Hydrogeophysical and Geotechnical Characterization of Soil and Groundwater at Two Crude Oil Spill Sites in Central and Eastern Niger Delta

Crude oil spills in the Niger Delta continue to impair shallow soils, groundwater quality, ecosystem services, and the geotechnical behaviour of near-surface sediments.

This study presents an integrated geochemical, hydrogeological, geotechnical, and geoelectrical characterization of two spill-impacted communities, Agbura in Bayelsa State and Bodo in Rivers State.

Five boreholes and nine vertical electrical soundings were established at each site to evaluate contaminant distribution relative to spill source, groundwater flow direction, depth of infiltration, and textural controls on contaminant mobility.

Groundwater and soil samples were analysed for physicochemical parameters, total petroleum hydrocarbon (TPH), and selected heavy metals, while grain-size and Atterberg-limit tests were used to classify soils and infer hydraulic behaviour.

Hydraulic-head contouring showed northeast–southwest flow at Agbura and northwest–southeast flow at Bodo, indicating preferential migration toward downslope receptors.

Groundwater close to the spill centres recorded elevated turbidity, chemical oxygen demand, biochemical oxygen demand, and TPH, with the poorest quality at closest to spill sites in both communities.

Water quality index status ranged from good to unsuitable, and heavy-metal pollution indices showed moderate to high pollution intensity near the impact points.The soils comprise clay, sandy clay, clayey sand, silty sand, and poorly graded sand, with average hydraulic conductivity of 3.11 × 10?6 m/s at Agbura and 8.53 × 10?6 m/s at Bodo.

Corresp ondingly, spill-affected geoelectric layers displayed anomalously high resistivity, commonly between 500 and 2000 Ùm.

The results demonstrate that the combined use of geochemical testing, geotechnical evaluation, and geoelectrical sounding provides a robus t basis for site screening, vulnerability assessment, and remediation planning in coastal deltaic terrain.