Soil gas surveys are used extensively as a screening tool for delineating contaminant plumes in the subsurface. For 20 years, local regulatory agencies accepted and often required soil gas surveys on sites to “pin point” contaminant hot spots for further investigation and delineation. In 2003 the DTSC provided guidelines for performing soil gas surveys and they are currently working on a revised guideline. More recently, soil gas surveys are used by regulators to evaluate whether a site is adequately remediated and provides no vapor intrusion risk to site occupants. In 2005, the DTSC provided an additional guideline on the evaluation and mitigation of vapor intrusion to indoor air. But are all soil gas surveys the same? Are different surveys necessary for different site conditions, or different project goals? What conditions affect the results of surveys? What types of lab analyses will provide the most accurate results for the project goals?

This lecture will discuss the theory behind soil gas migration, the many factors that affect migration and the variability of chemical constituent concentrations in the subsurface. Proper construction and placement of soil gas probes will be discussed as well as proper sampling techniques. The significance and variability of purge volume testing will be presented as well as the significance of purge volume testing on concentrations of specific chemical constituents. Examples of soil gas surveys from contaminated sites will be presented for plume delineation and vapor intrusion to indoor air. Soil gas monitoring, or the repeated measurement of soil gas from the same vapor probes over time, will be discussed as well as the affect of temperature and soil moisture on results. Lastly, anticipated future revisions to the current DTSC soil gas guidelines will be discussed as well as the use of soil gas surveys for the evaluation of the soil and groundwater remediation.

Anthony F. Severini, P.G.; B.S. and M.S. Geology, University of Connecticut

Mr. Severini is the President and Owner of Environmental Support Technologies (EST) headquartered in Irvine, California. Mr. Severini is a licensed Geologist in eight states including California. Mr. Severini holds a General Engineering “A” Contractor’s license, a C-57 Drillers License and is an AHERA Certified Asbestos Building Inspector and Management Planner. For over 30 years, Mr. Severini has performed environmental work on over 2000 sites spanning 44 states in the US. Mr. Severini provides expert witness testimony for environmental litigation on sites involving soil and ground-water contamination, environmental stigma, cost allocation, NCP applicability and financial damage assessment. He has both testified and provided expert opinions on court cases involving CERCLA claims, toxic torts, and PRP cost allocation. Mr. Severini has managed offices for Blasland, Bouck & Lee as well as TRC Companies. Currently, Mr. Severini oversees all operations of EST. EST is a field services company, with a fleet of direct-push drilling rigs, certified mobile laboratories and vapor extraction systems. EST has performed over 4,000 soil gas surveys in the past 20 years.

Web: www.est-inc.com
E-Mail: info@est-inc.com