U.S. EPA Contaminated Site Cleanup Information (CLU-IN)

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U.S. EPA Technology Innovation and Field Services Division

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U.S. EPA Region 9, 19 pp, 2018

EPA has completed cleanup of the one-acre former Intel Santa Clara 3 Site in Santa Clara, California. In July 1982, Intel found low-level VOCs in the groundwater confined to a shallow groundwater zone below the site. In February 1985, a groundwater extraction and treatment system began operating that consisted of two extraction wells with granular activated carbon treatment and discharged treated groundwater to the San Tomas Aquino Creek. When the 1990 Record of Decision was issued, the max TCE concentration was ~100 µg/L, which was above the 5 µg/L maximum contaminant level (MCL) cleanup criteria. Several pilot studies were conducted from 1994-2005 including in situ chemical oxidation which failed to achieve MCL levels. A 2010 ROD Amendment modified the remedy to monitored natural attenuation. Further testing revealed that TCE levels still measured above the MCL in monitoring wells SC3-3Rep and SC3-1Rep. Intel conducted a pilot test using PlumeStop® in September 2016. Follow-up injections were conducted around SC3-1Rep in September 2017 after TCE concentrations rebounded. After the second injection, TCE was not detected above the MCL for seven consecutive monthly monitoring events. All 18 post-injection results for well SC3-3Rep were non-detect for TCE. A trend analysis post-pilot test determined that groundwater restoration in the area of the two monitoring wells was complete and no further remedial actions were required.

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