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Frequently Asked Questions on Environmental Conditions

Q: What regulatory agency is overseeing the work?
The California Environmental Protection Agency, Dept. of Toxic Substances Control (DTSC) is the regulatory agency responsible for overseeing and approving this work (www.dtsc.ca.gov).

Q: What previous operations were conducted at the site?
Historically, manufacturing of electronic equipment and research and development operations occurred at the site. In addition, tech companies operated intermittently in former office buildings.

Q: What environmental investigations were performed at the University Terrace site?
As part of its due diligence, Stanford performs Phase I environmental analyses for all of its properties intended for development. For the University Terrace project, Stanford retained Haley Aldrich, a nationwide licensed environmental engineering firm with extensive experience assessing and remediating contaminated sites, as well as Dr. Paul Johnson, a recognized expert in environmental issues, to perform a peer review.

The first environmental investigation of the University Terrace site was performed in 2004 as part of the Environmental Impact Report (EIR) for the 2005 Mayfield Development Agreement between Stanford and the City of Palo Alto. Similar to properties throughout Silicon Valley, the environmental investigation found residual chemicals in soil from historic site operations in some portions of the site. A Mitigation Monitoring and Reporting (MMRP) plan was adopted as part of approval of the EIR and Development Agreement that stated that environmental conditions would be fully investigated and addressed during future site redevelopment activities. Pursuant to this MMRP, further investigations of the soil and groundwater were performed at the site from 2012 to 2015. Stanford has fully remediated some areas and has proposed a plan to address the remaining area.

Q: What were the findings of the environmental investigations?
The University Terrace property is comprised of three parcels: 1451, 1501 and 1601 California Avenue. The Phase 1 environmental assessment performed for the 1451 and 1501 California Avenue parcels identified no environmental conditions precluding residential development. Stanford received environmental clearance from DTSC in the form of No Further Action letters allowing for residential development for these parcels.

The Phase I environmental assessment performed in 2004 on the 1601 California Avenue parcel identified low levels of polychlorinated biphenyls (PCBs) and volatile organic compounds (VOCs) in subsurface soils. Stanford performed a Phase II environmental evaluation and human health risk assessment in 2015 when the last commercial lease for the property expired and the building slab was removed. During this evaluation, PCBs were found in shallow soil underneath the building and surface parking areas and TCE was found in soil gas (the air spaces in between particles of soil) within the central portion of the property beneath the demolished building, primarily at depths of 15 to 25 feet below the ground’s surface. Stanford is working with DTSC to address these historic environmental conditions on the 1601 California Avenue parcel.

Q: What are PCBs and TCE?
According to the US EPA, PCBs are a class of manmade chemicals that were used as coolants and lubricants in electrical equipment due to their non-flammability, chemical stability, high boiling point, and insulating properties. PCBs were banned in the United States in 1979 but remain in the environment for a long time.

TCE is a volatile organic compound that was historically used in dry cleaning operations and as a degreaser in manufacturing operations. TCE is found in ambient air quality in the Bay Area and in everyday consumer household products (e.g. adhesives, dry cleaning, paint removers, etc.)

Q: Can these conditions be mitigated to enable safe living conditions?
Yes – environmental issues related to historic property operations are commonly mitigated clearing the way for site redevelopment. Typically, PCBs adhere to soil particles and the most effective way to remove them is to excavate the soil and dispose of it at an appropriate landfill. In contrast, TCE vapor is difficult to remove. Although soil gas vaporizes safely in open air, it can get trapped underneath a building’s foundation and find its way through cracks and holes into the structure itself, potentially impacting indoor air quality (a process called vapor intrusion). Appropriate and acceptable measures to mitigate vapor intrusion in the near term include: sealing potential conduits where vapors may be entering a building; installing engineered vapor barrier systems underneath a building’s slab; installing soil vapor extraction systems outside of buildings, depending on site geology; or locating buildings sufficiently away from elevated soil gas locations.

Q: How did Stanford address PCBs found at the site?
In 2015, prior to site grading activities, Stanford hired and retained Haley Aldrich, a licensed environmental engineering firm, and Bayview Environmental Services, a licensed hazardous waste contractor to remove soil containing PCBs from underneath the demolished commercial building and eastern parking lot. Soil removal work was only considered complete once sampling confirmed there were no additional PCB impacts above allowable levels at the bottom of excavation surfaces and along excavation walls. Stanford has documented this work in a report entitled Remediation Completion Report – Excavation of Soil Containing Polychlorinated Biphenyls, which has been submitted to DTSC for review and approval. DTSC approval is anticipated in late 2015/early 2016.

Q: Is it possible that PCBs could have spread off-site and onto neighboring properties?
As part of its Phase I and II environmental assessments, off-site sampling was conducted at both 1451 and 1501 California Avenue which showed the extent of PCB impacts was limited to the 1601 California Avenue site and had not spread to neighboring properties.

Q: How is Stanford addressing TCE in the soil?
TCE above residential screening levels has been found in isolated areas at 15 to 25 feet below the ground’s surface. Given the depth where impacts are found, exposure to TCE is highly unlikely; however, under certain conditions, TCE can move as vapors through soil. If vapors move under a structure, it is possible for them to pass through cracks and other openings in a building’s structure, potentially impacting indoor air quality (a process called vapor intrusion). TCE is not a concern in outdoor environments, as the compounds naturally dissipate once they reach open air.

Stanford has proposed mitigating the risk of TCE vapor intrusion to levels below those that allow for residential development using several proven measures. These include placing up to 15 feet of clean and compacted soil over areas where elevated TCE was found, buffering houses from soil vapor risk by locating them sufficiently away from areas with elevated TCE, sealing utility corridors to prevent vapor migration, and installing protective vapor barriers under all homes.

Q: How can you be sure that TCE impacts won’t affect future residents?
A site-specific human health risk assessment performed by Haley Aldrich, a licensed environmental engineering firm concluded that Stanford’s proposed approach - - locating homes away from areas with elevated levels of TCE, placement of up to 15 feet of soil on top of impacted areas, and the voluntary installation of protective vapor barriers underneath houses - - is protective of future residential populations and the community.

In addition, Stanford retained Dr. Paul Johnson, co-creator of the Johnson and Ettinger Model for Subsurface Vapor Intrusion into Buildings, a model widely used by governmental organizations for vapor intrusion risk assessment, to perform a peer review of the investigation and analysis performed by Haley Aldrich. Dr. Johnson concluded that this multiple mitigation approach presents no risk to human health and the environment and goes well beyond industry standard. Stanford has submitted this plan to DTSC and expects agency approval in fall 2015/early 2016.

Q: Will Stanford install protective vapor barriers underneath homes?
Yes. Stanford has elected to install protective vapor barriers even through these barriers or other sub-slab ventilation systems are typically required when buildings are constructed directly over areas with elevated levels of TCE. University Terrace is not proposing to locate houses over areas with elevated levels of TCE in soil vapor and there will also be a substantial buffer zone between these areas and homes.

Q: Is it safe to grow fruits and vegetables in a backyard garden?
Yes. Soils with PCBs have been removed and disposed of off-site and excavated areas have been backfilled with clean fill material.

Q: Can my children and/or pets safely use common areas?
Yes. A human health risk assessment was conducted and the site is safe for your children and pets. Areas with elevated levels of TCE will be covered with up to 15 feet of clean fill which will serve as a robust vertical buffer.

TCE is measured at very low concentrations throughout the Bay Area. The steps being taken will ensure that any TCE concentrations found at the site are consistent with background levels typically found throughout the Bay Area.

Q: Why aren’t you removing all the TCE impacts similar to the PCB impacts?
The source areas for TCE have been removed. It is impracticable to remove soil to address low levels of residual VOCs in soil vapor. Over time, TCE naturally attenuates and the best and most effective way to deal with the unlikely event of vapor intrusion is to configure the project to create a buffer zone, place up to 15 feet of clean fill in areas with elevated TCE, and install protective vapor barrier systems underneath homes.

Q: Is it possible TCE impacts could spread to the residential properties in the future?
No, TCE impacts were found in well-defined, isolated locations. The specific makeup of underground soils prevents TCE from spreading outside of these isolated locations towards future residential properties. Homes will be located away from areas with elevated levels of TCE and as an added level of assurance, Stanford has elected to seal utility corridors and install protective vapor barriers underneath all homes.

Q: How can I get more information?
Please call the construction hotline at (650) 273-9616. You may also visit our website at: homesoncalave.stanford.edu.

DTSC also maintains project information, including copies of all technical reports, through Envirostor which can be accessed at: DTSC also maintains project information through Envirostor which can be accessed at: http://www.envirostor.dtsc.ca.gov.

To review the Supplemental Investigation and Risk Assessment Report – 1601 South California Avenue, Palo Alto, California, please contact Annette Walton, Director, Environmental Management at (650) 724-4945 or nettie@stanford.edu.



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