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Pacific Southwest, Region 9: Superfund

Serving Arizona, California, Hawaii, Nevada, the Pacific Islands, and Tribal Nations

Intersil, Inc.-Siemens Components

EPA #: CAD041472341

State: California(CA)

County: Santa Clara

City: Cupertino

Congressional District: 14

Other Names:

Bulletin Board

On 10/13/17, this website will no longer be updated. Site information will be migrated to the new web page at: http://www.epa.gov/superfund/intersil-siemens .
EPA appreciates your patience through this transition. If you have questions, please contact EPA staff listed below.


For more information, click any of the following to access the California State Water Resources Control Board GeoTracker web sites:

Description and History

NPL Listing History

NPL Status: Final

Proposed Date: 06/24/88

Final Date: 08/30/90

Deleted Date:

The Intersil/Siemens Superfund Site includes the following three areas: 1) the former Intersil facility, located at 10900 North Tantau Avenue, Cupertino; 2) the former Siemens facility, located at 10950 North Tantau Avenue, Cupertino; and 3) the Off-Site Study Area, located north of and hydraulically downgradient from the two former facilities in Sunnyvale. Investigations conducted in the 1980s as part of the California Regional Water Quality Control Board's (Regional Board’s) underground storage tank (UST) leak detection program found volatile organic compounds (VOCs) in soil on- and off-site. The primary VOC at the site is trichloroethene (TCE).

• Former Intersil Facility - Intersil, Inc. operated at the property from 1968 to 1988 and initiated investigations in 1983. The potential sources of contamination were removed between 1986 and1988, including waste neutralization systems, a waste solvent tank, and an above-ground chemical and hazardous waste storage area.

• Former Siemens Facility - Litronix and its successor, Siemens Microelectronics, Inc., operated at the property from 1970 to the mid-1990s. Until 1982, liquid wastes were stored in five USTs that were removed in 1982. From 1982 until cessation of operations, liquid wastes previously stored in USTs were temporarily placed in the hazardous materials storage area for off-site disposal or recycling. Investigations began in 1982 after the discovery of contaminants during the removal of the USTs.

Drinking water for Sunnyvale and Cupertino is not affected by this contamination. Calabazas Creek, an intermittent stream, is located approximately 1,500 feet east of the site.

Historically, the shallow saturated sediments at the site were divided into three water-yielding zones: the A zone, B zone, and C zone. Regional groundwater elevations rose approximately 50 to 55 feet between 1993 and 1998 from a historic depth of approximately 100 feet below ground surface (bgs). Based on 2013 water level measurements, groundwater is first encountered beneath the site at depths ranging from approximately 35 to 50 feet bgs. Due to the water level rise, the A zone has been further subdivided into A1, A2, A3, and A4 depth intervals.

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Contaminants and Risks

Contaminated Media
  • Groundwater
  • Air
  • Soil and Sludges

Groundwater, soil gas, and subsurface soil have been contaminated with VOCs, however, there is no longer any potential for people to come into contact with contaminated groundwater or soil. Groundwater extraction systems have been operating since the mid-1980s, and soil vapor extraction systems operated for many years at both facilities. Indoor air samples collected at the former Intersil and Siemens facilities and in the residential and commercial areas in the Off-Site Study Area provide no evidence that unacceptable vapor intrusion of VOCs into indoor air is occurring.

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Who is Involved

This site is being addressed through Federal, State, and potentially responsible parties' actions.

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Investigation and Cleanup Activities

Entire Site: In 1986, the Regional Board issued waste discharge requirements under the California Water Code that required Intersil, Inc. and Siemens Components to determine the extent of contamination in groundwater and soil. In 1989, the Regional Board issued site cleanup requirements and approved the work plan and schedule for on- and off-site investigative activities. In 1990, the EPA selected a remedy to address soil and groundwater contamination at the site. In 1990, the Regional Board issued Site Cleanup Requirements Order No. 90-119, which requires operation of ongoing remediation systems and groundwater monitoring.

Initial Actions

Initial actions included the removal of underground waste handling and solvent storage systems and surrounding soil, installation and operation of groundwater extraction systems, and installation and operation of soil vapor extraction systems.

Cleanup Ongoing

Ongoing cleanup activities include operation of groundwater extraction systems. Additionally, soil vapor extraction systems were previously operated, as discussed below.

Former Intersil Facility
A soil vapor extraction system operated from May 1988 to August 1993. Following the review of soil data collected to confirm that the system had achieved remedial objectives, the Regional Board approved shutdown. The system consisted of seven vapor extraction wells and eight vent wells.

A groundwater extraction system has been operating at the former Intersil facility since 1987. The original system consisted of six A4 depth interval extraction wells and one B-zone extraction well. With Regional Board approval, groundwater extraction from three A4 depth interval wells was curtailed in 2002 and 2003 and extraction from the B-zone well was curtailed in 2006 because of very low TCE concentrations. A new shallower extraction well was added in 2010. The current system consists of three wells screened in the A4 depth interval and one well in the A3 depth interval. Groundwater is being treated using granular activated carbon, and the treated groundwater is discharged to Calabazas Creek under a National Pollution Discharge Elimination System (NPDES) permit from the Regional Board.

The most recent vapor intrusion evaluation was completed in the new building at the former Intersil facility in June 2009. Site constituents were not detected in indoor air samples; therefore, the data indicate that unacceptable vapor intrusion is not occurring.

Former Siemens Facility
Soil excavation in 1991 removed approximately 182 cubic yards of soil containing VOCs and semi-volatile organic compounds. A soil vapor extraction system operated at the former Siemens facility from 1983 to 2005. The system was shut down on December 16, 2005. A VOC rebound study conducted in 2006 showed no significant rebound in the VOC concentrations compared to the baseline samples. With Regional Board approval, the system was permanently shut off in August 2006 following the sampling for the rebound study.

Interim remedial actions for groundwater remediation began in 1986 with start-up of a groundwater extraction system, which extracted on-site groundwater from two A-zone extraction wells. The system was expanded in 1988 to include a total of five A-zone wells and three B-zone wells. As part of the final remedy, the system was expanded in 1991 to include ten A-zone extraction wells and three B-zone wells. Based on mass removal rates, the Regional Board has approved modifications to the extraction well network. Currently, the groundwater extraction system at the former Siemens facility includes seven A-zone and one B-zone wells. Groundwater is being treated using granular activated carbon and the treated groundwater is discharged to Calabazas Creek under an NPDES permit from the Regional Board.

Bench and pilot studies conducted in 2006 and 2007 evaluated the feasibility and effectiveness of bioremediation via enhanced reductive dechlorination (ERD) to improve both the rate and efficiency of VOC mass removal from shallow groundwater at the former Siemens facility. The studies showed that ERD can reduce TCE concentrations in groundwater, but additional testing is needed to verify complete reduction of TCE.

Vapor intrusion evaluations were completed at the former Siemens facility in August 2000, August 2002, November 2002, March 2007, and February 2014. The data indicate that there is no risk to indoor workers associated with constituents of concern reported in subsurface soil or groundwater.

Off-Site Study Area
Remedial investigations conducted during the 1980s showed impact to the B zone, but no significant impact to the shallow A zone aquifer. Groundwater extraction from two B-zone wells began in 1990. This system was later expanded to include an additional B-zone extraction well. One extraction well was then curtailed in 2004 with Regional Board approval. Extracted groundwater is pumped to the former Siemens facility for treatment. Investigation conducted since the water level rise in the 1990s indicated elevated concentrations of VOCs in the A zone. Additional investigation is ongoing in shallow groundwater.

An indoor vapor intrusion evaluation was initiated in 2011 in residences and one commercial building in the Off-Site Study Area. Indoor air samples collected in 2012, 2013, and 2014 show no evidence of unacceptable vapor intrusion.

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Cleanup Results to Date

Construction of cleanup remedies has been completed and groundwater cleanup continues.

Former Intersil Facility
A soil vapor extraction system operated from May 1988 to August 1993. Following the review of soil data collected to confirm that the system had achieved remedial objectives, the Regional Board approved shutdown. Approximately 3,000 pounds of VOCs were removed by the system.

Groundwater extraction at the former Intersil facility has resulted in reduction of VOC concentrations in groundwater by over 99% in the A and B zones. As such, VOC influent concentrations to the extraction system have reached asymptotic conditions and the amount of VOCs removed has decreased significantly. Since groundwater extraction began in 1987 through 2013, over 480 million gallons of groundwater have been extracted and over 550 pounds of VOCs have been removed from the groundwater. Approximately 20 million gallons are being pumped per year.

Former Siemens Facility
Approximately 182 cubic yards of soil were excavated in 1991, removing approximately 1,500 pounds of VOCs and semivolatile organic compounds. A soil vapor extraction system operated at the former Siemens facility from 1983 to 2005; the system removed approximately 17,310 pounds of VOCs from the vadose zone.

Groundwater extraction at the former Siemens facility has resulted in reduction of VOC concentrations in groundwater by over 90% in the A zone B zones. Between 1986 and December 2013, the groundwater extraction system removed over 2,600 pounds of VOCs from the groundwater. Approximately 54 million gallons are currently being extracted per year.

Off-Site Study Area
Groundwater extraction within the Off-Site Study Area has resulted in reduction of VOC concentrations in groundwater by over 87% in the B zone. Since pumping began through 2013, approximately 905 pounds of VOCs have been removed. The system pumps approximately 30 million gallons per year.

September 2015 Five-Year Review Findings

In September 2015 EPA and the State of California completed the fifth Five-Year Review for the site. The Five-Year Review concluded that the cleanup remedy is protective of human health and the environment because there are currently no ways for people to be exposed to the contamination associated with the site, including from the vapor intrusion (indoor air) pathway. Three longer-term issues were identified:

Issue #1: Boundary of TCE plume in Off-Property Study Area has not been sufficiently defined.

Recommendation: Further evaluate and define TCE concentrations across the A Zone in the Off-Property Study Area.

Issue #2: A minor increasing trend of VOCs at low levels was observed in three B-Zone wells. A stable trend above cleanup standards was observed in two A- Zone wells and one B-Zone wells. Increasing trends may preliminarily indicate a lack of full control of the TCE plume by the selected remedy (extraction wells) and stable trends may preliminarily indicate ineffectiveness of the current remedy in achieving cleanup standards.

Recommendation: Improve the efficiency of the current pump and treat system and/or develop alternative methods of remediation.

Issue #3: Research has shown that 1,4-dioxane is an emerging contaminant that can be found at sites where 1,1,1-TCA is a COC. However, there is no information regarding the presence and distribution of 1,4-dioxane in the subsurface.

Recommendation: Add 1,4-dioxane to the list of contaminants to be monitored for in regular groundwater sampling and assess whether it should be considered a site COC.

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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.

General Electric Company is the responsible party for the former Intersil facility, SMI Holding LLC is the responsible party for the former Siemens facility, and both companies share responsibility for the Off-Site Study Area. Regional Board Order No. R2-2013-002 (amendment to Order No. 90-119) also named Alecta Real Estate USA, LLC and MOF II Tantau Holdings, Inc as secondarily responsible parties for former Intersil facility and former Siemens facility, respectively, based on their current status as property owners.

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Documents and Reports

Show details for Community InvolvementCommunity Involvement
Show details for Fact SheetsFact Sheets
Show details for Records of DecisionRecords of Decision
Show details for Technical DocumentsTechnical Documents

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Community Involvement

Public Meetings:

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Public Information Repositories

The public information repositories for the site are at the following locations:

Regional Water Quality Control Board,
San Francisco Bay Region,
1515 Clay Street, Ste 1400
Oakland, CA 94612

The most complete collection of documents is the official EPA site file, maintained at the following location:

Superfund Records Center

Mail Stop SFD-7C

95 Hawthorne Street, Room 403

San Francisco, CA 94105

(415) 820-4700

Enter main lobby of 75 Hawthorne street, go to 4th floor of South Wing Annex.

Additional Links

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EPA Site Manager
Melanie Morash
US EPA Region 9
Mail Code SFD
75 Hawthorne Street
San Francisco, CA 94105
EPA Community Involvement Coordinator
Alejandro Diaz
US EPA Region 9
Mail Code SFD
75 Hawthorne Street
San Francisco, CA 94105
EPA Public Information Center
State Contact
Roger Papler
California Regional Water Quality Control Board
1515 Clay Street
Suite 1400
Oakland, CA 94612
PRP Contact
Community Contact
Other Contacts
After Hours (Emergency Response)
(800) 424-8802

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