Article written by Joshua Emerson Smith. Click here to read this article on The San Diego Union Tribune website.

SAN DIEGO —  Sewage spilling over the border from Tijuana has plagued South Bay shorelines for decades. Ominous yellow and red signs warning of “contaminated water” are frequently posted in the sand from Imperial Beach to Coronado.

Concerns reached a fevered pitch last year after public health officials rolled out a sensitive new DNA-based protocol for testing water quality. A tidal wave of swimming restrictions and warnings followed, stretching through the tourist season.

As Tijuana’s plumbing has continued to crumble, beach closures across the South Bay last year soared to their highest total in more than a decade, according to data from the San Diego County Department of Environmental Health and Quality.

Coronado, frequently named among the nation’s top beach destinations, was plagued by sewage on 51 days, more than double its previous high in 2019.

Heavy rains and repeated mechanical failures in Mexico have kept shorelines shuttered for the beginning of this year. San Diego leaders are now bracing for what could be another brutal summer.

“I am absolutely appalled by the crisis of sewage contaminating our oceans, poisoning our environment and threatening beachgoers,” said county Supervisor Terra Lawson-Remer, whose district includes Coronado.

Beaches are closed only when bacteria levels exceed state thresholds for public safety and there is a “known sewage spill,” according to county health officials. What’s more common across Southern California is the standard yellow and white “advisory” signs posted 72 hours after a heavy rain.

What changed last year was the addition of “warning” signs, posted when bacteria levels spike and ocean currents are moving north from Mexico, but sewage cannot be plainly seen or smelled. The blue and red placards read: “Warning! Beach water may contain sewage and may cause illness.”

The new warning protocol, which gives beachgoers discretion over whether to get in the water, was instituted by the county over the Fourth of July weekend after city officials complained about repeated closures.

In total, signage alerting people to sewage contamination was posted last year on 133 days along the Silver Strand and a whopping 249 days in Imperial Beach. In Coronado, 44 of the 51 days that the city’s shoreline included sewage signage were during spring and summer months.

The Tijuana Sloughs, a once coveted surfing spot at the mouth of the river, hasn’t been open since December 2021.

Bummer summer

Local officials have been shocked by the sizable number of closure and warning days that came with sunny skies and clear weather, when people from around the world flock to places such as the Hotel del Coronado.

The iconic establishment, where rooms can run more than $1,000 a night, declined to comment for this article, other than to say its business “has not been significantly impacted by the closures.”

Still, numerous tourists who visited the area last summer told the Union-Tribune they’d think twice about booking another trip to the otherwise posh city.

Youth programs also were negatively affected. The Cal State Games Jr. Lifeguard competition in Coronado was canceled because of the warning signs, as was the city’s annual Fourth of July Rough Water Swim.

YMCA Camp Surf just north of Imperial Beach got hit especially hard. Enrollment was reportedly down as parents voiced concerns about the lack of ocean access. While individual swimmers have discretion over whether to get in the water, many business aren’t willing to risk the liability when signs are posted.

This year, YMCA’s popular summer program is hoping for the best but preparing for the worst, said Jamie Cosson, executive director of overnight camps.

“We’re getting a plan together right now to shuttle kids to beaches farther north if we have the closures,” he said. “We have a great facility, a great team. Now we just need to get kids to the ocean.”

The broken wastewater plant

The main culprit behind the summertime pollution is believed to be a defunct wastewater facility along the coast in Mexico at a place called Punta Bandera. Federal officials estimate the San Antonio de los Buenos treatment plant, about six miles south of the border, is spewing as much as 35 million gallons of raw sewage a day into the Pacific Ocean.

“This whole conversation wouldn’t be happening if we didn’t have the ongoing effluent from Punta Bandera,” said Imperial Beach Mayor Paloma Aguirre.

“Coronado is now getting to experience what we’ve been experiencing for a long time, unfortunately,” she added. “I feel for both our communities.”

The closures and warnings are necessary to protect beachgoers from dangerously high levels of bacteria and viruses, according to county public health officials. Swimmers who ignore the restrictions could be at risk of diarrhea, fever, respiratory disease, meningitis and even paralysis.

Water polluted with sewage, compared with the typical urban runoff that follows rainstorms, carries a much higher risk of dangerous pathogens, such as E. coli, norovirus and salmonella, officials said.

Not everyone’s concerned. Many people surf and swim at South Bay beaches even when closure signs are posted.

Coronado Mayor Richard Bailey has questioned whether his city’s beaches are any more polluted than in past years or if the threshold for a bacterial exceedance under the new DNA testing has been set unnecessarily low.

“Our main concern in Coronado is the simple question, ‘Is the water safe or not?’” he said. “Coronado’s objective is to make sure the policies in place around warnings and closures align directly with the actual water quality.”

He has repeatedly pointed out that last year beaches were closed even when the traditional culture method — in which scientists examine water samples for bacterial growth in a lab — was meeting state health standards for bacteria.

Falk Feddersen, a professor of oceanography at UC San Diego’s Scripps Institution of Oceanography, who has worked with the county on identifying sources of sewage coming from Mexico, has agreed that the test could use some fine-tuning.

So far, public health officials haven’t been willing to entertain that idea. San Diego is the first coastal county in the nation to institute a federally approved water-quality test using the DNA technology. The process was a decade in the making, including state and federal approvals and a peer-reviewed study.

There’s some hope for the future, though. Significant upgrades to wastewater facilities in Mexico are expected to kick off this year. More than $470 million has been slated for such work under a deal struck last year between Mexico and the United States.

That includes repairs to major pipelines, pumps and other facilities in Tijuana. The construction of a new wastewater treatment plant at Punta Bandera is expected by 2025. The U.S. has also agreed to double the capacity of its South Bay International Wastewater Treatment Plant, which services Mexico, by 2027.

Reports of sewage leaking over the border into the San Diego region stretch back at least to the 1930s. Significant improvements were made in the 1990s, but Tijuana’s wastewater facilities haven’t kept pace with growth while many poorer communities remain unconnected to the city’s sewer system.

Real-time beach conditions are posted at sdbeachinfo.com.