Time-lapse monitoring of a saline groundwater plume using electrical geophysical methods

Abstract

With increasingly stringent environmental conditions on operating licenses for industrial plants, the need for accurate monitoring of groundwater has become an important consideration for many companies. From 2004 to 2009, a variety of electrical geophysical methods have been deployed at Coogee Chlor Alkali’s Kemerton plant site (north of Bunbury in Western Australia) to monitor the extent and conductivity of a known saline groundwater plume originating from the plant site. Geophysics has been applied on an annual, ongoing basis for this objective and included electromagnetic conductivity mapping, Electrical Resistivity Imaging (ERI) and downhole logging (conductivity and gamma). These data have been analysed in conjunction with groundwater salinity data from monitoring boreholes and shown a marked decrease in the extent and conductivity of the saline plume from commencement of surveys to date. This correlates with the construction of a new salt dissolver system in 2005, the old one of which was thought to be the main contributor to increased levels of groundwater salinity originating from the plant. Whereas the borehole sampling regime provided Coogee with confirmation that the conductivity of the groundwater was decreasing, the geophysics was able to confirm that the boreholes were sampling the main body of the conductive plume and confirm that extent, as well as conductivity, of the plume was decreasing from year to year.