Intel operated a semiconductor manufacturing facility at 365 East Middlefield Road in Mountain View, California, from 1968 to 1981. The 2-acre site is part of the broader Middlefield-Ellis-Whisman Superfund Study Area. EPA added it to the National Priorities List in June 1986, and cleanup work has been underway in various forms ever since.
The site has 27 contaminants of concern spread across groundwater, soil gas, and soil. Trichloroethene, or TCE, appears in all three media and is the main driver of cleanup activity. Other volatile organic compounds found here include tetrachloroethene, chloroform, vinyl chloride, and several dichloroethane and dichloroethene compounds. Groundwater also contains inorganic contaminants, including arsenic, cadmium, lead, antimony, and phenol.
Intel began extracting and treating groundwater in 1982 using carbon adsorption. The company removed 4,600 cubic yards of contaminated soil by 1986, and soil cleanup is now complete. In 2005, Intel shifted to in-situ bioremediation, injecting emulsified soybean oil into the groundwater, with the most recent injection in 2020. A vapor intrusion remedy also protects people in buildings above contaminated zones, using methods such as sub-slab depressurization and enhanced ventilation. TCE levels across the property are now below 100 parts per billion, but the cleanup target of 5 ppb will take many more decades to reach.
EPA completed a Five-Year Review in September 2024. It found the groundwater and vapor intrusion remedies are protective of human health and the environment in the short term. However, it also flagged that the current approach will not meet cleanup targets for decades and recommended evaluating faster alternative technologies. The review also detected per- and polyfluoroalkyl substances, known as PFAS, above EPA standards in some extraction wells, triggering additional sampling and assessment. Contaminated groundwater is still migrating, and the site has not yet achieved sitewide readiness for anticipated reuse.
Community members who want to stay informed or ask questions can contact the EPA's Community Involvement Coordinator or Remedial Project Manager.
