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Pacific Southwest, Region 9: Superfund

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

Monolithic Memories

EPA #: CAD049236201

State: California(CA)

County: Santa Clara

City: Sunnyvale

Congressional District: 14

Other Names: Advanced Micro Devices AMD-Arques

Bulletin Board

The vapor intrusion mitigation work conducted by AMD at the on-site building (Former Building 3) has been completed. Confirmation sampling shows that no unacceptable vapor intrusion risk remains. EPA’s Fourth Five Year Report was completed in 2014. 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:

The former Monolithic Memories Superfund Site (the “Site”) comprised three buildings, at 1165 E. Arques Avenue, 1175 E. Arques Avenue, and 1160 Kern Avenue in Sunnyvale, California. Two buildings, referred to as Building 1 (1165 E. Arques) and Building 2 (1175 E. Arques), were used for semiconductor manufacturing from 1970 until 1987, when Advanced Micro Devices, Inc. (AMD) merged with Monolithic Memories, Inc. (MMI) and assumed responsibility for the Site. MMI began leasing the 1160 Kern property in 1974. The building on this property, Building 3, was used for office space, product handling and testing, and administration until it was closed in 2003. The 1165/1175 E. Arques property has been sold and redeveloped as a fitness center. The 1160 Kern Avenue property is currently occupied by a non-profit organization.

In 1982, soil and groundwater at the Site were found to be impacted with volatile organic compounds (VOCs) attributed to leaks from underground chemical storage tanks, acid neutralization systems (ANSs), and chemical handling areas associated with Buildings 1 and 2. The tanks and ANSs were removed, along with impacted soil. Soil vapor and groundwater extraction systems were installed and operated to remove VOCs from soil and groundwater. The Site cleanup is being conducted under an order from the California Regional Water Quality Control Board (Regional Water Board).

In 2005, AMD donated the 1165/1175 E. Arques property to a local charity, which then sold the property to TWC Storage, LLC (TWC). Buildings 1 and 2 and associated facilities, including the on-Site groundwater treatment system, were demolished to accommodate redevelopment. During demolition activities, TWC’s contractors damaged a transformer, spilling approximately 250 gallons of tetrachloroethylene (also known as Perc, or PCE) on the ground surface. TWC implemented soil and groundwater cleanup operations under oversight of the Regional Water Board.

VOCs from off-Site industrial operations to the south have contributed to a regional groundwater plume extending beneath and downgradient (north) of the Site. Impacts related to former Site operations are generally localized and limited to shallow (A Zone) groundwater, whereas impacts from the regional plume extend into the deeper (B) Zone.

The 1160 Kern Avenue property, which was never owned by MMI or AMD, is currently occupied by a non-profit organization.

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Contaminants and Risks

Contaminated Media
  • Groundwater
  • Soil and Sludges

The Site contaminants include PCE, 1,1-dichloroethane (1,1-DCA), 1,2-dichlorobenzene, and chlorobenzene, which have been detected in samples from shallow (A-zone) groundwater monitoring wells, and are generally detected near or below their respective cleanup goals. Chemicals associated with the regional off-Site VOC impacts from the south include trichloroethylene (TCE) and cis-1,2-dichloroethylene (cis-1,2-DCE).

Institutional controls are in place to ensure that no one can ingest or come in direct contact with contaminated groundwater. Soil impacted by VOCs from past Site operations has been removed or left in place at levels deemed safe after an analysis of potential risks. A passive sub-slab vapor mitigation system operates at the fitness center to mitigate the potential for VOCs from groundwater to impact indoor air (“vapor intrusion”). Vapor intrusion evaluation and mitigation efforts are being conducted at Building 3, where evidence of vapor intrusion was found based on air samples collected from near a floor drain in a restroom.

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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 overseeing the long-term cleanup activities at the Site.

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Investigation and Cleanup Activities

Initial Actions

Immediate Actions: Under State oversight, immediate actions included excavating impacted soils beginning in 1984, installation and operation of a groundwater extraction and treatment system (GETS) beginning in 1986, and installation and operation of a soil vapor extraction system between 1993 and 1997. The GETS was expanded in 1988 and 1992, and operated until 2005, when it was shut down with Regional Water Board approval to accommodate Site redevelopment. In addition, several localized soil excavations were completed in 2006 and 2008.

In response to the 2005 PCE spill, TWC excavated approximately 2,000 cubic yards of impacted soils in 2005. In 2006, a soil vapor extraction system was installed, and two chemical oxidation injection events were conducted. In 2007, a multi-phase extraction system was installed, and it operated through 2008. In 2009 and 2010, TWC injected a carbon-based substrate to stimulate growth of naturally-occurring microbes that break down target VOCs into environmentally benign end-products.

Cleanup Ongoing

AMD completed an investigation determining the type and extent of contamination at the Site. Based on the results of the investigation, EPA selected soil vapor extraction and groundwater extraction and treatment for the Remedial Action. Soil vapor extraction was conducted between 1993 and 1997, and groundwater extraction and treatment was conducted between 1986 and 2005. The groundwater extraction and treatment system (GETS) has not been operated since the Site was redeveloped in 2005. Concentrations of VOCs in groundwater related to former Site operations are at or approaching established cleanup levels, so further operation of the GETS is not anticipated.

Mitigation work related to vapor intrusion into a restroom in Building 3 has been completed, and evaluation of the effectiveness of the mitigation shows that no unacceptable vapor intrusion risk remains.

The site is being cleaned up under orders from the California Regional Water Quality Control Board.

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Cleanup Results to Date

Construction for all cleanup remedies is complete. VOCs in groundwater related to former Site operations are at or approaching cleanup levels, indicating the success of the past remedial actions. Regional groundwater impacts related to off-Site, upgradient source(s) are still present; continued operation of the GETS is not likely to remediate these upgradient source(s). Vapor intrusion mitigation at the fitness center and Building 3 is complete, and confirmation sampling shows that no unacceptable vapor intrusion risk remains.

Significant progress has been made to address the impact of the 2005 PCE spill, and TWC has requested No Further Action status related to groundwater impacts.

The Fourth Five Year Review was completed in September 2014 and concluded the following:

The remedy at the Monolithic Memories Site is currently protective of human health and the environment. Exposure pathways that could result in unacceptable risks are being controlled. Institutional Controls restrict the use of groundwater as a drinking water source.
In order to be protective in the long-term, the following actions need to be taken:
(1) Continue the preferential pathway investigation, mitigation and indoor air monitoring at 1160 Kern Avenue;
(2) Evaluate the need for restarting the pump and treat system; or
(3) Determine an alternate 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.

The PRP for the Site is Advanced Micro Devices, Inc.

Under “Public Information Repositories” delete Santa Clara City Library. Keep the Regional Board.

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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:

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
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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