A groundwater contamination site investigation can be conducted more efficiently and inexpensively if the area to be investigated can be minimized. Geophysical surveys provide information which can allow one to make such determinations. The use of multiple geophysical tools with independent results allows one to make more conclusive determinations as to the extent of the problem. Comparison of integrated geophysical results with “ground truth” information derived from borehole logs and groundwater quality data further eliminates uncertainties.