US, Mexico Sign Agreement to Fully Halt Tijuana River Pollution

On Dec. 15, through Minute 333 of the International Boundary and Water Commission (IBWC), the United States and Mexico formalized a binational collaboration framework aimed at stopping 100% of the pollution of the Tijuana River in San Diego.

Through this agreement, a set of technical, financial, and governance actions is established to carry out concrete sanitation projects in Tijuana. These include new wastewater treatment and sediment control infrastructure, which will have a positive impact on public health, the environment, and beaches on both sides of the border.

Lee Zeldin, Administrator, US Environmental Protection Agency (EPA), emphasized that the minute was negotiated and signed in record time, within less than five months, beating the Dec. 31 deadline established in the Memorandum of Understanding (MOU) signed in July by Zeldin and Alicia Bárcena, Mexico’s Minister of Environment and Natural Resources (SEMARNAT).

“This year, significant progress has been made toward achieving a 100% solution to the Tijuana River wastewater crisis, but all of it would have been in vain if we did not take the appropriate steps to account for the inevitable population growth of Tijuana and its surrounding areas,” Zeldin said.

In this regard, the minute states that the Mexican government will develop a master water infrastructure plan for Tijuana within six months. This plan will be supported by comprehensive technical studies designed to anticipate urban growth and prevent future crises.

In addition, a binational working group will be established within three months to assess the feasibility of constructing an ocean outfall system for the San Antonio de los Buenos Wastewater Treatment Plant (SABWWTP), along with an evaluation of the technical and financial feasibility of expanding the SABWWTP from 18.26MGD to 43.37MGD.

Furthermore, according to the minute, a sedimentation basin will be built at Smuggler’s Gulch, located near the international border, before the 2026–2027 rainy season. The Tecolote–La Gloria Wastewater Treatment Plant, with a capacity of 3MGD, will also be constructed before December 2028.

Both countries will assume shared financial responsibility, through the North American Development Bank (NADB), to ensure the operation and maintenance of the infrastructure and prevent its deterioration over time. This new framework reaffirms that the solution to border sanitation does not rest on a single country, but rather represents a shared responsibility.

Ron Johnson, US Ambassador to Mexico, noted that Minute 333 represents a historic step in the shared commitment to protecting the health and environment of communities on both sides of the border. “This agreement demonstrates what we can achieve when we work together with urgency, transparency, and mutual respect. I am proud to stand with our Mexican partners as we move toward a cleaner, safer, and more prosperous future for the Tijuana–San Diego region,” he said.

The Tijuana River wastewater crisis dates back decades, when untreated sewage flowed from Mexico into Southern California. For years, this has led to beach closures due to foul odors, degradation of the Tijuana River Valley, and illness among people on both sides of the border. Specialists warn that chemicals from the polluted river are carried into the air, where they can cause headaches, nausea, burning eyes, and other symptoms in nearby neighborhoods.