Sewage contamination on Tijuana River prompts San Diego County beach closures

Precipitation carrying tainted water through the Tijuana River into the Pacific Ocean triggered beach closures Tuesday evening from the international border to Seacoast Drive in Imperial Beach.

Signs warning swimmers of sewage-contaminated water along the Tijuana Slough National Wildlife Refuge and Border Field State Park will be posted until bacteria levels return to normal, according to the San Diego County Department of Environmental Health.

Such water pollution has occurred for years during the rainy season, regularly preventing beachgoers in San Diego’s South Bay region from using sections of their coastline.

The pollution from stormwater runoff adds to spills from aging pipes and potentially hazardous discharges from the deteriorating San Antonio de Los Buenos sewage treatment plant in Punta Bandera, located about six miles south of the border.

According to a Union-Tribune analysis of beach-closure data from the county, Imperial Beach has had sections of its shoreline off-limits to swimmers for more than a third of the year on average in the last decade.

When the system is working correctly, pumps in the Tijuana River divert flows of treated wastewater to the treatment plant along the coast.

However, even mild precipitation can overwhelm the system, causing public utility officials in Baja California to shut down the pumps. Tijuana received less than half an inch of rain Tuesday, according to the National Weather Service.

joshua.smith@sduniontribune.com

Smith writes for the San Diego Union-Tribune.