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Pacific Southwest, Region 9: Superfund

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

TRW Microwave, Inc. (Building 825)

EPA #: CAD009159088

State: California(CA)

County: Santa Clara

City: Sunnyvale

Congressional District: 14

Other Names: Aertech Industries FEI

Bulletin Board

EPA completed its fourth Five-Year Review in 2014, concluding that the site is protective but that vapor intrusion indoor air assessments should be completed at the on-property building and nearby residential neighborhood.

Description and History

NPL Listing History

NPL Status: Final

Proposed Date: 06/24/88

Final Date: 02/21/90

Deleted Date:

The former TRW Microwave Superfund Site (TRW Site), part of the “Triple Site” in Sunnyvale, California, is located at 825 Stewart Drive and neighbors multiple other sites, including: the Advanced Micro Devices (AMD) Buildings 901/902 Thompson Place Superfund Site (AMD 901/902 Site), the AMD 915 DeGuine Drive Superfund Site (AMD 915 Site), the Philips Semiconductors Site (Philips Site; formerly Signetics Inc.), which includes the properties at 811 Arques Avenue, 440 North Wolfe Road, and facilities along Stewart Drive, and the Mohawk Laboratories Site. A groundwater plume composed of volatile organic compounds (VOCs), including trichloroethene (TCE), extends from these sites more than a mile north in Sunnyvale to past Highway 101.

The TRW Site, together with three other operable units (OUs), was covered by a 1991 Record of Decision (ROD) for the Triple Site, all located in Sunnyvale. The four OUs for the Triple Site are as follows:

    (1) The AMD 901/902 Site OU;
    (2) The Philips Site OU;
    (3) The TRW Microwave Site OU; and
    (4) The Companies Offsite Operable Unit (OOU), a commingled plume of contaminants which originated from the other three operable units (and has contributions from other sites in the area).
    At the time of adoption of the 1991 ROD, the OOU was defined as a 100-acre area, downgradient and north of the Triple Site in an area bounded by the Sunnyvale East Drainage Channel on the west and Santa Paula Avenue on the east, and as the area inside a 5 micrograms per liter (g/L) isopleth for trichloroethene (TCE) in groundwater. Over 100 residences and at least 4 schools are present within the OOU.

    The TRW Site was occupied by Aertech Industries from 1968 until it was sold to TRW, Inc (TRW). in 1984. In 1987, TRW sold the facility to FEI Microwave, Inc. In 1993 FEI Microwave stopped production and in 1995 the site was acquired by Stewart Associates and leased to research and development companies until 2001. The exterior of the building was remodeled between 2001 and 2003, including demolition of part of the existing structure and construction of a new two-story building. In December 2002, TRW merged with Northrop Grumman. In 2004, the property was purchased by Pacific Landmark, the current owner (as of 2013). During these changes in site ownership, TRW, and then Northrop Grumman retained responsibility for site cleanup.

    The primary activity at the TRW Site was assembling and testing microwave components until semiconductor processing began in 1970. Primarily solvents and small quantities of acids were used in the assembly areas for semiconductors. Solvents, acids, and heavy metals were used in the fabrication areas and plating shop. The paint shop used paints and solvents.

    Groundwater beneath the TRW Site is contaminated with volatile organic compounds (VOCs). Acid rinse water generated by the assembly processes was neutralized on-site and discharged to the City of Sunnyvale sewer system. An underground ammonia gas acid neutralization system was installed when the facility first opened. Floor drains and acid sinks in the plating shop were connected to buried plumbing that carried acid waste to the neutralization system. This system was closed in 1986, and the underground piping was sealed. The system was replaced with three aboveground tanks. Spent solvents were stored in one of four on-site underground tanks. After 1982, solvents were stored in drums and transported off-site. The closest residence is located approximately 1,200 feet north of the site. Municipal wells for the cities of Santa Clara and Mountain View tap a deep aquifer as a drinking water source that has not been affected by the contamination.

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    Contaminants and Risks

    Contaminated Media
    • Groundwater
    • Soil and Sludges

    VOC contamination was historically present in soil but has since been remediated to below regulatory criteria. Currently, groundwater contains various VOCs, however, institutional controls are in place to ensure that no one can ingests or come in direct contact with contaminated groundwater. Drinking water is not affected by the contamination. Drinking water in this area comes from the Hetch Hetchy Reservoir in the Sierra Nevada Mountains, and is regularly tested to ensure that it meets all applicable state and federal requirements.

    A vapor intrusion investigation is currently ongoing at the one on-site building (which is currently unfinished and unoccupied), which indicates that vapor intrusion into the building is occurring (a process whereby vapors from the contaminated groundwater move upwards through the soil and enter the indoor air of nearby buildings). Additional investigation and mitigation work is underway to address the vapor intrusion risks, which will be completed prior to any tenants occupying the building.

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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

    Initial Actions

    Initial Actions: Four spent solvent underground tanks, along with some soil, were removed in 1973, 1976, 1980, and 1983. In 1984, 120 cubic yards of contaminated soils were excavated and transported to an EPA-approved hazardous waste facility. The site was backfilled to the surface with gravel and concrete was poured over the gravel to prevent rainwater from seeping into the pit. TRW installed and operated a soil vapor extraction (SVE) system in the vicinity of the former source area excavation from 1993 to 1998. Testing indicated that no further soil remediation was necessary and the SVE system was removed in 1998.

    The water extraction pit created during the initial source area excavations was part of a groundwater extraction system operated by TRW between 1985 and 2001 to prevent VOCs from migrating off-site and to extract the groundwater for cleanup. On-site groundwater was treated by an air stripper and then discharged to Calabasas Creek. In 2000 and 2001, pumps in groundwater extraction wells were turned off to allow for site redevelopment activities and initiation of enhanced anaerobic bioremediation (EAB) in the former site source area. Based on groundwater testing that showed improved groundwater conditions, regulatory approval was received for continued shutdown of the groundwater extraction system.

    Cleanup Ongoing

    EAB was initially implemented in 2000 and has been ongoing in an effort to reduce contaminant concentrations at the TRW Site. Multiple injections of different EAB substrates have been performed since 2000 in and immediately downgradient of the former site source area.

    In 1984, the State issued an order requiring AMD, Philips, and TRW to develop a joint plan to prevent further migration of contaminants. New orders in 1989 required TRW to submit an investigation and proposed cleanup plan with AMD and Philips. In 1991, the State and EPA issued a combined Record of Decision (ROD) for TRW and the surrounding AMD and Philips sites. The companies installed extraction wells to prevent migration of the VOC-impacted groundwater north of Highway 101. The extracted groundwater is treated at the Philips on-site treatment system.

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    Cleanup Results to Date

    The removal of tanks and contaminated soil has reduced the potential for exposure to contaminated materials at the TRW Microwave (Building 825) site while groundwater continues to be treated. EAB activities have significantly reduced concentrations of VOCs detected in groundwater at the TRW site.

    EPA’s fourth Five-Year Review was completed in 2014, reviewing the protectiveness of the remedy at the TRW Site and the adjacent residential neighborhood – the “Offsite Operable Unit” or “OOU.” The OOU extends north from the TRW Site and encompasses an area of about 100 acres. The area includes four schools and over 400 residential properties.

    The fourth Five-Year Review concluded that the remedy at the TRW Site currently protects human health and the environment because exposure pathways for soil and groundwater are being controlled. Exposure pathways to contaminated groundwater that could result in unacceptable risks are prevented through an environmental covenant.

    The risk due to vapor intrusion is controlled as long as the on-property building remains unoccupied and the exposure pathway remains incomplete. However, in order for the remedy to be protective in the long-term, EPA’s Record of Decision (ROD) will need to be amended to reflect a revised final soil and groundwater remedy for the site, since the remedy selected in the ROD is no longer operating. EPA also recommended the following: (1) adding source area and down-gradient B3 zone wells to the suite of annual monitoring wells, to more fully characterize groundwater contamination in the source area and down-gradient B3 zone; and (2) investigating and implementing optimization options for the in-situ bioremediation work, to better capture contaminants that are migrating offsite. The first recommendation was addressed on March 1, 2016, when EPA approved a Technical Memorandum prepared by the Responsible Parties, which recommended re-designating one monitoring well (well T-9C) to a B3 zone well to be monitored annually moving forward. EPA also approved a recommendation in the Technical Memorandum to not require adding source area wells, which would create potential vapor intrusion pathways into the on-property building.

    Additionally, the Five-Year Review concluded that a protectiveness determination of the remedy at the OOU cannot be made until further information is obtained. Vapor intrusion assessments must be conducted to determine if indoor air pathways are complete. If unacceptable levels are encountered in a particular building, mitigation plans will be implemented to ensure that levels of VOCs in indoor air are protective.

    EPA began indoor air sampling in the OOU neighborhood in 2015 and expects that these activities will take approximately two years to complete, at which time a protectiveness determination can be made.

    A vapor intrusion investigation is currently ongoing at the one on-site building (which is currently unfinished and unoccupied), which indicates that vapor intrusion into the building is occurring (a process whereby vapors from the contaminated groundwater move upwards through the soil and enter the indoor air of nearby buildings). Additional investigation and mitigation work is underway to address the vapor intrusion risks, which will be completed prior to any tenants occupying the building.

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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 Northrop Grumman Systems Corporation.

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    Documents and Reports

    Hide details for Fact SheetsFact Sheets
    12/01/13South Bay Groundwater Sites - Vapor Intrusion Evaluations (Dec. 2013 Update)
    07/31/14Letter - Indoor Air Sampling Update, City of Sunnyvale
    Hide details for Records of DecisionRecords of Decision
    09/11/91Final Record of Decision
    Hide details for Technical DocumentsTechnical Documents
    01/01/01Vapor Intrusion Documents
    09/29/99First Five Year Review Report
    09/30/04Second Five Year Review Report
    09/30/09Third Five Year Review Report
    08/07/14EPA Notice of Lead Agency Transfer
    09/30/14TRW Microwave, Inc. (Bldg. 825) Fourth Five Year Review Report
    11/11/14Work Plan for Additional Source Area Injection Activities - Former TRW Microwave Site, 825 Stewart Drive, Sunnyvale, California
    11/12/14Work Plan Addendum for Source Area Removal Activities
    03/31/15Northrop Grumman Technical Memorandum in Response to 2014 Five-Year Review Report
    01/25/16Addendum to the Technical Memorandum in Response to the 2014 Five-Year Review Report - Former TRW Microwave Site, 825 Stewart Drive, Sunnyvale, California
    03/01/16EPA Approval - TRW Microwave Site (Sunnyvale, CA) - Tech Memo & Tech Memo Addendum
    04/19/16Conceptual Site Model - Former TRW Microwave Site, 825 Stewart Dr.
    05/04/16Background Water Quality Evaluation Work Plan - Former TRW Microwave Site, 825 Stewart Drive, Sunnyvale, California
    11/15/16Background Water Quality Evaluation Report
    02/13/17Correspondence - TRW Microwave Site - Proposed Path Forward
    03/15/17Correspondence - EPA Approval - Background Water Quality Evaluation Report - TRW Microwave Site
    03/17/17Annual Groundwater Monitoring and Remedial Progress Report - Former TRW Microwave Site, Sunnyvale, California

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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:

    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
    PRP Contact
    Community Contact
    Other Contacts
    After Hours (Emergency Response)
    US EPA
    (800) 424-8802

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