The U.S. Environmental Protection Agency (EPA) and Mexico have advanced several wastewater infrastructure projects aimed at reducing sewage flows into the Tijuana River and improving treatment capacity along the U.S.-Mexico border, according to a quarterly update reported on 2 October 2026 (Wastewater Digest). The headline procurement signal is the award of the first major construction contract to expand the South Bay International Wastewater Treatment Plant (SBIWTP) to 50 million gallons per day (MGD).
Key takeaways
- EPA's third-quarter 2026 update reports the Parallel Gravity Line was completed in August 2026 (Wastewater Digest).
- Construction began on Phase 2 of the Tijuana River Gates, and the first major contract to expand the South Bay International Wastewater Treatment Plant to 50 MGD was awarded in September 2026 (Wastewater Digest).
- On the Mexico side, four degraded sewage conveyance lines are being rehabilitated, with construction progress reported in meters on the Poniente, Oriente, Carranza and Insurgentes collectors (Wastewater Digest).
- Approximately 16,622 feet of the Tijuana River pilot channel has been cleared ahead of the wet-weather season (Wastewater Digest; The Presidential Prayer Team).
- EPA and the U.S. International Boundary and Water Commission are coordinating with San Diego and Tijuana agencies on infrastructure ahead of a potentially strong El Niño winter (Wastewater Digest).
What happened: U.S.-side construction milestones
In its third-quarter 2026 update, EPA reported that the Parallel Gravity Line was completed in August 2026 and that construction has begun on Phase 2 of the Tijuana River Gates (Wastewater Digest). The same update confirmed that the first major construction contract to expand the South Bay International Wastewater Treatment Plant to 50 MGD was awarded in September 2026, building on a prior expansion that lifted capacity to 35 MGD in August 2025 (Wastewater Digest).
The U.S. International Boundary and Water Commission is preparing the full design for the SBIWTP expansion, with approval expected in October 2026, while early work to maintain the existing plant and prepare for construction is already underway (Wastewater Digest). The update also notes that crews cleared approximately 16,622 feet of the Tijuana River pilot channel in preparation for the wet-weather season (The Presidential Prayer Team).
EPA Administrator Lee Zeldin characterised the update as evidence of urgent progress under the 2025 U.S.-Mexico agreement known as Minute 333, stating: "This latest public update highlights the urgent progress being made to fully implement last year's agreement. Safeguarding human health and the environment is EPA's foremost responsibility, and we are committed to ensuring that every American has access to clean air, land, and water" (The Presidential Prayer Team).
What happened: Mexico-side conveyance work and El Niño planning
On the Mexico side, rehabilitation has advanced on four degraded sewage conveyance lines. As of the quarterly update, construction had reached 460 meters of the 705-meter Poniente Interceptor, 421 of 1,600 meters of the Oriente Interceptor, 986 of 1,100 meters of the Carranza Collector, and 205 of 5,431 meters of the Insurgentes Collector (Wastewater Digest). The reported package of additional work also includes rehabilitation of the Antiguo Force Main and Pump Station 1, relocation of 10 MGD of treated effluent from two Tijuana wastewater treatment plants to the Rodríguez Reservoir, and rehabilitation of the Matadero and Laureles II pump stations (Wastewater Digest). Mexico hosted a binational stormwater workshop in July as part of commitments under Minute 333 (Wastewater Digest).
EPA and the U.S. International Boundary and Water Commission are coordinating with agencies in San Diego and Tijuana to assess infrastructure ahead of a potentially strong El Niño winter (Wastewater Digest).
| Project element | Status reported in Q3 2026 update |
|---|---|
| Parallel Gravity Line | Completed in August 2026 |
| Tijuana River Gates, Phase 2 | Construction began |
| SBIWTP expansion to 50 MGD | First major construction contract awarded in September 2026 |
| Poniente Interceptor (705 m) | 460 m constructed |
| Oriente Interceptor (1,600 m) | 421 m constructed |
| Carranza Collector (1,100 m) | 986 m constructed |
| Insurgentes Collector (5,431 m) | 205 m constructed |
| Tijuana River pilot channel clearing | Approximately 16,622 ft cleared |
Specification read
The reported target of 50 MGD translates to roughly 189,270 m³/day at the SBIWTP, with a prior step to 35 MGD (about 132,489 m³/day) already in service since August 2025; the 10 MGD effluent relocation (about 37,854 m³/day) from two Tijuana plants to the Rodríguez Reservoir is a separate conveyance and reuse stream (Wastewater Digest). The treatment train required at this class of facility runs screening → primary clarification → biological treatment (commonly A2O, MBR, MBBR or SBR) → tertiary filtration and disinfection, with the SBIWTP award sitting at the biological-stage capacity expansion and the Mexico-side interceptor work sitting upstream at the conveyance and screening stage; the supplied sources do not report influent BOD or COD, so the exact pollutant load on the new train is not stated (Wastewater Digest). For a procurement context, the engineering interpretation below restates scale in the units a buyer uses: if your plant is a large cross-border municipal facility in the 130,000–190,000 m³/day range handling mixed domestic sewage under U.S. EPA effluent limits and storm-driven peak flows, the reported September 2026 contract award and the pending October 2026 SBIWTP design approval are the near-term triggers to track for bid packages, contractor prequalification, and biological-stage equipment supply timelines (Wastewater Digest).
Municipal operators scoping similar upgrades can compare against our Municipal treatment hub and our reference design for Integrated Sewage Treatment plants, or review the Industries We Serve index for adjacent flows. Process designers can also read the SBR for Gelatin Wastewater: 2026 Process Design & Buyer's Guide for batch-reactor sizing logic and the Textile Wastewater Treatment in Ghana (2026 Buyer's & Engineering Guide) for a comparable bid-package workflow.
FAQ
What was awarded in the SBIWTP expansion?
EPA's Q3 2026 update reports that the first major construction contract to expand the South Bay International Wastewater Treatment Plant to 50 MGD was awarded in September 2026, with the U.S. International Boundary and Water Commission's full design approval expected in October 2026 (Wastewater Digest).
How much interceptor work is left in Tijuana?
As of the quarterly update, construction had reached 460 of 705 m on the Poniente Interceptor, 421 of 1,600 m on the Oriente Interceptor, 986 of 1,100 m on the Carranza Collector and 205 of 5,431 m on the Insurgentes Collector (Wastewater Digest).
What is the lead time for the next SBIWTP design decision?
The Q3 2026 update says the U.S. International Boundary and Water Commission is preparing the full design for the SBIWTP expansion, with approval expected in October 2026 (Wastewater Digest).
Are influent pollutant concentrations reported?
No. The supplied sources state only flow capacities and construction progress; influent BOD and COD for the new train are not reported, so the exact biological-stage loading is not stated (Wastewater Digest).
