Electrical resistivity imaging of Regina landfill: A non-invasive characterization and leachate distribution study and contamination transport modelling

Electrical resistivity imaging is used increasingly as a geophysical exploration technique in contaminated land research. The presented work demonstrates the efficiency of electrical imaging in monitoring pollution plume evolution under the landfill and geological mapping around the landfill, employing electrical resistivity and time domain induced polarization (IP) methods. Nine electrical resistivity imaging (ERI) surveys were conducted in the summer of 2005, in which five surveys around the landfill mapped the geology and four on the landfill mapped the leachate distribution. The ERI survey coupled with ground truthing by borehole logging revealed the geology around the landfill has a clay layer varying 5 to 20 m followed by a sand zone with a varying thickness of 5 to 40 m, followed by till. The ERI conducted north and south of the landfill indicated the presence of large areas of leachate accumulation with low resistivity values of less than 8 Om and IP values greater than 20 mV/V measured in terms of chargeability. The ERI profile conducted at the north top of the landfill mapped the presence of a high resistive zone at 30 m below the surface, possibly due to the high organic load of the backfilled oil disposal pit.; A three dimensional groundwater movement and contamination transport model was developed using the data from the ERI survey and previous studies. The groundwater movement model was developed by using MODFLOW and GMS V6.0 was used for the preprocessor and postprocessor environments. The model consists of two layers (a top sand layer and a bottom gravel layer) representing the Condie aquifer system. The groundwater flow model was developed using MODFLOW and the contaminant transport model was developed by using the MT3D. The saturated areas in the clay layer, observed from the ERI survey, were used as sources of contamination along with the existing source from the Provincial Correction Center (PCC).; The simulation of chloride resulted in identifying the existence of two chloride plumes to the north and south of the landfill; the chloride concentration is decreasing from the PCC source.