HR: 09:30h
AN: H21A-07    [PDF]
TI: Amplitude Variation With Offset (AVO) Analysis of Ground Penetrating Radar Data for Direct Detection and Delineation of NAPL Contamination
AU: * Jordan, T E
EM: tejordan@buffalo.edu
AF: University at Buffalo Environmental Geophysics Research (EGR) Lab, Dept of Geology 876 Natural Sciences Complex, Buffalo, NY 14260 United States
AU: Baker, G S
EM: gbaker@geology.buffalo.edu
AF: University at Buffalo Environmental Geophysics Research (EGR) Lab, Dept of Geology 876 Natural Sciences Complex, Buffalo, NY 14260 United States
AB: Amplitude and phase variation with offset analysis of ground penetrating radar data (APVO/GPR) can improve the differentiation of non-aqueous phase liquid (NAPL) from stratigraphic changes. Previous controlled experiments have shown that common offset (CO) GPR methods can detect the presence of NAPL in soil by examining amplitude and travel time (velocity) anomalies. Unfortunately, stratigraphic changes such as the presence of a silt or clay lens or perched water table may produce similar amplitude and velocity anomalies. Therefore, it is difficult to delineate NAPL in a terrain with unknown stratigraphy exclusively using CO data collection methods. Forward models based on the Fresnel equations predict that amplitude responses exist at various incidence angles that will allow for differentiating NAPL from hydrogeologic changes. Models generated as part of this study indicate that analyzing the difference in amplitude responses from linearly polarized electric field vertically oriented (EV) to the horizontally oriented (EH) signals at various incidence angles improves target discrimination. A case history is presented demonstrating that collecting common-midpoint (CMP) GPR data using EH and EV polarized signals at anomalous CO amplitude responses and analyzing the data using APVO and normalized residual polarization (NRP) methods can improve the detection and differentiation of NAPL from stratigraphic changes in the subsurface. These results are corroborated using a capacitively coupled resisitivity instrument and subsequent intrusive sampling.
UR: http://www.geophysics.buffalo.edu
DE: 0994 Instruments and techniques
DE: 1829 Groundwater hydrology
DE: 1894 Instruments and techniques
SC: Hydrology [H]
MN: 2003 Fall Meeting