The U.S. and Mexico on Thursday took collaborative steps toward curbing a long-standing, cross-border environmental crisis: the unfettered sewage flow from Tijuana into Southern California.
Environmental Protection Agency (EPA) Administrator Lee Zeldin and his Mexican counterpart Alicia Bárcena Ibarra signed a memorandum of understanding (MOU) that addressed the “environmental, public health and national security consequences” of transboundary wastewater contamination.
The officials expressed their intentions to “permanently stop untreated wastewater from polluting coastal communities,” while reaffirming previous commitments and endorsing new strategic projects.
“What the residents of Southern California need and deserve, what they’ve been waiting for, for too long, isn’t just a solution that is a Band-Aid for that moment, but a permanent, 100 percent solution,” Zeldin told reporters from Mexico City prior to the signing.
The crisis at the heart of the MOU involves the passage of polluted wastewater from Mexico into southern San Diego County via ocean plumes and the Tijuana River.
This fetid flow — rife with both pathogens and toxic chemicals — stems from inadequate treatment near Tijuana. For years, these circumstances have closed down beaches and sickened Navy SEALs.
Following demands from California Democrats in March that the EPA chief visit the region, Zeldin did so in April — and demanded that Mexico put a stop to the situation.
Recalling his previous visit to reporters on Thursday, Zeldin described smelling “that foul smell that so many residents of Southern California have been complaining about for so long.”
He said that upon leaving the area, there was a “burning desire at the Trump administration to dedicate a tremendous amount of energy, of time, to make sure that the residents of Southern California would be receiving this good news as quickly as possible.”
The administration, he explained, prioritized three major milestones — all of which gained Mexico’s approval in Thursday’s MOU.
The first, he explained, revolved around Mexico’s outstanding commitment to allocate $93 million toward completing water infrastructure projects specified in a previous treaty, called Minute 328.
In the MOU, Mexico expressed its intention to spend $46 million in 2026 and $47 million in 2027 on these initiatives, which include major rehabilitations of wastewater treatment channels, pumps, backup power supplies and other equipment.
The second key pillar, according to Zeldin, focused on expediting the timelines for getting projects done faster. As such, the MOU contains construction schedules for calendar year 2026 and 2027, adhering to a “project priority schedule.”
The third goal of the MOU, Zeldin said, was the stipulation that the U.S. and Mexico would seek to engage in a new agreement — a new “minute” — on new initiatives necessary ”to get over the finish line.”
The parties, according to the MOU, intend to secure that minute by Dec. 31 and execute its actions immediately, through existing or new binational workgroups.
“This isn’t just an agreement for 2025,” Zeldin said. “It was a product of a conversation of where do we need to be in 2030 and 2035, and beyond.”
The MOU does, however, include some immediate action for 2025, such as Mexico’s pledge to divert 10 million gallons per day of treated sewage from the Arturo Herrera and La Marita wastewater treatment plants to a site further upstream of the Rodríguez Dam — at an internal cost of $13.3 million.
Mexico also agreed to rehabilitate a wastewater collector known as the “Parallel Gravity Line” for about $8.42 million.
The EPA chief also emphasized President Trump’s personal passion about solving this crisis, noting that “none of this would have been possible” without his participation.
Zeldin recalled that after Trump heard a story about the environmental and national security impacts on Navy SEALs, the president concluded “that he wanted to get this done.”
In response to the MOU announcement, Tom Kiernan, president and CEO of American Rivers, described the partnership in a statement as “a massive step forward for the Tijuana River.”
“We appreciate the Trump administration’s dedicated effort to restore this river back to the vibrant resource it once was,” Kiernan added.
Kristan Culbert, the organization’s associate director of California river conservation, added that “communities along the Tijuana River have suffered this public health crisis for far too long.”
“We are hopeful and optimistic that the Trump administration will be the catalyst for a major turnaround for this river,” Culbert said.
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