On July 24, 2025, the U.S. Environmental Protection Agency (EPA) Administrator Lee Zeldin and Mexico’s Secretary of the Environment and Natural Resources (SEMARNAT), Alicia Bárcena Ibarra, signed a ”Memorandum of Understanding” (MOU) to clean up sewage pollution in the Tijuana River, which has long affected communities on both sides of the border.
The signing took place during the Council of the Commission for Environmental Cooperation (CEC) in Montreal, Canada. The agreement follows months of discussions following Administrator Zeldin’s April 2025 visit to San Diego, California, during which he met with local officials and community members affected by the pollution.
A river in crisis
The Tijuana River, stretching 120 miles from Mexico into Southern California before flowing into the Pacific Ocean, has for decades carried billions of gallons of untreated sewage and industrial waste across the border.
This contamination has led to repeated beach closures, health problems, and environmental damage throughout the region.
According to The New York Times, San Diego County residents have suffered severely. A 2025 report by the Office of the Naval Inspector General found that more than 1,100 Navy recruits developed gastrointestinal illnesses after training in polluted southern San Diego waters.
The CDC also reported that nearly half of the 40,900 households in the region have experienced health issues such as rashes and respiratory problems likely linked to sewage exposure.
What’s causing the sewage contamination?
Multiple factors contribute to the crisis, including Tijuana’s aging wastewater infrastructure, rapid population growth, industrial expansion, and urbanization. Since 2018, San Diego County has received more than 100 billion gallons of raw sewage, according to CBS News.
Environmental advocates, including the San Diego Coastkeeper, note that the crisis stems from outdated infrastructure, poor maintenance, and limited funding.
Many of Tijuana’s sewer lines and treatment facilities were never designed to handle today’s wastewater volume, resulting in frequent overflows.
Unpredictable weather patterns, such as prolonged droughts and intense “atmospheric river” storms, worsen the situation by overwhelming the system and allowing untreated sewage to spill directly into rivers and the ocean.
Experts also point to regulatory and management failures, emphasizing the need for stronger binational coordination and governance reform to ensure effective long-term solutions.
The US-Mexico MOU: A path forward
The MOU between the United States and Mexico aims to resolve decades-long transboundary wastewater management issues, improve public health, and restore the environmental quality of the Tijuana River basin.
The agreement supports the accelerated implementation of Minute 328 projects. It sets a goal to develop a new Minute agreement by December 31, 2025, expanding the plan to address future population and infrastructure needs.
Key commitments include:
- The United States will expand the South Bay International Wastewater Treatment Plant, doubling its capacity from 25 to 50 million gallons per day by December 2027, with an interim expansion to begin this summer.
- Mexico will complete its previously pledged sewage infrastructure improvements under Minute 328 by the end of 2027 or earlier, releasing $93 million in committed but previously unallocated funds.
EPA Administrator Lee Zeldin hailed the MOU as a potential “permanent 100% solution” to the sewage crisis.
However, environmental experts warn that continued oversight and accountability are essential to ensure both nations fulfill their commitments and prevent history from repeating itself.
Source:
Walton, B. (2025, July 28). Federal Water Tap, July 28, 2025: U.S., Mexico Sign Tijuana River Sewage Pollution Deal. Circle of Blue. Retrieved from https://www.circleofblue.org/newsletter/federal-water-tap-july-28-2025-u-s-mexico-sign-tijuana-river-sewage-pollution-deal/
United States and Mexico Reach Agreement to Permanently and Urgently End Decades-Long Tijuana River Sewage Crisis. (2025, July 24). US EPA. Retrieved from https://www.epa.gov/newsreleases/united-states-and-mexico-reach-agreement-permanently-and-urgently-end-decades-long
ICYMI: Wall to Wall Coverage Highlighting the Trump Administration’s Agreement with Mexico for 100% Solution to Decades-Long Tijuana River Sewage Crisis. (2025, July 28). US EPA. Retrieved from https://www.epa.gov/newsreleases/icymi-wall-wall-coverage-highlighting-trump-administrations-agreement-mexico-100
Musegaas, P. (2024, May 2). Understanding the Tijuana River Sewage Crisis – An Overview of Causes and Consequences. San Diego Coastkeeper. Retrieved from https://www.sdcoastkeeper.org/blog/tijuana-river-sewage-crisis-causes-consequences/
Friedman, L. (2025, July 25). U.S. and Mexico Sign Deal to Stop Sewage Release Into Tijuana River. The New York Times. Retrieved from https://www.nytimes.com/2025/07/25/climate/tijuana-river-sewage-agreement.html
U.S., Mexico agree on steps to solve decades-old Tijuana River sewage crisis. (2025, July 25). CBS News. Retrieved from https://www.cbsnews.com/news/us-mexico-agree-on-steps-to-cut-flow-of-tijuana-river-sewage-across-border/
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