ABSTRACT
The technical acceptance, popularity, accuracy, and use of soil gas survey techniques have increased tremendously over the past five years. Due to the volatile nature of many solvents and fuel hydrocarbons, soil sample analytical results are often inaccurate (not representative) due to loss of volatile organic compounds (VOCs) from samples during sample collection, transport, and analysis. In-situ measurement of soil gas samples is often a more accurate means of assessing the presence and extent of VOCs in unsaturated medium-to coarse-grain geologic materials. The volatile nature of many solvents and fuel hydrocarbons has made vapor extraction the preferred remediation technique for soil impacted by these chemicals and, therefore, it is prudent to sample the gas or vapor phase to evaluate remediation progress. This chapter describes the objectives and limitations of soil gas surveying, provides specific investigative methods and procedures, and presents two case studies conducted in Southern California.
