The study is a post impact assessment of a petroleum effluent dump site located in Midwestern Nigeria carried out with a view to investigating the implication of exploration activities earlier carried out in the area and the vulnerability of the area to future developmental program. The effluent dump was nearly circular measuring about 50m - 60m in diameter. The study area was selected as the area radially situated on the periphery. The area was divided into three areas: areas covering the periphery of the effluent dump to 50m radius (i.e. cir. 0 – 50m); areas radially covering 50 – 100m (i.e. cir. 50 – 100m), and the area covering 100 – 200m radius (i.e. cir. 100 – 200m). The control was taken as an area located 500m from the effluent dump site. The mean ambient air quality measurements for the different radial dimensions from the effluent dump site were within Federal Ministry of Environment/Department of Petroleum Recourses (FMEnv/DPR) limits. No significant changes in soil pH were observed. Heavy metal composition of soil was significantly higher near the periphery of the dumpsite than away near to the control site. The mean plant density of the project site showed that herbaceous layer was 13 plants per meter squared very close to the effluent dump site compared to 51 plants in the control site. There were no trees near the effluent dump site, but there were 303 trees/ha in the control site. Vegetation of the farmlands situated between 100m -200m comprised mainly Cynodon dactylon, Cyperus iria, Eleusine indica, Euphobia heterophylla, Manihot esculenta, Paspalum conjugata, Sida acuta, Zea mays. Musa paradisiaca. Soils very close to the effluent dumpsite were rich in hydrocarbon degrading microorganisms than soils in the control site.
