Tailings Pond Outfiltration Monitoring with Electrical Conductivity Surveying

A new, shallow penetration electromagnetic (EM) surveying method for the detection and monitoring of contaminated mining water, called NOVEL-EM, was developed between 2013 and 2015. It has been used at several mine sites in Finland and abroad. The method is comprised of instrumentation, systematised on-site measurements, processing, and modelling procedures which aim to achieve high accuracy and repeatable data and the results of water chemistry changes in the surface or groundwater layer within a depth range of 0–10 m. This article depicts the baseline setting one mine site, one monitoring line time-lapse result, and an example of how the water electrolyte content has evolved along the exemplified monitoring line. The second part of the article discusses modelling potential, although monitoring itself does not require numerical modelling. Layer-based modelling provides several supplementary uses. Constrained modelling can more accurately focus resistivity changes on layers of primary interest. Water chemistry calculations are possible with ground models. Finally, modelling can help to develop data processing as scoping calculations show the influence and significance of various physical conditions that are encountered, such as the variability of ground temperature. It has been verified that detected anomalies are related to changes in water chemistry, and the monitoring line network has been expanded over the course of the years.