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Pacific Southwest, Region 9: Superfund

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

National Semiconductor Corp.

EPA #: CAD041472986

State: California(CA)

County: Santa Clara

City: Santa Clara

Congressional District: 14

Other Names:

Bulletin Board

Vapor intrusion indoor air sampling and mitigation is currently ongoing in Santa Clara and Sunnyvale.
This sampling is taking place in buildings that are over the trichloroethene (TCE) contamination in shallow groundwater. See below for the latest information and the "Documents & Reports" section for reports.

Description and History

NPL Listing History

NPL Status: Final

Proposed Date: 10/15/84

Final Date: 07/22/87

Deleted Date:

The National Semiconductor Corporation (National Semiconductor) manufactures electronic equipment at this 50-acre site. Underground storage tanks, sumps, and pipes are the suspected sources for contaminated groundwater and soil. Since 1982, National Semiconductor has closed its leaking tanks, instituted a groundwater pump and treat system, and removed contaminated soil from selected areas of the facility. The contaminants of concern are primarily chlorinated organic solvents, which, along with other nearby National Priority List (NPL) sites, have contaminated a common groundwater area. Although these nearby sites are listed separately on the NPL, the cleanup activities at some of the sites are being coordinated as part of an area-wide cleanup approach. Approximately 300,000 people live within 3 miles of the site and depend on groundwater as a source of drinking water.

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Contaminants and Risks

Contaminated Media
  • Groundwater
  • Soil and Sludges

Volatile organic compounds (VOCs) have contaminated the soil and shallow groundwater. People who accidentally ingest or come in direct contact with contaminated groundwater or soils may be at risk; however, there is no current pathway by which people can come into contact with contaminants.

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Who is Involved

This site is being addressed through Federal, State, and potentially responsible parties' actions. The State is the lead agency for this site, and therefore is the primary contact.

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Investigation and Cleanup Activities

This site is being addressed in two stages: immediate actions and two long-term remedial phase focusing on cleanup of the entire site and the source of contamination.

Initial Actions

Immediate Actions: In 1982, 36 cubic yards of soil and a waste solvent tank were removed. Since 1982, approximately 400 cubic yards of chemically affected soils have been removed. The company initiated a program of pumping and treating the groundwater to contain the contaminated plume while further site studies are underway.

Cleanup Ongoing

Entire Site: In 1989, National Semiconductor began investigating the type and extent of contamination at the site. The investigation was completed in 1991, and the EPA selected the final remedy for the site. Construction of the remedy began in 1991. The final cleanup remedy, which includes soil vapor extraction and operation of the groundwater extraction and treatment system, is underway and will continue for many years until cleanup goals are met.

Cleanup Ongoing

Source Control: An investigation to determine the nature and extent of the source of contamination at the site was completed in 1991. The remedy chosen to address source contamination is soil vapor extraction. The California Regional Water Quality Control Board (CRWQCB) is currently treating the three most contaminated areas of the twelve source areas, and the remaining nine areas are operational.

This site is being cleaned up under cleanup orders from the Regional Board.

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Cleanup Results to Date

The removal of contaminated soil and the operation of a groundwater pump and treatment system and soil vapor extraction have reduced the potential of exposure to contamination at the National Semiconductor Corp. site while final cleanup activities are underway.

EPA completed the 4th Five Year Review for the National Semiconductor Site in Sept. 2013 and concluded the following:

A protectiveness determination cannot be made until a vapor intrusion assessment is completed at all buildings overlying the contamination. Recent indoor air sampling at on-property buildings south of the Central Expressway have indicated that there is vapor intrusion; however, the exposure levels are below screening health levels while the heating, ventilation, and air conditioning (HVAC) systems are operating.

All other exposure pathways that could result in unacceptable risks are being controlled, and institutional controls are preventing exposure to, or the ingestion of contaminated groundwater.

To be protective in the long term, the following actions should be taken:

    (1) Record new restrictive covenants;
    (2) Revise site management plans to include operation and maintenance (O&M) requirements for the HVAC systems; and
    (3) Amend the Site Cleanup Requirements (SCR) and Record of Decision (ROD) to select a new remedy.

Once the source area and downgradient vapor intrusion assessment is completed a protectiveness determination will be made.

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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.

The PRP for the site is Texas Instruments.

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Documents and Reports

Show details for Fact SheetsFact Sheets
Show details for MapsMaps
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,
1515 Clay Street
Suite 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
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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