Reprocessing Gpr Data From The Cfb Borden Experiment Using Apvo/Gpr Techniques

This paper presents reprocessed GPR data from a 1991 Canadian Forces Base (CFB) Borden<br>experiment conducted by Brewster and Annan (1994). The purpose of our research is to<br>determine if a modified amplitude and phase variation with offset analysis of the ground<br>penetrating radar (APVO/GPR) data is a feasible technique for monitoring a dense non-aqueous<br>phase liquid (DNAPL) release. Forward models using the Fresnel reflection coefficient equation<br>accounting for low loss conditions indicate that conductivity is inversely related to the maximum<br>absolute value reflection coefficient max R observed for incidence angles of 0 through 89<br>degrees. The injection of a low conductivity DNAPL into a saturated sand decreases<br>conductivity by displacing some ground water. Conductivity values then increase as the DNAPL<br>migrates vertically downward. It is anticipated that values of max R increase as DNAPL is<br>injected followed by a decrease as the DNAPL drains. The ability to detect changes in the<br>amplitude of reflectors due to zones of anomalously conductive liquids may be an additional<br>method for monitoring NAPL releases. The APVO/GPR technique may also be useful for<br>determining the conductivity of subsurface reflectors.