Pacific Southwest, Region 9: Superfund
Serving Arizona, California, Hawaii, Nevada, the Pacific Islands, and Tribal Nations
Hewlett-Packard (620-640 Page Mill Road)
EPA #: CAD980884209
County: Santa Clara
City: Palo Alto
Congressional District: 14
EPA is currently evaluating the potential for vapor intrusion in buildings overlying the shallow groundwater contamination area. On December 3, 2013 EPA sent a letter to the State of California's Regional Water Quality Control Board providing guidelines for vapor intrusion sampling and evaluation at this and 10 other South Bay State-lead sites.
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Description and History
NPL Listing History
NPL Status: Final
Proposed Date: 06/24/88
Final Date: 02/21/90
Hewlett-Packard manufactured optoelectronic equipment on this 10-acre site from 1962 to 1986. In 1981, at least 300 gallons of waste solvents leaked from an underground storage tank. The company excavated the tank and approximately 100 cubic yards of contaminated soil in 1981 and transported the materials to a hazardous waste disposal facility. Since 1982, the company has been pumping and treating contaminated groundwater from the shallow, chemically affected, aquifer. Five municipal backup supply wells draw water from a deeper aquifer located within 3 miles of the site. The nearest residential areas are located approximately 1/8 of a mile northeast of the facility.
Contaminants and Risks
- Soil and Sludges
Volatile organic compounds (VOCs) were detected in groundwater under the tank area and in the soils sampled from the former tank location. Potential health risks include accidentally ingesting or coming into direct contact with contaminated groundwater or soil. Chemicals in the shallow aquifer have migrated off site.
Who is Involved
This site is being addressed through Federal, State, and potentially responsible parties' actions.
Investigation and Cleanup Activities
This site is being addressed in two stages: immediate actions and a long-term remedial phase focusing on cleanup of the entire site.
Immediate Actions: In addition to the tank and soil excavation activities conducted in 1981, Hewlett-Packard excavated an additional 810 cubic yards of soil around the former tank area in 1987. Pumping and treating contaminated groundwater has been underway since 1982.
Entire Site: In 1989, under State oversight, Hewlett- Packard initiated an investigation to determine the nature and extent of contamination remaining at the site and to identify alternative cleanup remedies. The investigation was completed and a final cleanup remedy was selected in 1995. The remedy includes groundwater extraction and treatment, and soil vapor extraction and treatment.
Cleanup Results to Date
The excavation and disposal of the storage tank and contaminated soil and the continuing treatment of contaminated groundwater have reduced the potential for exposure to hazardous materials at the Hewlett-Packard (620-640 Page Mill Road) site.
Vapor Intrusion Study Overview
The Third Five Year Review completed in September 2010 concluded the following:
- Although Hewlett-Packard has evaluated the vapor intrusion potential in the past to the satisfaction of the Regional Water Quality Control Board, recent changes in the evaluation methods (primarily the adoption of a multiple lines of evidence approach) require additional analysis of the vapor intrusion pathway for certain portions of the Site.
- All other exposure pathways that could result in unacceptable risks are being controlled, and institutional controls are preventing exposure to, or the ingestion of, contaminated groundwater.
- The groundwater monitoring program in the Off-Property Study Area should be expanded to characterize the extent of TCE contamination in the A1U, A1, and A2 Zones.
- Additionally, in the Off-Property Study Area, the vapor intrusion exposure pathway should be re-evaluated within approximately 18 months.
- A Five-Year Review Addendum should be completed at the conclusion of the vapor intrusion exposure pathway report.
Vapor Intrusion Study Results to Date
To assess any risks to indoor air as a result of vapor intrusion (VI) from the site, a VI study has been ongoing since 2012, which has included 34 single-family residences, six multi-family buildings and eight commercial buildings. All of the single-family residences were offered testing and 14 of the residents requested that their homes be tested. No detectable levels of trichloroethylene (TCE) - the site contaminant of concern (COC) - were found. Testing of the multi-family residences found no evidence of vapor intrusion occurring into living spaces. Sampling of the commercial properties will occur once site access agreements are finalized.
The sampling is being broken up into three phases: phase 1 - single-family homes; phase 2 - multi-family residences; and phase 3 - commercial buildings.
Each multi-family building in the study area was evaluated and tested. Prior to testing, EPA and Stantec, the consultant to HP and Varian, conducted a pre-testing walk-through for each multi-family building, where a photoionization detector capable of low parts per billion (ppb) detection was used to determine if there were preferential pathways requiring testing. All potential conduits for vapors were evaluated, and EPA determined where the canisters would be placed for indoor air testing. Samples were collected from elevator shafts, next to sumps, in areas in garages with low airflow, and near cracks in the slabs. Potential confounding indoor air sources that could result in false positive data were identified that should be removed or contained prior to testing.
All of the results from the indoor air testing in apartments and hallways came back non-detect for TCE.
There were some low TCE results in two of the underground garages, but all below action levels. Results for the buildings’ 19 garages ranged from 0.65 to 0.72 micrograms per cubic meter (ug/m3) TCE, and for the garage in the 20th building results ranged from 0.20 to 0.36 ug/m3. In the 20th building's garage two chemical storage closets were tested that had TCE levels of 0.18 and 1.2 ug/m3 using a grab sample technique, but these detections were likely from indoor sources in the room and not from vapor intrusion.
Grab samples were also obtained from elevator pits (using tubing to get air from the pit) to determine if there was a potential for those vapors to get into living spaces. In the 20th building, one elevator pit was sampled and yielded a TCE result of 10 ug/m3. The hallway of the second floor in front of that elevator was sampled with no TCE detected (the first floor opens up to an outside space). The elevator shaft was then re-tested, as well as apartments on the second floor near that elevator and from every floor hallway that the elevator opened up into. No detections in any of the living spaces were found, and the TCE results for the elevator pit retesting was 6.8 ug/m3.
In summary, while there were detections of TCE in the garages and/or elevator shafts in the 19th and 20th residential buildings, subsequent evaluation of potential pathways and indoor spaces found no evidence of vapor intrusion occurring into any indoor living spaces, nor the potential for this to occur.
A figure (Figure 2 - TCE Concentrations in First Encountered Groundwater) from the work plan that shows the testing area is included below in the Documents and Reports section.
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.
On-line information about the PRPs for the site is not yet available.
Documents and Reports
Public Information Repositories
The public information repositories for the site are at the following locations:
U.S. Geological Survey Library,
345 Middlefield Road,
Menlo Park, CA 94025
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
1515 Clay St.
Oakland, CA 94612
After Hours (Emergency Response)