San Gabriel Valley (Area 2), also called the Baldwin Park site, sits in Los Angeles County, California. It was added to the National Priorities List on May 8, 1984. Contamination was first found in 1979 after decades of improper chemical handling by local industries. The affected groundwater underlies portions of Azusa, Irwindale, Baldwin Park, West Covina, La Puente, and Industry, and the San Gabriel Groundwater Basin supplies drinking water to more than one million people.
The site has 13 contaminants of concern, all found in groundwater. Key chemicals include trichloroethene (TCE), perchloroethylene (PCE), carbon tetrachloride, perchlorate, and N-nitrosodimethylamine (NDMA). TCE, PCE, and carbon tetrachloride are industrial degreasers. Perchlorate comes from solid-fuel rockets, and NDMA is linked to liquid-fuel rockets. Other contaminants include 1,4-dioxane and 1,2,3-trichloropropane. Contamination plumes run more than eight miles long and reach depths beyond 1,000 feet. The highest PCE reading recorded was 38,000 micrograms per liter, more than 7,500 times the federal and state limit.
EPA selected a pump-and-treat remedy in March 1994. Five sub-projects with a combined treatment capacity of more than 30,000 gallons per minute are built and running. Treatment methods include ion exchange for perchlorate and nitrate, ultraviolet light and hydrogen peroxide for NDMA and 1,4-dioxane, and air stripping or granular activated carbon for volatile organic compounds. As of December 2023, more than 223 billion gallons of groundwater have been treated, more than 122,000 pounds of contamination have been removed, and more than $400 million has been spent on treatment facilities. The systems distribute treated water to over 100,000 local homes and businesses. EPA identified 21 significant contributors to the contamination. Five "Cooperating Respondents" are funding the cleanup under an EPA order from 2000, amended in 2002.
Human exposure is currently under control, meaning no unacceptable exposure pathways exist. Groundwater migration is also under control, with contamination stabilized and no unacceptable discharge to surface water. All water supplied to homes and businesses is regularly tested to meet drinking water standards. Physical construction is not yet complete, and the site has not been deleted from the National Priorities List. A five-year review completed September 15, 2022, confirmed the remedy continues to protect human health and the environment. The next review is estimated between September and November 2027.
Community members can review site records at five local libraries, including the Baldwin Park, Hacienda Heights, La Puente, and West Covina libraries, as well as the EPA Region 9 Regional Records Center in San Francisco. David Yogi serves as the Community Involvement Coordinator and Wayne Praskins is the Remedial Project Manager, both reachable through EPA Region 9. Christine Bucklin of the California Department of Toxic Substances Control handles state-level coordination.
