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Leak, Purge, and Gas Permeability Testing to Support Active Soil-Gas Sampling
Citation:
DiGiulio, D., C. Ruybal, K. Rue, AND Richard T. Wilkin. Leak, Purge, and Gas Permeability Testing to Support Active Soil-Gas Sampling. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-18/225, 2018.
Impact/Purpose:
Active soil gas sampling has been used to evaluate risk posed by vapor migration from ground-water and soil to indoor air (vapor intrusion). This use of active soil gas sampling has prompted development of improved quality assurance and quality control measures for soil gas sampling. This study investigated several aspects of active soil gas sampling to aid in improvement of quality assurance and quality control measures. The findings from this investigation will be useful to environmental practitioners and regulatory agencies as guidance to improve protocols for active soil gas sampling.
Description:
Active soil-gas sampling has been used as a reconnaissance method in support of soil and groundwater sampling of volatile and biodegradable organic compounds for over 30 years. More recently, soil gas sampling has been used directly to evaluate risk posed by vapor migration from groundwater and soil to indoor air (vapor intrusion). This has prompted development of improved quality assurance and quality control measures. To supplement improvement in this area, four aspects of active soil gas sampling were investigated: (1) continuing calibration and flow testing of portable gas analyzers; (2) leak testing of above ground components of the soil gas sampling train and the borehole of vapor probes (including leakage between screened intervals of a vapor probe cluster) and groundwater monitoring wells used for soil gas sampling; (3) selection of vapor probe construction materials and equations suitable for gas permeability testing; and (4) purge testing to evaluate stabilization of fixed gases and hydrocarbon concentrations prior to collection of a soil gas sample for fixed-laboratory analysis. Findings from this investigation should be useful to environmental practitioners and regulatory agencies in improving the state-of-the-art of active soil gas sampling collection.