ABSTRACTA resistivity survey was made in the vicinity of a landfill in a glacial aquifer to determine the extent of ground‐water contamination. The survey consisted of 12 electrical soundings with the Winner probe configuration. An examination of the sounding curves and logs of nearby test borings suggested a three‐layer geoelectric model for studying water quality variations.The thicknesses and the resistivities of the upper two layers were fixed. Differences in apparent resistivity were assumed to be due only to differences in specific conductance of ground water in the saturated zone (third‐layer resistivities). Apparent resistivities at the largest probe spacing, 102 feet (31 m), were then computed for a range of assumed third‐layer resistivities. Specific conductances corresponding to third‐layer resistivities were then computed using an assumed formation factor of 4.5. A relation between apparent resistivity at the 102‐foot spacing and specific conductance was developed for converting apparent resistivities to specific conductances. Quadratic trend surfaces developed for specific conductances measured at monitoring wells and computed from apparent resistivity are shown to be in good agreement.Under favorable conditions, interpretation of electrical sounding curves provides a basis for estimating specific conductance of ground water from surface resistivity methods. This leads to a quantitative assessment of ground‐water contamination which compares favorably with that determined from mon