Site Name: Santa Clara 3 Superfund Site
Address: 2880 Northwestern Parkway Santa Clara,
EPA ID: CAT000612184
EPA Region: 9
Media: Ground water
Contaminants: volatile organic compounds (VOCs),
History of Contamination
No source of the ground water contamination has ever been positively identified at the SC3 site. It has been determined that there is no source continuing to contribute pollutants to existing ground water.
Description of Plume
The current plume covers an area approximately 80 feet by 20 feet (Figure 1). The vertical extent of ground water contamination in the upper water-bearing zone (A-zone) extends to a depth of 27.5 feet below ground surface.
Intel Corporation (Intel) conducted extensive source investigations between 1982 and 1988 and no source of the low-level contamination at the site was identified. In 1985, as an effort to remove the contaminants, Intel began extracting and treating ground water at the site.
By the time the EPA Record of Decision (ROD) was issued in 1990, ground water extraction had reduced VOC concentrations by over 90% and the concentrations were leveling off (Figure 2). The selected remedy in the ROD included: (1) a deed restriction to preclude use of the A zone until cleanup standards are achieved; (2) ground water monitoring; (3) pumping ground water from three extraction wells; (4) treatment of pumped ground water with a granular activated carbon system (GAC); (5) discharge of treated ground water to surface water as specified by the existing National Pollutant Discharge Elimination System (NPDES) permit; and, (6) evaluation of pulsed pumping as a demonstration project at the site. Pulsed pumping is the cycling of extraction wells on and off in an attempt to improve VOC cleanup.
In 1991, Intel implemented the Cyclic Pumping Demonstration Project (the Project). Several pumping scenarios were evaluated during the Project in an effort to optimize the extraction program's efficiency.
Trials One through Four of the Project demonstrated that no ground water extraction was just as effective as cyclic and continuous extraction at containing and reducing the VOC concentrations. The final trial of the Project (Trial Five) included monitoring ground water with the pumps at rest for an extended period. In 2006, Intel voluntarily injected an oxidizing product in an attempt to further reduce the residual VOCs at the site. Since July 1993, when the pumps were turned off, the plume footprint has remained stable and wells show a slow declining concentration trend.
Based on the most recent (June 2015) monitoring results, only TCE in one site well remains above the cleanup standard. The Maximum TCE concentration in this well is approximately 9 parts per billion (ppb), while the cleanup standard is 5 ppb. The TCE remaining onsite does not, and will not, pose a risk to human health or the environment. In 2009 EPA agreed that no additional active remediation is warranted at the site. In September 2010, EPA issued a ROD amendment that officially changed the remedy to "Monitored Natural Attenuation".