An Investigation Into the Sources on Both Sides of the Border — and Whether San Diego’s Own Infrastructure Shares the Blame
The Navarro Report | San Diego
On September 1, San Diego County supervisors voted to design and build a local treatment system that could ultimately cost close to a billion dollars, funded in part by local tax revenue, to capture and clean contaminated water from the Tijuana River before it reaches South Bay communities. The vote followed more than 1,300 consecutive days of beach closures, documented respiratory illness linked to airborne hydrogen sulfide, and repeated disruption to Navy SEAL training exercises in Coronado. It is a genuinely significant local commitment. But a nearly billion-dollar county investment raises an essential question that deserves more scrutiny than it has received: where, precisely, is this pollution coming from, and is San Diego’s own infrastructure part of the problem it is now spending heavily to solve?
The evidence, drawn from federal, state, and independent engineering assessments, points overwhelmingly to origins on the Mexican side of the border — but with a genuine, if smaller, contributing failure on the American side that complicates any simple narrative of blame.
The largest and most consequential source is Tijuana’s own wastewater infrastructure, collapsing under decades of explosive population growth. Tijuana’s population has roughly doubled since the 1990s and is projected to grow from about 1.8 million in 2020 to 2.4 million by 2050, pushing wastewater generation from roughly 67 million gallons a day toward 92 million — a volume exceeding the combined treatment capacity of every facility built to handle it. The city’s sewage flows through two main pathways: a portion is diverted to the South Bay International Wastewater Treatment Plant on the U.S. side, and the remainder is conveyed by pump stations and pipelines six miles south of the border to the San Antonio de los Buenos plant at Punta Bandera, which discharges into the Pacific well south of San Diego.
For years, the Punta Bandera facility barely functioned. A 2022 federal environmental review found the plant’s condition so degraded it did not meaningfully improve the water quality of what it discharged, and it was, in effect, dumping close to 40 million gallons of raw sewage daily either directly onto Tijuana beaches or into the Pacific, where prevailing currents routinely pushed contamination north into Imperial Beach and Coronado. Mexico completed a rehabilitation of the plant last year, but even at full operation it can treat only about 18 million gallons a day — roughly half of what actually needs processing — meaning a substantial volume of raw sewage continues reaching the ocean regardless.
Compounding that structural shortfall is a pattern of acute infrastructure failures on the Mexican side that have repeatedly overwhelmed the system in recent years. In June 2026, a ten-mile pipeline in Tijuana known as the Parallel Gravity Line collapsed, sending flows in the Tijuana River spiking from roughly 10 million gallons to 34 million gallons in a single weekend as untreated sewage bypassed treatment entirely. A separate rupture in March 2025 sent millions of additional gallons into the valley after days of rain strained what engineers have consistently described as a dilapidated system. Investigators tracing a 2024 surge in odor complaints identified the failure point as a specific pumping station, the Punto de Bombeo de Control Integral Lomas de Agua, whose malfunction went undetected for weeks before flows were redirected. These are not one-time accidents; they are the predictable, recurring consequence of a collection system that has not received adequate investment relative to the volume it must handle.
But it would be inaccurate, and journalistically irresponsible, to place the entirety of the blame south of the border. The South Bay International Wastewater Treatment Plant — the facility on U.S. soil, operated by the U.S. section of the International Boundary and Water Commission — has itself been a documented and substantial point of failure. Between 2010 and 2021, the plant received only about $4 million in maintenance funding even as its equipment steadily deteriorated, and a 2022 federal assessment found 36 percent of its physical assets in critical condition. Tropical Storm Hilary in August 2023 exposed the consequences of that deferred maintenance directly, causing an estimated $8 million in damage and knocking the aging primary treatment system offline for extended periods. California Representative Scott Peters and members of the state’s congressional delegation formally demanded an accounting from the State Department, asking pointedly how a facility expanded as recently as 2002 had been allowed to fall into such disrepair, and who inside the U.S. government bore responsibility.
Congress has since appropriated more than $600 million to rebuild and expand the South Bay plant’s capacity from 25 million gallons a day toward 50 million, a project now substantially underway. That is a genuine acknowledgment that U.S.-side deferred maintenance materially worsened the crisis, independent of anything happening in Tijuana. It is a meaningfully different failure than Mexico’s — an underfunded, poorly maintained facility rather than an absent one — but it is a failure of American governance nonetheless, and it means the pollution reaching San Diego’s beaches and air has never been solely a story of what Mexico failed to build.
Even a fully repaired and expanded South Bay plant, however, will not resolve the underlying imbalance. Both the rebuilt American facility and Mexico’s Punta Bandera plant, running at full capacity, will still fall well short of what a metropolis the size of Tijuana actually generates. Kenia Zamarripa, a regional infrastructure analyst quoted in reporting on the crisis, put the core problem plainly: investment upstream in Tijuana has never been aligned with what the scale of the crisis actually requires, and the border region has consistently reacted only once a failure becomes impossible to ignore, rather than funding the sustained maintenance that would prevent one.
That is the essential context missing from celebratory coverage of the county’s new billion-dollar commitment. San Diego’s plan to build local treatment capacity is a reasonable, even necessary, response to a crisis the region cannot simply wait out. But it treats a downstream symptom of a problem whose primary source remains Tijuana’s undersized and chronically underfunded wastewater system, while leaving unanswered the harder, binational question of why decades of agreements — including a 2022 accord committing a combined $474 million to infrastructure fixes — have consistently underdelivered relative to the pollution’s actual scale. Until that upstream investment gap closes on both sides of the border, San Diego taxpayers will likely find themselves financing an increasingly expensive game of catch-up against a problem that originates largely, though not entirely, beyond the reach of any single county’s budget.
Human-Directed AI Journalism — This piece was researched, directed, and edited by Jose E. Navarro, with AI-assisted drafting and fact-compilation support.