Synertek Inc. ran semiconductor manufacturing at a Santa Clara, California facility from 1974 until 1985. Underground storage tanks leaked chlorinated solvents into the soil and groundwater during that time. The tanks and contaminated soils were removed in 1985, but groundwater contamination with volatile organic compounds (VOCs) had already spread roughly 700 feet north of the property. The site was added to the federal Superfund National Priorities List (NPL) in 1989, which flags it as a priority for cleanup under the EPA's Superfund program.
EPA has identified 23 contaminants of concern, all found in groundwater. They include chlorinated solvents such as trichloroethene (TCE), 1,1,1-trichloroethane, and vinyl chloride, along with petroleum-related chemicals like benzene, toluene, and xylene. The list also includes ketones, alcohols, phthalate esters, phenol, carbon disulfide, and 1,2,4-trichlorobenzene.
A groundwater extraction and treatment system ran from 1987 to 2001, treating about 72 million gallons of groundwater and removing roughly 84 pounds of VOCs. TCE concentrations dropped by more than 90 percent over that period. After the system shut down, monitoring from 2001 to 2011 showed continued decreases through natural attenuation, a process where microorganisms and natural conditions break down contaminants on their own. A pilot study from 2011 to 2013 tested enhanced in-situ bioremediation, which speeds that natural process, and showed promising results. Drinking water in the area is not affected because the City of Santa Clara supplies treated public water that meets all drinking water standards. Indoor air sampling in 2013 and 2015 found no unacceptable vapor intrusion from VOCs at on-property or off-property buildings.
EPA's 2017 five-year review found the remedy protective of human health and the environment right now, but noted a new long-term remedy is needed because the extraction system no longer operates. A Focused Feasibility Study is underway to compare cleanup alternatives. The chosen approach will be recorded in an amended Record of Decision after a public comment period. Groundwater is monitored every six months, and the contamination plume remains stable. The most recent five-year review was completed in September 2022, with the next one estimated between September and November 2027. The site has not been deleted from the NPL. Two businesses currently operate at the location, employing 39 people.
Community members with questions can contact EPA's Community Involvement Coordinator or the Remedial Project Manager. For state-related questions, contact the San Francisco Bay Regional Water Quality Control Board.
