California’s border crisis worsens: Untreated sewage could flow into U.S. for a full week

San Diego, California – Authorities are warning San Diego’s South Bay residents to prepare for an increase in sewage odors and potential pollution as a major sewer repair project begins on the Mexican side of the U.S.-Mexico border. The work, scheduled to start Tuesday, May 13, marks the second and final phase of the International Collector sewer line connection in Mexico. Authorities expect the work to take about a week to complete.

The International Boundary and Water Commission (IBWC), San Diego County’s Air Pollution Control District (APCD), and other local agencies have cautioned that the construction could temporarily increase the volume of untreated wastewater flowing into the U.S. That influx could worsen odors in communities near the Tijuana River Valley and raise pollution levels at South County beaches.

The sewer line under repair plays a vital role in moving untreated wastewater to two treatment facilities—the South Bay International Wastewater Treatment Plant in the U.S. and the San Antonio de los Buenos Plant in Mexico. Officials say completing the project is critical to preventing potentially catastrophic infrastructure failures and improving the reliability of Tijuana’s aging sewage system.

The IBWC overseeing the cross-border project stated that it has been coordinating closely with Mexican authorities to divert as much wastewater as possible to treatment plants using bypass lines. The agency is also in regular contact with construction managers in Mexico to monitor progress and share updates with the public.

The county’s Air Pollution Control District monitors hydrogen sulfide levels and odor complaints from residents living near the Tijuana River Valley. Officials say the strong rotten egg-like smell associated with hydrogen sulfide may intensify during construction. In response, the county encourages residents to reduce their exposure by staying indoors when odors are strong, keeping windows and doors closed, and using air purifiers or air conditioning when available.

Authorities are advising residents with chronic respiratory conditions such as asthma or chronic obstructive pulmonary disease to have rescue medications ready. If symptoms caused by the odors become persistent or severe, medical attention should be sought. For those affected, the county offers free air purifiers through its AIRE Program to help reduce indoor air pollution.

On Friday, EPA Administrator Lee Zeldin posted on X, formerly Twitter, that the agency had submitted a proposed “100% solution” to Mexico to permanently end the long-standing sewage crisis along the border. Zeldin said technical teams from both countries will meet soon to discuss the details and try to reach an agreement.

The county has also launched an interactive online dashboard to help residents track real-time data on South County beach water quality and odor levels. Further updates and resources are available on the IBWC and county public health websites.