CHARACTERIZING HYDROGEOLOGIC PROPERTIES NEAR ALMA, MICHIGAN, USING FOUR-DIMENSIONAL GROUND PENETRATING RADAR

Geophysics researchers such as Birken, Versteeg, Brewster and Annan successfully used ground penetrating radar (GPR) in hydrogeologic studies. Birken and Versteeg determined hydrogeologic quantities such as hydraulic conductivity, flow pathways and flow velocities in three dimensions, showing how qualitative spatial data can be used to obtain ground water flow and contamination migration directions. Brewster and Annan used ground penetrating radar at the Canadian Forces Base Borden, using a 200 MHz antenna with GPR to observe a controlled release of DNAPL. These researchers used 4-D GPR to accomplish their studies. 4-D GPR provides a non-invasive, non-destructive method to acquire 3-D data temporally. As Birken and Versteeg state, if over time the earth material over the interested volume does not change then changes in the 3D GPR profile over time most likely result from groundwater movement. This groundwater movement can be shown using difference cubes, which show temporal changes in the 3D models.

This presentation describes the results of using 4-D GPR in Lumberjacks Park to characterize hydrogeologic properties non-invasively. Lumberjacks Park, located approximately 15 miles west of Alma, Michigan, contains glacial terrain. The project's goals were to use 4-D GPR and show temporal variations in hydrogeologic properties, and also gain a better understanding of GPR usage in a glacial setting. The investigators used a 200 MHz antenna with GPR over a 1 month time period to examine temporal changes under a 60' by 30' grid, next to the Pine River. The river height and holes dug with a soil auger were used for ground truthing. After 2-D processing and the creation of an integrated proxy cube for hydrogeologic properties; the GPR data was loaded up into Rockware's Visual Seismic 3.0 software for data interpretation. This study showed subtle changes in hydrogeologic properties over the course of the month's data acquisition. As these results show, 4-D GPR could be a very useful tool in evaluating hydrogeologic properties non-invasively, non-destructively, and inexpensively.