Crews performing repairs to a system of pipes meant to send sewage flows from the Tijuana, Mexico, area to treatment plants on both sides of the U.S.-Mexico border reported a rupture beginning the night of March 8 that sent millions of gallons of sewage into the Tijuana River Valley and, eventually, into the Pacific Ocean on the U.S. side of the border.

The spill came after a few days of rain strained the dilapidated water management system in the river valley on both sides of the border. The flow caused an accumulation of debris that blocked one of the South Bay International Wastewater Treatment Plant's junction boxes resulting in minimal flows reaching the plant in southern San Diego County.

"We are working closely with [Mexican authorities] to ensure adequate flows arrive at the SBIWTP to maintain our biological treatment process," said Dr. Maria-Elena Giner, commissioner of the U.S. section of the International Boundary Water Commission in a statement, The IBWC is a federal agency created by treaty to manage water issues between the two nations across the entire southern border from Texas to California. 

The U.S. section of the IBWC said Mexican authorities are waiting for a break in the rain so their personnel can repair the Sanchez Taboada collector, a part of the old international collector system. This collapsed pipeline will result in a discharge of approximately 3.4 million gallons per day to the Tijuana River for approximately six weeks, according to the statement. The U.S. section of the IBWC and U.S. Environmental Protection Agency continue to hold daily calls with Mexico to get updates about the International Collector project.

The international collector is a mostly new pipeline intended to deliver raw sewage to wastewater treatment plants in the both U.S. and Mexico. The old international collector system had pipes that ran uphill in several sections and were prone to breaking down because of gravity in addition to being older and in disrepair. Mexican construction crews are currently installing a bypass to prevent sewage from escaping while the new collector is completed and put online.

Giner's statement also said Mexico continues to search for the source of the sewage flows originally escaping from the old international collector pipe system that was being rehabilitated and partially replaced. "They assure us they have developed a contingency plan to divert these flows during the rehabilitation project."

EPA Administrator Lee Zeldin posted on the X social media platform March 8, "I was just briefed that Mexico is dumping large amounts of raw sewage into the Tijuana River, and it’s now seeping into the U.S. This is unacceptable. Mexico MUST honor its commitments to control this pollution and sewage," he wrote.

Giner said she was encouraged by Zeldin's statement and the mayor of Imperial Beach, Calif., Paloma Aguirre, had written a letter to Zeldin March 3 asking for a new review of the situation on the border, estimating that 31 billion gallons of raw sewage, polluted stormwater and trash had entered her community via the Tijuana River since 2023. Aguirre said she was encouraged that the EPA got involved. 

“I’m glad that he acknowledged that this is a crisis,” Aguirre said in a statement. The U.S. section of the IBWC most recently agreed to more testing for affected communities and Veolia Water North America, which operates the South Bay plant for the commission, has faced lawsuits from residents about the fouled air and closed beaches. Veolia's personnel helped Mexican authorities with emergency work on the ruptured international collector pipes in the last week.

The ongoing international collector rehabilitation and replacement project includes relining and replacing sections of pipe, increasing the reliability of the collector while reducing leaks. Giner's statement said the work was to be completed in one phase, which would have sent approximately 25-30 millions gallons daily of wastewater into the Tijuana River over the course of about three to four weeks. 

Mexico agreed to change plans after U.S. section of the IBWC, EPA, and the U.S. State Department urged it to implement a bypass solution while final connections were made. When completed, the bypass should prevent more than half a billion gallons of wastewater from reaching the river by the time the project is finished later this year.

The new international collector is planned to have the capacity to carry up to 60 million gpd of wastewater and sludge to the South Bay International Wastewater Plant and the San Antonio de los Buenos plant on the Mexican side of the border, bringing more resiliency to the sewage infrastructure in Tijuana and reducing transboundary flows.

Giner has been praised by officials on both sides of the border for bringing action and transparency to dealing with the ongoing crisis over the last four years but she and the incoming Trump administration have not yet agreed to extend her term as the commissioner-engineer in charge of the U.S. section of the federal agency.