Background: Electrical resistivity tests at a project site could be a valuable economical alternative to typical geotechnical soil exploration and a reliable source of data. In the present study, the soil at a constructed underground water tank site in Qassim Region – Saudi Arabia is investigated using the electrical resistivity testing method. Objective: The study aims to compare the results of traditional soil boreholes that were conducted at various stages of the project lifetime with the interpretation of soil resistivity test results. Methods: Eight soil boreholes were drilled at the water tank site to capture the nature of soil layers. The electrical resistivity of soil layers at the site is measured and used to investigate the ground subsurface of the project site. The geophysical software, ZondRes2d is utilized to analyze and interpret the collected data. Results: Both geotechnical soil boreholes and geophysical electrical resistivity tests revealed similar soil profiles with three main layers comprising of backfill material, clay with expansive nature, and weathered limestone and marl. The results of the electrical resistivity tests are also affirmative of available resistance values of different soils in the literature. Conclusion: The study shows that electrical resistivity testing is reliable in capturing the soil nature which presents an attractive tool for preliminary investigation of the soil-related problems of distressed structures.

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