EPA: U.S., Mexico to Address Tijuana River Chemical Pollution
The U.S. Environmental Protection Agency announced Dec. 15 that the United States and Mexico have signed a new agreement, known as Minute 333, outlining additional infrastructure, monitoring and planning actions intended to reduce untreated wastewater flows from the Tijuana River into Southern California.
According to the agency, the agreement was signed by the U.S. and Mexican sections of the International Boundary and Water Commission and builds on a July memorandum of understanding between the two countries. The latest iteration includes provisions to account for future population growth in the Tijuana region and does not obligate additional U.S. funding for Mexico-side projects, the EPA said.
The Tijuana River has carried untreated sewage, industrial waste and stormwater into California for decades, contributing to repeated beach closures, environmental degradation in the Tijuana River Valley and health concerns in nearby communities, according to federal and state agencies.
Minute 333 outlines a series of actions, including development of a water infrastructure master plan for Tijuana within six months, creation of a binational working group to evaluate wastewater treatment expansion options and establishment of an operations and maintenance account through the North American Development Bank to support long-term system reliability.
Planned infrastructure actions include construction of a sediment basin in Matadero Canyon before the 2026–2027 rainy season and development of the Tecolote–La Gloria Wastewater Treatment Plant, designed for a capacity of 3 million gallons per day by December 2028, according to the agreement. The working group will also assess the feasibility of expanding the San Antonio de los Buenos Wastewater Treatment Plant and adding an ocean outfall.
The latest agreement follows growing scrutiny of cross-border pollution impacts in the region. As previously reported by Chemical Processing, a recent peer-reviewed study documented elevated concentrations of hydrogen sulfide and other airborne pollutants linked to contaminated river flows, with measured levels far exceeding California air quality standards in nearby communities. Researchers concluded that sustained monitoring and coordinated infrastructure improvements on both sides of the border are necessary to reduce public health risks.
According to the EPA, implementation timelines and progress updates under Minute 333 will be reviewed regularly by U.S. and Mexican authorities as projects advance.