California border officials press state to speed fixes for cross‑border sewage, airborne pollution

Supervisor Paloma Aguirre, chair pro tem of the San Diego County Board of Supervisors, told the State Water Resources Control Board on Sept. 16 that cross‑border flows from the Tijuana River have produced a “public health and environmental crisis” for South San Diego residents. “This crisis, this emergency is the biggest public health and environmental crisis in the Western Hemisphere hands down,” Aguirre said during the board’s public forum. She said researchers from University of California, Riverside; University of Texas at Austin; San Diego State University; and UC San Diego measured hydrogen sulfide peaks “of 4,000 plus, per minute” during overnight hours and reported chronic exposures for residents.

Aguirre described foam visible by satellite in the riparian area and warned that a manmade culvert under Saturn Boulevard increases turbulence and releases gases near schools and day cares. She said the Tijuana watershed has delivered what she characterized as “over a 100,000,000,000 gallons of wastewater” into U.S. waters since 2018 and that San Ysidro’s international wastewater treatment plant, recently upgraded with congressional funds, treats river-adjacent flows but not the river flow itself. Aguirre asked the board to consider expediting a targeted infrastructure removal at the Saturn Boulevard hot spot and to allocate Proposition 4 bond funding to mitigate emissions that she said affect children, the elderly and immunocompromised residents.

Diana Nuri Cumbo, mayor of Calexico, addressed a related cross‑border problem from the Imperial Valley, telling the board that the New River carries industrial and sewage contaminants into the Salton Sea and that evaporation is making dust and pollutants airborne: “The New River isn’t just a Collexico problem nor an Imperial County problem, but a California problem that demands our continued attention,” she said. Cumbo noted the nearly $50 million in state funding appropriated for border water quality and said several local projects are shovel ready.

Board Chair Joaquin Esquivel acknowledged the presentations, said the board has received legislative direction on Prop 4 dollars, and said staff and regional leaders are working with local officials to determine how to allocate funds and whether emergency rulemaking is needed. Esquivel said the board will continue internal discussions and follow up with local leaders about timelines for expending the appropriation.

Why it matters: Board and local officials framed the border flows as both coastal and airborne public‑health issues affecting tens of thousands of residents along the San Diego and Imperial County border region. The speakers tied scientific monitoring and community health surveys to a request for near‑term infrastructure work and use of recently appropriated state bond funds.

Details and context: Aguirre described multiple treatment plants in the cross‑border system, noting San Antonio de los Buenos treats wastewater from western Tijuana and that San Ysidro’s facility treats about 35 million gallons per day following recent upgrades. She said those plants are not designed to treat river flows. Aguirre cited a CDC Community Assessment for Public Health Emergency Response (CASPER) survey and a separate CDC chemical exposure study that, she said, found widespread self‑reported illness among residents in affected neighborhoods. Cumbo said the New River runs 60 miles from Mexico into Imperial County and contributes to the Salton Sea’s worsening conditions and airborne dust.

Board response and next steps: The board did not take formal action at the meeting. Chair Esquivel said staff will continue internal deliberations about how best to spend the appropriation and the regional board’s work with local partners, and he pledged follow‑up meetings with local officials to discuss timelines and allocation options. Local officials requested the board consider expediting the Saturn Boulevard infrastructure change as a near‑term mitigation.

Sources: Public forum presentations by Supervisor Paloma Aguirre and Calexico Mayor Diana Nuri Cumbo; board chair Joaquin Esquivel’s remarks during the Sept. 16, 2025 State Water Resources Control Board meeting.