Intel Corp. (Santa Clara 3)

Investigation and Cleanup Activities

Initial Actions

In 1985, the potentially responsible party installed and began operating a groundwater extraction and treatment system until 1993.

Cleanup Ongoing

In 1990, under EPA oversight, Intel completed an investigation of the nature and extent of contamination at the site. The remedy selected by the EPA in 1990 included: groundwater extraction and treatment with an expanded granular activated carbon system to treat the groundwater, discharging the treated groundwater to San Tomas Aquino Creek; monitoring groundwater; and performing a demonstration project to evaluate various groundwater pumping strategies for cleaning up residual VOCs left behind in aquifer material.

Several pumping scenarios were evaluated in an effort to optimize the efficiency of the groundwater extraction and treatment system and in 1991 Intel implemented a cyclic pumping strategy until July 1993. VOC concentrations were leveling off, and the groundwater extraction and treatment system was no longer effective at recovering significant quantities of contaminants. Therefore, the groundwater extraction was turned off in July 1993, and natural attenuation monitoring began. Concentrations of groundwater contamination have decreased slightly; however cleanup levels were not met.

During the period of groundwater extraction, approximately 45 million gallons of groundwater were extracted and treated. Approximately 28 pounds of TCE, the primary contaminant, had been removed. The majority of contaminant mass was removed during the first few years of operation of the groundwater extraction system. Deed restrictions for use of the property were put into place in 1992 and modified in 2008. The deed restriction prohibits the drilling of groundwater wells for domestic or industrial use and restricts the land use.

In 2006, Intel prepared a Focused Feasibility Study (FFS) to compare the ROD-selected groundwater extraction and treatment remedy to other remedial alternatives, such as in-situ remediation technologies. The purpose of the FFS was to determine what other technologies can be implemented in order to achieve more effective and efficient cleanup of the remaining low- level groundwater contamination. Based on the findings of the FFS, Intel performed an in-situ chemical oxidation treatability study at the Site. Intel injected a controlled subsurface oxidizing reaction that reduces VOC concentrations. Deployment of this technology is a potential way to achieve cleanup standards at the Site. The alternative technology did not reduce the remaining contaminant concentrations to achieve the ROD cleanup levels.

In December 2007, Intel prepared a Chemical Oxidation and Technical Impracticability Evaluation Report. This report stated that groundwater restoration at the Site would not likely occur under further pumping or non-pumping conditions in a reasonable timeframe, due to the complex site geology and matrix diffusion, However, since 2007 all but two wells have achieved the cleanup goals.

In 2010, EPA amended the ROD to use Monitored Natural Attenuation to address the remaining low levels of TCE in the groundwater. MNA involves letting naturally occurring physical, chemical, and/or biological processes reduce the amount of contaminants in groundwater.

In March 2010, Intel conducted indoor air sampling to evaluate whether vapor intrusion could expose future building occupants to Site contaminants. There was one detection of vinyl chloride and one detection of TCE, but both were well below EPA Regional Screening Levels (RSLs) for industrial indoor air.

June 2011: EPA completed a fourth Five Year Review for the site and determined that the remedy is protective of human health and the environment. The groundwater contamination has been reduced to below drinking water standards in all but a very limited area; the remedy is expected to achieve drinking water standards site-wide and be protective for the long-term. Any groundwater exposure pathway that could result in unacceptable risks is currently being controlled through a land use covenant that restricts soil excavation and certain types of property development, and prohibits the drilling of groundwater wells.