Geophysical methods provide a non-invasive, safe, cost-effective method for delineating subsurface contaminant plumes. Integrating these tools into contaminated site surveys reduces the number of boreholes needed to characterize the site while simultaneously providing more spatial coverage in reduced time (and therefore cost) and minimizing operator exposure and thereby enhancing personnel safety.
Ground Penetrating Radar
Ground penetrating radar (GPR) will often detect subsurface contaminants such as hydrocarbons (oil, gasoline, etc) and chlorinated solvents (TCE, PCE, for example) because those contaminants tend to be more or less conductive that the groundwater, depending on their type and age. Other factors include contaminant concentration, depth, and soil types. Interpretation of GPR can also produce maps of subsurface geology as an indication of the potential flow pathways of the contamination in the ground. This tool is easily implemented in Arctic conditions, and can simultaneously produce information about other site conditions such as aquifers or buried ice lenses.
Update: Logic Geophysics is now offering GPR refraction surveys to delineate hydrocarbon contamination. This advanced technique provides improved resolution of contaminant location. Contact us for more details!
Electrical Resistivity Imaging
Electrical resistivity methods are often able to map subsurface contamination by measuring the difference between the background conductivity and the conductivity of the contaminated areas. This tool works well for contaminant plumes emanating from landfills and for leachate plumes from geotechnical work such as mining.
Other Electromagnetic Tools
The EM-31 can provide measurements of apparent conductivity down to approximately 6 meters. Other tools such as the EM-34 can reach as deep as 60 meters as required. Data processing and interpretation can often correlate data anomalies with the presence of groundwater contamination and other subsurface features of interest, such as buried structures.