GEOLOGICAL AND HYDROGEOLOGICAL CHARACTERIZATION OF A HYDROCARBON IMPACTED SITE IN THE NIGER DELTA

This study was conducted in K-Dere, Rivers State, Nigeria to determine the impact of oil spill contamination on soil and groundwater resources in the area. A total of twelve (12) wells were drilled at random to a depth of 10 m using an auger. The method of soil and groundwater analysis involved visual examination and laboratory analysis. Characterization of soils in the area revealed a predominance of fine and medium grained sand underlain by alternating layers of fine, silt and clayey formations. Soil samples from BH-04, BH-05, BH-06, BH-07, BH-07 and BH-11 have a weak to strong hydrocarbon smell and shows light to heavy sheen. Groundwater in all drilled holes was turbid and encountered at depths from 4.27 to 6.37m. BH-06 has a very strong smell and heavy sheen. Free phase hydrocarbon was also found in BH-06. The chemical concentration of Total Petroleum Hydrocarbons (TPH), Poly Aromatic Hydrocarbons (PAH) and BTEX (Benzene, Toluene, Ethylbenzene, Xylene) were determined from the groundwater samples. TPH ranged from <10µg/l to 222,000µg/l. BH-04, BH-06, BH-07 and BH-11 had TPH concentration above DPR intervention value of 600µg/l for water. Napthalene ranged from <0.3µg/L to 537µg/L. BH-04 and BH-06 had Napthalene concentration above the DPR intervention value of 70µg/L. Anthracene ranged from <0.045µg/L to 40.9µg/L. Only BH-06 exceeded DPR intervention value of 5µg/L. Phenanthrene ranged from <0.066µg/L to 135µg/L. Again, BH-06 exceeded the DPR intervention value of 5µg/L. Fluoranthracene ranged from <0.051µg/L to 14.4µg/L. Only BH-06 exceeded the DPR intervention value of 1µg/L. Benzo (a) anthrancene concentration in the groundwater samples ranged from <0.051µg/L to 3.52µg/L. Again, BH-06 exceeded the DPR intervention value of 1µg/L. Apart from benzene with a concentration of 2.5µg/L and Ethylbenzene with a concentration of 1.11µg/L in BH-06, all other BTEX compounds in groundwater in the area had concentrations <1µg/L and were within DPR intervention values. This result shows that the soils and groundwater in the area are heavily impacted by oil contamination. Groundwater is shallow (up to 0m bgl) and the direction of flow is towards the north-westerly and south-easterly directions. BH-06 which has a high hydraulic head also shows the highest level of soil and groundwater contamination in the area. It is therefore recommended that remediation be carried out in the area to prevent further damage to the soil and groundwater resources in the surrounding areas.