Pacific Southwest, Region 9: Superfund
Serving Arizona, California, Hawaii, Nevada, the Pacific Islands, and Tribal Nations
Intel Corp. (Mountain View Plant)
EPA #: CAD061620217
County: Santa Clara
City: Mountain View
Congressional District: 14
Other Names: Part of the Middlefield-Ellis-Whisman (MEW) Study Area
EPA’s Final Third Five-Year Review report for the MEW Site is available to view [Click here].
On this page
Description and History
NPL Listing History
NPL Status: Final
Proposed Date: 10/15/84
Final Date: 06/10/86
The former Intel Corp. facility is located at 365. E. Middlefield Road in Mountain View, California. The facility formerly manufactured semiconductors at this 2-acre property from 1968 until 1981. The Intel site is one of three Superfund or National Priorities List (NPL) sites that are being cleaned up simultaneously. The other two Superfund sites are the Fairchild Semiconductor Corp. (Mountain View Plant) site and Raytheon site. The sites are located in the Middlefield-Ellis-Whisman (MEW) Study Area. Site investigations at several of these facilities during 1981 and 1982 revealed significant soil and groundwater contamination by toxic chemicals, primarily volatile organic compounds (VOCs).
Contaminants and Risks
- Soil and Sludges
The primary contaminants of concern are trichloroethene (TCE) and other volatile organic compounds (VOCs) in groundwater. The soil has been cleaned up to meet the soil cleanup standards.
Who is Involved
This site is being addressed through EPA and potentially responsible parties' actions.
Investigation and Cleanup Activities
The contamination addressed in the MEW Record of Decision is both facility-specific and regional. Each individual MEW Company is responsible for investigation, cleanup, and source control for soil and groundwater contamination at their individual facility-specific properties south of U.S. Highway 101. Contaminated groundwater that has bypassed the source control areas and has mixed together with other contaminated groundwater from other source areas is considered part of the regional groundwater contamination plume, or the “regional plume.”
- The MEW Regional Groundwater Remediation Program systems south and north of U.S. Highway 101 are designed to contain and clean up contaminated groundwater where the contaminated plume has mixed together with other contaminated groundwater and where the source of contamination has not been identified. The Navy and NASA Ames both operate groundwater extraction and treatment systems to contain and clean up contaminated groundwater at their areas of responsibility on Moffett Field, in addition to the regional system operating North of 101 on Moffett Field.
It is important to note that groundwater currently is not used for drinking water or other potable uses. Groundwater in the area is, however, a potential future source of drinking water and therefore groundwater cleanup standards have been established.
Groundwater Remedy In June 1989, EPA issued a Record of Decision selecting the soil and groundwater cleanup remedy for the MEW Site. The soil remedy includes: excavation, with treatment by aeration; and soil vapor extraction with treatment by vapor-phase granular activated carbon. The groundwater remedy includes: slurry walls (barriers beneath the surface) to contain contaminants; and extraction and treatment systems to contain and clean up groundwater contamination using granular activated carbon and/or air-stripping systems.
Because the groundwater contamination at the MEW Site has migrated northward and has mixed with contamination from sources at the NAS Moffett Field Superfund site, the groundwater remedy selected in the MEW Record of Decision also applies to the commingled regional groundwater contamination area on former NAS Moffett Field (the West-Side Aquifers), but not the entire former NAS Moffett Field facility.
Intel Facility-Specific Work - 365 E. Middlefield Road
Groundwater extraction at the former Intel Mountain View facility began in 1982 from one extraction located on Lot 3 (365 East Middlefield Road). The well was completed across both the upper A Aquifer and the B1 Aquifer.
Between 1982 and 1984, approximately 27.5 million gallons of groundwater were pumped resulting in an approximately 1,600 pounds of VOCs removed. The extraction well was destroyed in 1984 when Intel conducted a source area removal action.
In 1985, four new groundwater extraction wells were installed. Three of these wells were completed in the A Aquifer and one well was completed in the B1 Aquifer. EPA approved the shut down of extraction well PW-1A in 1996 after an investigation determined that taking the well off-line did not effect the overall capture zone at the facility. Intel managed the operation of the extraction wells and treatment system and shares responsibility with Raytheon for the source control extraction well for Lots 3, 4, and 5, including Well I-1B2.
The Intel groundwater treatment facility consisted of two 2,000-pound canisters of GAC operated in series. Between June and August 1998, the treatment system was relocated from along the east side of the existing site building to a location near the southwest corner of the property in preparation for tenant improvements. Although changes were made to influent and effluent piping, no changes were made to the two liquid-phase GAC vessels.
In 1998, a diffused aeration tank or air stripper was installed within the treatment pad enclosure to aerate the extracted groundwater prior to carbon absorption, thus decreasing the potential for exceedances of the NPDES effluent requirements. In April 2003, the use of the diffused aeration tank was discontinued and groundwater treated with GAC was plumbed to discharge to the City of Mountain View sewer. The system has the permitted option of discharging to a storm drain located along the eastern property boundary. The storm drain leads to Stevens Creek.
Over 74 million gallons of groundwater have been treated and 2,000 pounds of VOCs removed since system start-up in 1982.
Intel has been implementing an in-situ bioremediation pilot test at its former facility at 365 East Middlefield Road in Mountain View to try to reduce VOC concentrations in the “hot spot” areas in a shorter period of time. During the pilot test, the groundwater extraction and treatment system is not operating. See Intel's annual progress report for more information.
Vapor Intrusion Remedy
The existing soil and groundwater remedy at the MEW Site does not address risks from long-term exposure through the vapor intrusion pathway. Since the issuance of EPA’s 1989 Record of Decision, new information has been developed regarding the toxicity of TCE and potential vapor intrusion into buildings overlying shallow groundwater contamination. In 2003, as part of EPA’s Five-Year Review of the MEW Study Area, EPA began evaluating whether VOCs in shallow groundwater are potentially migrating upward through the soils and cracks in the floors or through plumbing conduits and other preferential pathways, and impacting indoor air.
Based on indoor air sampling of both commercial and residential buildings in the area conducted in 2003 to 2007, EPA has confirmed the presence of the subsurface vapor intrusion pathway into a number of structures overlying the shallow groundwater TCE plume. EPA’s main concern is whether the chemicals from the Site measured in indoor air pose an unacceptable risk of chronic health effects due to long-term exposure (25 years or more). It is EPA’s policy not to set cleanup levels or take action to reduce levels that are less than ambient background levels.
Some of the sampled buildings indicated indoor air contaminant concentrations that were elevated above background levels and above EPA Region 9’s TCE interim action level in indoor air for long-term exposure. In each of these buildings, the MEW Companies, Navy and NASA implemented interim measures (e.g., sealing cracks/conduits, upgrading/modifying ventilation systems, installing air purifying systems) to reduce the indoor air contaminant concentrations.
In 2010, after amending the MEW Record of Decision, EPA selected a remedy that addressed potential long-term exposure of TCE, and other VOCs at unacceptable levels, through the vapor intrusion pathway, For more information, please access the 2010 Record of Decision Amendment for the Vapor Intrusion Pathway document either by clicking here or finding it in the Records of Decision subsection of the Documents and Reports section below.
The Third Five-Year Review
The Third Five-Year Review, completed on September 29, 2014, presented the following conclusions and recommendations -
The vapor intrusion remedy selected in the 2010 ROD Amendment for the MEW Site is expected to be protective of human health when fully implemented. In the interim, remedial activities completed to date have adequately addressed all exposure pathways that could result in unacceptable risks at the MEW Site. To be protective in the long-term, the vapor intrusion remedy implementation procedures need to be assessed to take into account the impact of the potential TCE short-term exposure risks on current MEW Site remedy operational framework.
The groundwater remedy at the MEW Site is currently protective of human health and the environment because exposure to groundwater is being controlled. In order to be protective in the long term, the following recommendations and follow-up actions need to be completed:
- Determine the source of the TCE hot spot areas on Evandale Avenue and extent of TCE contamination in the A and B1 aquifer zones;
- Evaluate alternative cleanup strategies inside the slurry walls and implement treatability studies that do not necessarily require maintaining inward and upward gradients to control source area contamination;
- Evaluate and implement the current optimization pilot tests and treatability studies of alternative groundwater cleanup technologies at the facility-specific source areas, TCE hot spot areas, and representative areas of the regional groundwater contamination plume to expedite contaminant mass removal and cleanup timeframe; and
- Based on evaluation of the information collected, complete a Feasibility Study to evaluate remedial alternatives that can effectively meet the vapor intrusion remedial action objective to accelerate the reduction of the source of vapor intrusion (i.e., Site contaminants in shallow groundwater and soil gas) to levels that are protective of current and future building occupants, such that the need for a vapor intrusion remedy would be minimized or no longer be necessary.
In 1985, the EPA issued an Administrative Order On Consent to Intel, Fairchild Semiconductor, and Raytheon, requiring the three companies to conduct a joint site investigation. In 1991, EPA, Intel and Raytheon signed a Consent Decree, an agreement under which Intel and Raytheon agreed to design and construct the groundwater extraction and treatment systems for the regional groundwater contamination.
Cleanup Results to Date
Under EPA’s direction and oversight, Intel has implemented the soil and groundwater cleanup program at the former Intel facility. The soil cleanup has been completed at the Intel site and all the former MEW facilities.
From 1982 to 2005, Intel pumped and treated groundwater by carbon adsorption. By 1986, Intel had removed approximately 4,600 cubic yards of contaminated soil. Other immediate actions performed by the company included removing tanks and sealing contaminated wells to prevent contaminant migration.
Groundwater cleanup will continue to operate for many decades in order to meet the TCE groundwater cleanup standard of 5 parts per billion. The groundwater remedy has reduced contaminant concentrations throughout the multiple aquifer zones. The groundwater is not being used as a potable water supply, and there are no direct exposure pathways to the contaminated groundwater while groundwater cleanup continues.
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.
Under EPA's direction and regulatory oversight, Intel Corporation is responsible for investigating and cleaning up the soil and groundwater at the Intel-Mountain View Superfund Site. In addition, the following individual companies are responsible for investigating and cleaning up the groundwater at the MEW Site. These companies are collectively referred to as the MEW Companies:
- Fairchild Semiconductor Corporation
- Intel Corporation
- Raytheon Company
- Schlumberger Technology Corp. (Schlumberger)
- Renesas [formerly NEC Electronics America, Inc. (NEC)]
- SMI Holding LLC (SMI)
- Vishay General Semiconductor (Vishay)
- SUMCO Phoenix Corporation (SUMCO)
- National Semiconductor Corporation
- Tracor X-Ray
- Union Carbide
National Semiconductor Corporation, Tracor X-Ray, and Union Carbide are not involved with the active investigation and cleanup of the MEW Site.
Documents and Reports
Public Meetings: A community advisory group, the MEW Community Advisory Board, meets to learn about and discuss MEW Superfund Study Area investigation and cleanup issues.
EPA has awarded a Technical Assistance Grant (TAG) to the Pacific Studies Center. The TAG provides money for activities that help the community understand technical information at the MEW Site. Please contact Lenny Siegel, TAG Administrator, at 650-961-8918 or LSiegel@cpeo.org for more information.
Public Information Repositories
The public information repositories for the site are at the following locations:
Mountain View Public Library,
585 Franklin Street,
Mountain View, CA 94041
Monday-Thursday 10 am to 9 pm
Friday and Saturday 10 am to 6 pm
Sunday 1 pm to 5 pm
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
a Project of the Pacific Studies Center,
278A Hope Street
Mountain View, CA 94041
After Hours (Emergency Response)