The resistivity cone penetration test (RCPTu) combines the downhole measurement of soil resistivity and the logging capabilities of the cone penetration test (CPTu). The RCPTu provides a rapid, reliable and economic means of determining soil permeability, stratigraphy, and strength in addition to providing relative measurements of electrical resistivity. The ability to determine groundwater and soil resistivity along with other soil parameters in one operation allows for the accurate profiling of contaminated groundwater plumes as well as some estimate of the rate and direction of groundwater flow through the soil. Identification of the lateral and vertical extent of contaminants enables the engineer/scientist to rapidly implement a remediation or recovery program thereby mitigating the potential damage caused by contaminated groundwater seepage.

Below is an illustration of a resistivity cone. 

RCPTu