Fourth Five Year Review Report for the San Gabriel Valley Area 2 Superfund Site, Los Angeles, California

This is the fourth Five-Year Review of the San Gabriel Valley Area 2 (Site) located in the San Gabriel Valley in Los Angeles County, California. The purpose of this Five-Year Review is to review information to determine if the remedy is and will continue to be protective of human health and the environment.

The Site addresses approximately 10 square miles of groundwater contamination in eastern Los Angeles County within the San Gabriel Valley. Groundwater contamination is believed to result from the cumulative impact of decades of improper chemical handling and disposal practices at numerous industrial operations in the Valley. The Site contamination originates at current and former industrial facilities in and near Azusa, California and extends to the southwest through portions of the cities of Irwindale, Baldwin Park, West Covina, and Industry. The most prevalent contaminants in groundwater are trichloroethylene, tetrachloroethylene, carbon tetrachloride, perchlorate, n-nitrosodimethylamine (NDMA), and 1,4-dioxane.