Pacific Southwest, Region 9: Superfund
Serving Arizona, California, Hawaii, Nevada, the Pacific Islands, and Tribal Nations
TRW Microwave, Inc. (Building 825)
EPA #: CAD009159088
County: Santa Clara
Congressional District: 14
Other Names: Aertech Industries FEI
4th 5-Year Review Complete
EPA completed its fourth Five-Year Review in 2014, concluding that the site remedy is protective but that an indoor air vapor intrusion investigation should be completed at the on-property building (completed 2015) and nearby residential neighborhood (ongoing).
On this page
Description and History
NPL Listing History
NPL Status: Final
Proposed Date: 06/24/88
Final Date: 02/21/90
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 De Guigne 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 beyond Highway 101.
The TRW Site, together with three other operable units (OUs), was covered by a 1991 Record of Decision 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 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).
The TRW Site was occupied by Aertech Industries from 1968 until it was sold to TRW Inc (TRW) in 1974. 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, and then by Hines in 2014 and then GI Partners, the current owner, in 2016. 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.
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.
Contaminants and Risks
- Soil and Sludges
VOC contamination was historically present in soil but has since been remediated to below levels of concern. Currently, groundwater beneath the site contains various VOCs. However, institutional controls are in place to ensure that no one can ingest 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. 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.
A vapor intrusion investigation conducted at the one on-site building in 2013 (which was unfinished and unoccupied at the time), indicated that vapor intrusion into the building was occurring. Vapor intrusion is a process whereby vapors from contaminated groundwater move upward through the soil and enter the indoor air of nearby buildings. Additional investigation and mitigation work were completed in 2014 to address the vapor intrusion risks, and included the removal of impacted soil and groundwater beneath the building, installation of a building subslab vapor system as a precautionary measure, and sealing of the floor slab during the building remodel that was conducted prior to occupancy by the new/current tenants. A subsequent vapor intrusion investigation conducted in the building in 2015 indicated that vapor intrusion has been successfully mitigated and indoor air concentrations have been reduced to levels that EPA considers protective of human health.
Who is Involved
This site is being addressed through Federal, State, and potentially responsible parties' 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 soil 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 gravel pit created during the initial source area excavations became part of a groundwater extraction system operated by TRW between 1985 and 2001 to clean up the on-site groundwater and prevent VOCs from migrating off-site. Extracted groundwater was treated by an air stripper and then discharged to Calabasas Creek. In 2000 and 2001, pumps in the groundwater extraction wells were turned off to allow for initiation of enhanced anaerobic bioremediation (EAB) in the former site source area. Based on groundwater testing that showed improved groundwater conditions, the groundwater extraction system was shut down.
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 in and immediately downgradient of the former site source area since 2000.
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 for TRW and the surrounding AMD and Philips sites. The companies installed off-site 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.
Cleanup Results to Date
The removal of tanks and contaminated soil have reduced the potential for exposure to contaminated materials at the TRW Site. Groundwater extraction and subsequent EAB activities have significantly reduced and/or eliminated VOC concentrations in groundwater at the site, and ongoing groundwater sampling indicates that EAB processes are continuing to have a beneficial effect.
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 adjacent AMD and Philips sites) 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 also being controlled by successful mitigation efforts that have eliminated exposure pathways to contaminated subsurface vapors.
However, in order for the remedy to be protective in the long-term, EPA’s Record of Decision will need to be amended to reflect a revised final soil and groundwater remedy for the site, since the remedy selected in the Record of Decision (groundwater extraction) 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 Northrop Grumman Systems Corporation, which recommended re-designating a previously mischaracterized B2 zone 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-site 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 from the OOU area. 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 of human health.
EPA began indoor air sampling in the OOU neighborhood in late 2015 and expects that these activities will take approximately two years to complete, at which time a protectiveness determination can be made.
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 TRW Site is Northrop Grumman Systems Corporation.
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
After Hours (Emergency Response)