The United States and Mexico signed an agreement on Thursday to end the flow of raw sewage into the Tijuana River, which crosses the border into California and for years has contaminated and closed beaches and caused illnesses in both countries.
The environmental cooperation comes at a time when the two countries have been otherwise sparring on issues like tariffs, immigration and drug trafficking.
Every day, millions of gallons of sewage flow into the Tijuana River starting in Mexico and ending in California, where the polluted water is dumped in the ocean. The sewage frequently overwhelms wastewater treatment plants in both countries. The problem has worsened in recent years as Tijuana’s population has grown, treatment plants in both countries have fallen into disrepair, and climate change has fueled increasingly strong storms.
Lee Zeldin, the administrator of the Environmental Protection Agency, who traveled to Mexico to sign the memorandum of understanding with Alicia Bárcena Ibarra, Mexico’s environment secretary, wrote in a statement that the countries are aiming for a “permanent, 100% solution.”
Under the deal, Mexico agreed to complete an allocation of $93 million toward sanitation infrastructure, and complete all projects by Dec. 31, 2027, the E.P.A. said. The United States, which had withheld funds for water infrastructure improvements on the border, will release money to complete the rehabilitation of a pump station and other projects.
“The Trump administration is proud to deliver this massive environmental and national security win for Americans in the San Diego area who have been living with this disgusting raw sewage flowing into their communities for far too long,” Mr. Zeldin said in a statement.
Ms. Bárcena Ibarra said in a statement the agreement “strengthens collaboration to address environmental and health challenges along the Northern border.”
San Diego County residents have suffered acutely. The Office of the Naval Inspector General this year found that more than 1,100 Navy recruits contracted gastrointestinal illnesses after training in southern San Diego waters. And nearly half of the 40,900 households in the region have experienced health problems, including rashes and shortness of breath, that were most likely attributable to the sewage, according to the U.S. Centers for Disease Control and Prevention.
The agreement comes three months after Mr. Zeldin visited San Diego to begin negotiations with Mexico. It drew praise from local officials, including from Democrats, but some environmental advocates said more needs to be done.
Jim Desmond, a Republican supervisor of the San Diego County Board of Supervisors, wrote on X that the announcement “marks a significant step forward.” He said the federal government had previously failed to hold Mexico accountable for the sewage flowing into California. “Our beaches must be clean, safe, and open year-round — anything less is unacceptable,” he wrote.
Todd Gloria, the mayor of San Diego and a Democrat, thanked Mr. Zeldin on X and called the deal “a huge step toward ending this crisis.”
Matthew Tejada, senior vice president of environmental health for the Natural Resources Defense Council, an environmental group, called the agreement a good start. “It’s great that we’re starting to roll up our sleeves” on this issue, he said.
But he added that the wastewater improvements are enormous and complicated infrastructure projects that are likely going to be hit with unexpected problems, including worsening levels of runoff and sewage exacerbated by climate-fueled storms. “These are really tough projects to implement, with really elusive outcomes,” he said.