Since the 1930's, raw sewage flowing into the United States from Mexico has posed a serious threat to public health and the environment in the South Bay communities of San Diego. This problem has gradually worsened over the years with the substantial growth of Tijuana's population and industrial sector. Large volumes of untreated wastewater still flows into the Tijuana River valley today.

In July 1990 the U.S. and Mexico agreed to build an International Wastewater Treatment Plant (IWTP) on the U.S. side of the border as part of a regional solution. This facility is now treating sewage flows that exceed the capacity of the existing Tijuana sewage treatment system. In doing so, it plays a key role in restoring the environmental quality of the Tijuana River valley and safeguarding the health of its residents.