Emergency repairs to the Parallel Gravity Line — Tijuana’s primary wastewater pipeline that transports sewage near the U.S.-Mexico border — began on May 14. The operation continued through the weekend, and officials from the U.S. and Mexico said that the work prevented additional sewage from entering the U.S. during the remediation.
The International Boundary and Water Commission announced in a May 14 press release that work had begun on a leak in the Parallel Gravity Line. In the release, officials said repairs would take 24 hours and the Mexican side of the IBWC would divert sewage flow from the Tijuana sanitation system to the South Bay International Wastewater Treatment Plant in San Diego, possibly resulting in stronger odors in the Tijuana River and resulting in beach closures.
The repairs are due to the ongoing Tijuana River pollution crisis, which has caused recurring public health concerns in South San Diego County communities. The crisis spans nearly three decades, worsening between 2020 and 2023 due to failing sewage infrastructure in Mexico. Additionally, lack of oversight by the U.S. government has contributed to the crisis, according to San Diego Coastkeeper, an environmental nonprofit dedicated to water health in San Diego County.
Research published by the National Institute of Health showed that about 70% of surveyed households near the Tijuana River reported physical symptoms linked to sewage exposure, including gastrointestinal, skin, and respiratory illnesses. The study also found that sewage-related microbes can spread through coastal aerosols, raising concerns about airborne exposure to pathogens such as norovirus and hepatitis A. Transboundary flows from the river are a major driver of the crisis, releasing up to 35 million gallons of untreated wastewater, toxic industrial waste, and trash into the Tijuana River Watershed daily.
The Parallel Gravity Line carries wastewater in central parts of Tijuana to the South Bay International Wastewater Treatment Plant. The aging line is tied to repeated leaks and emergency repairs, as officials work to rehabilitate decades-old sewage infrastructure contributing to the cross-border pollution crisis. The pipeline is a critical component of Tijuana’s wastewater system, and failures in the line have repeatedly raised concerns among environmental groups and local residents on both sides of the border.
Phillip Musegaas, executive director of local environmental organization San Diego Coastkeeper, said in a statement on Jan. 1, 2026, “Mexico’s failure to enforce its own environmental laws, coupled with its utter neglect of critical sewage infrastructure, has contributed greatly to the border pollution crisis.”
The Tijuana River Coalition — a group of more than 50 community-based organizations, elected officials, academic and public health institutions — said the emergency repairs are only a temporary step and urged officials to move faster on permanent infrastructure solutions. In a statement to The UCSD Guardian, Rachele Hayward, spokesperson for the Tijuana River Coalition, explained that permanent infrastructure improvements are still needed to address ongoing sewage pollution.
“While we welcome short-term progress on wastewater treatment infrastructure, we also need to see governments accelerate movement towards long-term solutions such as river diversion and fixing the outflow,” Hayward said.
Those efforts are necessary “to fix, prevent, and heal the pollution in Southern Californian and Mexican communities and protect our children’s health,” Hayward said.
In the IBWC press release, U.S. IBWC Commissioner W.C. “Chad” McIntosh warned Mexican officials that the U.S. would not tolerate transboundary sewage flows and called for immediate action to prevent further contamination. McIntosh said officials were closely monitoring the repairs and wastewater flows during the 24-hour operation to ensure untreated sewage did not enter U.S. waters.
Mexican officials with the IBWC announced in a separate press release on May 16 that repairs to the wastewater line were successful. Although the procedure increased wastewater flows to the South Bay International Wastewater Plant, the facility was able to treat the increase without issue, according to the release.
The San Diego County Department of Environmental Health has closed the Imperial Beach shoreline since Dec. 24, 2021 due to sewage impacts associated with transboundary flows. Local officials and residents have continued calling for long-term infrastructure investments and binational cooperation to address the recurring pollution crisis affecting coastal communities in South San Diego County.
