Environmental, Hydrogeology
Soil and Groundwater Quality Assessment in Oil Spill Areas of Agbura, Bayelsa State, Nigeria
Authors: Paago, J.B. and Oborie, E. Abstract An assessment of soil and groundwater quality in the oil spill affected parts of Agbura, Bayelsa State, Nigeria, was carried out to evaluate the concentration of key physicochemical parameters and determine the level of contaminationin the area. Soil and groundwater samples were collected from five boreholes drilled to 6m depth at distances ranging from 100m to 500m from the primary oil spill site. Results of laboratory analysis indicate that the groundwater pH and electrical conductivity (EC) were within World Health Organisation (WHO) and Environmental Guidelines and Standards for the Petroleum Industry in Nigeria (EGASPIN) limits with values ranging from 6.1 to 6.9 and 37.45to257.38μS/cm respectively. Turbidity was higher than the recommended standard, and biochemical oxygendemand (BOD) exceeded acceptable limits across all samples. Total petroleum hydrocarbon (TPH) levels varied from 0.2310 to 0.9382 mg/l, with values at the impact site significantly above regulatoryvalues. Heavy metals such asFe and Pb were found in concentrations surpassing recommended limits in most of the samples analysed. The water quality index (WQI) revealed that thegroundwater quality deteriorated closer to the spill site, with samples from the impact site classified as “unsuitable” and”poor,” while samples away from the spill site were classified as “good.” Soil analysis showed TPH concentrations that ranged from 0.294 to 1.0661 mg/kg, with levels decreasing with depth and distance from the spill site. Other heavy metals showed variable contamination patterns, influenced by proximity to the spill. These findings highlight significant contamination of groundwater and soil, particularly near the spill site, emphasizing the need for continuous monitoring and remediation efforts in the study area.
Engineering Geology, Environmental
Assessment of Natural Geohazards in the Niger Delta Coast, Nigeria
Author: Fidelis A. Abija Abstract The coastal zone is a dynamic environment under hydrodynamic forcings and adverse consequences of geohazards with potential for disasters. In this this studies, ASTER DEMs and LandSat 4,5 imageries have been analyzed in ArcGIS to determine the amount and rates of coastal subsidence, shoreline movements and coastal erosion and supplemented with secondary tide and wave data to model wave conditions in the face of climate change. Results indicates that the average ground subsidence was -2.6m at a rate of – 0.144m/yr. on the Bayelsa coast and -3.75m at a rate of -0.208m/yr on the Rivers coast. The rate of coastal erosion along the Akwa Ibom, Rivers and Bayelsa States in the Niger Delta coastline depicts a linear erosion of -13,054m, -17,519m and -81,532m in Akwa Ibom, Rivers andBayelsa respectively with erosion rates of -5.5m/yr along Akwa Ibom, -7.2m/yr along Rivers and -11.1m/yr along the Bayelsa coastline. The net shoreline retreat equivalent of incidental erosion was -8,590m along the Akwa coastline, – 9,240m along Rivers coastline and -70,383m along the Bayelsa coastline. Modeled hydrodynamics parameters predicted waves with mean wavelength of 178.95m, wave celerity of 13.01m/sec, group wave celerity of 11.27m/sec with maximum horizontal velocity of 0.4m/sec exerting an energy flux of 15, 902.00w/m. In considerations the stack realities of climate change, vulnerability assessment, integrated coastal zone management and climate change adaptation strategies for coastal protection are recommended.
Engineering Geology, Hydrogeology
Groundwater Contamination due to the Activities of Auto – Mechanics in Lagos Metropolis, South-western Nigeria
Authors: Umbugadu, A.A. and Akinwumi, T.V. Abstract The release of wastes generated from the activities at automobile workshops leads to heavy metals contamination of groundwater which can be harmful to human health. The study is aimed at investigating the physicochemical andheavy metal contamination of groundwater from three automobile workshops at Super, Jankara and Kola areas located at Alimosho, Ifako – Ijaye and Agege Local Government areas of Lagos State. Fifteen (15) samples were collected from residential houses near the automobile workshops, at 5m – 75m depth and taken to Federal Institute of Industrial Research (FIIRO) laboratory at Oshodi, Lagos. Electrical conductivity (EC), pH, temperature and total dissolved solids (TDS) were measured onsite using a 107 model pH meter. The samples were analysed for lead, magnesium, manganese, cadmium, arsenic, chromium and mercury using Atomic Absorption Spectroscopy; Perkin Elmer model Analyst 3000.The TDS value of all the samples in this research ranged from 0.017 mg/l – 0.097mg/l which is within the W.H.O. standards of 500mg/l. The pH value of all the analysed groundwater samples ranged from 4.4 – 7. This implied that groundwater in the study area are slightly acidic to neutral. The groundwater samples from JW03 are below the acceptable pH limit of W.H.O while the groundwater from the remaining 14 sampling points have pH values less than 6.5, hence, they are slightly acidic. Only two sampling points in Jankara; JW06 and JW07, falls within the W.H.O acceptable limit while the remaining samples have values lower than 6.5. The electricalconductivity in the water analysed ranged from 0.72 μS/cm – 194 μS/cm. The electrical conductivity value of all the water samples analysed are below the W.H.O standard of 1000μS/cm. This result reflects a low input of solute in the groundwater. The temperature values of the groundwater samples of the three areas of the research ranged from 26.8 ºC – 37.8ºC with a median value of 30.2ºC. The values exceeded that of W.H.O limit of 25ºC. The concentration of heavy metal in groundwater of the three mechanic workshops are in this trend; Pb>Mn>Cd>Cr. Arsenic was not detected in all the groundwater samples from the three mechanic workshops. The metal Pb have a range of 0.382 mg/l – 1.895mg/l and an average of 1.070mg/l, Mn ranged from 0.067 mg/l – 2.0933mg/l with an average of 0.7468mg/l, Cd ranged from 0.146 mg/l – 0.5937mg/l with an average of 0.36mg/l while Cr ranged from 0.036 mg/l -0.098mg/l with an average of 0.060mg/l.
Engineering Geology
Exploring Subsoil Geotechnical Properties for Foundation Design of a Proposed Modern Market in Port Harcourt, Rivers State, Southern Nigeria
Authors: Morrison, T. and Esonanjor, E.E. Abstract A geotechnical soil investigation was performed to determine the subsoil conditions at the proposed site to provide parameters for the design of foundation for a proposed modern market in Port Harcourt. Both field study and laboratory analysis of samples were done. Field works included five (5) number boreholes drilled to 20.3m by the use of Shell and Auger manually operated rig, six (6) number 10Tm CPT tests conducted to refused depth ranging from 12.00 to 21.00m and SPT-N values determinations. Disturbed and undisturbed soil samples were collected foranalysis. The disturbed samples were analyzed according to BS standard for index properties such as grain size analysis, Atterberg limits, moisture content, and bulk density, while relatively undisturbed samples were analyzed for strength properties and parameters. From the results, the subsoil in the area consists of a thick layer of lateritic clayey/sandy clay with a plasticity index of 40%, coefficient of volume compressibility (mv) 0.278m2/KN and cohesion 40KN/m2 at the top followed by a larger of 9.75m thick medium dense five to coarse sand with frictional angle 28 to 3500. Safe bearing capacities were computed for pad footings and raft foundation in the range of 122 to 173kPa and 122 to 151kPa respectively at various foundation width and LB rations. Groundwater was encountered between 5.64m and 6.10m below ground level.
Engineering Geology
Uncertainties in Subsurface Characterisation For Building Construction: Case Studies of Two Site Investigations in Lagos Metropolis
Authors: Olagunju, K.T., Olobaniyi, S.B., Oyedele, K.F. and Adefuwa, A. Abstract Geotechnical frameworks and calculations rely on adequate characterisation of the subsurface soil units. Boring tests and their distribution provide, not only geotechnical parameters but also to reveal geotechnical units and lateral extent, which are particularly important for safe and cost-effective foundation design. This study presents two cases of geotechnical site investigation involving boring tests in two areas of Lagos metropolises that raised concerns about uncertainties in subsurface characterisation caused by the inadequacy of field techniques employed. This study revealed the limitation of geotechnical designs at A and B, largely due to the uncertainty of subsurface characterisation induced by inadequate quality and quantities of field tests. Using data from geotechnical boring(percussion drilling) and resistivity survey (2D tomography and VES), the occurrence of unusual ironstone was established between 9 to 15m depth at Site A, which prevented further drilling with a percussion rig. However, this ironstone occurrence is non-lateral as the resistivity obtained in 2D profiles ranges from 15 Ωm – 74 Ωm from the surface to 35 m, suggestive of Clay and Sand. Thereby complicating geotechnical design. Notably, one boring is grossly inadequate for characterising the complexity of the geology at Site A. Similarly, a forensic investigation atSite B indicates the inadequacy of one boring test since the correlation of results from three new borings revealed a complex geology which was missed using only one. Installed piles on this site were mostly seated on Organic Clay between 15 and 30m depth. Evidence presented in these case studies underscores the importance of comprehensive subsurface characterisation to enhance design decisions for geotechnical recommendations.