VAPOR INTRUSION ISSUES Case Study Experience – Silicon Valley, CA Example of Governmental Agency Actions

Asset Acquisition, Silicon Valley, CA  Palo Alto, California (Stanford Research Triangle)  Property located above existing large scale chlorinated solvent plume  Single Tenant, Triple Net.  Tenant: Prominent San Francisco Law Firm  Historical use issues, but inconsequential.  New ESA Standard Recommends Vapor Intrusion Evaluation

Approach to Testing  Hired Certified Industrial Hygienist  Sampling Methodology was vacuum canisters  NOTE: Standard methodology, may be too “sensitive”.  Controlled methodology for testing  HVAC Off (reducing stack effect and outdoor air intake)  Testing on Weekends  Multiple data points inside and outside building for comparison

Consultant Conclusions:

Needed to hire a Toxicologist…  Toxicologist obtained data that showed that “background” concentrations of dichloroethane was 0.21 micrograms/cubic meter.  However, still concluded that “some source of pollution was present within the building” that was “contributing to dicloroethane concentrations within the building.”  Conclusion was that although within the cancer risk, it still triggered a Proposition 65 Notification Requirement.