Integrated vertical radar profiles (VRP) and multi-fold GPR for site characterization

Non-invasive characterization of contaminated sites and brownfields is being used to support planning and correlation of sampling and in decision-making and monitoring of rehabilitation procedures. We exploit a combination of surface (linear/azimuthal multi-fold) and borehole [vertical radar profiling (VRP)] techniques for an integrated and constrained assessment of the radar velocity field. The test of the method is performed with a Mala Geoscience system equipped with 100 MHz borehole and 100-250 MHz surface antennas. We test the technique at a disposal site where mixed industrial and solid urban waste is piled on alluvial sequences. The stratigraphic column includes sandy loams with variable fractions of silt and clay, a gravel and coarse sand aquifer, a bottom clay layer of variable thickness. Two shallow layers, an allochthonous soil, 0 to 80 cm thick from topographic surface, lying on coke ashes mixed with industrial debris (100 to 170 cm thick), attenuate the radar wave due to strong scattering and low resistivity. Maximum penetration from surface is restricted to approximately 250 cm. Borehole measurements are used to integrate surface methods and reconstruct the velocity field. Results of the radar experiment are validated by laboratory measurements, performed with a network analyzer, and by FDTD numerical simulation.