Silicon Valley and superfund sites

Silicon Valley got its name from the manufacturing era that began in the early 1960s and lasted into the 1980s, when factories located in Santa Clara County produced microchips and semiconductors with extensive use of acids and solvents such as Trychorethylene (TCE). After being used, these chemicals were stored in underground tanks.

In the early '80s, high rates of cancer and birth defects were detected in Silicon Valley and studies linked these to the chemicals leaking from many of the underground tanks, which had contaminated the soil and the ground water. Of the 96 sites inspected at the time 75 presented leaks.

In 1980 the U.S. Congress created the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), a new program managed by the Environmental Protection Agency, charged with identifying and cleaning up highly toxic sites, or Superfunds, across the Country. When clean up began in Silicon Valley, 29 Superfund sites were identified, based on the Hazard Ranking System and placed on the National Priority List (NPL) of Superfund Sites. The Superfund clean up that started in the '80s included removal of the underground tanks and contaminated soil. Treatment of the ground water also began and continues on many sites to this day.  As sites have been deemed clean they are removed from the NPL and no longer considered Superfund sites.

Today there are a total of 1,336 Superfund sites in the U.S.; 23 are located in Santa Clara County, the highest concentration of Superfund sites per county.


In the early 2,000s testing showed chemical contamination inside buildings located near Superfund sites. Further research showed that some of the chemicals of Superfund sites were migrating through the ground water and eventually evaporated creating toxic plumes that, when trapped inside buildings, could expose people to harmful vapors. Since then, vapor intrusion mitigation has been an integral part of the clean up effort, where both passive and active vapor intrusion mitigation methods are used to ensure that buildings are isolated from toxic plumes located below ground. However, the plumes keep moving and extending beyond the boundaries of Superfund sites; despite monitoring and mitigation efforts, in some cases, the plumes continue expanding, reaching houses, commercial buildings and schools in nearby neighborhoods.

THE EPA in the trump era

The 2018 Budget Proposal presented by the Trump Administration calls for a 31.4% reduction in the EPA budget. The cuts would include among others, a 25% decrease in funds for the Superfund sites clean up and a reduction of about a quarter of the agency workforce. Although the clean up of many of the sites in Silicon Valley is funded by the companies responsible for the pollution, such drastic cuts would harm the clean up process. Some of Superfund sites in Silicon Valley will need continous clean up for decades to come and communities will need to remain vigilant and advocate for the health of their environment in the face of reduced government involvement.


about the photographer

Federica Armstrong is a documentary photographer based in Santa Clara County, she works with non-profit organizations, produces editorial pieces and personal projects related to social and environmental issues. You can view more of her work at

Federica is also the founder and director of the Palo Alto Photography Forum, a lecture series showcasing award-winning photographers and promoting conversations and engagement on global and local issues through visual storytelling.