Pacific Southwest, Region 9: Superfund
Serving Arizona, California, Hawaii, Nevada, the Pacific Islands, and Tribal Nations
EPA #: CAD042728840
County: Santa Clara
City: Santa Clara
Congressional District: 15
On this page
Description and History
NPL Listing History
NPL Status: Final
Proposed Date: 10/15/84
Final Date: 07/22/87
The site was constructed in about 1970 and is located at 3050 Bowers Avenue, a light industrial and commercial area of Santa Clara. A large industrial building occupies most of the site. Most buildings in the vicinity are low-rise developments containing office space and research and development facilities. The facility has been used to manufacture equipment for the fabrication of semiconductor wafers from 1974 to the present. During the 1970s, Volatile Organic Compounds (VOCs) were used as industrial solvents for cleaning and degreasing. Acids, caustics, and other chemicals were also used at the facility. The site is located in the Santa Clara Valley, a structural basin filled with marine and alluvial sediments. The natural groundwater flow direction beneath the site is to the north towards San Francisco Bay. Municipal water supply wells tap an extensive, deep, regional, confined aquifer that lies generally greater than 200 to 300 feet below ground surface (bgs).
Groundwater at the site is contaminated with Volatile Organic Compounds (VOCs), primarily of 1,1,1-trichloroethane (1,1,1-TCA), 1,1-dichloroethane (1,1-DCA), and 1,1-dichloroethene (1,1-DCE). In November 1983, VOCs were discovered in a monitoring well down gradient from three Underground Storage Tanks (USTs) on the west side of the large building. Site investigation began shortly after the contamination was discovered. Groundwater monitoring and extraction wells were installed and groundwater extraction began in November 1984. In January 1985, Applied Materials removed the tanks, excavated the contaminated soils, and constructed a groundwater extraction pit.
The site overlies the Santa Clara Valley groundwater basin. Groundwater from this basin provides up to 50% of the municipal drinking water for over 1.4 million residents of the Santa Clara Valley. The site became a Superfund site primarily because of the past chemical releases' potential threat to this valuable groundwater resource.
Contaminants and Risks
Groundwater contains VOCs such as trichloroethylene (TCE). The contaminants in the groundwater could pose a threat to human health if the groundwater is used as a source of drinking water in the future. Presently, there do not appear to be any threats associated with exposure to these contaminants, because area drinking water wells have not been affected by the contaminant plume. Soils were thought to contain VOCs, but studies have shown that they are not contaminated.
Who is Involved
This site is being addressed through Federal and potentially responsible parties' actions.
Initial Actions: In 1984, Applied Materials installed a system to pump and treat contaminated groundwater. The system consists of three extraction wells, an extraction pit, and a dual-column air stripper. In 1985, underground storage tanks and some of the surrounding soil were excavated, and an excavation pit was built. In addition, a down-gradient extraction well and a second deep monitoring well were installed to determine the extent of contaminant migration. When the groundwater treatment plant was operating, the treated groundwater was discharged to a storm drain system, which flows into San Tomas Aquino Creek and South San Francisco Bay.
Soil: In 1990, under the direction of the San Francisco Regional Water Quality Control Board, the potentially responsible parties began a study of the hazards posed by contaminated soil beneath the manufacturing facility. In 1993, it was determined the surface soils are not contaminated and that the saturated soils under the building would be cleaned through the groundwater remedy.
Groundwater: Under state supervision, Applied Materials completed an investigation into the extent of groundwater and soil contamination at the site. In 1990, the EPA chose to continue using the existing pump and treat system, installed in 1984, to remove contaminants from the groundwater. Groundwater extraction began in 1985 and continued through 2002 until contaminant concentrations in groundwater approached declining, asymptotic levels. The pump and treat system operation was discontinued in 2002. Chemical attenuation and plume stability monitoring is ongoing.
Cleanup Results to Date
Construction of all cleanup remedies is complete. Groundwater extraction began in 1985 and continued through December 2002 when the extraction system was discontinued due to declining contaminant concentrations. Since 2002, monitoring of the plume stability and chemical attenuation processes have continued.
The fourth five year review report completed in September 28, 2010, concluded that -
Currently, all monitoring data show that the contaminant concentrations continue to decrease, and with the institutional control in place to restrict the use of ground water as a drinking water source, the remedy is considered to be protective of human health and the environment. EPA is recommending continuation of annual monitoring in the four remaining wells.
Potentially Responsible Parties
Potentially responsible parties (PRPs) refers to companies that are potentially responsible for generating, transporting, or disposing of the hazardous waste found at the site.
The named PRP for this site is:
Applied Materials, Inc.
Documents and Reports
Public Information Repositories
The public information repositories for the site are at the following locations:
EPA Site Manager
Mail Code SFD
75 Hawthorne Street
San Francisco, CA 94105
EPA Community Involvement Coordinator
Mail Code SFD
75 Hawthorne Street
San Francisco, CA 94105
EPA Public Information Center
Regional Quality Control Board
1515 Clay Street, 14th Floor,
Oakland, CA 94612
After Hours (Emergency Response)