In 1945, an Alhambra weedicide distributor poured toxic waste substances into his floor drain. The weedicide passed through the sewage treatment plant without change and entered the Rio Hondo River where it was carried into the coastal plain. Although diluted, the chemicals sank into the underground aquifer used by the City of Montebello, contaminating at least 11 domestic water wells that provided water to 25,000 people in South Montebello. Despite expensive efforts to clean the water, users continued to endure bad tastes and odors for about five years. This incident dramatically increased the urgency for state legislation to regulate industrial waste disposal and groundwater protection. It resulted in California's Water Quality Control Act of 1949 which is held as the nation’s first comprehensive water pollution law.
