Resistivity Imaging for Mapping of Groundwater Contamination at the Municipal Landfill La Chureca, Managua, Nicaragua

The purpose of this study was to map and describe groundwater contaminations at the La Chureca landfill. The groundwater level in the landfill is higher than in the surrounding area creating a local deviation from the regional groundwater flow. Due to this the contaminated groundwater from the landfill spreads out in the nearby soil and groundwater. The resistivity imaging results clearly show a top layer of around 10 metres thickness with low resistivity, where the resistivity has an inverse correlation with distance to the landfill. The soil samples show that the upper 10 m of the soil consists of loose permeable volcanic ashes with high water content, which are followed by a compact impermeable layer of tuff. The correlation between low resistivity and contaminated groundwater is confirmed by chemical analyses of groundwater samples. The compact layer of tuff appears impermeable enough to stop the contamination from penetrating deeper than approximately 10 m, which is supported by the resistivity imaging that show no traces of low resistivity below the top layer. Based on the combined results the contamination plume seems to stretch around 400 m in the southern direction and not more than 1000 m in the western direction.