The Stringfellow Quarry Company operated a hazardous waste disposal facility in Pyrite Canyon, about 50 miles east of Los Angeles, from 1956 to 1972. More than 34 million gallons of liquid industrial waste were stored there. The site was added to the EPA's Superfund National Priorities List (NPL) in 1983, and active cleanup work has been underway in various forms since 1981.
Contamination affects soil, surface water, and groundwater across the site. Volatile organic compounds (VOCs) found in groundwater include trichloroethene, tetrachloroethene, chloroform, and chlorobenzene. Heavy metals such as cadmium, chromium, copper, lead, zinc, and arsenic are also present in groundwater. Pesticides including DDT and its breakdown product DDE have been detected in both groundwater and soil. Other contaminants include perchlorate, ketones, phenol, toluene, cyanide, and various salts.
California's Department of Toxic Substances Control (DTSC) has been the primary responsible party since 2002, with EPA providing oversight. The site is divided into four zones and five operable units (OUs), each targeting a specific area or problem. Cleanup tools include groundwater pumping and treatment systems, the Pyrite Canyon Treatment Facility for pesticides and metals, and the Community Wellhead Treatment System for perchlorate. More than 600 monitoring wells track groundwater movement. Records of Decision, which are formal cleanup plans, were issued in 1983, 1984, 1987, 1990, and 1996. A site-wide remedial investigation and feasibility study was completed in 2017.
Human exposure to contamination is currently under control. However, groundwater migration is not yet stabilized, meaning contaminated groundwater is still spreading. Local residents get drinking water from the Jurupa Community Services District, which meets safe drinking water standards. Work on perchlorate contamination in Zone 4 is still in the investigation phase, with a formal cleanup decision for that area expected between late 2027 and early 2028. The most recent five-year review was completed in September 2021, and the next review is due by September 30, 2026.
Community members can stay involved through the site's Advisory Committee, which meets quarterly and includes government partners and local residents. Spanish translation is available at meetings upon request. Copies of the upcoming five-year review will be posted online and made available at EPA's Superfund Records Center in San Francisco and the Glen Avon Library in Riverside, California. Questions can be directed to EPA or DTSC staff assigned to the site.
