Minute No. 333

Comprehensive Actions to Address the Border Sanitation Problem at San Diego, California

The Commissioners met at the Mexican Section offices in Tijuana, Baja California on December 15, 2025 at 11:00 a.m. to consider projects and activities intended to provide a comprehensive solution to the border sanitation problem at San Diego, California – Tijuana, Baja California.

The Commissioners referenced the United States-Mexico Treaty for Utilization of Waters of the Colorado and Tijuana Rivers and of the Rio Grande, signed February 3, 1944, specifically Article 3, by which the Governments “agree to give preferential attention to the solution of all border sanitation problems.” Through a series of subsequent Minutes, the Commission focused on the border sanitation problem at San Diego-Tijuana, most recently through Minute 328, “Sanitation Infrastructure Projects in San Diego, California – Tijuana, Baja California for Immediate Implementation and for Future Development,” dated July 19, 2022.

They also highlighted Minute 320, “General Framework for Binational Cooperation on Transboundary Issues in the Tijuana River Basin,” signed October 5, 2015. Through this Minute, the Commission established work groups to identify activities that could be undertaken in the Tijuana River watershed with a focus on the priority issues of water quality, sediment, and solid waste.  Through the Minute 320 process, the Commission developed the “Initial Binational Tijuana River Spill Notification Protocol,” which identifies incidents subject to the notification requirement and establishes that “The two Sections of the IBWC, in consultation with the Minute 320 Water Quality Work Group, will continue to update and identify additional situations that require notification under this protocol, which will be established in future Binational Tijuana River Spill Notification Protocols.”   The Commissioners noted that planned maintenance outages, repairs, and rehabilitation projects that result in the discharge of wastewater to the Tijuana River are not routinely reported through the initial protocol, and they identified a need to develop a new protocol to cover this situation.  They also noted that infrastructure projects in Tijuana planned by the North American Development Bank (NADBank) and Mexico’s National Water Commission (CONAGUA) under the framework of the Border Water Infrastructure Program require the capture and conveyance of sewage through the collection system to avoid pollution of the Tijuana River.

The Commissioners referenced Minute 283, “Conceptual Plan for the International Solution to the Border Sanitation Problem in San Diego, California/Tijuana, Baja California,” dated July 2, 1990, which states, in  Recommendation 16, that “The Government of Mexico will assure that there are no discharges of treated or untreated domestic or industrial wastewaters into waters of the Tijuana River that cross the international boundary, and that in the event of a breakdown in collection or other detention facilities designed to prevent such discharges, the Government of Mexico will take special measures to immediately stop such discharges and make repairs. Should Mexico request it through the Commission, the United States Section will attempt to assist with equipment and other resources in the containment of such discharges and temporary repairs under the supervision of the Commission.”

Further, they noted that Minute 258, “Modification of the United States Portion of the Plan for the Channelization of the Tijuana River,” dated May 27, 1977, specifies in Resolution 4, “That each Government operate and maintain at its expense the part of the channelization project located in its territory…”

The Commissioners acknowledged that despite the efforts that both Governments have made under the cited Minutes and other agreements of the Commission, it has not been possible to achieve a comprehensive solution to the San Diego-Tijuana border sanitation problem, particularly due to the City of Tijuana’s accelerated population growth and the speed at which the service life of the city’s sanitation infrastructure is depleted  and exceeded.    In this sense, they observed that it is appropriate to undertake actions, in addition to those identified in previous Minutes, to address the adequate disposal of wastewater, sediment, and solid waste in the Tijuana River and wastewater discharged into the Pacific Ocean from the Tijuana River and at Punta Bandera.  They highlighted the need to improve, rehabilitate, and expand the sanitation infrastructure, as well as to establish mechanisms that enable better short-, mid-, and long-term management of such infrastructure, to benefit the environment and the health of residents on both sides of the border. 

The Commissioners further noted that on July 24, 2025 in Mexico City, the Administrator of the United States Environmental Protection Agency (EPA), Lee M. Zeldin, and Mexico’s Secretary of the Environment and Natural Resources, Alicia Bárcena Ibarra, signed the “Memorandum of Understanding between the United Mexican States and the United States of America on Addressing the Sanitation and Environmental Crisis in the Tijuana-San Diego Region” (MOU).  In the MOU, the countries reaffirmed the International Boundary and Water Commission’s (IBWC) commitments under Minute 328, currently in its implementation phase, and the public acknowledgements by United States President Donald Trump and Mexican President Claudia Sheinbaum of the importance of resolving the border sewage problem at San Diego-Tijuana.  The MOU further identified actions the countries intend to take to fulfill and accelerate implementation of the Minute 328 projects and related activities.

The U.S. Commissioner indicated the importance of Mexico completing the Minute 328 projects on schedule, as verified quarterly during binational technical meetings convened by EPA and CONAGUA.  He explained that EPA has indicated that Border Water Infrastructure Program funding to initiate new projects in Tijuana, other than those identified in Minute 328 and the MOU, would be contingent on confirmation that projects in MOU Sections 3.a. and 3.b. remain on schedule to complete construction.

The MOU also identifies a series of actions that both countries intend to include in a new Minute to be signed by no later than December 31, 2025.  Minute 333 includes those actions. In addition, they highlighted Section 1.a.iii. of the MOU, which indicates the expectation that the U.S. and Mexican Commissioners of the IBWC would “Develop a joint communication strategy to notify stakeholders of issues and project progress regularly.”   

I.  Proposed Actions in the MOU.

The Commissioners reviewed for inclusion in this Minute the list of actions that were identified in the MOU and considered and further developed them as follows:

  1. Initiate engineering and financial feasibility studies for installing an ocean outfall at the San Antonio de los Buenos Wastewater Treatment Plant (SAB WWTP), building upon prior studies conducted by the North American Development Bank (NADBank) and the State Public Utilities Commission of Tijuana (CESPT). The Commissioners observed the appropriateness of analyzing the possible construction of an ocean outfall for the SAB WWTP. In light of the above, they determined that it would be appropriate to convene an interagency binational work group (hereinafter the Minute 333 Work Group) that would evaluate existing engineering and financial feasibility studies and, within 3 months from this Minute’s entry into force, make a recommendation to the Commissioners on additional studies and work that may be needed, so they could in turn make a recommendation to their Governments within 3 months thereafter about any potential additional actions that could be taken. 
  2. Assess the technical and financial feasibility of expanding treatment capacity of the San Antonio de los Buenos Wastewater Treatment Plant in Tijuana from 18.26 million gallons per day (MGD) (800 liters per second [lps]) to 43.37 MGD (1900 lps).  The Commissioners determined that the Minute 333 Work Group could assess the technical and financial feasibility of the potential expansion of the SAB WWTP. They considered that this assessment could be undertaken following completion of the Tijuana water infrastructure master plan and mass balance analysis described in paragraphs I.K. and I.L. of this Minute. 
  3. Construct and maintain the sediment basin at Matadero Canyon. The Commissioners noted that Mexico’s Defense Department (SEDENA) intends to construct a sediment basin in Matadero Canyon (Smuggler’s Gulch) in Mexico near the international boundary as part of a highway construction project in that area. The sediment basin is expected to significantly reduce the amount of sediment entering the United States through Matadero Canyon (Smuggler’s Gulch).  The Commissioners noted that Commission engineers from the San Diego and Tijuana offices could provide oversight to ensure the required maintenance is performed on that infrastructure by the State Government of Baja California, jointly with the State Public Utilities Commission of Tijuana (CESPT). The Commissioners emphasized the importance of constructing the sediment basin prior to the start of the region’s 2026-2027 rainy season. 
  4. Construct the Tecolote-La Gloria Wastewater Treatment Plant with a capacity of 3 MGD (131 lps).  The Mexican Commissioner reported that the State of Baja California is planning to construct a new wastewater treatment plant, known as Tecolote-La Gloria, located in Tijuana 5 miles (8 kilometers) south of the U.S.-Mexico border. The plant would have a capacity of 3 MGD (131 lps).   The Commissioners highlighted the importance of constructing this plant in order to address the flow of untreated wastewater being discharged to the Pacific Ocean in Mexico. The Mexican Commissioner advised that the State of Baja California would undertake the project, including its development, design, and construction, with anticipated completion no later than December 2028.  
  5. Develop and encourage consistent implementation of best practices and guidelines for stormwater management and construction runoff control to reduce inflow rates and downstream deposition of trash and sediment. The U.S. Commissioner proposed to share information with the Mexican Commissioner about stormwater management practices and guidelines in the United States.  The Mexican Commissioner proposed to convene a binational workshop in Tijuana with participation from authorities at the three levels of government, as well as construction contractors, on stormwater management and construction runoff control practices to evaluate best practices in the United States and Mexico so that these practices may be implemented in Tijuana.  The Commissioners noted that if the initial workshop is held within 6 months of this Minute’s entry into force, some of the best management practices could potentially be initiated before the region’s 2026-2027 rainy season.Additional workshops could be organized in the future to exchange information about new methodologies.
  6. Through Minute 320, identify sediment and trash projects that can be cost-shared amongst appropriate entities.  The Commissioners referenced the proposed projects identified by the Minute 320 Binational Core Group, many of which are focused directly or indirectly on sediment and solid waste management.  Furthermore, they pointed to the successful ongoing pilot project that emerged from the Minute 320 process for a Tijuana River trash boom in United States territory near the international boundary, but which lacks an ongoing funding source, sponsor, and operator.  They also referred to challenges faced in securing funds to implement Minute 320 priority projects.  They noted the importance of continuing with the Minute 320 implementation process, by convening a Minute 320 Binational Core Group meeting within 6 months of this Minute’s entry into force to prioritize projects and identify different potential funding mechanisms and sources.  They also noted the importance of ensuring that projects have long-term ownership and durability, and highlight attention to transboundary Tijuana River basin issues.  
  7. Develop a routine schedule and cost-sharing formula for cleaning and sediment dredging operations in the Tijuana River.  The Commissioners determined that, prior to the region’s 2026-2027 rainy season, their engineers based in San Diego and Tijuana, in consultation with the two Sections’ Headquarters, could develop a proposed program, including estimated costs, for clearing and removing sediment and solid waste from the Tijuana River channel, taking into consideration the areas adjacent to the international boundary under each Section’s jurisdiction and, in consultation with the responsible institutions in the two countries, other areas of the Tijuana River. 
  8. Share information from Mexico with the United States on the anticipated additional flows to the Tijuana wastewater system from the proposed Rosarito Desalination Plant.  The State of Baja California has undertaken studies in preparation for construction of a desalination plant at Playas de Rosarito to provide water for domestic use in the Tijuana-Rosarito region.  Said studies identify current domestic demand in the region and the expected increase to the water supply resulting from the construction of the plant. In this sense, within 3 months of this Minute’s entry into force, the Mexican Section intends to share with the U.S. Section the relevant information regarding the additional flows that are expected to be received in the Tijuana wastewater system, and, if applicable, when any updated studies are undertaken, share the relevant information within 3 months after they are completed.  This information should be considered in the Tijuana water infrastructure master plan and mass balance analysis described in paragraphs I.K. and I.L of this Minute.    This information is expected to assist in determining the potential additional demand on Tijuana’s wastewater treatment capacity.
  9. Evaluate supplementary treatment for the SAB WWTP effluent (e.g., ozonation for disinfection, odor control, and reduction of chemical usage). The Commissioners determined that the Minute 333 Work Group identified in paragraph I.A. above could be tasked with undertaking this evaluation.  This Work Group should report back to the Commissioners with the results of said evaluation, including estimated costs, within 12 months of this Minute’s entry into force. 
  10. Create an Operations and Maintenance (O&M) account at the North American Development Bank (NADBank) which would set aside a portion of all dollars provided to Mexico to be held for future O&M costs. The O&M account should be developed in partnership with NADBank and a new binational workgroup, which would explore and design alternative O&M strategies to ensure proper maintenance of infrastructure investments, ultimately extending their operational lifespan.  The Commissioners observed that lack of financial resources to perform adequate O&M has led to deterioration of the region’s sanitation infrastructure. In light of this, the binational work group led by EPA and CONAGUA, in coordination with the Commission, has initiated meetings to explore and design alternative O&M strategies, including the operating framework for the O&M account at NADBank, as well as the identification of funding sources, financing structures, and implementation procedures. The Commissioners are requesting that the binational work group present its recommendations to the Commission within 12 months of this Minute’s entry into force.
  11. Develop a Tijuana water infrastructure master plan to ensure that sufficient water infrastructure is planned and constructed commensurate with anticipated population growth.  The Commissioners considered it important to have an updated water infrastructure master plan for Tijuana. They observed that various planning efforts can be taken as a basis to develop this plan. In this sense, they indicated the State Government of Baja California could coordinate this effort with NADBank, if considered necessary, to prepare a scope of work within 6 months of this Minute’s entry into force that would allow for said plan to be developed based on the prior studies that have been done in recent years.  Once the scope of work is prepared and costs estimated to prepare the master plan, within 3 months thereafter, the Government of Mexico through the State Government of Baja California would determine the means to develop the plan.  
  12. Conduct a comprehensive mass balance flow analysis of the Tijuana water system.  In order to conduct the comprehensive mass balance flow analysis of the Tijuana water system, the Commissioners noted the importance of preparing a scope of work for this study as a specific task to be performed by the Minute 333 Work Group within 3 months of this Minute’s entry into force, with the goal to complete the study within 12 months of this Minute’s entry into force. 
  13. Develop a transparent and real-time binational monitoring system to account for flow inputs and outputs in the Tijuana River and water quality data from the treated effluent discharged by the following wastewater treatment plants:  South Bay (SBIWTP), SAB WWTP, Tecolote-La Gloria, Arturo Herrera, and La Morita.  The Commissioners considered it appropriate for the Minute 333 Work Group to develop a scope of work to design a real-time binational monitoring system in consultation with appropriate federal, state, and local entities, taking into consideration interim monitoring efforts that could be established while the broader system is under development. They indicated such a system should include the reach of the Tijuana River from the Alamar River confluence to the international boundary, effluent flow data for the aforementioned wastewater treatment plants, and influent flow data for the SBIWTP and SAB WWTP. Once the effluent from the Arturo Herrera and La Morita Wastewater Treatment Plants is no longer discharged to the Tijuana River, data for these plants would be removed from the monitoring system.  Such system would include equipment (such as flow meters) and measures to reduce vandalism of the equipment. They also noted the desirability of establishing an information exchange program on the quality of effluent from the aforementioned wastewater treatment plants as soon as practical, within 6 months of this Minute’s entry into force.

II.  Resolutions

Based on the above, the Commissioners adopted the following Resolutions, subject to the approval of both Governments:

  1. In furtherance of Section 1.a.iii. of the MOU, the Commission shall develop a new binational Tijuana River spill notification protocol to ensure notification of instances where, despite the use of best practices to avoid discharges into the river as required under existing Minutes and protocols, discharges of untreated wastewater to the Tijuana River occur. 
  2. The Commission shall establish an interagency binational Minute 333 Work Group and shall direct it to:
    1. Evaluate the existing engineering and financial feasibility studies for possibly constructing an ocean outfall for the SAB WWTP and, within 3 months of this Minute’s entry into force, make a recommendation to the Commissioners on additional studies and work that may be needed, who in turn shall make a recommendation to their respective Governments within 3 months thereafter about any potential actions that could be taken.  
    2. Assess the technical and financial feasibility of expanding treatment capacity of the SAB WWTP from 18.26 MGD (800 lps) to 43.37 MGD (1900 lps) as described in paragraph I.B. above.
    3. Evaluate supplementary treatment for the SAB WWTP effluent, as described in paragraph I.I. above, and inform the Commissioners of the results of the evaluation within 12 months of this Minute’s entry into force. 
    4. Prepare a scope of work within 3 months of this Minute’s entry into force in order to complete a mass balance flow analysis of the Tijuana water system, as described in paragraph I.L. above, within 12 months of this Minute’s entry into force. 
    5. Prepare a scope of work to develop a transparent, real-time binational monitoring system on flow inputs and outputs to the Tijuana River as described in paragraph I.M. above, taking into consideration interim monitoring efforts that could be established while the broader system is under development.
    6. Implement a systematic information exchange program on quality data of the effluent discharged by the wastewater treatment plants identified in I.M. above, as soon as practical, within 6 months of this Minute’s entry into force. 
  3. Prior to the start of the region’s 2026-2027 rainy season, the Government of Mexico shall construct a sediment basin in Matadero Canyon (Smuggler’s Gulch) in Mexico near the international boundary.  The Commission shall oversee the adequate operation and maintenance of said sediment basin by the State Government of Baja California and the State Public Utilities Commission of Tijuana (CESPT). 
  4. The Government of Mexico, through the State Government of Baja California, shall construct the Tecolote-La Gloria Wastewater Treatment Plant by no later than December 2028 as described in paragraph I.D. above. 
  5. The Mexican Section shall convene a workshop in Tijuana about stormwater management practices and control of construction runoff, within 6 months of this Minute’s entry into force, to evaluate best practices in the United States and Mexico that could potentially be initiated in Tijuana prior to the region’s 2026-2027 rainy season, as described in paragraph I.E. above.
  6. The Commission shall identify different potential mechanisms and funding sources for implementation of sediment and solid waste control projects identified through the Minute 320 process, with a particular focus on projects that have long-term ownership and durability, and that highlight attention to transboundary Tijuana River basin issues.  To that end, the Commission shall convene a Minute 320 Binational Core Group meeting within six months of this Minute’s entry into force.
  7. The Commission shall prepare a schedule and cost-sharing formula, prior to the region’s 2026-2027 rainy season, for sediment and solid waste removal from the Tijuana River channel, as described in paragraph I.G. above, taking into consideration the areas adjacent to the international boundary under the jurisdiction of each Section, and, in consultation with the responsible institutions in the two countries, other areas of the Tijuana River.
  8. The Mexican Section shall share with the U.S. Section, within three months of this Minute’s entry into force,  information pertaining to the potential additional water flows that would be introduced to the Tijuana wastewater system as a result of expanded water availability from the construction of the proposed desalination plant in Playas de Rosarito, B.C., and, if applicable, when any updated studies are undertaken,  the Mexican Section shall share with the U.S. Section the relevant information within 3 months after the studies’ completion, as described in paragraph I.H. above.
  9. The Commission shall coordinate with the binational O&M work group described in paragraph I.J. above to develop strategies to ensure proper maintenance of the region’s sanitation infrastructure in order to extend its service life through the corresponding investments, including strategies related to the operating framework for the O&M account at the NADBank, as well as the identification of funding sources, financing structures, and implementation procedures.  The Commission shall ask the Work Group to present recommendations to the Commission within 12 months of this Minute’s entry into force. 
  10. The Government of Mexico, through the State Government of Baja California, shall prepare, within 6 months of this Minute’s entry into force, a scope of work for development of a Tijuana water infrastructure master plan, and, if considered necessary, shall coordinate this effort with NADBank. Once the scope of work is prepared and costs estimated to prepare the master plan, within 3 months thereafter, the Government of Mexico, through the State Government of Baja California, shall determine the means to develop the plan.
  11. The Commission shall make available to the public any data generated or obtained pursuant to the monitoring and information exchange program described in Resolutions 2.e) and 2.f) above.    The Commission shall establish suitable criteria by which information from the studies and projects from Resolutions 2.a), 2.b), 2.c), 2.d), 7, and 8 above may be made available to the public in both countries.
  12. All activities undertaken pursuant to this Minute shall be subject to the availability of funds, resources, and corresponding personnel, as well as to applicable laws and regulations in each country. 
  13. This Minute shall enter into force upon the date of the later notification in an exchange of notifications between the Sections of the Commission confirming approval of this Minute by their respective Governments. 

The meeting was adjourned.

// signed                                                               //signed

W.C. McIntosh                                                  Adriana Beatriz Carolina Reséndez Maldonado
United States Commissioner                    Mexican Commissioner

 

// signed                                                               // signed 

Sally E. Spener                                                Manuel Alejandro Morales Galván
United States Section Secretary             Mexican Section Secretary

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Last updated on December 15, 2025