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Electrical resistivity imaging of conductive plume dilution in fractured rock.

Research output: Contribution to journalJournal article

  • Robin E. Nimmer
  • James L. Osiensky
  • Andrew Binley
  • Kenneth F. Sprenke
  • Barbara C. Williams
<mark>Journal publication date</mark>08/2007
<mark>Journal</mark>Hydrogeology Journal
Issue number5
Number of pages14
Pages (from-to)877-890
<mark>Original language</mark>English


Electrical resistance tomography (ERT) was used to monitor a conductive plume dilution experiment that was conducted in fractured basalt in order to assess its applications in this type of fractured-rock environment. Tap water was injected into an injection well for 34 days to dilute a pre-existing potassium chloride (KCl) plume at a site in Idaho, USA. No further fluids were introduced artificially during a 62-day monitoring period. Both surface ERT and cross-borehole ERT were used to monitor dilution and displacement of the plume. A square grid of land-surface electrodes was used with the surface ERT. Three-dimensional images of surface ERT delineated areas of increased and decreased resistivities. Increasing resistivities are attributed to dilution/displacement of the KCl solution by tap-water invasion or the influx of seasonal recharge. Decreasing resistivities resulted from redistribution of residual KCl solution. Cross-borehole ERT was conducted between the injection well and each of seven surrounding monitoring wells. Polar plots of the injection-well resistivity data in the direction of each monitoring well delineate specific locations where tap water seeped from the injection well via preferential flow paths determined by time-dependent resistivity increases. Monitoring-well data indicate locations of clustered and isolated regions of resistivity changes.