Tijuana Sewage Crisis Deepens US-Mexico Tensions

The ongoing crisis of untreated sewage flowing from Tijuana into the Pacific Ocean is intensifying diplomatic and political tensions between Mexico and the United States. High-level talks between Mexican and US environmental officials aim to find solutions to the transboundary pollution problem.

Alicia Bárcena, Mexico’s Minister of Environment and Natural Resources (SEMARNAT), will meet this week in San Diego, California, with Lee Zeldin, Administrator, US Environmental Protection Agency (EPA), to address the persistent discharge of wastewater from Tijuana into the Pacific Ocean. Zeldin has previously taken a firm stance on the issue, publicly pressuring Mexico to take responsibility and invest in infrastructure improvements. “Mexico must fully honor its commitment to control their country’s growing pollution and sewage impacting the United States. The time for excuses, delays, or exceptions is over,” Zeldin said in a statement earlier this year.

This meeting comes in the wake of recent accusations by Republican Senator Tim Sheehy, who claimed that Mexico discharges approximately 19 million L of contaminated water into the Pacific Ocean daily. According to Sheehy, this pollution endangers the health of thousands of Americans every year.

In response, President Claudia Sheinbaum emphasized that Mexico is close to fully operating a new wastewater treatment plant in Tijuana, which is expected to significantly reduce pollution in the Pacific. She also pointed out that the United States has yet to fulfill part of a bilateral agreement signed under former President Joe Biden, highlighting the shared responsibility between the two countries in addressing this environmental crisis.

Sheinbaum linked the senator’s remarks to the US political calendar, where several states are preparing for gubernatorial elections. “They might be campaigning, but Mexico should not become a tool for any US politician’s campaign,” said the Mexican president.

Despite the current diplomatic back-and-forth, the problem is not new. Since 2018, more than 100 billion gallons of raw sewage and solid waste have flowed into San Diego from Tijuana due to an overwhelmed and underfunded wastewater system, exacerbated by population growth. The resulting contamination has led to the repeated closure of San Diego-area beaches and caused illness among Navy SEALs and local residents, as reported by Politico.

One of the most heavily impacted areas has been Imperial Beach, where the shoreline remained closed for over 1,000 consecutive days, from December 8, 2021, until September 2024, before partial reopening was allowed when water quality met state standards. Amid this scenario, on April 17, 2025, the local council passed a resolution outlining several priorities to address the ongoing public health crisis. While the resolution is largely symbolic, since Imperial Beach lacks jurisdiction over the proposed measures, it aims to send a message to the federal government and state and local partners.

The resolution calls for the International Boundary and Water Commission (IBWC), a binational body that manages water-related conflicts between the two countries,  to accelerate the design and construction of the Tijuana River Diversion Project, which would capture and treat cross-border flows. It also urges the IBWC to expedite the implementation of a permanent trash capture system for the main Tijuana River channel.

Moreover, the resolution strongly opposes the construction of a 50-million-gallon-per-day desalination plant in Playas de Rosarito, part of Mexico’s National Water Plan, unless Mexico completes the wastewater recycling projects outlined in IBWC Treaty Minute 328 and can demonstrate sufficient treatment capacity and funding for any new potable water deliveries.

Participants also urged US Congress to consider enacting enforcement mechanisms to regulate or restrict the export of potable water to Tijuana during public health emergencies declared by San Diego County. According to the resolution, Tijuana depends on the United States for 90% of its water imports. Another proposed measure includes limiting commercial border crossings at US ports of entry during such declared health emergencies. However, some community leaders expressed concern over the potential economic consequences of such actions. “Limiting cross-border activity even temporarily would have serious repercussions for our region,” said Marcy Weaver, CEO, Chula Vista Chamber of Commerce.

Amid the growing controversy, the Trump administration on Monday demanded the immediate resignation of María-Elena Giner, Lead Commissioner, IBWC. Giner, appointed by former President Biden in 2021, defended her tenure, citing significant progress, including a US$250 million investment to improve wastewater treatment infrastructure near the San Diego border. Chad McIntosh, currently the EPA’s deputy administrator, has been named Giner’s replacement.

The transboundary pollution issue falls under the framework of the 1944 Water Treaty, a binational agreement that regulates the use of shared rivers along the border. Under this treaty, Mexico is required to deliver 2,158 million m3 of water to the United States every five years. However, prolonged drought conditions have left Mexico more than three and a half years behind schedule, having fulfilled only 28% of its current delivery obligation.

Using this water debt as leverage, President Trump threatened to impose new tariffs and sanctions on Mexico unless it fulfills its treaty obligations, arguing that thousands of South Texas farmers rely on that resource. President Sheinbaum, on her part, noted that during Wednesday’s upcoming meeting, technical teams from both countries will work to determine how much water remains available in the Río Bravo (Rio Grande) to supply Texas.