Soil Conductivity Standard Operating Procedure

The conductivity probe provides a four-pole "Wenner" array that is advanced through the soil using Direct Push Technology (DPT). As the probe is advanced, an electrical current is discharged through the soil from the outer two poles. The inner poles measure the voltage. Before logging, the instrumentation cable is connected to the conductivity probe and is then pre-strung through the hollow probe rod. To complete the assembly, the cable is connected at the surface to the soil conductivity instrumentation and computer which are housed in a portable case. The rods are loaded on a specially designed rod cart for easy dispensing, storage and decontamination. Once the operator and probe are set up over the hole, and all instrumentation has been activated, the probe and rod string are driven through the subsurface by the percussion of the DPT rig. Simultaneously and continuously, the polar array on the probe senses current and voltage and directs this data into the computer where it is converted into conductivity. A stringpot mounted on the probe senses movement of the probe. This signal is also fed into the computer where Windows-based software provides a real-time display of conductivity versus depth and probing speed. The data is stored in a spreadsheet with a compatible format for later graphing and analysis.

Subsequent to each log, the probe can be clamped in a special test jig to test the electrical integrity (isolation and continuity) of the conductivity probe. The test takes only a few minutes and assures the operator that a damaged probe has not compromised log quality. Finally, the rod cart can be wheeled to the decontamination area and hosed down or pressure washed to provide simple and thorough decontamination.