Enviroprobe recently conducted a 3D ERI survey to locate underground voids. The target property was a residential property with a house. Several sinkholes had opened on the ground surface and there were cracks on the basement walls of the house. In order to locate/delineate potential underground voids more accurately, 3D instead of 2D ERI surveys were conducted in both the front yard and the backyard of the property.

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The ERI surveys were conducted in a 3D pattern with electrodes only planted on the ground surface. Within the property, a grid size of 80'x130' was laid out in the backyard and a grid size of 60'x130' was laid out in the front yard.

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An Advanced Geosciences SuperSting R8 resistivity system was utilized to perform the survey. The system is an 8-channel electrical resistivity data acquisition system which can be 8 times as fast as the old R1 resistivity system.

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The program EarthImager 3D of Advanced Geosciences was used to process the data.

A high resistivity zone indicating a potential underground void was found in each grid.