To address the decades-long San Diego sewage crisis that has contaminated the Tijuana River, the United States and Mexico signed a Memorandum of Understanding (MOU) in Mexico City on July 24, 2025. The agreement, signed by Mexican Environment Minister Alicia Barcena and U.S. Environmental Protection Agency (EPA) Administrator Michael Regan, aims to provide a long-term solution to the cross-border flow of untreated sewage that impacts ecosystems, local economies, and public health.

Source: X-Mexican Environment Secretary Alicia Bárcena and EPA Administrator Lee Zeldin in Mexico City on July 24, 2025. 

A Longstanding Environmental Crisis

Every day, millions of gallons of raw and treated sewage are transported from Tijuana’s overburdened infrastructure into the Pacific Ocean near Imperial Beach via the Tijuana River, which runs 120 miles from Mexico to Southern California. Since 2018, more than 100 billion gallons of trash and industrial chemical-laden sewage have contaminated San Diego’s seas, causing beach closures for more than 1,000 days in a row and health problems for Border Patrol agents, Navy SEALs, and locals. Amidst more general U.S.-Mexico problems like immigration and drug trafficking, the crisis has been a recurring source of stress, made worse by Tijuana’s aged infrastructure and fast population expansion.

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Bilateral Commitments for Change

Critical infrastructure projects are accelerated by the MOU, which builds upon Minute No. 328 of the 2022 International Boundary and Water Commission (IBWC). Mexico would spend $93 million to accelerate improvements, such as rebuilding the Parallel Gravity Line and diverting 10 million gallons of treated sewage per day from coastal areas by December 2025. By 2027, some projects will be completed four years ahead of schedule.

By August 2025, the South Bay International Wastewater Treatment Plant in the United States is expected to have increased its daily capacity from 25 to 35 million gallons. The San Antonio de los Buenos plant, which was recently restored after years of releasing 23 million gallons of sewage into the ocean every day, will also have its capacity doubled by Mexico.

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Community and Environmental Impact

Imperial Beach, where “Keep Out of Water” posters have discouraged visitors and surfers, has found hope thanks to the deal. California is distributing air purifiers after citizens were ill due to airborne contaminants from evaporated sewage foam. Local officials, including Jim Desmond, Chair of the San Diego County Board of Supervisors, acknowledged the praise for the agreement but still expressed the need for ongoing action on the river, as it remains the primary source of pollution.

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Moving Toward a Serious Solution

The MOU only addresses Tijuana’s growth and maintenance costs in pursuing a “100% solution.” Mexican President Claudia Sheinbaum has hailed the agreement as a sign of binational progress. Local proponents, such as Supervisor Paloma Aguirre, have called for a more straightforward agreement regarding the river and its pollution to avoid further complications, especially given the over $653 million already spent since 2020 and the previous delays associated with the San Diego sewage crisis. The long-term goals will also be finalized with a new Minute by December 2025.

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