Hydro-geochemical characterization and groundwater modelling of the subsurface around Ughelli West Engineered Dumpsite in the Western Niger Delta, Nigeria

Abstract

Geoelectric, geochemical investigation, and groundwater modelling were integrated in areas surrounding the Ughelli West Engineered dumpsite in the Western Niger Delta. The study focused on assessing the environmental impact of the dumpsite on its surrounding groundwater. The geochemical analyses revealed that the leachates generated from the dumpsite have significant potential to contaminate the surrounding environment. The BOD5/COD ratio was less than 0.1, indicating that the dumpsite is old with stabilized leachate of low biodegradability and in the methanogenic phase of anaerobic degradation. The groundwater chemistry in monitoring wells outside the dumpsite and at other control sites showed no significant impact of the dumpsite on groundwater quality. Groundwater models showed groundwater flow in the north-western direction and significant vertical movement of contaminants up to depths of about 60 m beneath the dumpsite after a period of 3 years. The contaminant plume, however, had not moved considerably laterally away from the dumpsite. The location of the dumpsite within areas of low vulnerability due to the presence of clay/sandy clay between 1.3 and 6 m thick around the dumpsite limited the lateral migration of leachate in groundwater.