GPR Imaging of Clastic Dikes at the Hanford Site, Hanford, Washington

We used ground penetrating radar (GPR) data to help determine the spatial distribution and the subsurface geometry of clastic dikes at the Hanford Site. This information will help to improve the understanding of the hydrological role of these ubiquitous clastic dikes at the Hanford Site. We collected 100 MHz ground penetrating radar (GPR) 3-D surface reflection data at two sites, the 216-S-16 (S-16) Pond and the Army Loop Road sites, and 2-D reflection data along a 6.9 km linear transect (Traverse site) near the Army Loop Road site. The dikes are distinguished in the GPR data by a strongly attenuated zone, disruptions in the continuity of reflections, and diffractions where reflections are disrupted. In general, the data quality is better at the Army Loop Road and Traverse sites than at the S-16 Pond site, probably due to the presence of cobbles at the S-16 Pond site. A high-moisture, fine-grained unit probably causes the strong reflections at the Army Loop Road site and the Traverse survey site. The signal penetration varies between 5 and 12 m below the land surface.