Time series electrical potential field measurements for early detection of groundwater contamination

Abstract
The adequacy of groundwater monitoring systems that consist of up‐gradient and downgradient monitoring wells is often questioned by regulatory agencies. Groundwater contaminants frequently migrate along preferred pathways formed by lateral and vertical heterogeneities within definable stratigraphic units. Many monitoring wells must be completed correctly within individual heterogeneities to provide for early detection of contaminant migration along these preferred flowpaths. The adequacy of a specific groundwater monitoring system is usually directly dependent upon the number of monitoring wells. Time series electrical potential field measurements in combination with groundwater monitoring wells can greatly improve the capability of groundwater monitoring systems to detect the presence of contaminants. An electrical geophysical method known as the mise‐á‐la‐masse method involves the measurement of electrical current flow through earth materials under investigation. Changes in the electrical potential field over time due to the presence of groundwater contaminants can provide early detection of leaks from waste disposal facilities. A modification of the mise‐á‐Ia‐masse method was used in a controlled field experiment to track the evolution of a tracer plume over a 155‐hour period. Electrical potential differences between 171 potential electrodes and a reference electrode were measured over time to delineate the evolving tracer plume. Changes in the electrical potential field from baseline conditions over time provide a means for detecting the presence of tracer where no monitoring wells exist.