STORY: :: Imperial Beach, California

Imperial Beach is a Southern California community wedged between San Diego and Tijuana, and it's the kind of place where you'd like to stroll the pier, walk the sand, and surf the waves.

:: June 27, 2024

But for the smell...

"It smells here on the beach. It smells at my home. I live right across the street from the beach."

... and the yellow warning signs.

"It's crazy because I live right across the street from the beach and I have a granddaughter who comes but I'll bring her here, where I sit, but I won't put her in the sand because obviously the water comes up and goes down or play in the water."

The reek and the caution is because each day, millions of gallons of raw sewage originating in Mexico is gushing into the Pacific Ocean just south of here. Paloma Aguirre is the mayor of Imperial Beach.

:: Paloma Aguirre, Imperial Beach Mayor:

"We're living the biggest environmental crisis in the nation in my opinion. We have been named, sadly the most polluted beach in the entire United States."

:: Chris Helmer, Imperial Beach Environmental & Natural Resources director:

"So this is what 50 million gallons a day of untreated wastewater looks like. It's kind of sad story where this flow has been flowing like this for two and a half years. That's why our beaches have been closed for over 900 days in Imperial Beach."

Chris Helmer is the director of environmental and natural resources for the city of Imperial Beach, and he's standing alongside the Tijuana River. A mix of treated and untreated wastewater flows into this river from an overburdened and aging treatment plant on the American side of the U.S.-Mexico border.

The International Wastewater Treatment Plant was built in 1997 to treat sewage from the city of Tijuana. It belongs to the International Boundary and Water Commission, a creation of U.S.-Mexican treaty agreements.

Morgan Rogers gave Reuters a tour of the facility, where he said the plant's capacity was strained until it failed.

:: Morgan Rogers, South Bay International Wastewater Treatment Plant:

"So back in March of last year, all five of our primary sedimentation tanks are out of service. So we've been out of compliance with a permit for a while."

When Reuters visited, only one of the plant's five primary tanks - each with nearly the capacity of an Olympic swimming pool - was working properly.

(Rogers) "You can see season flow going through here. But Joe, we're making some good progress to get we need at least three of these tanks online to properly treat the wastewater. So we're expecting that we'll be in compliance again. In the August timeframe."

Rogers said a $30 million upgrade will help bring the plant back to compliance. And he said the plant is also about to undergo a $600 million expansion to double capacity, of which $400 million has been budgeted.

But this struggling treatment plant is only one source of the raw sewage spoiling local beaches.

:: Tijuana, Mexico

About 6 miles south of the border, a tunnel beneath the coastal highway releases gushing wastewater into the Pacific.

It is outflow from San Antonio de los Buenos, Tijuana's broken-down sewage treatment plant.

Mexico says a new $33 million plant under construction is scheduled to come online by Sept. 30.

The total amount of sewage flowing into the ocean is a matter of dispute. But its impact is clear.

(Helmer) "So while Mexico is not officially admitting that they're dumping this amount of water, it doesn't take much deduction to be able to figure out that this is actually sewage, you can see you can smell it, you can visually inspect it as it's flowing into the river valley south of the border, which we have done."

:: Phillip Musegaas, Executive director, San Diego Coastkeeper:

"We've known how to treat sewage for over 100 years, we just need to have the political will and the money to invest in it to treat it properly, because we should not, absolutely not have people living next to a river of raw sewage and toxic chemicals. That's, it's insane."

Phillip Musegaas is the executive director of San Diego Coastkeeper, an environmental organization.

"And that has huge ecological environmental impacts, has enormous public health impacts that we're just learning and learning more about. And it also has ecological impacts to the marine environment and the Pacific Ocean, to the environment here in the Tijuana River Estuary, which is a national wildlife refuge. It's a globally recognized tidal wetland. It's one of the few remaining tidal estuaries on the West Coast of the US, but it's being slowly destroyed and contaminated by this toxic flow of pollution."