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1 t01 June 1999 AGE-NC Project No 95-0137 Page 18 of 26 ' For the IAS pilot test, wells MW-1, MW-2, MW-3, MW-4, VW-1 and VW-2 were utilized for observation points Each well was fitted with air-tight well caps, valves and tubing for monitoring pressure and organic vapor concentrations in each well Dissolved oxygen concentrations, induced pressure, depth to water and organic vapor concentrations were measured in these wells Induced pressure was measured at the wells using Magnehelic differential pressure gauges, organic vapor concentrations were measured at each well head using an organic vapor meter with a photo- ionization detector(PID), ground water depth was measured using a Solinst water level meter, and dissolved oxygen was then measured using a YSI Model 55 dissolved oxygen meter After collection ' of measurements, the air-tight well cap was replaced Data collected during the IAS pilot test is summarized in Appendix D ' Results Initially, dissolved oxygen concentrations showed no increase in an of the observations Yg Y ' wells, but an increase was noted after two days (48 hours) of testing at most monitoring points The overall increase of dissolved oxygen in wells nearest the sparging points(MW-2,MW-3,VW-1) indicates circulation of the injected air and augmentation of dissolved oxygen concentration in ground water surrounding the sparging point Dissolved oxygen data collected during the pilot test indicates that intimate contact and interaction between the injected air and ground water was ' occurring, and therefore IAS should effectively reduce hydrocarbon concentrations in ground water and the saturated portion of the vadose zone through stripping dissolved hydrocarbons and stimulating hydrocarbon-degrading bacterial, if present During the IAS pilot test, ground water elevation increases between 0 2 to 0 4 feet in wells MW-2, MW-3 and VW-2 were noted, indicating ground water mounding The tendency for ground water ' mounding during performance of IAS can cause the dissolved hydrocarbon plume to migrate beyond its original horizontal extent ' The highest concentration of organic vapor (OV) was detected in VW-1, ranging from 200 ppm at the initiation of the IAS test to 2,140 ppm after 24 hours of testing The increase in OV ' concentrations may indicate that volatilization of hydrocarbons was occurring within the saturated vadose zone in response to the air sparging ' Increased concentrations of organic vapor were observed at surrounding ixionitoring wells Induced pressure and dissolved oxygen concentrations showed an initial increase during the pilot test, but 'diminished over the time of the test These two anomalies may have been caused by channeling of ' the air flow from the sparging points developing as the test progressed A lower injection pressure, of less than 12 psi and a reduced flow rate of less than 4 scfm, combined with surging the injected air should be utilized to minimize the effects of air channeling and promote maximum interaction of the injected air with ground water A closer injection well spacing would be required with a lower Advanced GeoEm3ronmental,Inc 1