US, Mexico Sign Minute 333 to Tackle Tijuana River Pollution

The US Environmental Protection Agency (EPA) announced the signing of Minute 333, a new bilateral agreement between the United States and Mexico designed to address the sewage contamination affecting the Tijuana River. The agreement, reached by the US and Mexican Sections of the International Boundary and Water Commission (IBWC), introduces additional actions intended to support a permanent resolution to the issue.

The Tijuana River has suffered from untreated wastewater crossing into Southern California for decades, causing repeated beach closures, environmental damage in the Tijuana River Valley, economic losses, and public health concerns on both sides of the border. 

According to US officials, Minute 333 was negotiated within a relatively short timeframe and builds directly on a Memorandum of Understanding (MOU) signed in July between EPA Administrator Lee Zeldin and Mexico’s Minister of the Environment and Natural Resources, Alicia Bárcena. The agreement incorporates the long-term infrastructure measures outlined in Section 4 of the MOU, which address regional population growth. 

“Through close partnership and sustained effort, the United States and Mexico are delivering real solutions to a decades-old challenge. This agreement demonstrates what we can achieve when we work together with urgency, transparency, and mutual respect. I am proud to stand with our Mexican partners as we move toward a cleaner, safer, and more prosperous future for the Tijuana-San Diego region,” said US Ambassador to Mexico Ron Johnson.

Key Actions under Minute 333

Minute 333 expands on prior agreements, including Minute 328 signed in 2022, by incorporating future population considerations, additional infrastructure projects in Mexico, enhanced operational requirements, technical data sharing, and communication mechanisms with authorities and the public. Among the agreed actions are:

• Creation of an operations and maintenance account at the North American Development Bank

• Development of a Tijuana water infrastructure master plan within 6 months

• A binational working group created within three months to assess the feasibility of constructing an ocean outfall for the San Antonio de los Buenos Wastewater Treatment Plant (SABWWTP) and evaluate the technical and financial feasibility of expanding SABWWTP from 18.26MGD to 43.37MGD

• A sediment basin in Matadero Canyon near the international boundary, before the 2026–2027 rainy season, built by Mexico

• The Tecolote-La Gloria Wastewater Treatment Plant with a capacity of 3 MGD, scheduled for completion by December 2028, built by Mexico

Bilateral Understanding on Rio Grande Water Management

Minute 333 comes amid broader water management discussions between the two nations. Last week, Mexico and the United States reached a bilateral understanding to strengthen water management in the Rio Grande basin under the 1944 Water Treaty, following prolonged drought and heightened political pressure. Mexican authorities reiterated that the country has not violated the treaty, noting that its provisions allow flexibility during extraordinary droughts and require compliance to be assessed over the full five-year cycle rather than short-term deadlines.

The agreement follows technical negotiations focused on managing the current cycle and addressing the water deficit carried over from the previous cycle, as permitted under Art. 4 of the treaty. As of Oct. 24, 2025, Mexico had delivered 1,091 million m3, slightly over half of the required volume, according to the US section of the IBWC. Mexico plans to release an additional 249.2 million m3 starting in mid-December 2025, while both governments aim to finalize a broader plan by Jan. 31, 2026, covering remaining obligations and deficit repayment.