Assessment of geospatial capability index for siting waste dump/landfill to control groundwater geopollution using geographic information system (GIS) approach: case study of Abakaliki area and environs, Southeastern Nigeria

Understanding spatial variation of rock and soil is important for capability precision as well as groundwater contamination or geopollution management. In view of waste dump/landfills, geoenvironmental hazards ravaging our land including surface and groundwater contamination, site suitability indexing, spatial distribution and characteristics of underlying rock and soil matter are studied. Rock and soil samples were collected in a systematic grid pattern using simple drill core rig and hand auger. Geostatistical and soil property analyses were conducted on each grid. Groundwater aquifer vulnerability to leachate was studied using depth to water table, recharge (precipitation), aquifer material, topographic slope, impact on vadose zone/vadose zone material and hydraulic conductivity (DRASTIC) and geophysical methods. Human population growth analysis indicates tremendous waste generation. Flash points of waste generation and dumping were noted. Geographical positioning system was used to take record of sampling point coordinates. Using a sufficient dataset, each grid indicative factor is objectively scaled, weighed and assigned a numerical rating according to their relative importance employing site suitability (S) analysis approach in an empirical equation. Results were imported into a geographic information system (GIS) platform to generate thematic maps. The results showed that subsurface rock and soil characteristics are neither spatially nor vertically homogeneously distributed. Thematic maps were generated and further interpolated in the GIS domain to produce a composite waste dump/landfill suitability index map.