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AGUAS NEGRAS: In 2 Mexican beach towns, raw sewage is running through the streets

This project was supported by the Pulitzer Center on Crisis Reporting.

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This special reporting project from KJZZ's Fronteras Desk and the Arizona Daily Star explores an ongoing sewage crisis in Guaymas, Sonora. The port city’s deteriorating system frequently sends raw sewage running through the streets, onto beaches and into the Sea of Cortez. Earlier this month, the governor declared the situation a sanitary and environmental emergency.

Sewage spills in Guaymas are causing a health and environmental emergency

Listen to Part I


Sewage trickles down an arroyo just outside Teresa Cortez’s house in Guaymas — a southern Sonoran port city home to the tourist-beloved beach destination San Carlos.

For years now, residents in Guaymas have been living with a collapsing drainage system riddled with leaks and clogs, broken pumps and pipes. But during the summer monsoons this year, the situation reached a crisis point.

Teresa Cortez stands near a huge pond of water created by sewage that is leaking from a pipe near her house in Guaymas, Sonora. Kendal Blust/KJZZ

“It’s stressful. Infuriating,” said Cortez, a 52 year-old, life-long resident of the city who is raising four young grandchildren. “Because it smells horrible.”

It’s a hot September morning, and once again, wastewater has bubbled up from a clogged pipe nearby, flooding the arroyo and stagnating in huge, green, foul-smelling pools outside her home.

More from Kendal Blust on The Show with host Mark Brodie


The nauseating stench burns your eyes and throat. It keeps her up at night with headaches.

“And if I, an adult, a grown up, can’t sleep because of the stink, just imagine! I have a 3-year-old grandson, and another who’s 4,” she said. “The smell gets in the house, even with everything closed up. We can’t sleep. They complain about headaches. Their eyes and noses sting because of the smell that gets inside."

Teresa Cortez sits in her living room with four of her grandchildren. They have all suffered this summer from the stench of sewage that runs in an arroyo near the house. Guillermo Soberón Tirado

The kids can’t even go outside to play anymore, she said, because of the stink and the health risks.

Health risks

Exposure to sewage can cause Hepatitis A, diarrhea, eye and skin irritation or infections — even cholera, said Silvia Montero, a doctor who works for the city’s public health department.

“It’s a huge problem,” she said. “A lot of people are getting sick because of the sewage.”

And it’s not just liquid sewage people need to worry about, she added. Once the wastewater dries, it becomes bacteria-laden dust that can blow into people’s eyes, mouths and food. No matter how many precautions people take, she said, it can be hard to escape the dust.

Contact with sand and sea water that has been contaminated can also pose a risk, said José Arreola, director for the Northwest Center for Biological Research in Guaymas, known as CIBNOR.

Little work has been done to study the health impacts of the sewage spills in Guaymas, he said, and it would be hard to separate illness caused by wastewater from other factors, like poor trash collection that leaves garbage often rotting in the streets. Still, he said, it’s clear it’s impacting people’s well-being.

“It’s absolutely a problem,” he said. “There’s no doubt this is having adverse effects on public health.”

And for residents like Cortez and her family, there’s no escape.

After more than 26 years in her home, she said she can’t imagine moving.

“And anyway, where would I go?” she asked. “Anywhere I go in Guaymas, it’s the same.”

Pedestrians make their way across Avenida Serdán in Guaymas, where wastewater is running through the street on Sept. 9, 2021. Kendal Blust/KJZZ

Sewage in the streets

Downtown, sewage gurgles up from a manhole, overflowing onto the main street. Passing cars send waves of wastewater sloshing onto the sidewalk as pedestrians carefully pick their way across streets glistening with the rank runoff — much of which eventually flows straight into the sea.

“You get very sad when you see the sewage that’s going toward the ocean,” said Tomás Thomas, co-owner of Marvida brewery in San Carlos — the tourist haven just northwest of Guaymas known for its beautiful beaches, spectacular sunsets and striking mountains that roll right down to the sea.

“And San Carlos has all these activities like scuba diving, hiking. It’s got a lot of restaurants, a lot of sightseeing, a lot of activities,” he said. “And residents, they call it ‘sleepy San Carlos.’ It’s calm, quiet. There are no stoplights in the town, that gives you an idea.”

“And there’s no other place on the coast of Sonora that’s like this,” he said.

But he worries that the town’s tourism potential is at risk with frequent sewage leaks, like one that plagued a popular beach known as Cotton Cove all summer, sending sewage flowing from a manhole down a cobbled pathway and onto the sand where beachgoers splash in the surf.

Like many of the leaks in San Carlos and Guaymas, that one has been recurrent, sometimes taking days or weeks to fix, and quickly coming back because underlying issues like broken pumps are rarely resolved. And in some parts of town, wastewater regularly pools outside of homes and restaurants, the stink souring patrons' meals.

“It could be reckless,” said Thomas, who is also concerned about the public health impacts. “And it could definitely hurt business, you know, and the image of our brewery on the marina.”

Sanitary emergency

Authorities admit there’s a problem.

Last month, Gov. Alfonso Durazo declared a sanitary emergency, setting aside nearly half a million dollars to address the immediate crisis, and promising to invest in a long-term solution.

“It’s clear there’s an urgent problem. It’s obvious,” said Heriberto Aguilar, head of the state infrastructure department, known as SIDUR, which is taking a leading role in the state’s planned interventions.

Sewage trickles down a cobbled pathway onto Cotton Cove beach in San Carlos, Sonora. Emily Bregel/Arizona Daily Star

“This never should have happened. It never should have happened because there should have been a program earlier to attend to the issue so we didn’t get to this situation. The problem is that there was no maintenance of the system, and now we’re in a serious situation, very serious,” he said.

The current administration understands that Guaymas is on the verge of a health and environmental crisis, and cannot wait to take action, he said.

But it won’t be easy, said Ivan Cruz, who oversaw the state water commission, called CEA, in Guaymas for two years, until he was replaced in September when new state leaders took office.

“We’ve always seen Guaymas as a very complicated, very complex system with a lot of challenges. A lot, a lot of challenges,” he said. “All the challenges that there are in every other water operating system in Sonora, Guaymas has all of them.”

Those include obsolete and poorly maintained infrastructure; shallow pipes due to the city’s rocky soil; and a hilly landscape that makes it difficult and costly to pump sewage to oxidation lagoons, which themselves provide insufficient wastewater treatment.

It’s also chronically underfunded.

Financial troubles

“Without resources, it’s really difficult to provide good service. And the service isn’t good, the public is going to say, ‘Oye, why should I pay you for providing such poor service,’” he said. “It creates a vicious cycle.”

Last year, during the pandemic, payments rates in Guaymas were as low as 19% — down from about 60% pre-pandemic, he said. That means the water commission in Guaymas barely has funds to pay its workers, much less address serious systemic issues, even with significant state subsidies. This year alone, CEA officials estimate they put about $4 million into the insolvent Guaymas operation, which has also accumulated about $15 million of debt, according to a statement from current officials.

But it’s not just unpaid bills.

“The reality is that, even when the department brings in 100% of what it charges, even then it’s not enough to cover operating costs,” Cruz said. “That’s one of the biggest challenges for Guaymas, to update its water rates so that it reflects the real costs and can break this vicious cycle and start investing in the system.”

A salon owner in downtown Guaymas set up a ramp across a stream of sewage on the streets outside his business on Sept. 9, 2021. Kendal Blust/KJZZ

Former state CEA director Sergio Avila agreed, insisting the only way to fix the current crisis in Guaymas is to bring payments in line with costs.

The problem is, Guaymas is one of just three municipalities in Sonora where water and sewage systems are operated at the state rather than local level. But the municipal government still controls the water rates, and has little motivation to make the unpopular decision to increase the cost when CEA bears the responsibility for providing services.

But Guaymas is far from alone in facing serious sewage issues, and even locally operated systems face many of the same challenges: a high-ranking official with Hermosillo’s water utility told KJZZ in 2019 that maintenance of the capital city’s aging sewer system is minimal, and breaks and collapses cost the city millions of dollars in repairs annually. In 2019, a man was killed in a sinkhole caused by the city’s deteriorating infrastructure.

‘We don’t know who to believe’

Current officials promise to tackle the problem in Guaymas. But some locals find it hard to trust leaders after decades of inaction.

“I hope so,” said Claudia Fourcade, 24. “But the truth is, we don’t even know who to believe anymore.”

She has little confidence this administration will be different from previous ones, and it’s easy to see why: a broken pipe just outside her front door runs with green liquid, flowing out into the street. Day and night her home reeks with the stench of sewage. She said it’s been like this for years. Occasionally it gets fixed, but the problem just keeps coming back.

“I’ve lived in this house my entire life,” she said. “There have always been sewage issues.”

She and several neighbors are staging a protest after making multiple complaints to the water commission without a response, she said.

They’ve barricaded the road with bags of trash and debris, and hold up signs demanding to be heard and attended to.

Nearby, a few drivers complain about being rerouted by the demonstration. But Fourcade said they should put themselves in her shoes — waking up every day in this stench. Unable to enjoy meals or feel clean. It makes her daughters, just 5 and 7, sick to their stomachs.

“No one can feel what it’s like to live here,” she said. “It’s horrible living like this.”

Brenda Lopez works at her outdoor tortillas stand in Guaymas, near where sewage is flooding the street on Sept. 9, 2021. Kendal Blust/KJZZ

Bad for business

Nearby, Brenda Lopez is working at an open-air tortilla stand.

“Sales have gone down a lot,” she said. “Because people don’t want to buy things in this filth.”

Her business is suffering, and so is her family.

Her 6-year-old son, who’s playing nearby with some other children, has spent 12 days with diarrhea and vomiting, which she believes is caused by exposure to the sewage in the street here.

“I don’t even know what to do anymore,” she said. “Help us, help please! It’s too much to bear this every day. It’s too much.”

Like many in Guaymas, she said, she can’t take much more.

Floating wetlands and new commitments: Solutions in Guaymas are possible, but not guaranteed

Listen to Part II


It’s a sticky, overcast September morning, and a trio of researchers are heaving a gray rubber rowboat off the back of a truck onto the edge of a huge lagoon in Guaymas.

They pick up yellow oars and row out into murky waters, lined with bright green cattails and castor plants swaying in the breeze on this sticky, overcast morning.

Pelicans and white herons fly overhead, and a noisy coot makes its presence known along the shore.

It would be an idyllic scene, if it weren’t for the smell — an acrid stomach-turning stench.

This is La Salada. And its four ponds are filled with countless gallons of Guaymas’ sewage.

“These are oxidation lagoons. It's primary treatment, and the water goes to the ocean there,” said Jaqueline García Hernández, pointing to three large outflow pipes discharging into the nearby bay.

Floating wetlands on the La Salada oxidation lagoon in Guaymas, Sonora, are designed to help treat sewage that flows into the ponds. Guillermo Soberón Tirado

Garcia runs the Environmental Sciences Lab at CIAD, a federally funded research center in Guaymas.

Without a conventional treatment plant, sewage from Guaymas’ nearly 120,000 residents is pumped across the city’s hilly terrain to La Salada’s four oxidation ponds, she said. The lagoon relies on time-dependent natural processes to reduce organic matter and pathogens.

But the population has exploded, increasing by more than a third in the last 30 years, and these pools are no longer doing their job, Garcia said.

“It’s not enough for the amount of water. I think the volume is too much,” she said.

That leaves insufficiently treated water pouring straight into a small bay of the Sea of Cortez, still carrying levels of fecal coliforms up to 350 times the legal limit in Mexico. Federal environmental regulations require wastewater being dumped into the ocean to contain less than 2,000 fecal coliform parts per 100 milliliters.

The four ponds of the La Salada oxidation lagoon are now insufficient to treat all of the wastewater pumped in. Guillermo Soberón Tirado

Problems in the sea

Fecal coliforms, a bacteria found in the intestines of warm-blooded animals, are often used as a proxy for fecal contamination and other pathogenic bacteria in water.

The flow of wastewater in the ocean can have serious negative effects both to humans and the environment, said José Arreola, CIBNOR director.

“In addition to all of the fecal bacteria and other pathogens that are a public health risk, urban wastewater also carries other contaminants as well as nutrients, like nitrogen and phosphorus, that can create serious problems in the sea,” he said.

Those problems include harmful algal blooms and depleted oxygen levels that can kill aquatic life.

But Garcia and her team hope they’re on to a method that can significantly improve the lagoon’s performance and reduce the pathogens and nutrients in the water by creating a system of floating wetlands on the final oxidation pond.

“I think we can help reduce nutrients and fecal coliforms. So those are the most important contaminants to harm the ocean,” she said.

Floating wetlands

Floating wetlands on the La Salada oxidation lagoon in Guaymas, Sonora, are designed to help treat sewage that flows into the ponds. Guillermo Soberón Tirado

These wetlands, crafted on a tight budget, use mesh platforms held afloat by plastic bottles to grow cattails on the surface of the pond.

The plants help remove dangerous pollutants and nutrients, and inject oxygen into the wastewater.

So far, their results have been promising, Garcia said. A 2019 pilot project showed wetlands placed near one of three drains into the sea significantly reduced levels of fecal coliforms compared to the other two outflows — though they were still well above environmental standards.

But Garcia said she feels confident that with funding to expand the wetland project to cover the entire final pond with floating cattails, they could eventually bring the water into compliance. And for much less cost than a conventional wastewater treatment plant, she added.

“We are doing something, but this is just a research project,” she said. “But it could work for Guaymas. It would cost a tenth of a water treatment plant and I think it would be a good solution for Guaymas.”

She thinks it would only cost about $100,000 to redesign the lagoons to maximize water contact with the wetlands and dramatically reduce nutrients and pathogens in the water.

“The common knowledge is that you need a water treatment plant to treat all of the sewage, but these new treatments are equally efficient or even better,” she said.

And because so many cities in Mexico and around the world rely solely on oxidation lagoons, she hopes their wetlands research will provide an inexpensive upgrade.

A gray heron rests on a floating wetland installed in the final pond of the La Salada oxidation lagoon in Guaymas, Sonora. Guillermo Soberón Tirado

Conventional treatment

Some experts, however, are skeptical.

“It is very optimistic to say that you could ever achieve any water quality standard for fecal coliforms at the end of a pipe no matter how many floating wetlands you have out there,” said David Walker, a research scientist at the University of Arizona’s Department of Environmental Sciences.

In the United States, oxidation lagoons are never used as the only form of sewage treatment, he said. Instead they are usually “polishers” for water that’s already passed through a conventional plant.

Even when lagoons have a high removal rate for pathogens like fecal coliform bacteria, that may not mean the water is safe, he said.

Insufficiently treated wastewater pours out of the La Salada oxidation lagoon in Guaymas, Sonora, and into a bay on the Sea of Cortez. Kendal Blust/KJZZ

“If you’re starting at a huge level (of pathogens), like what’s found in raw sewage, it’s really not difficult to show a high rate of removal efficiency,” he said. “This doesn’t mean the effluent is by any means safe, because that 10% residual could still be many fold higher than what would be considered safe to release into the environment.”

Experts have been saying for decades that Guaymas needs multiple modern treatment plants — two for the city and another for nearby tourist town San Carlos, which also relies solely on its own three-pond oxidation lagoon. Water treated there is used to irrigate a nearby golf course, but water-quality testing has turned up inconsistent results at the lagoon.

In August, a busy tourist month, levels of fecal coliform bacteria were 40 times higher than Mexico’s national standards. But just six weeks later results had dramatically improved and were in compliance with environmental norms, suggesting that the effectiveness of the ponds depends on the volume of wastewater being pumped into the lagoon, Garcia said.

As San Carlos continues to grow, the lagoons will likely become less and less effective, particularly without proper maintenance.

Sewage in San Carlos, Sonora, is all pumped into three oxidation ponds. The water from the final pond is used to irrigate a golf course. Guillermo Soberón Tirado

And government officials now say they are taking steps toward constructing at least one water treatment plant to address the overburdened lagoons.

Government response

“What we’re doing is reconfiguring the whole system so that part of the wastewater will be treated in conventional plants and the other part in the lagoons, which will allow the oxidation lagoons to operate at the volume of input it was designed for and produce acceptable results,” said Aguilar, the state infrastructure department head.

“The other part is building a treatment plant for the rest of that water, which then can be used to irrigate public gardens and parks,” he added.

The state water commission has said it’s working to acquire a 24-acre parcel of land in the northern part of the city for the facility.

This plan is part of the state government’s efforts to address what it declared in November as a health and environmental emergency in Guaymas caused by a neglected and deteriorating sewage system.

“It’s a crime against nature, and having sewage flowing through the center of the city is unworthy of the people,” Aguilar said. “We never should have reached this point. It means we’ve failed.”

Sewage water flows down an arroyo in Guaymas, Sonora, and into a bay on the Sea of Cortez. Guillermo Soberón Tirado

Aguilar, who was appointed in September when Gov. Alfonso Durazo took office, said much of the problem is caused by years of poor maintenance, as well as a growing population.

Over the next three years, officials promise major investments, including repairing broken pumps and replacing outdated pipes, as well as building a new treatment plant.

They will also try to address the water commission’s dismal financial situation, in part by raising water rates that leaders say are far too low to cover costs. So far, however, local officials — who set the rates — have only approved an incremental increase that water commission leaders say won’t be enough to fill the gap between actual costs and user fees.

Still, Aguilar said the state government has a strong motivation to find the funds necessary to address the current crisis.

“If we don’t resolve the basic sewage issues, we can’t aspire to greater tourism potential or to develop our port,” he said, referring to two major priorities of the current administration. “So first things first. And that pushes us to resolve this with the resources that it takes.”

‘A good system’

Jaqueline Garcia and Germán Leyva paddle out into the La Salada oxidation lagoon to fix some floating wetlands that were blown off course during a recent storm. Kendal Blust/KJZZ

But the Guaymas researchers aren’t giving up on their floating wetlands at La Salada.

They’re still optimistic about the potential to dramatically improve water quality here for a fraction of the cost of a conventional treatment plant.

“I have faith in this wetland system,” Garcia said. “Because it’s not very expensive, and it’s low maintenance.”

While officials are promising the new treatment plant, she said the reality is conventional plants are not only expensive to build, but also to maintain.

“They are very expensive in energy and maintenance and they usually stop working in a few years. So it’s not working in Mexico,” she said. “And water treatment plants also leave some contaminants out. The wetlands are very efficient in treating those. So it’s a good system.”

And a realistic one that can be implemented now.

Garcia and her fellow researchers aren’t opposed to a conventional treatment plant for Guaymas, and they admit it would bring real benefits. But they’re not going to wait around for one.

Emily Bregel, reporting for the Arizona Daily Star in Tucson, contributed reporting for this article.

Kendal Blust was a senior field correspondent at KJZZ from 2018 to 2023.