| Abstrakt: |
An evaluation of data detailing in situ air sparging (IAS) systems at 59 sites has been assembled into an American Petroleum Institute insitu Air Sparging Database (API-IAS Database). The database was developed to provide site managers insights concerning the state-of-the-art of IAS system design, operation, and evaluation. The IAS radius ofinfluence (ROI) is often evaluated based on changes in a number of physical, chemical, or biological monitoring parameters. Measurements of groundwater dissolved oxygen levels was the technique used most often to determine the ROI. Other parameters such as pressure changes in the vadose and saturated zones, groundwater mounding, air bubbling in wells and tracer gases were also used to aid in the determination of the IAS ROI. A review of 37 pilot studies revealed that the IAS ROI is generally between 10 to 26 ft. IAS technology is generally beingapplied in sandy soils. The application of IAS technology was deemedinfeasible at seven sites where soils contained high levels of siltsor clay. Analysis of design and operation data at 40 IAS sites revealed that a typical IAS well is 2 in. in diameter, with a 2-ft screen,positioned 5 to 10 ft beneath the water table. The wells typically were operated at an overpressure (ie., pressure in excess of that required to overcome the hydrostatic head) of less than 5 psi with a flowrate of less than 5 cfm. At several sites when IAS system pressures and flows were doubled, only slight increases in ROI resulted. Significant reductions of dissolved volatile organic hydrocarbon (VOCs) were observed at 12 sites as a result of IAS. However, long-term water quality data following an IAS system shutdown was very limited. [ABSTRACT FROM AUTHOR] |
