Addressing the Tijuana River sewage crisis

December 17, 2025
By Edward Coffey, EPA Region 9 Public Affairs

SAN DIEGO — Communities in the Tijuana River Valley along San Diego County’s beaches have long endured the complex realities of the pollution and raw sewage flowing from Mexico through the Tijuana River and into the Pacific, impacting nearby beaches. In recent years, worsening conditions have made it harder to breathe with the smell of rotten eggs from hydrogen sulfide gas from sewage-tainted flows sending residents and visitors indoors and out of the water.

Residents in the area have endured more than 1,300 consecutive days of beach closures and water concerns since 2021. The odors stem from flowing and stagnant sewage, decaying organic material and environmental conditions that trap and intensify the smell. Weather, tides and the volume of raw sewage influence how far impacts stretch, from Imperial Beach to Silver Strand Beach in Coronado during storms.

“The communities are definitely feeling on a daily basis when the water’s not getting treated,” said Tara Flint Silva, a life scientist and project manager with EPA Region 9’s Water Division. “It causes air quality concerns and beaches are closed, all the things we see on the news all the time.”

Flint Silva is part of a team of staff and managers at EPA with years of experience working bi-nationally and across agencies to address U.S.-Mexico border environmental issues like water quality and cross-border pollution. As a San Diego-based project officer focused on cross-border wastewater infrastructure, she coordinates closely with the International Boundary and Water Commission (IBWC) to advance near-term fixes and long-term projects. She emphasized the stakes for communities downwind and downstream and the necessity of expediting the International Wastewater Treatment Plant (IWTP) construction timeline.

“This is one of two international wastewater treatment plants along the border,” Flint Silva said. “The ability for this plant to treat [Tijuana River] water, all of it that comes across, helps not only the health of the Tijuana River environmentally, the ecosystem, but also the local economy and public health.”

The U.S. and Mexico are accelerating upgrades at the IWTP to intercept sewage in the Tijuana River. A 10 million-gallon-per-day (MGD) expansion is boosting capacity from 25 MGD to 35 MGD, part of a rapid build completed in roughly 100 days to expand capacity while a permanent fix is built over the coming months and years. Once treated, wastewater is discharged via the South Bay Ocean Outfall, a pipeline approximately three miles offshore.

The 10 MGD expansion gives IWTP’s treatment capacity a 40% increase, significantly reducing wastewater flowing into the Tijuana River and addressing the foul smell affecting residents in the area. The original target to expand the plant to 50 MGD was scheduled for 2031, but EPA Administrator Lee Zeldin and Secretary of the Environment and National Resources of Mexico Alicia Bárcena Ibarra signed a new memorandum of understanding (MOU) on July 24, 2025, accelerating the timeline by four years and obligating Mexico to spend $93 million for remaining projects. In addition to the MOU, a recent signing of the new agreement between the U.S. and Mexico, called Minute 333, marks additional progress to permanently end the decades-long issue of sewage flows across the border.

“EPA is working all the time, talking to people on both sides of the border to really try and get things done as quickly as possible,” Flint Silva said. “It’s a really complicated system and I think people are really working as hard as they can to get it done.”