Soil gas sampling is increasing in frequency across the country as vapor intrusion continues to gain regulatory attention. When evaluating the potential for vapor intrusion at a particular site, it is useful to collect soil gas samples to find out how vapors and contaminants of concern are migrating in the subsurface, and whether or not those vapors are migrating indoors. Soil gas sampling, used in conjunction with state specific screening criteria and/or modeling, is often an intermediate step between screening based on groundwater concentration and collecting indoor air samples.

The goal of soil gas sampling is to collect a sample of the vapor that resides in the interstitial soil pores near a source of contamination and/or near a potential receptor structure. To sample soil gas, a temporary or permanent soil vapor probe is installed. If the well is installed incorrectly or is not sealed properly, leaks to the ambient air may occur. This can dilute or otherwise influence the concentrations seen, potentially leading to incorrect decision making.

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