Groundwater flow sensor monitoring of air sparging

A field experiment was conducted to determine the efficacy of a single air sparging point at different injection rates. Seven HydroTechnics Inc. In Situ Groundwater Velocity Sensors were installed around a single air injection well to study the groundwater flow regime when air was injected into the saturated zone at 5, 10, and 20 standard cubic feet per minute (scfm). Horizontal groundwater flow velocities were significantly reduced 15 ft up gradient at each injection rate of 5, 10 & 20 scfm. In fact, at 20 scfm, the horizontal flow velocity was reduced to 0.02 feet/day (ft/day), and the groundwater flow direction was deflected away from the sparge area. This indicates the possibility that once air is injected into the subsurface at rates greater than 10 scfm, contaminated groundwater in shallow areas of the aquifer is diverted from the most effective regions of an air sparging system. Groundwater flow velocity changes during mounding or groundwater displacement episodes lasted less than 24 hours, which had little impact on the distribution or spreading of hydrocarbon contamination (2-3 feet dispersion).