Tijuana’s water utility says the city is currently sending no untreated wastewater across the U.S. border, a claim that comes after months of acknowledged cross-border sewage flows and growing pressure from American advocacy groups to escalate the issue into trade negotiations. CESPT, Tijuana’s municipal water and sewer authority, says a fourth pump at the CILA Pumping Station is now fully operational, bringing the system’s total capacity to between 1,400 and 1,450 liters per second. But the history of this binational sewage crisis, stretching back decades, suggests that “zero flow” snapshots can be fragile.
Decades of Cross-Border Sewage and Two Bilateral Agreements
The Tijuana wastewater US border problem did not start recently. Both governments have been managing transboundary sewage under the 1944 Treaty on International Water Distribution, which obligates Mexico and the United States to resolve border sanitation issues through CILA, the International Boundary and Water Commission. For years, that framework proved insufficient. Untreated flows from Tijuana’s overtaxed sewer system contaminated beaches in Imperial Beach, California, forced closures at Coronado and Silver Strand, and degraded the Tijuana River Valley on the U.S. side.
In 2022, both countries signed Acta 328 in El Paso, Texas. That agreement authorized infrastructure projects to modernize Tijuana’s treatment and pumping systems along the border corridor. It also set terms for Mexico to send a controlled volume of wastewater to the South Bay International Wastewater Treatment Plant (known as PITAR) on the U.S. side, currently receiving roughly 1,100 liters per second under normal operations.
Then in December 2025, President Donald Trump announced the signing of Acta 333, calling it a “historic agreement” to permanently resolve the Tijuana River sewage crisis. Acta 333 goes further than its predecessor. It commits both countries to expanded treatment capacity, infrastructure investment, reinforced monitoring, and, for the first time, planning that accounts for Tijuana’s rapid demographic growth. Previous agreements had not factored in population projections for a city that now exceeds 2 million residents and continues to grow.
In July 2024, Mexico’s environment secretary Alicia Bárcena Ibarra and CONAGUA director Efraín Morales López (CONAGUA is Mexico’s national water commission) announced a joint $693 million investment to address the crisis. That funding covers upgrades on both sides of the border, including expansion of the PITAR plant to handle 2,200 liters per second, nearly double its previous capacity.
Two Outages in Six Months Preceded the “Zero Flow” Claim
CESPT’s technical director José Díaz Verdugo acknowledged that cross-border flows did occur between November 2024 and March 2025. During that five-month window, the JB.1 gate on the U.S. side was taken offline for construction. U.S. authorities requested that Mexico reroute flows across the border while the work proceeded. Díaz Verdugo described this as a planned, coordinated arrangement, not an emergency spill.
A separate incident was less orderly. Roughly six weeks before Díaz Verdugo’s July 21 statement, the Costa Coronado pumping plant in Playas de Tijuana suffered a failure that required a complete four-to-five-day shutdown for repairs. During that outage, untreated wastewater had nowhere to go but toward the coast and the border. CONAGUA completed a parallel two-kilometer pipeline to restore capacity, and the fourth CILA pump came online shortly after.
These outages illustrate why even brief system failures carry outsized consequences. When a single pumping station goes down in Tijuana, there is no meaningful buffer. Sewage reaches the ocean within hours, flowing north along the coast to Imperial Beach and the Tijuana River Estuary. Beach closures in Imperial Beach have exceeded 1,000 cumulative days over the past decade, according to data from the San Diego County Department of Environmental Health.
Wildcoast Pushes for USMCA Review of Border Sewage
Serge Dedina, executive director of the conservation group Wildcoast and former mayor of Imperial Beach, has called for the cross-border sewage issue to be reviewed under the USMCA, the trade agreement that replaced NAFTA in 2020. The USMCA includes environmental provisions and a dispute resolution mechanism that could, in theory, compel enforcement actions if either country fails to meet environmental commitments.
CESPT’s response has been to point to Acta 328 compliance. Díaz Verdugo emphasized that Mexico is meeting its obligations under the bilateral framework, including modernization of the San Antonio treatment plant (rehabilitated to 800 liters per second capacity), the Arturo Herrera plant (currently treating 250 of its 450 liters per second capacity), and the La Morita plant, which is still under rehabilitation with a design capacity of 250 liters per second plus a future 127-liter module.
The total treatment capacity across Tijuana’s network, once all rehabilitations are complete, would still need to keep pace with a sewer system that serves one of Mexico’s fastest-growing metropolitan areas. Every new colonia connected to the grid adds volume. Every rainstorm pushes stormwater into sewer lines not designed to handle it.
Acta 333’s implementation timeline has not been publicly detailed. The next scheduled bilateral review under the CILA framework is expected before the end of 2025. This story was first reported by La Jornada Baja California.