Minesite groundwater contamination mapping

Abstract

A number of electromagnetic and electrical methods have been applied jointly to map groundwater contamination near minesite landforms. The main methods being investigated are transient electromagnetic (TEM) and direct current (DC) resistivity soundings, DC profiling, self potential (SP), and induced polarisation (IP) measurements, combined with any existing hydrogeological and hydrogeochemical data. At the tailings dam of the disused Brukunga pyrite mine in South Australia, reaction of groundwater with the tailings causes the formation and discharge of sulphuric acid. Geophysical methods have been investigated to determine whether they can be used to characterise variations in depth to watertable and map preferred groundwater flow paths through the tailings dam. The results of the geophysical surveys show that it is difficult to determine any preferred channels of groundwater flow from SP profiling data alone, but TEM and DC sounding measurements have enabled accurate determination of watertable levels and aquifer resistivity. The shallowest and most resistive part of the aquifer occurs in the southeast of the site, and we deduce that a possible source of fresh groundwater entering the site occurs here. It has been recommended that efforts to reduce acid formation in the tailings dam should concentrate on reducing this inflow of groundwater.