San Diego County supervisors voted on 2 September 2026 to pursue a new sewage treatment system on the US side of the border, aimed at stopping polluted water from the Tijuana River before it reaches San Diego communities and beaches New York Post. The county will spend $1.8 million to study potential treatment systems over the next year and a half, with the work developed in three phases.
Key takeaways
- San Diego County supervisors voted on 2 September 2026 to pursue a new US-side sewage treatment system for Tijuana River pollution New York Post.
- The county has committed $1.8 million to study potential treatment systems over the next 18 months, with delivery planned in three phases New York Post.
- Millions of gallons of sewage-contaminated water can pour across the border and foul the Tijuana River, with beach closures reaching Coronado New York Post.
- Hydrogen sulfide levels near one South Bay hotspot have reached 4,500 times typical urban readings, prompting free air purifiers for eligible households New York Post.
- Supervisor Joel Anderson cast the lone vote against the plan, warning the project could become a multibillion-dollar undertaking New York Post.
What happened
The plan, spearheaded by Supervisors Paloma Aguirre and Terra Lawson-Remer, responds to a six-decade pattern of cross-border spills in which millions of gallons of sewage-contaminated water pour across the border, foul the Tijuana River and wash into the Pacific New York Post. Beach closures have reached as far north as Coronado, and video posted by Chef Andrew Gruel showed murky yellow-green water covering the city’s normally packed summer beach New York Post.
Aguirre framed the board’s action as a break with the past: “We’ll keep working with Washington and Mexico, but we will set the pace and we won’t wait on anyone else’s timeline,” she said of Tuesday’s vote New York Post. In a county board letter, Aguirre and Lawson-Remer added: “After 60 years, that is the gap that has no solution: the U.S. side of the Tijuana River is not treated at all” New York Post. Lawson-Remer put it more bluntly: “The time has come to end this environmental injustice” New York Post.
Health and odour impacts have driven the urgency. Researchers have found that sewage-related contaminants can become airborne, and hydrogen sulfide has reached 4,500 times higher than typical urban levels near one South Bay hotspot, leading the county to offer free air purifiers to eligible households New York Post. Supervisor Jim Desmond said he wants to “see Mexico stand up and fix this issue” but added that San Diego should “at least plan for the worst-case scenario” New York Post. Anderson cast the lone dissenting vote, warning that the project could run into billions of dollars and that “the county just doesn’t have that kind of money” New York Post.
Specification read
The reported $1.8 million is a study budget spread over roughly 18 months, not a build price, so no design flow in m³/day has been published for the proposed facility. Class sizing for a trans-boundary interceptor treating a flow measured in millions of gallons per spill event typically lands in the 50,000–200,000 m³/day range once captured (general industry range, not from the sources), with raw wastewater BOD in the 150–400 mg/L and TSS in the 150–500 mg/L band typical of mixed municipal-infiltration sewage (general industry range, not from the sources). A plant of that class requires a full train: coarse and fine screening, grit removal, primary clarification, biological treatment (A2O or MBR are the most common for tight effluent limits, with MBBR or SBR as alternatives), tertiary filtration, and UV or chlorination disinfection. This project sits at the conceptual and study phase, so it bears on the front-end definition — influent characterisation, site selection and train selection — rather than on a specific unit operation. For a plant manager scoping the same profile — high variable load, high sulphide, discharge to a coastal recreational water body with strict bacteriological limits — the buyer language is influent characterisation study, biological train selection (MBR vs A2O), and disinfection sizing to meet beach-water contact standards. See our Municipal sector overview and our reference on Integrated Sewage Treatment for the relevant treatment trains, with side-by-side detail in the MBR vs Conventional Activated Sludge for Chemicals Wastewater in El Segundo: 2026 Engineering Comparison piece.
FAQ
What did San Diego County actually approve on 2 September 2026? Supervisors voted to pursue a US-side sewage treatment system for the Tijuana River and committed $1.8 million to a multi-phase study over the next 18 months New York Post. No construction award or design flow has been reported.
What size of plant is this likely to require? No design flow has been published. Comparable trans-boundary interception projects typically sit in the 50,000–200,000 m³/day band (general industry range, not from the sources), and the $1.8 million study will define the actual envelope.
What is the expected lead time from study to commissioning? The study phase alone runs about 18 months, and a dissenting supervisor warned the full build could become a multibillion-dollar undertaking New York Post. A full procurement-to-commission timeline for a class of this size is typically 5–9 years (general industry range, not from the sources).
Which treatment train should a buyer evaluate first? For mixed municipal sewage with tight coastal discharge limits, MBR or A2O are the front-runners, with MBBR as a lower-footprint alternative and UV or chlorination for final disinfection (general industry range, not from the sources). Selection should be driven by influent variability and sulphide control rather than by unit cost alone.
