The Tijuana River has been at the center of a transboundary pollution crisis on the U.S./Mexico border for decades, resulting in public health impacts, closed beaches and massive environmental degradation of the Tijuana River Estuary and coastal marine waters from Tijuana to Coronado. Despite public pledges to fix the sewage problem once and for all, the U.S. and Mexican governments have so far utterly failed to make real progress.  The crisis has only gotten worse as Tijuana’s population has grown rapidly, immigration pressures at the border persist, and the U.S. agency responsible for treating much of the sewage has let its treatment plant fall into almost complete disrepair. Since October 2023, a staggering 31 billion gallons of raw sewage, polluted stormwater and trash have flowed down the Tijuana River into the Tijuana River Valley and the Pacific Ocean, closing numerous San Diego beaches , and sparking major concerns over public health risks, coastal water pollution and the degradation of the Tijuana River Estuary. This failure has significant repercussions for cross-border water quality and the well-being of communities in the San Diego region.

How did we get here, and why hasn’t there been more progress? The answer is complicated, but we hope to untangle the sorry history of this crisis and find a path forward to make meaningful change. 

Overview of the Tijuana Sewage Plant Crisis

The Tijuana sewage plant crisis is rooted in the complex interplay of rapid urbanization, inadequate infrastructure, and strained binational relations. The South Bay International Wastewater Treatment Plant, located 2 miles west of the San Ysidro Port of Entry, was designed to manage sewage from Tijuana, one of Mexico’s fastest-growing cities. Built in a joint US/Mexico effort in the early 1990’s, its primary function was to treat wastewater pumped from Tijuana before it was discharged into the Pacific Ocean. The South Bay Plant’s system also includes four ‘canyon collectors,’ structures designed to capture untreated flow coming into the U.S. from Mexico through steep canyons and pump it to the Plant for treatment. The International Boundary and Water Commission, the federal agency operating the South Bay Plant, was required to treat the wastewater according to strict terms in the Clean Water Act permit issued by the San Diego Regional Water Quality Control Board(Water Board).The Permit’s discharge limits are set to protect public health and the coastal environment on both sides of the international boundary. However, the plant’s capacity has been significantly outpaced by the city’s explosive growth and the increasing volume of wastewater generated.

In Tijuana, the Mexican government operated several wastewater treatment plants and a system of pipelines and pump stations designed to pump its untreated sewage to the South Bay Plant for treatment. This included the San Antonio de los Buenos treatment plant, which was supposed to discharge treated wastewater into the Pacific Ocean just south of the border. The plant was not maintained or operated properly, and has been discharging nearly 40 million gallons per day of raw sewage onto a Tijuana beach and into the Pacific Ocean for years, adding to the chronic contamination of coastal waters and local beaches. 

Key events leading to the current crisis include repeated failures and overflows, notably in the 2000s and 2010s, where tens of millions of gallons of raw sewage spilled into the Tijuana River and subsequently into the Pacific Ocean. These incidents were often triggered by infrastructure breakdowns, extreme weather conditions, and the lack of adequate maintenance and upgrades in both Mexico and the U.S. The scale of the problem is immense, affecting wide areas from Tijuana to San Diego, compromising water quality, shutting down beaches, endangering marine ecosystems, and posing serious health risks to local communities. With the crisis worsening in 2023 , residents on both sides of the border have had enough. It has become increasingly clear that not enough is being done to fix this problem and that action must be taken to provide comprehensive and sustainable solutions.

Causes of the sewage plant crisis

The Tijuana sewage pollution crisis is primarily attributed to a combination of outdated infrastructure, inadequate maintenance, and natural factors. These elements have been compounded by regulatory and management failures, increasing the severity of the crisis overall. The core of the issue lies in the sewage treatment plant’s inability to cope with the volume of wastewater generated by Tijuana’s rapid population growth and urban expansion. Many of the city’s sewer lines and the treatment facility itself are antiquated and were not designed to handle such a heavy load, leading to frequent overflows and breakdowns.

Lack of regular maintenance and investment in upgrading the infrastructure have exacerbated the problem, with funds often falling short of what is required for such an expansive overhaul.  The unpredictable cycles of drought and heavy, short duration rainfall from “atmospheric river” events have further stressed the already overburdened system, causing untreated sewage to bypass the plant and flow directly into the Tijuana River and the ocean. Regulatory and management failures also play a significant role; there is a critical need for more stringent oversight and coordination between the U.S. and Mexico to ensure that both preventative measures and responsive actions are timely and effective. This multifaceted crisis underscores the necessity for comprehensive strategies that address not only the technical deficiencies but also the binational governance structures overseeing water quality and environmental protection in the region. 

Impact of the sewage plant crisis on San Diego County

The Tijuana sewage plant crisis has had profound and diverse impacts on coastal San Diego County communities, affecting public health, local ecosystems, and the economy. The discharge of untreated sewage containing very high levels of fecal bacteria into shared water bodies has led to frequent beach closures in the county, posing direct health risks from contaminated waters and impacting marine life and habitats. In Imperial Beach, the South County community closest to the border and Tijuana River, its public beaches have been closed for virtually 850 days and counting, denying residents their right to safely enjoy this public resource. These closures and the associated pollution from industrial waste spillage have also had a detrimental effect on tourism, a vital component of the local economy, discouraging visitors from enjoying some of San Diego’s most popular coastal areas. Local businesses, particularly those reliant on beachgoers and water sports enthusiasts, have faced economic downturns during peak Tijuana River pollution incidents, highlighting the extensive economic ramifications of the sewage crisis beyond just environmental and health concerns.

Environmental and Health Impacts

Health Risks

The health risks associated with the Tijuana sewage plant crisis are significant, posing a range of hazards as evidenced by medical and environmental studies. Public health researchers have identified that exposure to untreated sewage can lead to a range of waterborne diseases, including gastrointestinal infections, hepatitis, and respiratory illnesses, particularly among swimmers and others who come into direct contact with contaminated waters. Environmental studies have highlighted the presence of pathogens and chemicals in the sewage that can cause serious health issues over both short and long terms. In addition, recent research suggests that sewage related bacteria and pathogens can become aerosolized under certain conditions, presenting an immediate health risk to residents living near the border who may be breathing contaminated air. Furthermore, the persistent pollution can exacerbate problems like asthma and skin diseases, impacting the quality of life for residents in affected areas and placing increased demands on local healthcare systems.

Impact of Sewage Pollution on Marine Life and the Tijuana Estuary 

It’s no shocker that Tijuana sewage pollution has had severe detrimental effects on marine life, significantly impacting our local marine ecosystems. Scientific research indicates that untreated sewage introduces high levels of nutrients, bacteria, and toxins into marine environments, which can lead to algal blooms that deplete oxygen in the water and cause massive die-offs of fish and other marine organisms. Additionally, pollutants like heavy metals and chemicals found in sewage can accumulate in the tissues of marine mammals, leading to long-term health problems and affecting the reproductive success of species. These disruptions not only harm individual species but also destabilize food webs and degrade the overall health of reefs, seagrass beds, and other critical habitats. What’s more, pollutants accumulated in marine life have the potential to harm community members that eat locally sourced seafood. 

The Tijuana River Estuary has also been severely degraded from decades of sewage, chemicals, trash and sediment being dumped into it on both sides of the border.  This is especially alarming, since the Estuary is one of the few remaining “protected” tidal estuaries in North America, and has been recognized as a “Wetland of Global Importance” by the UN’s Ramsar Convention, an international treaty intended to protect coastal wetlands and estuaries globally.  The Estuary and offshore habitats are home to hundreds of terrestrial and marine species, and provide undeveloped habitat that is critical to protecting and promoting biodiversity.  But decades of pollution have taken their toll.  Excessive flows of sediment and trash have built up in the Estuary, slowly filling in and transforming coastal marsh habitat into dry land and allowing huge volumes of plastic trash to break down into microplastics that further impact the Estuary and eventually coastal marine waters. It is essential that a holistic solution is funded and implemented in the U.S. and Mexico to properly treat sewage, capture and dispose of trash and remove toxic chemicals from the waste stream so that the Estuary and coastal Pacific Ocean will have a chance to recover and rebuild its ecological resilience.