Comparison of Two Soil Gas Methods Used during a Field Investigation

Soil gas surveys were employed to help determine the nature and extent of contamination resulting from the past operation of source area ST58, the Old Quartermaster Service Station, at Eielson Air Force Base, Alaska. Two Intrusive methods were used for comparison, active conventional gas extraction and the passive Petrex method. Results were comparable, with gasoline identified as the main subsurface contaminant In both surveys. Close spatial correlation was also achieved among screening instruments and laboratory analyses. Contaminant concentrations corresponded very well with unsealed blueprints showing the locations of the above‐ground storage tanks and associated piping, subsequent test pit soil samples, and excavation results. The contamination probably occurred as a result of surface spills and leaks from discontinuities and/or breaks in the underground piping. A finer grid was employed in the Petrex method survey and produced better‐resolved contours. The use of conventional gas extraction provided...