Tijuana River Watershed Public Updates

In accordance with the Memorandum of Understanding (MOU) signed by the United States and Mexico in Mexico City on July 24, 2025, U.S. Environmental Protection Agency (EPA) and Secretariat of Environment and Natural Resources (SEMARNAT) are providing the following quarterly public updates.

EPA and SEMARNAT are committed to fully and faithfully implementing the July 2025 MOU and implementing a permanent solution to the Tijuana River sewage crisis that’s afflicting communities on both sides of the U.S.-Mexico border. EPA and SEMARNAT also agree that, in accordance with the MOU, transparency and public participation are key to successfully achieving a durable solution to this crisis.

September 30, 2026 Quarterly Public Update

• South Bay International Wastewater Treatment Plant (SBIWTP) expansion to 35 MGD was completed August 2025. 
• Parallel Gravity Line was completed August 2026. 
• The U.S. Section of the International Boundary and Water Commission (USIBWC) is approaching the start of major construction on the treatment capacity expansion, to 50 MGD, of the SBIWTP: 
  • Early work packages are underway to restore and maintain the current treatment plant and prepare for the expansion. 
  • The first major construction phase for the expansion of the primary treatment works has been negotiated within budget and was awarded in September 2026. Construction is expected to begin soon after. 
  • The full design of the expansion is nearing completion and is on track for approval in October 2026. 
• Coordinating wet-weather readiness for El Niño winter: EPA and USIBWC have begun coordinating with regional agencies in San Diego and Tijuana to assess infrastructure integrity, including the Rodríguez Reservoir, in preparation for a potentially strong El Niño winter expected to bring heavy rain and a heightened risk of flooding from October through April. 
• Channel clearing ahead of wet-weather season: As of late September, USIBWC had completed approximately 16,622 feet of maintenance work on both sides of the Tijuana River pilot channel, including vegetation removal, mowing, erosion repair, and embankment reshaping. 
• Effluent relocation of La Morita and Arturo Herrera Wastewater Treatment Plants (WWTPs): This project diverts 10 MGD of treated effluent away from the Tijuana River to the Rodriguez reservoir for recharge. Construction began in February 2026 and is on track for completion by December 2027. 
• Pump Station 1 (PB-1): This project eliminates potentially catastrophic discharges due to unreliable pumping capacity. Construction began in April 2026 and is on track for completion by November 2027. Related, the PB-1 Back-up Power Supply project construction was re-sequenced in favor of urgent repairs to the Antiguo Force Main, though the project will still be certified by the North American Development Bank (NADBank) by December 2026. 
• Antiguo Force Main: Urgent repairs to this 2027 project have begun. Once complete next year, the full replacement of this 14,000-ft pipe will directly reduce the risk of untreated wastewater discharges to canyons on the US side and convey those flows for treatment at the San Antonio de los Buenos Wastewater Treatment Plant (SABWTP).  
• Tijuana River Gates: This project reduces an estimated 5 MGD of flows from entering the Tijuana River. Phase 1 is fully funded by Mexico with 8 of 11 segments completed to date. Phase 2, funded by EPA’s Border Water Infrastructure Program (BWIP), began construction in September 2026 to advance simultaneously with Phase I, and is on track for completion in early 2027. 
• Pump Stations Matadero and Laureles II: Mexico has obligated funds for this project and construction is expected to begin in December 2026. These pump stations are in two different binational canyons and once rehabilitated, will help keep flows out of the U.S. and direct them to WWTPs in Tijuana. 
• The following conveyance lines are being rehabilitated due to significant degradation, and once completed, will prevent potential sewage discharges into the Tijuana River from line ruptures: 
  • Poniente Interceptor rehabilitation: 460 of 705 meters have been constructed with expected completion in December 2026   
  • Oriente Interceptor rehabilitation: 421 of 1,600 meters have been constructed with expected completion in December 2026 
  • Carranza Collector rehabilitation: 986 of 1,100 meters have been constructed with expected completion in December 2026 
  • Insurgentes Collector rehabilitation: 205 of 5,431 meters constructed with expected completion in July 2027 
• Stormwater Best Practices Workshop: Mexico convened a binational workshop in July 2026, fulfilling Minute 333 requirements. Participants from the City of Imperial Beach and San Diego Regional Water Quality Control Board shared best practices for construction runoff and stormwater management. Mexican agencies engaged extensively and discussed opportunities to update local regulations to incorporate improved practices. 
• Mass balance flow analysis: Through the Minute 333 work group led by both sections of the IBWC, Mexico will lead the contracting of a comprehensive mass balance flow analysis of the Tijuana wastewater system. Contract procurement is expected by the end of 2026, with final completion by the end of 2027. 
• Operations & Maintenance (O&M) Work Group: The binational O&M work group is developing a suite of O&M strategies that incentivizes proper operations and maintenance of infrastructure investments. Recommendations will be shared with the IBWC Commissioners in December 2026. 
• The Tijuana Infrastructure Master Plan: The Tijuana Master Plan will ensure that sufficient water infrastructure is planned and constructed commensurate with anticipated population growth. The Master Plan Scope of Work will be finalized in December 2026.  

EPA and SEMARNAT look forward to providing future quarterly public updates in furtherance of the July 2025 MOU. Interested members of the public may submit comments or questions to EPA or SEMARNAT using the contacts listed below: 

• Email the EPA Press Team 
• Email SEMARNAT 

June 30, 2026 Quarterly Public Update

• Recognizing Mexico’s progress in meeting MOU commitments, EPA released previously agreed to Border Water Infrastructure Program (BWIP) funds to begin construction on Pump Station 1 (PB-1) and Tijuana River Gates projects.
  • PB-1: Mexico began construction on this essential project on April 27th. The project will eliminate potential catastrophic discharges and increase total pumping capacity to 80 million gallons per day (MGD). Project completion is expected in November 2027.
  • Tijuana River Gates: This project will eliminate at least 5 MGD of sewage from entering the Tijuana River. Phase 1 project completion is expected by mid-July 2026. Phase 2 is currently in procurement. Project completion is expected at the end of January 2027.
  • These two projects will help improve wastewater reliability, prevent spills, manage flow, reduce pollution, and lower the risk of flooding.
• U.S. International Boundary and Water Commission (USIBWC) reports continued progress towards expanding the South Bay International Wastewater Treatment Plant (SBIWTP) to increase treatment capacity to 50 million gallons per day (MGD).
  • USIBWC is advancing early work packages that lay the groundwork for the full expansion to 50 MGD, including site preparation and procurement of long-lead equipment to keep the project on schedule.
• Parallel Gravity Line: The rehabilitation of the Parallel Gravity Line will prevent future ruptures and spills from entering the U.S. through canyons along the border. Project completion is expected in August 2026.
  • In May, two separate sections of the Parallel Gravity Main collapsed within roughly two weeks. Mexico reported the first collapse on May 14 and completed emergency repairs on May 16.
  • A second collapse was reported on May 31, with emergency repairs completed on June 4, 2026. Both ruptures have been fully repaired.
  • For both events, the SBIWTP received excessive flows, and USIBWC took preventative action by deploying additional staff and equipment to treat over 40 MGD. Because of this urgent response, U.S. IBWC successfully prevented transboundary flow from reaching San Diego-area residents. USIBWC Commissioner Chad McIntosh contacted his Mexican counterpart, Commissioner Adriana Reséndez of the Mexican Section, to press for a 24/7 repair effort and urge Mexico to do everything possible to keep wastewater out of the Tijuana River.
• Since surpassing its 2026 funding commitment, Mexico is advancing procurement and construction of critical sewer line and pump station rehabilitations, which will prevent sewage discharges into the Tijuana River:
  • Insurgentes Collector rehabilitation – construction to begin on June 29
  • Two pump stations: PB-Matadero and Laureles PB-2 – in procurement phase
  • Poniente Interceptor rehabilitation – in construction phase with expected completion in December 2026  
  • Oriente Interceptor rehabilitation – in construction phase with expected completion in December 2026
  • Carranza Collector rehabilitation – in construction phase with expected completion in December 2026
• The U.S. and Mexico have advanced progress on a suite of actions after Minute 333 was enacted in December 2025, including infrastructure projects, research studies, and planning for operation and maintenance (O&M) of critical sites and systems that will account for future population growth in Tijuana. This includes the following:
  • Mexico completed the sediment basin at Matadero Canyon in May 2026, meeting the pre‑rainy‑season construction goal and reducing sediment and debris impacts.
  • The binational O&M Workgroup continues developing long-term strategies to ensure critical infrastructure is maintained along the border.
  • The binational Minute 333 Work Group reviewed existing engineering and financial feasibility studies for an ocean outfall at the San Antonio de los Buenos Wastewater Treatment Plant and prepared a scope of work to conduct a comprehensive mass balance flow analysis of the Tijuana water system.
  • The Minute 333 Work Group is also advancing a scope of work for a transparent, real-time binational monitoring system to track flow inputs and outputs to the Tijuana River, strengthening accountability between both countries.

EPA and SEMARNAT look forward to providing further quarterly public updates in furtherance of the July 2025 MOU. Interested members of the public may submit comments or questions to EPA or SEMARNAT using the contacts listed below:

• Email the EPA Press Team
• Email SEMARNAT

March 20, 2026 Quarterly Public Update

• On December 15, 2025, U.S. and Mexico signed a historic new agreement, called Minute 333, committing both nations to new actions, including infrastructure projects, evaluations, enhanced monitoring, and planning for operation and maintenance (O&M) of critical sites and systems that will account for future population growth in Tijuana, Mexico. The following commitments are underway:
  • An interagency binational Minute 333 Work Group has been established to evaluate the following commitments:
    • Review existing engineering and financial feasibility studies by the end of March 2026 on the construction of an ocean outfall at the San Antonio de los Buenos Wastewater Treatment Plant and provide a recommendation on additional studies and work that may be needed.
    • Prepare a scope of work by April 2026 to conduct a comprehensive mass balance flow analysis of the Tijuana water system.
    • An O&M work group has been established by EPA to develop alternative O&M strategies to fund future O&M along the border.
• With the signing of Minute 333, the U.S. met all of its obligations under the MOU for 2025. That includes:
  • the completion of a 10 gallons per day (MGD) expansion of the South Bay International Wastewater Treatment Plant (SBIWTP) in 100 days;
  • a 100-day review of all Minute 328 projects to ensure completion at the earliest possible date; and
  • issuing the first-ever quarterly public update on MOU implementation progress.
• Mexico has begun construction of the effluent relocation project from the Arturo Herrera and La Morita Wastewater Treatment Plants. This is a phased project, with Phase 1 having an anticipated completion in mid 2027 and costing $16M. Phase 2 is anticipated for completion in December 2027. Once completed, this will prevent 10 MGD of effluent from being discharged to the Tijuana River.
• Mexico continues to make progress on the rehabilitation of the Parallel Gravity Main. Mexico secured $8.9M for this project and construction began in November 2025 with estimated completion in July 2026.    
• Since Mexico has met the requirements in the MOU to begin the Effluent Relocation and Parallel Gravity Main and is exceeding their 2026 funding commitment, EPA is releasing U.S. Mexico Border Water Infrastructure Program (BWIP) funds to begin the Tijuana River Gates and PB-1 projects.  These projects will prevent 5 MGD of transboundary sewage from entering the Tijuana River, and BWIP funds will ensure the PB-1 project remains on track. Immediately beginning construction also maximizes the 9-month timeline reduction secured following the July 2025 MOU signing.
• Mexico has obligated $59M in state and federal funding to begin the following projects in 2026, surpassing the $46M funding commitment for 2026 as agreed to in the MOU.
  • Insurgentes Collector rehabilitation
  • Two pump stations: PB-Matadero and Laureles PB-2
  • Poniente Interceptor rehabilitation
  • Oriente Interceptor rehabilitation
  • Carranza rehabilitation
  • Diversion of 10 mgd of treated effluent to the Rodriguez Dam
  • Rehabilitation of the Parallel Gravity line

EPA and SEMARNAT look forward to providing further quarterly public updates in furtherance of the July 2025 MOU. Interested members of the public may submit comments or questions to EPA or SEMARNAT using the contacts listed below:

• Email the EPA Press Team
• Email SEMARNAT

November 21, 2025 Quarterly Public Update

Accomplishments

• U.S. Section, International Boundary and Water Commission (USIBWC) completed 10 million gallons per day (mgd) interim expansion of the South Bay International Wastewater Treatment Plant (SBIWTP) on August 28, 2025. The facility is now fully operational and capable of handling 35 mgd of wastewater.
• On October 30, 2025, a list of projects to be further expedited was released, a product of a US-Mexico binational working group. This was done in accordance with Section 5 of the MOU. EPA and its partners were able to compress project timelines by 9 additional months for two key Mexico-side projects, including Tijuana River Gates and Rehabilitation of PB1 A and B. 
  • In total, the MOU has memorialized time savings of approximately seven (7) years for projects in Mexico and over five (5) years for projects in the United States. 
• Mexico expects to secure funding for the following projects, which will begin construction in 2026:
  • Insurgentes Collector
  • PB-Matadero and Laureles PB-2
  • Poniente Interceptor
  • Oriente Interceptor
  • Carranza Collector
  • Backup power supply for PB1.
• In September 2025, Mexico initiated the construction of the First Phase of the Tijuana River Gates, a collection pipes project, with Mexican state and federal funds.
• Mexico is initiating the process for the construction of the following priority projects:
  • Diversion of 10 mgd of treated effluent entering the Tijuana River from the Arturo Herrera and La Morita wastewater treatment plants to a site upstream of the Rodriguez Dam.
  • Rehabilitation of the Parallel Gravity Line. 
• U.S. and Mexico IBWC Commissioners met August 15; September 24; October 1, 7, 16, 22, 23, and 30; and November 10 and 14. International cooperation is key to fully and faithfully implementing the MOU.
• USIBWC completed a nanobubble ozonation pilot project for the Tijuana River. Preliminary results showed promise at reducing odors and bacteria. Results of the data analysis will be forthcoming. 
• USIBWC started planning to accelerate the expansion of SBIWTP to 50 mgd. This is currently in the planning phase. Public updates to come. 
• U.S. EPA and Mexico SEMARNAT are developing strategies for operations and maintenance (O&M) costs and accounts. EPA and SEMARNAT set up a Binational O&M workgroup (EPA, SEMARNAT, CONAGUA, NADBank and both IBWC sections) to work on this issue.
• New Treaty “Minute.” The U.S. and Mexican Sections of the IBWC are in final negotiations to undertake additional actions to address transboundary pollution at San Diego-Tijuana, leading up to signing by the end of December 2025.

EPA and SEMARNAT look forward to providing further public updates in furtherance of the July 2025 MOU. Interested members of the public may submit comments or questions to EPA or SEMARNAT using the contacts listed below:

• Email the EPA Press Team
• Email SEMARNAT