Air sparging is a groundwater remediation technique that introduces air into the subsurface to<br>enhance the removal of contaminants. The effective application of this technique requires a<br>knowledge of the spatial distribution and magnitude of air saturation achieved during the sparging<br>process. This paper discusses the use of ground penetrating radar (GPR) reflection surveys,<br>borehole GPR, and geophysical well logging techniques to determine the steady state air<br>saturation distribution within a sandy aquifer during an air sparging experiment performed at<br>Canadian Forces Base (CFB), Borden, Ontario. Air was injected at a depth of 3 m below the<br>water table using a flow rate of 200 m3/day (5 scfm). Surface GPR reflection surveys, borehole<br>GPR surveys and geophysical well logs were acquired prior to the injection of air, and after the<br>eighth day of sparging.<br>GPR reflection surveys, sensitive to changes in air saturation with depth, mapped large flat lying<br>pockets of trapped air, that had moved to, and presumably past, the edges of the test site.<br>Borehole GPR surveys and neutron logging provided quantitative estimates of air saturation<br>throughout the test cell, giving maximum air saturations of 60% near the centre of the test area<br>and 20% at the edges. Electromagnetic (EM) induction logs indicated that as a result of surface<br>water pumping, more conductive water from a deeper inorganic plume moved into the zone being<br>sparged, but could not be used to determine air saturation.


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