The Ministry of Environment and Natural Resources of Mexico (Semarnat) and the United States Environmental Protection Agency (EPA) have signed a Memorandum of Understanding (MoU) aimed at addressing the long-standing issue of untreated wastewater in the Tijuana–San Diego border region.
The agreement was formalized during the 32nd Session of the Council of the Commission for Environmental Cooperation (CEC), held in Mexico City. It establishes a framework for bilateral cooperation to advance infrastructure projects designed to reduce pollution impacting both countries.
Key provisions of the MoU include the proposed expansion of the San Antonio de los Buenos Wastewater Treatment Plant in Tijuana, which has faced capacity challenges due to population growth and increased industrial activity. The technical and financial feasibility of the project will be assessed by the International Boundary and Water Commission (IBWC), the binational agency responsible for managing shared water resources along the border.
The agreement also calls for joint oversight of ongoing improvements at the South Bay International Wastewater Treatment Plant in California. Additionally, the two countries will implement a coordinated communications strategy to provide regular public updates on project developments.
Mexico is expected to begin construction in 2025 on a system to divert 10 tributaries currently discharging into the Tijuana River. Further infrastructure rehabilitation—such as pipelines, gravity-fed lines, collectors, and treatment facilities—is planned for 2026 and 2027.
Both governments expressed their intent to finalize a new agreement by the end of 2025. This would outline specific steps for engineering studies, construction, maintenance, and the expansion of wastewater infrastructure. Oversight would be carried out by existing or newly formed binational technical working groups under the guidance of the IBWC.
These coordinated efforts are part of a broader initiative to improve public health, environmental conditions, and water quality in communities along the U.S.–Mexico border.
