County health officials have posted a water-quality advisory for the San Mateo Creek outlet at Trestles, part of San Onofre State Beach. The notice, effective yesterday at 5:01 PM, warns of possible contamination at the creek mouth and along the Trestles shoreline. Beachgoers, surfers, and pet owners are being told conditions could pose a health risk until testing clears the area.
The change was announced by the County of San Diego’s Beach and Bay program through its SD County Beach Info feed. According to SD County Beach Info, an advisory was issued for the San Mateo Creek outlet ("Trestles") with an effective time of March 10 at 5:01 PM, and the county's beach-status page showed the site listed under advisories at the time of posting.
Beach Status Change, Effective March 10, 2026 at 5:01pm – Advisory issued for San Mateo Creek outlet, “Trestles”, San Onofre.
— SD County Beach Info (@SDBeachH2O) March 11, 2026
For more information visit https://t.co/fvWGWvCAfb
Where the advisory applies
The notice is focused on the San Mateo Creek outlet where the creek meets the ocean beneath the railroad trestles at Trestles. The site lies within San Onofre State Beach, according to California State Parks, and is identified as a monitored sampling station in regional documents maintained by the San Diego Regional Water Board.
What the advisory means
Advisories posted near creek outlets typically warn the public to avoid water contact because runoff or elevated bacteria levels can make ocean water unsafe for recreation. Agencies routinely put up warning signs around affected outlets and keep advisories in place until resampling shows the water meets health standards, as outlined in federal beach-safety guidance from the EPA.
How to stay updated
For the most current status, the County of San Diego directs the public to its Beach and Bay pages or the SD County Beach Info feed, and it also maintains a recorded advisory hotline at 619-338-2073. Per sdbeachinfo.com, advisories, warnings and closures are posted there whenever officials change beach status.
Local impact
Trestles is one of Southern California’s best-known surf complexes and is slated to host Olympic surfing for the 2028 Los Angeles Games, which gives water-quality notices outsized attention among surfers and event planners. Short advisories can affect local lineups and the planning of competitions that rely on Lower Trestles' consistent waves, as reported by the Times of San Diego.
