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Pacific Southwest, Region 9: Superfund

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

Teledyne Semiconductor

EPA #: CAD009111444

State: California(CA)

County: Santa Clara

City: Mountain View

Congressional District: 14

Other Names:

Bulletin Board

Vapor intrusion indoor air sampling is ongoing in the neighborhood around the site, and mitigation work is in progress at buildings found to be affected by vapor intrusion. EPA’s Fourth Five-Year Review was completed in Sept. 2014, concluding that the vapor intrusion investigation needs to be completed before a “protectiveness determination” can be made. See below for the latest information and reports.

Description and History

NPL Listing History

NPL Status: Final

Proposed Date: 10/15/84

Final Date: 07/22/87

Deleted Date:

Teledyne Semiconductor has operated as a semiconductor manufacturer at this 1-acre site since 1962. In 1982, Teledyne reported to the California Regional Water Quality Control Board (CRWQCB) that soil and groundwater were contaminated with solvents from an underground solvent storage tank. The State inspected the site and found that contaminants had migrated north of the site and affected approximately 50 private domestic wells. Furthermore, contaminated groundwater that migrated north from another NPL site, Spectra-Physics, Inc., merged with the contaminated plume of the Teledyne site. The two firms are cleaning up the sites jointly. These sites are among the 28 sites in the South Bay Area of San Francisco. Facilities at these sites have used a variety of toxic chemicals, primarily chlorinated organic solvents, which have contaminated a common groundwater basin. Although the sites are listed separately on the NPL, the EPA intends to combine cleanup activities at some of the sites as part of an area-wide approach to the contamination. The site is located in a densely populated, urban area. Approximately 189,000 people live within a 3-mile radius of the site. The distance from the site to the nearest residence is 200 feet.

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Contaminants and Risks

Contaminated Media
  • Groundwater
  • Soil and Sludges

Soil was contaminated with volatile organic compounds (VOCs). Groundwater is contaminated with VOCs. Drinking water is not affected by this contamination. Drinking water for this area comes from the Hetch Hetchy Reservoir in the Sierra Nevada, not from regional groundwater.

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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

Cleanup Ongoing

Since the late 1980s, Teledyne and Spectra-Physics have operated onsite and offsite groundwater extraction wells to remove TCE and hydraulically control the groundwater plume. In 2003, most of the groundwater extraction system was shut down due to decreased pollutant mass removal efficiency. In 2003, the Responsible Parties (RPs) pilot-tested and monitored natural attenuation for two years and concluded that this approach would not attain cleanup standards in a reasonable time.

In 2006, the Regional Board directed the RPs to re-characterize the Teledyne source property using high-resolution investigation technology to help focus further cleanup efforts. This work discovered and delineated previously unknown TCE hot spots at the site. In 2011, the dischargers pilot-tested an “in situ” method: enhanced bioremediation with recirculation. This involved injecting a carbohydrate solution as a food source for naturally occurring microbes, adding a microbial solution to accelerate the bioremediation process, and re-circulating the carbohydrate/microbe solution through a system of extraction and injection wells. The microbes consumed the carbohydrate solution and destroyed the TCE in place, creating harmless dechlorination byproducts such as carbon dioxide and salts.

The pilot study reduced groundwater-TCE levels from as high as 80,000 parts per billion (ppb) to below 100 ppb, and in some wells to less than 5 ppb (the cleanup standard). This work is ongoing.

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Cleanup Results to Date

Construction of all cleanup remedies is complete. Contaminated soil has been removed. Ongoing extraction and treatment of the groundwater continues to reduce the potential for exposure to contaminants at the Teledyne Semiconductor site. Groundwater treatment will continue until established cleanup goals are met.

The Fourth Five-Year Review was completed in Sept. 2014, concluding that the vapor intrusion indoor air investigation needs to be completed before a “protectiveness determination” can be made.

The following issues and recommendations were identified in the report:

Issue #1 – The performance of the selected remedy in the Record of Decision, groundwater extraction and treatment, has declined and new remedial actions are being investigated.

Recommendation – Complete a Record of Decision Amendment or prepare an Explanation of Significant Differences selecting new remedial actions and including updated institutional controls.

Issue #2 – The Five-Year Review vapor intrusion evaluation indicated that the subsurface-to-indoor air pathway is a concern at the site.

Recommendation – Continue to monitor and provide mitigation for vapor intrusion, including step-outs to lower concentration areas of the shallow TCE groundwater plume.

The Five-Year Review further stated the following:

A protectiveness determination of the remedy at the Teledyne Semiconductor and Spectra-Physics, Inc. Joint Superfund Sites cannot be made at this time until further information is obtained. Additional vapor intrusion assessments must be conducted to determine if indoor air pathways are complete. When unacceptable levels are encountered in a particular building, mitigation plans are developed and implemented to ensure that levels of volatile organic compounds (VOCs) in indoor air are protective. It is expected that these actions will take approximately two years to complete, at which time a protectiveness determination can be made. To be protective in the long-run, a new remedy should be selected due to the declining effectiveness of the existing remedy.

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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.

Online information about the PRPs for the site is not yet available.

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Documents and Reports

Show details for Community InvolvementCommunity Involvement
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:

California 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
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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