There are 29 Superfund sites in Silicon Valley- the most concentrated number of Superfund sites in America. Nineteen of these sites were contaminated by high tech firms in the manufacturing of computer chips which used highly toxic chemicals including, trichloro-ethylene, Freon, trichloroethane and poly-chlorinated biphenyls (PCBs).           A Superfund site is any land in the United States that has been contaminated by hazardous waste and identified by the Environmental Protection Agency (EPA) as a candidate for cleanup because it poses a risk to human health and/or the environment. {For more info: Go to Superfund Site!} August 8, 2006 10am-5pm The tour is full. ............................................................ Where: The tour begins in San Jose/ ISEA and travels across Silicon Valley. ............................................................ Why: Because we like you and to make you ask more questions! ............................................................