South Bay - International Wastewater Treatment Plant

The South Bay International Wastewater Treatment Plant (SBIWTP) is owned and administered by the U.S. Section of the International Boundary and Water Commission (USIBWC) and is operated and maintained under contract by a private contractor. The SBIWTP was built in 1996 on a 75-acre site near the international boundary in the United States immediately north of the City of Tijuana, Baja California, Mexico and is located at 2995 Clearwater Way, San Diego, CA 92154.

The SBIWTP is permitted to treat up to 25 million gallons per day (mgd) monthly average of raw sewage and other wastewater flows originating from Tijuana consisting of 1) sewage flows exceeding the capacity of Tijuana's sewage collection and treatment and conveyance facilities and 2) dry weather transboundary flows collected from five canyon collectors. The five collectors are located immediately north of the international boundary: Stewart’s Drain, Silva Drain, Canyon del Sol, Smugglers Gulch, and Goat Canyon. These canyons are all tributaries to the lower Tijuana River and estuary.

In 1996, US IBWC, with funding from the U.S. Environmental Protection Agency (USEPA), completed the advanced primary treatment components of the SBIWTP. In 2010, an activated sludge treatment component was added to the SBIWTP to provide secondary treatment.

Along with secondary treated wastewater from the City of San Diego's South Bay Water Reclamation Facility, the SBIWTP discharges secondary treated wastewater to the South Bay Ocean Outfall, which extends westward into the Pacific Ocean approximately 23,600 feet offshore and terminates in a diffuser-wye structure approximately 95 feet below sea level.

The SBIWTP's discharge to the Pacific Ocean through the South Bay Ocean Outfall is currently regulated under Order No. R9-2021-0001 as amended by Order Bo. R9-2023-0009, National Pollutant Discharge Elimination System (NPDES) Permit No. CA0108928, Waste Discharge Requirements for the United States Section of the International Boundary and Water Commission South Bay International Wastewater Treatment Plant Discharge to the Pacific Ocean Though the South Bay Ocean Outfall. Order No. R9-2021-0001 was adopted by the San Diego Regional Water Quality Control Board (San Diego Water Board) on May 12, 2021. Also on May 12, 2021, the San Diego Water Board issued Cease and Desist Order (CDO) No. R9-2021-0107, Cease and Desist Order for the United States Section of the International Boundary and Water Commission, South Bay International Wastewater Treatment Plant Discharge to the Pacific Ocean Through the South Bay Ocean Outfall. The CDO requires USIBWC to address shortcomings, inadequacies, and maintenance issues at the SBIWTP to ensure consistent compliance with the NPDES Permit.

On December 21, 2021, the San Diego Water Board adopted Order No. R9 2021-0220, amending the CDO to revise certain time schedules and require USIBWC to submit quarterly compliance assurance reports.

On March 8, 2023, the San Diego Water Board adopted amendments to the 2021 NPDES Permit.

On December 18, 2023, the San Diego Water Board adopted Time Schedule Order (TSO) No. R9-2023-0189, United States Section of the International Boundary and Water Commission South Bay International Wastewater Treatment Plant Discharge to the Pacific Ocean Through the South Bay Ocean Outfall. The TSO directs USIBWC to take certain actions to correct and prevent further violations of the 2021 NPDES Permit and includes the directive to comply with the secondary effluent limitations in the NPDES Permit by August 15, 2024.

The TSO requires USIBWC to present an oral report to the San Diego Water Board within approximately 180 days of the adoption of the TSO, summarizing USIBWC's efforts to achieve compliance with the directives in the TSO. The Commissioner of USIBWC, Dr. Maria-Elena Giner, provided the update in person at the May 8, 2024, San Diego Water Board meeting.

The CDO and TSO are available on the San Diego Water Board web page:

Cease and Desist Order No. R9-2021-0107 as amended by Order No. R9-2021-0220

Time Schedule Order No. R9-2023-0189

For a copy of other documents referenced above, please email rb9_records@waterboards.ca.gov.

Border water quality updates, including SBIWTP status updates, are included in the San Diego Water Board Executive Officer Reports:

Executive Officer Reports | San Diego Regional Water Quality Control Board