TY - JOUR
T1 - Air distribution in the Borden aquifer during in situ air sparging
AU - Tomlinson, D. W.
AU - Thomson, N. R.
AU - Johnson, R. L.
AU - Redman, J. D.
N1 - Funding Information:
Funding for this research was provided by the University Consortium, Solvents-in-Groundwater Research Program which is sponsored by: Boeing, Ciba-Geigy, General Electric, Eastman Kodak, Laidlaw Environmental Services, the Natural Sciences and Engineering Research Council of Canada, and the Ontario University Research Incentive Fund. Sensors and Software of Mississauga, Ontario, provided the PulseEKKO IV borehole and surface GPR equipment.
PY - 2003/12
Y1 - 2003/12
N2 - A field experiment was conducted at Canadian Forces Base Borden (CFB Borden) to assess the air distribution from a single in situ air sparging injection point. This aquifer consists of fine to medium sand deposited in horizontal layers. The permeability at the study location varied from 10 -10 to 10-14 m2 and distinct low permeability horizons were present at approximately 1.2, 2.0, and 2.9 m below the water table. Prior to air injection, a 15×15-m portion of the vadose zone was excavated to the water table (∼1 m below ground surface) in order to visually observe air release distribution at the water table. The water table was actively maintained 5 cm above the excavated surface. The sparging system operated for a period of 7 days with an injection flow rate of 200 m 3/days (5 scfm). The resulting subsurface air distribution was assessed using a variety of techniques including neutron logging, borehole and surface ground penetrating radar, piezometric head measurements, surface visualization, and hydraulic testing. Through this combination of tests, it was demonstrated that variations in permeability and, hence, capillary pressure at the site were sufficient to cause the injected air to spread laterally, forming stratigraphically trapped air pockets beneath the low permeability horizons. The formation of these air pockets eventually resulted in a buildup of capillary pressure that exceeded the air entry pressure and allowed some air to migrate up through the lower permeability layers. Each of the assessment techniques employed generated information at different spatial scales that prevented a direct comparison of the results from the various techniques; however, the results from all techniques proved to be critical in the interpretation of the experimental data. As a consequence, the different assessment techniques should not be viewed as alternatives, but rather as complimentary techniques.
AB - A field experiment was conducted at Canadian Forces Base Borden (CFB Borden) to assess the air distribution from a single in situ air sparging injection point. This aquifer consists of fine to medium sand deposited in horizontal layers. The permeability at the study location varied from 10 -10 to 10-14 m2 and distinct low permeability horizons were present at approximately 1.2, 2.0, and 2.9 m below the water table. Prior to air injection, a 15×15-m portion of the vadose zone was excavated to the water table (∼1 m below ground surface) in order to visually observe air release distribution at the water table. The water table was actively maintained 5 cm above the excavated surface. The sparging system operated for a period of 7 days with an injection flow rate of 200 m 3/days (5 scfm). The resulting subsurface air distribution was assessed using a variety of techniques including neutron logging, borehole and surface ground penetrating radar, piezometric head measurements, surface visualization, and hydraulic testing. Through this combination of tests, it was demonstrated that variations in permeability and, hence, capillary pressure at the site were sufficient to cause the injected air to spread laterally, forming stratigraphically trapped air pockets beneath the low permeability horizons. The formation of these air pockets eventually resulted in a buildup of capillary pressure that exceeded the air entry pressure and allowed some air to migrate up through the lower permeability layers. Each of the assessment techniques employed generated information at different spatial scales that prevented a direct comparison of the results from the various techniques; however, the results from all techniques proved to be critical in the interpretation of the experimental data. As a consequence, the different assessment techniques should not be viewed as alternatives, but rather as complimentary techniques.
KW - Air distribution
KW - Air sparging
KW - Geophysics
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U2 - 10.1016/S0169-7722(03)00070-6
DO - 10.1016/S0169-7722(03)00070-6
M3 - Article
C2 - 14607473
AN - SCOPUS:0242522965
SN - 0169-7722
VL - 67
SP - 113
EP - 132
JO - Journal of contaminant hydrology
JF - Journal of contaminant hydrology
IS - 1-4
ER -