The Intersil Inc./Siemens Components Superfund site covers 15 acres in Cupertino, California, where two semiconductor manufacturers operated until the late 1980s and mid-1990s. The site includes the two former facilities and an off-site study area to the north. EPA added it to the National Priorities List in 1990 after investigations in the 1980s found volatile organic compounds (VOCs) in soil and groundwater. Localized spills, leaking underground storage tanks, and waste disposal systems are the likely sources. Drinking water for Cupertino and Sunnyvale residents has not been affected.
Trichloroethene (TCE) is the primary contaminant of concern. Groundwater and soil also contain 1,1,1-trichloroethane, 1,1-dichloroethene, 1,2,4-trichlorobenzene, butyl acetate, phenol, trichloroethane, and xylene. These contaminants appear in both groundwater and soil across the site and pose unacceptable risks to human health or the environment without controls in place.
General Electric Company and SMI Holding LLC are the primary responsible parties. Cleanup at the former Intersil facility included soil vapor extraction from 1988 to 1993, which removed about 3,000 pounds of VOCs, and ongoing groundwater extraction that has cut VOC concentrations by over 99% since 1987. At the former Siemens facility, about 182 cubic yards of contaminated soil were excavated in 1991, soil vapor extraction ran from 1983 to 2005 and removed roughly 17,310 pounds of VOCs, and groundwater extraction has achieved over 90% concentration reduction. In the off-site study area, groundwater extraction has reduced concentrations in the B zone by over 87%. Treated groundwater is discharged to Calabazas Creek under permit.
Main construction was completed in September 1992. Human exposure is under control across the entire site, and groundwater migration is stabilized. Indoor air sampling at both former facilities and nearby residential and commercial areas found no unacceptable vapor intrusion. The former Intersil building was demolished and replaced by a commercial building. Kaiser Permanente now operates a medical facility on the former Siemens property. As of December 2024, eight businesses on site employed 30 people. Long-term response action began in October 2024 under EPA oversight, and operation and maintenance continues under state oversight. EPA completed the seventh Five-Year Review on September 26, 2025, finding the remedy short-term protective of human health and the environment.
Community members with questions can contact the EPA Community Involvement Coordinator or the Remedial Project Manager. Site records are available at the EPA Regional Records Center at 75 Hawthorne Street, Room 3110, in San Francisco, or by calling (415) 947-8717.
