On 7 September 2026, the San Diego County Board of Supervisors formally launched a multi-phase plan to build a new U.S. treatment plant near the U.S.-Mexico border dedicated to capturing and treating untreated Tijuana River sewage flows, separate from the existing South Bay facility The Coronado News. The board unlocked approximately $6 million in reserves, directing $1.8 million into the first phase of the Tijuana River Capture and Cleanup Initiative, with a Saturn Boulevard box culvert project receiving an additional $4 million San Diego Union-Tribune.
Key takeaways
- Board voted 4-1 to establish the Tijuana River Capture and Cleanup Initiative on 1 September, with $1.8 million from the Unlocked Reserves Framework funding an 18-month planning study San Diego Union-Tribune.
- Project would be a new U.S. plant near the border, separate from the South Bay International Wastewater Treatment Plant operated by the U.S. section of the International Boundary and Water Commission The Coronado News.
- Phase 1 will build on a 2021 U.S. EPA river diversion study that estimated $63 million in capital cost to divert 163 million gallons per day to advanced primary treatment, with a 40-year life-cycle treatment cost estimated at $640 million The Coronado News.
- A separate $4 million allocation funds design, engineering and environmental review for a Saturn Boulevard box culvert fix, with total construction estimated at $23 million and a 2027 interim solution already underway The Coronado News.
- Long-term financing may come from a countywide half-cent sales tax measure on the 3 November ballot, projected to generate $360 million in its first year with 22.5% dedicated to Tijuana River Valley sewage mitigation San Diego Union-Tribune.
What happened
Background: a river carrying raw sewage across the border
More than 200 billion gallons of untreated water carrying sewage, industrial chemicals, pesticides, heavy metals and per- and polyfluoroalkyl substances have entered the United States through the Tijuana River since 2018, according to county figures cited in the board letter The Coronado News. At a river hot spot near Saturn Boulevard, hydrogen sulfide has been measured at 500 parts per billion, exceeding the state standard of 30 ppb The Coronado News. The existing South Bay International Wastewater Treatment Plant, expanded to treat 35 MGD in 2025 and scheduled for full 50 MGD operation in December 2027 under a U.S.–Mexico agreement at a $300 million federally funded cost, treats wastewater Mexico conveys to it but does not treat river flows The Coronado News.
The decision: a new plant and a permanent Saturn fix
On 1 September, supervisors voted 4-1, with Supervisor Joel Anderson opposed, to approve the Tijuana River Capture and Cleanup Initiative and convert the ad hoc subcommittee on the crisis into a standing committee with permanent oversight San Diego Union-Tribune. A second measure funding the Saturn Boulevard box culvert design, engineering and environmental review passed unanimously San Diego Union-Tribune. Board chair Terra Lawson-Remer said the action reflects years of unmet promises to South Bay communities San Diego Union-Tribune. Vice Chair Monica Montgomery Steppe said the package "lays the groundwork to build a locally controlled treatment system on the San Diego side of the border" San Diego Union-Tribune.
| Line item | Amount | Source of funds |
|---|---|---|
| Phase 1 study (new border plant) | $1.8 million | County Unlocked Reserves Framework |
| Saturn Boulevard box culvert design/permitting | $4 million | County reserves |
| Total reserves unlocked | ~$6 million | County reserves |
| EPA 2021 diversion study capital | $63 million | EPA study (2021) |
| EPA 2021 study 40-year life-cycle treatment cost | $640 million | EPA study (2021) |
| Saturn box culvert total construction | $23 million | County estimate |
| South Bay plant upgrade to 50 MGD (federal) | $300 million | U.S.–Mexico agreement |
What happens next
Phase 1 is expected to return to the board within 18 months with site selection, permit mapping, cost estimates and financing options for the new plant, building on the 2021 EPA river diversion study The Coronado News. The Saturn Boulevard box culvert design will move forward alongside a $2.5 million interim pipe-extension project, with construction anticipated in 2027 San Diego Union-Tribune. Supervisor Jim Desmond said he supported the measures but framed the underlying problem binationally: "This is Mexico's fault" San Diego Union-Tribune.
Specification read
For a buyer reading this as a procurement signal, the headline hydraulic target is the EPA's 2021 diversion figure of 163 million gallons per day, which converts to roughly 617,000 m³/day at 1 MGD ≈ 3,785 m³/day, and the secondary line is the existing South Bay plant's 50 MGD upgrade (about 189,000 m³/day) scheduled for December 2027 The Coronado News. The county's $1.8 million Phase 1 work sits upstream of any equipment award and is strictly planning, siting, permit mapping and cost estimating, so no treatment train has been specified yet, but the EPA reference design is "advanced primary" treatment at 163 MGD with a $63 million capital and $640 million 40-year operating envelope, implying a coarse screening → grit removal → primary clarification → disinfection train sized for very high wet-weather flows and variable loadings from sewage, industrial chemicals and PFAS (general industry range, not from the sources). The Saturn Boulevard package, by contrast, is conveyance and odour control (a larger box culvert to reduce turbulence that releases hydrogen sulfide), not a biological or tertiary upgrade, and pairs with a $2.5 million interim pipe-extension already underway San Diego Union-Tribune. If your plant looks like a sub-regional U.S.–border facility handling ~150,000–200,000 m³/day of mixed municipal and industrial inflow with rising PFAS and hydrogen sulphide compliance pressure, the event that matters is not today's vote but the 18-month Phase 1 clock and the November sales-tax ballot, which together will decide whether 2027–2028 procurement runs through a U.S. county-led tender on advanced primary equipment or continues to ride the federally funded South Bay upgrade. See Municipal and Integrated Sewage Treatment for the equipment classes that typically sit behind an advanced primary line of this size, and Industries We Serve for the cross-border, mixed-strength use case. Related reference projects include Surrey Connect puts North Shore Wastewater Plant cost at $5.5B, September 2026 and DAF vs Clarifier for Chemical Plant Wastewater in Springdale, US: 2026 Factory Guide, with sizing and cost benchmarks in Compact Sewage Treatment Unit Cost Price: 2026 B2B Pricing Guide.
FAQ
What is the headline flow the new plant must handle?
The 2021 EPA river diversion study cited by the county targets 163 million gallons per day, about 617,000 m³/day, to advanced primary treatment The Coronado News. The county's Phase 1 board letter does not yet commit to that exact capacity, site or total project cost.
How much money is on the table right now?
About $6 million in reserves has been unlocked, with $1.8 million directed to Phase 1 planning and $4 million to Saturn Boulevard box culvert design and permitting The Coronado News. Longer-term capital could reach hundreds of millions: the EPA study cites $63 million in capital and $640 million over a 40-year life cycle for the 163 MGD case The Coronado News.
What is the lead time before a supplier sees a tender?
Phase 1 returns to the board within 18 months with siting, permit, cost and financing options, so a formal equipment tender is unlikely before late 2027 at the earliest The Coronado News. The 50 MGD South Bay plant upgrade is scheduled for full operation in December 2027 under the existing U.S.–Mexico agreement The Coronado News.
How should a vendor shortlist for a project like this?
Shortlist on demonstrated delivery of advanced primary or primary-plus-clarifier trains in the 100,000–600,000 m³/day range, with hydrogen sulphide and odour-control references for any Saturn-style conveyance work (general industry range, not from the sources). Track the November sales-tax vote and the board's 18-month Phase 1 return for confirmed capacity, site and procurement vehicle before engaging on price.
