Imperial Beach CA | What Happened..
Imperial Beach, CA, a coastal community located at the southernmost tip of San Diego County, has long been a place of natural beauty, with its sandy shores, diverse wildlife, and iconic views of the Pacific Ocean. However, beneath its picturesque surface lies a decades-long environmental crisis that has plagued the region and its residents.
History of Contamination in Imperial Beach, CA
Historical Background
Imperial Beach (IB) sits at the mouth of the Tijuana River, making it a downstream recipient of cross-border pollution from Mexico. For decades, the city has faced chronic contamination driven by untreated sewage flows from Tijuana and associated industrial and chemical pollutants. The issue dates back to at least the mid-20th century: by the early 1960s, rapid growth in Tijuana had outpaced its sewer infrastructure. Mexico attempted to build a sewage canal toward the coast, but funding ran dry in 1962 – resulting in raw sewage flowing north across the border into the Tijuana River valley and the Pacific Ocean (Promises, Promises: The Tijuana sewage crisis timeline – The Coronado News). In response, U.S. authorities constructed an emergency pipeline in 1966 to divert Tijuana’s sewage to San Diego’s treatment plant during infrastructure failures (Promises, Promises: The Tijuana sewage crisis timeline – The Coronado News). Despite these early measures, cross-border spills became a persistent problem through the 1970s and 1980s, frequently fouling the Tijuana River National Estuarine Research Reserve and IB’s beaches. Major failures in Tijuana’s sewage system routinely sent millions of gallons of waste through the river; for example, winter storms in 1980 broke a Mexican sewer line and unleashed ~15 million gallons per day of sewage through the estuary, forcing health officials to quarantine miles of beach up the coast (Promises, Promises: The Tijuana sewage crisis timeline – The Coronado News). Such events highlighted the severe public health threat and ecological damage, as coastal waters and wetlands were tainted with human waste, trash, and toxic substances. Residents and researchers have reported brown sewage plumes in the surf zone, tons of garbage deposited in the estuary, and a stark decline in local wildlife.
The contamination is not only bacterial but also chemical in nature. Untreated wastewater from Tijuana’s urban and industrial areas carries a toxic stew of pollutants. Heavy metals (like lead, arsenic, and zinc), volatile chemicals, and pesticides have been detected in the river and coastal sediments after decades of unregulated dumping () (). One study in 2024 identified 170 different pollutants in Tijuana River sediment, including carcinogenic polycyclic aromatic hydrocarbons (PAHs) and banned pesticides such as DDT, at levels exceeding health thresholds (). Many of these contaminants originate from maquiladoras and other industries in Tijuana that historically discharged waste into the watershed with lax oversight (). This legacy of industrial pollution, layered atop the ongoing sewage problem, has created a complex environmental crisis. Officials note that the wastewater flows constitute “a much broader environmental threat” than just sewage, with hazardous substances embedded in the riverbed and potentially impacting soil, groundwater, and ocean water quality () ().
Key Pollution Incidents
1960s – Cross-Border Sewage Begins: In 1961–1962, Tijuana’s partially built sewage canal failed to contain the city’s waste. Raw sewage flowed down canyons and across the international border, polluting the Tijuana River valley and Pacific shoreline (Promises, Promises: The Tijuana sewage crisis timeline – The Coronado News). By 1966, an emergency binational connection was in place to send overflow sewage to San Diego’s Point Loma treatment plant during crises (Promises, Promises: The Tijuana sewage crisis timeline – The Coronado News). This ad-hoc fix marked the first of many stopgap measures.
1979–1980 – Major Sewage Spills: Tijuana’s main sewage pumping station suffered a major failure in 1979, causing most of the city’s wastewater to bypass treatment. The following winter, in January 1980, heavy storms caused a rupture in a sewage line. An estimated 15+ million gallons per day of raw sewage surged through the Tijuana River and estuary into the ocean (Promises, Promises: The Tijuana sewage crisis timeline – The Coronado News). Imperial Beach and neighboring shorelines were closed for public health; health officials quarantined a 4-mile stretch of coast (reaching north to Coronado) due to dangerously polluted waters (Promises, Promises: The Tijuana sewage crisis timeline – The Coronado News). These events underscored the need for a long-term solution as spill after spill hit the region in that era.
1990s – Binational Treatment Plant Constructed: After years of negotiations, the U.S. and Mexico agreed in 1990 to build a dedicated sewage treatment facility near the border. The South Bay International Wastewater Treatment Plant (SBIWTP) in San Diego’s South Bay was authorized in 1990 (costing ~$256 million, mostly U.S.-funded) (Promises, Promises: The Tijuana sewage crisis timeline – The Coronado News). Construction began in 1994, and by 1999 the plant and a 4.5-mile ocean outfall pipe were completed (Promises, Promises: The Tijuana sewage crisis timeline – The Coronado News). The plant was designed to treat 25 million gallons per day (MGD) of Tijuana’s sewage and discharge the treated effluent offshore in the Pacific (Promises, Promises: The Tijuana sewage crisis timeline – The Coronado News). This significantly reduced routine dry-weather sewage flows in the 1990s. However, the plant’s capacity and uptime proved insufficient over time – peak flows and infrastructure breakdowns continued to send untreated water through the river when the system was overwhelmed or offline.
February 2017 – Massive Sewage Spill: In early 2017, an infrastructure failure in Tijuana led to one of the largest single sewage spills on record. Over the course of about two weeks (Feb 6–23, 2017), an estimated 143 million gallons of raw sewage spilled into the Tijuana River upstream in Mexico (Promises, Promises: The Tijuana sewage crisis timeline – The Coronado News). The contamination poured into the Pacific, polluting beaches from Imperial Beach north to Coronado. Residents reported foul odors and illness, and the incident drew widespread media attention and outrage. It highlighted that despite the binational plant, major breakdowns were still occurring, releasing enormous volumes of waste.
2018–2020 – Escalating Crisis and Legal Action: Chronic pollution continued unabated, and water quality at Imperial Beach hit new lows. By 2018, after repeated incidents of sewage and even chemical discharges, local governments took action. The City of Imperial Beach (joined by the City of Chula Vista and the Port of San Diego) filed a lawsuit in 2018 against the U.S. International Boundary and Water Commission (IBWC) for failing to stop the cross-border flows (Promises, Promises: The Tijuana sewage crisis timeline – The Coronado News). Around the same time, the Surfrider Foundation and other environmental groups also sued or petitioned for relief, fed up with
ongoing violations of clean water standards (Promises, Promises: The Tijuana sewage crisis timeline – The Coronado News). In winter 2019 and 2020, heavy rains again flushed huge volumes of contaminated runoff through the Tijuana River. In response, the U.S. Congress in 2020 appropriated $300 million (under the USMCA trade agreement) to fund infrastructure to curb Tijuana River pollution (Promises, Promises: The Tijuana sewage crisis timeline – The Coronado News). Yet beach closures continued regularly – in fact, IB beaches were off-limits due to pollution for 295 days in 2020 alone ( Bacterial and Chemical Evidence of Coastal Water Pollution from the Tijuana River in Sea Spray Aerosol - PMC ).
2022 – Settlement and Binational Agreement: Years of advocacy and legal pressure yielded some progress by 2022. In April 2022, Imperial Beach and other plaintiffs reached a settlement with the U.S. IBWC, in which federal authorities committed to new mitigation measures for the sewage and chemical pollution (Promises, Promises: The Tijuana sewage crisis timeline – The Coronado News). That same year, the U.S. and Mexico announced a formal binational plan (IBWC Minute 328) to invest in pollution control projects on both sides of the border (Promises, Promises: The Tijuana sewage crisis timeline – The Coronado News). The agreement includes expanding the South Bay treatment plant’s capacity (planned to double to ~50 MGD) and building new infrastructure to capture and treat flows in the Tijuana River watershed (Promises, Promises: The Tijuana sewage crisis timeline – The Coronado News). This marked a turning point toward implementing long-term fixes.
2023 – Record-Breaking Pollution and Emergency Measures: In 2023, the situation reached an alarming peak. Unusually heavy winter rains (particularly a January storm) produced the highest one-day volume of sewage-tainted flow through the river since 1993 (This is ‘on the level of the Flint water crisis,’ warn advocates at California’s southern border - Western City Magazine). Over the year, an estimated 40 billion gallons of polluted water crossed into the U.S. – four times the volume seen the previous year (This is ‘on the level of the Flint water crisis,’ warn advocates at California’s southern border - Western City Magazine). Imperial Beach’s shoreline was essentially continuously contaminated; by mid-2023 the city’s beaches had been closed for over 1,000 consecutive days (California secures critical funding to address Tijuana River sewage crisis in Imperial Beach and surrounding communities | Governor of California), a grim milestone making IB home to some of the most chronically polluted beaches in the U.S. (California’s Most Polluted Beach Is Making Change, but Residents Are Still Suffering the Effects | Pulitzer Center). The extreme conditions in 2023 prompted local officials to escalate calls for help – San Diego County declared a public health emergency, and officials at city, county, and federal levels urged California’s governor and the U.S. President to declare a state of emergency to expedite response efforts.
Government and Environmental Responses
Binational Treaties and Infrastructure: Addressing Imperial Beach’s pollution has required cooperation between U.S. and Mexican authorities. Under a 1944 treaty and subsequent agreements, Mexico has the primary responsibility to prevent sewage from reaching the U.S., while the U.S. is tasked with providing backup infrastructure to capture any cross-border flows In practice, this meant building facilities on the U.S. side to intercept and treat Tijuana’s wastewater. The flagship project was the South Bay International Wastewater Treatment Plant, completed in the late 1990s as a joint effort (funded mostly by the U.S.) The plant, located in San Ysidro just north of the border, was designed to treat 25 MGD of sewage piped from Tijuana and discharge the effluent 3+ miles offshore. Additional “canyon collector” systems were built in five border canyons (Stewart’s Drain, Smuggler’s
Gulch, Goat Canyon, etc.) to catch smaller dry-weather flows seeping across the border and pump them to the plant.
These measures initially helped reduce pollution, but they were not foolproof. Over the years, lack of maintenance and under-sizing of infrastructure eroded their effectiveness. Imperial Beach officials note that the SBIWTP has “often not been fully operational” due to deferred maintenance and historically poor management, and it cannot handle the sheer volume of transboundary flows in major events. When the plant is overwhelmed or broken down, sewage simply flows untreated through the river or coastal estuaries. Even in the best case, the plant never had capacity to treat the 40+ MGD of sewage-laden water that can flow daily in the Tijuana River during routine conditions