This story aired in the July 22, 2025 episode of Crosscurrents.

Click the above button to listen.

Today, we have part five in a seven-part series looking at sea level rise in California. From the San Diego / Tijuana Border all the way up to Humboldt Bay, we’re visiting some of the people and places that are dealing with flooding, coastal erosion, and pollution… all made worse by rising tides.

KALW’s Emergency and Disaster Preparedness reporter Wren Farrell is the lead producer on this series. Before we get into part five, here’s a quick conversation with Wren.

HANA BABA: Hi Wren.

WREN FARRELL: Hi Hana

HANA: So, catch us up. What have listeners missed?

WREN: A LOT! If you haven’t had the chance to listen to the episodes we’ve aired so far, I recommend going back and listening. But really quickly I’ll say we’ve heard three stories about the way flooding is being exacerbated by sea level rise and climate change, and how different communities are responding to it. We also heard a story down in Santa Cruz, about how coastal erosion and rising tides are impacting surf breaks, and coastal infrastructure, and what the community there is trying to do about it.

HANA: Great, so what’s next?

WREN: Next, we’re going down to the San Diego, Tijuana border.

For decades, pollution from both sides of the U.S. / Mexico border have seeped into the Tijuana River. These impacts have only been made worse by climate change. From the border community of Imperial Beach at California’s Southern tip, reporter Philip Salata tells us more about how pollution, history, politics, and environmental racism all add up to a massive public health crisis.

——

Story Transcript

SARAH DAVIDSON: We’re going to go ahead and get started. Good morning, everyone.

REPORTER: It was a day of ceremony, everyone came dressed in respirators and masks. Behind them the rust-red U.S.–Mexico border wall traced the horizon toward the Pacific Ocean. Above, Border Patrol helicopters drowned out the murmur of the crowd. The occasion? The Tijuana River just got second place nationwide.

KRISTAN CULBERT: We are honored to have worked with the SurfRider foundation and Mar de Colores to list the Tijuana River as number two on our list of America’s most endangered rivers of 2025.

REPORTER: Second place in “most endangered rivers.” It’s a bittersweet announcement for Kristan Culbert from American Rivers, an environmental advocacy group, but it’s one many activists in the region hope will be a gamechanger. It’s been years of work to turn heads nationwide toward what residents of South San Diego communities have had to turn away from for decades – the foul stench of billions of gallons of untreated wastewater flowing into the Tijuana River past residents along its path into the Pacific Ocean.

AGUIRRE: Just this morning, I opened the door to my home and I got hit in the face with the smell of hydrogen sulfide.

REPORTER: Imperial Beach Mayor Paloma Aguirre takes off her mask to address the crowd.

AGUIRRE: I call upon our governor and our president to take immediate action, because if this were happening anywhere else in the nation, especially in affluent communities, we would have had interventions already.

REPORTER: So where exactly are we? The Tijuana River Valley straddles the U.S.–Mexico border. It draws water from mountains and canyons in both countries. It snakes its way west through the city of Tijuana. It then crosses the border into the U.S. where it opens out into a wetland and flows into the ocean.

The sewage in this area is supposed to be treated by water treatment plants on both sides of the border.

As it is, the region produces more sewage than the treatment plants can deal with. And in the last years, the plants have been severely underfunded and have fallen into disrepair.

So that means the sewage either ends up in the ocean or it ends up in the river – which also flows out to the ocean.

In fact, this is actually a seasonal river, normally dry for most of the year. Not anymore. Now it flows year round with sewage. There’s been almost 1300 consecutive days of beach closures.

The thing is, this problem has been years in the making. For more than a century U.S. companies have set up on the border, drawing people to Tijuana for work.

In the 90s came the North American Free Trade Agreement, or NAFTA. The agreement offered tax incentives to multinational companies to build factories along the river in Mexico. Workers throughout Latin America were forced to look north for jobs. They often had to settle in makeshift communities that grew faster than the grid.

But while the city boomed, infrastructure lagged.

And today, while the region continues to grow, so does the sewage-crisis, and it’s growing faster than any solutions the U.S. or Mexico have brought to the table.

Here’s Imperial Beach Mayor Aguirre again.

AGUIRRE: The river is flowing between 20 and 40 million gallons of flow per day, and it’s carrying not just these pathogens, but also chemicals, toxic metals, industrial waste that is going absolutely untreated through our communities.

REPORTER: It’s impacting people and the environment. The Tijuana River wetlands are choked by chemical pollutants and sediment from the sewage runoff. It’s been killing off fish in the protected marsh. And now with sea levels rising, when there’s a high tide, the ocean water with sewage in it gets pushed back into the streets of Imperial Beach.

CSANADI: Okay, so let’s show you where the lab is and stuff. I think my lab assistant, Igor, has taken the day off.

REPORTER: Tom Csanadi is showing me his makeshift lab setup in his garage. Instead of cultivating sourdough in his retirement, Csanadi is cultivating sewage bacteria from ocean water collected from in front of his house.

CSANADI: So I have culture plates. I can sterilize the sampler, take the samples from the ocean water, or from the sand or whatever surface, and I’ve cultured the Tijuana River too and I can plate them out on these culture plates, and basically just kind of set them. I don’t have an incubator, so I just set them in a kind of a warmish spot here, and just give it a little time, usually within a day or so, something grows, typically by day three or so, it blazes.

REPORTER: He picks up a sample to show me what he means. The culture plate is a feverish explosion of color on a tiny white canvas. It’s fecal bacteria, confirming what he and his wife smell.

Csanadi was a pediatrician by trade; his wife Marvel Harrison a psychologist. When Csanadi and Harrison retired, they settled in what they thought was their dream home on the boardwalk of the beach town of Imperial Beach. It’s so close to Mexico, they can see it from their house.

HARRISON: Little Imperial Beach, 27,000 people, is a small town with global issues.

REPORTER: Harrison tells me how residents have to keep their windows closed and sealed, and how even that does not prevent many of them from feeling symptoms associated with inhaling hydrogen sulfide, one of the volatile gasses emanating from the river. There’s nausea, headaches, gastrointestinal and respiratory issues.

Harrison says she has also been extremely concerned by the living here feels stressed, anxious and just stuck.

HARRISON: It all begets depression. When one of the scientists was doing a public health inventory and study and conversation with a person, the woman simply said, I don’t have any choice. I can’t stay here. I can’t move. I think about killing myself, and that’s real.

REPORTER: Now, unwilling to stay quiet, the retired couple are hard at work again. They’ve formed a group of community organizers and experts to fight for solutions to the sewage crisis.

HARRISON: It includes scientists to take care of the science part, public health people, medical people like ourselves and community members, different philanthropic organizations with the overall goal to as soon as possible mitigate the crisis we’re in.

Courtesy of Philip Salata Contaminated Tijuana river water rushes out of a storm water drain.

REPORTER: They’ve even been to D.C. to advocate for more funds to solve the problem.

Harrison and Csanadi see the problem within a bigger context. They weave between each other when they talk and both return to one theme.

CSANADI: There is a very, very strong and deep element of racism in this, as well economic and environmental racism because it’d be just absolutely impossible to imagine if billions of gallons of raw sewage were dumped into a community like La Jolla or Monterey, San Francisco, or Long Beach. How that would not get international attention on day one and not get remedied immediately?

REPORTER: They are aware they live in a predominantly Latinx community and that many of their neighbors who are being impacted by the crisis don’t have the same privileges they do. So when a law firm approached them about joining a class action lawsuit against the U.S. federal government and the private company running the water treatment plant on the border, they were hesitant. They didn’t want to sign on unless they were part of a larger more representative coalition of neighbors. Others joined and now, there are several major lawsuits in the works today.

Some people in the U.S. actually blame Mexico for the problem but on the other side of the border, they are facing the issue in their own way.

Driving across the U.S. Mexico border myself, I couldn’t help but grab my recorder when I smelled that smell.

SOUNDS OF A CAR BEING DRIVEN

I’m about several miles still from the border, and the smell of the sewage, just this rotten egg and chemical smell just poured through the air filtration system into my car with windows closed.

To get to where I’m going, I have to cross the international border, navigate traffic through the city of Tijuana and then head west to the beach. It takes about an hour, but it’s actually not that far from the Csanadi and Harrison’s house in Imperial Beach.

I can actually see it through the cracks in the border wall.

I’m here at this colorful park right at the border wall to meet Margarita Diaz, a waterkeeper. Actually, she is an architect by trade, but…

DIAZ: Many people tell me you’re not working in your profession. And I always say, “Yes, I’m working in my profession because I’m constructing a better world.”

REPORTER: Diaz runs a nonprofit coastal advocacy group focused on Playas de Tijuana, a seaside neighborhood just outside of the city center. It’s grown immensely over the last decades. Because just as the river crisscrosses the border, so do people.

DIAZ: We have a lot of migration, like, so we have migration from the south and from the North. San Diego is a more expensive city. So you have the wealthy that say, like, “It’s halfway or a third to live in front of the ocean and pay less rent than living in San Diego. So we’re coming here.” So what has happened is the developers are saying, like, “Here we have dollars. Let’s construct.”

REPORTER: Diaz points out an irony: while it may be that Mexico’s sewage treatment plants aren’t catching up with how much sewage is being produced, some of that sewage is being produced by Americans who are taking advantage of cheap rent in a Mexican Beach community.

For over a decade her group has been testing water quality along the beaches on the Mexican side of the border and publishing the results monthly. When the sewage treatment plant down here fails, it ends up in the ocean, and the sewage can flow north and affect Imperial Beach, causing that terrible smell. But it can also stick around the beaches here. Her work is the first to show how the Tijuana River sewage crisis is impacting local communities here, too.

Diaz says that might be in part because in Tijuana, people are quite disconnected from its coast.

DIAZ: When I came to Tijuana and started working, I noticed that Tijuana doesn’t recognize itself as a coastal city. And I was very impressed. I go, like, “Why? Why! You have a beautiful, beautiful coast. You have – you’re on the ocean, you’re like, you’re a coastal city.” And nobody sees it.

REPORTER: By focusing on the water quality, she began to turn around the story that the sewage crisis is only affecting U.S. Americans and that it’s all Mexico’s fault.

Her work has been able to fill in the other part of the story and she’s made her data publicly accessible, so residents in Playas would know whether it’s safe to go into the water or not.

She also takes that data to advocate that the solution needs to be binational, because naturally it’s one large system.

To prove her point, Diaz shows me a map of Mexico etched on the cement near the border. She says that the borders between Mexican states are curvy and follow natural features. But the U.S. Mexico border unnaturally cuts the watershed.

DIAZ: And you can see the only straight lines that we have are here!

REPORTER: She says officials on both sides are not fully addressing this as a binational issue. But environmental problems, especially this one, can’t be treated as two problems divided by a line, she says.

DIAZ: We are one community, one coastal community. We’re linked, we’re together in this, and we are related. One works with the other one. You cannot see San Diego without Tijuana. You cannot see Tijuana without San Diego. It’s both sides. They need us. We need them. So we have to work like that.

REPORTER: Like climate change, this doesn’t stop at the border. In fact borders often make environmental issues even more complicated to address. They’re messy, they involve many factors and impact communities in different ways. So rather than focusing on the parts of the problem that may matter more to us, it may help us to see it in its totality, and take responsibility for it.

On the U.S. Mexico border, I’m Philip Salata for Crosscurrents.