The San Diego Regional Water Quality Control Board (Water Board) filed a complaint on September 4, 2018 against the United States Section of the International Boundary Water Commission (IBWC), alleging violations of the Clean Water Act (CWA) related to contamination in the Tijuana River. Relying on a 1944 U.S./Mexico treaty, the complaint alleges that the IBWC is responsible for addressing waste entering the U.S. from Mexico along the Tijuana River watershed.