Border Field State Park. Photo by Chris Stone

San Diego County’s environmental health department closed the shoreline near the Tijuana Slough Thursday, cautioning people against coming into contact with the ocean.

The Tijuana River enters San Diego County from Mexico and flows through the southernmost part of the county before it empties into the Pacific Ocean.

Sewage-contaminated runoff that enters the river in Mexico may be moving north along the shoreline, according to a statement Thursday from the county Department of Environmental Health and Quality.

The “water contact closure” covers the shoreline at Tijuana Slough National Wildlife Refuge and Border Field State Park. Officials base such decisions on results from bacterial counts in samples when they exceed California health standards.

The order includes beaches from the border to the south end of Seacoast Drive in Imperial Beach. Closure signs will remain in place until daily water sampling results meet standards for recreational use, county officials said.

Officials also issued a “precautionary advisory” for the rest of the Imperial Beach shoreline on Thursday due to non-river-related impacts, including a south swell.

They issued an advisory for Moonlight State Beach at Cottonwood Creek in Encinitas as well due to the potential for bacteria counts exceeding health standards.

That means county officials suggest beachgoers “avoid water contact in the advisory area.”

Beaches in southern San Diego County have been closed off and on all year.

More information about the Tijuana River is available by calling the U.S. International Boundary & Water Commission at 619-662-7600.

Updates from the county on beach closures are available online. Residents also may call the 24-hour hotline at 619-338-2073

Show comments