San Fernando and San Gabriel valley groundwater are contaminated with toxic solvents and other chemical compounds that a new study says were definitely dumped by humans. A research team found that solvents showed up in high concentrations more than nine times as often in both of the valleys than in other parts of the state.
The paper compares data collected by the federal agency with information from the California Department of Public Health about Los Angeles area aquifers.
Public supplies draw from water from below the surface of both valleys. The U.S. Geological Survey has been testing that well water for hundreds of pollutants.
Southern California water agencies are well aware that metal plating, machinery degreasing and dry cleaning have all left volatile organic compounds and solvents behind as waste. Perchlorate, a contaminant discarded from the rocket industry, showed up in about 11 percent of regional samples.
The study confirms the depth of research about major chemical contaminants and can serve as a baseline for emerging contaminants, like pharmaceuticals, that warrant future testing. Water agencies from both the San Fernando and San Gabriel Valleys are pushing for federal aid to clean up contamination there.