U.S. river diversion and treatment

San Diego County is designing a system to capture Tijuana River water on the U.S. side and treat it before it reaches the estuary and the ocean.

Why it matters

It's the only project aimed at storm flows, which average about 109 million gallons a day (2015 to 2019 data) and overwhelm everything built so far.

On September 1, 2026, the Board of Supervisors voted 4-1 to spend $1.8 million from county reserves on the first of three phases. Over about 18 months, staff will work out treatment levels, cost, possible sites and financing. Next, the board would choose a preferred project; then comes permitting and environmental review.
Construction depends on a half-cent countywide sales tax measure on the November 3, 2026 ballot. Supporters say it would fund this project. The San Diego County Taxpayers Association opposes it, pointing to the tax having no end date, no yearly performance targets, and an oversight committee without a taxpayer-advocate seat. What's on the ballot covers both sides.
The site, size, and treatment method haven't been chosen.

San Diego County.

The election result, the design's size and location, and how much storm flow it could handle.