population growth and governmental delay, the United States and Mexico are finally making substantial investments in combatting the sewage from Tijuana.
The South Bay International Wastewater Treatment Plant was repaired and expanded from 25 million to 35 million gallons per day.
Mexico restored the San Antonio de los Buenos Wastewater Treatment Plant, which had discharged untreated sewage.
Repairs and renewed operation of Tijuana’s PB-CILA pumping and diversion system have reportedly substantially reduced dry-weather wastewater entering the United States.
A trash boom in the river intercepted approximately 1,500 tons of debris during the 2025–26 wet season.
As a result of these investments, more sewage is being collected and treated, the system can better withstand some failures, and an extraordinary amount of trash has been intercepted. But they have not yet delivered clean beaches and air, and not every project identified as part of the long-term solution has been funded. Those distinctions should guide the county as it considers an additional treatment project.
More work is scheduled through 2027, and the most important elements of that program have substantial funding commitments including over $650 million for the repair and expansion of the South Bay plant to reach 50 million gallons per day of average treatment capacity and 75 million gallons per day of peak capacity.
Mexico has committed approximately $93 million for work on its side of the border, and the US released previously appropriated funds for projects in Mexico.
The funded 2027 program is estimated to prevent as much as 90% of the untreated wastewater now reaching coastal waters.
But even the 2027 program will not treat an unlimited volume of water and constructed capacity is not the only issue. The facilities must be staffed, powered, monitored, repaired, and eventually replaced, which has been part of the issue and is where an important funding gap remains.
The post-2027 program is even less financially certain.
Against this background, the San Diego County Board of Supervisors approved the Tijuana River Capture and Cleanup Initiative. The county will spend $1.8 million on an 18-month engineering and alternatives analysis. This is the only part of the new county initiative presently funded.
The study will examine a U.S.-side system capable of intercepting polluted river water after it crosses the border and directing it to treatment before it reaches downstream communities and beaches.
Such a system could fill a genuine gap.
The South Bay plant principally treats wastewater captured and conveyed to it. It does not intercept all contamination already flowing through the river’s main channel. A county project might capture residual dry-weather sewage, treat the most polluted portion of initial storm runoff, provide backup when Mexican infrastructure fails and give San Diego greater control over protecting its communities.
For those reasons, the engineering analysis deserves support.
Support for a study, however, should not be mistaken for approval of a new treatment plant, which the EPA previously evaluated but placed behind repair and expansion of the South Bay plant, because of its cost. A new diversion, conveyance and treatment system could cost hundreds of millions of dollars or more and take years to design, permit, and build.
The county proposal does not identify a funding source. Possible sources include a county sales tax, bonds supported by local revenue, state funds, federal appropriations, or a combination of them. However, each potential source presents risks.
The county could also assume responsibility for operating and maintaining a major wastewater facility. That obligation would continue for decades and could compete for funding with other county services. Building another plant before securing permanent operating revenue would risk repeating past mistakes.
Most importantly, the county does not know how much pollution will remain after the funded projects become operational in 2027. Designing a plant around current conditions could produce an unnecessarily large and costly facility. Conversely, if post-2027 monitoring shows continuing dry-weather sewage, hazardous industrial contamination and frequent beach closures, a diversion system could become essential.
Therefore, the authorized engineering study should consider the present program and the status of its funding and address all options including additional collection and storage, stronger industrial source controls, expansion of existing facilities, and targeted treatment of residual dry-weather or first-flush storm flows.
Before any commitment, the county should require at least one full wet and dry season of reliable performance data after the 2027 projects are operating. It should identify the characteristics of the remaining pollution, determine the required treatment, establish who would own and operate the facility, and secure a funding source that does not undermine other essential services.
San Diego County should prepare for the possibility of another major project, but it should not assume that conclusion before the presently funded program has been completed and evaluated.
Editor’s note: John Tato graduated from Coronado High School in 1965. He retired from the U.S. Department of State in 2005.
