Resistivity (Ω-method) method for environmental monitoring: a new approach

Abstract

A large number of landfills and waste disposal sites have been located on or in alluvial and glacial deposits. Fine-grained silts and clay layers in these alluvial deposits, or man-made liners of rolled clay, perhaps combined with a polymer sheeting, are important barriers and retardants to vertical leachate migration underneath the landfills. Ideally, these barriers prevent leachates from contaminating groundwater, and resistivity surveys are useful to study site integrity, provided a sufficient resistivity contrast exists. In this article, we introduce a different approach for resistivity monitoring of landfills, waste fluid ponds, salt storage sites, or other sites where environmental concerns exist as to the migration of materials through porous or fractured media. The method is based on the measurement of the horizontal gradient of the vertical electric field as a function of receiver distance. Numerical model responses over a hypothetical landfill model are presented to demonstrate the method. Model results show that monitoring the vertical electric field and presenting the horizontal gradient of the vertical electric field as a function of sampling distance provides good sensitivity to track the movement of an anomalous resistivity zone. The theory is complete, but the method needs to be field tested to determine operational sensitivity and repeatability.