Rapid ElectroMagnetic Induction profiling for pre-drill risk reduction in water-well siting

Drilling a productive water well in heterogeneous hillside terrain often comes down to choosing the right spot within a few tens of meters. We describe a rapid electromagnetic induction (EMI) survey designed to guide such a decision. Using a CMD-DUO system at 925 Hz with three coil separations (10, 20, 40 m) and two orientations (HCP/VCP), we profiled ~100 m across an agricultural field above a perennial spring. Apparent conductivity increases systematically toward the western end of the transect, with the deepest configurations showing the strongest contrast. Inversion in EMagPy yields a laterally restricted conductive body at ~8–15 m depth (overall RMSPE < 5%). We interpret this anomaly as a plausible drilling target, consistent with perched saturation or wetter colluvium feeding the downslope discharge, while acknowledging that EMI alone cannot distinguish saturation from clay enrichment. The workflow illustrates how dense, multi-configuration EMI profiling and transparent inversion can reduce pre-drill uncertainty at low cost.