The analysis of dissolved contaminant fate and transport away from source areas containing non-aqueous phase liquids (petroleum hydrocarbon) is an important component in the evaluation of risk posed to down gradient receptors, of monitoring plan development, and of remedial alternative selection. Typically, individual source-plumes systems are evaluated on a site specific basis; however, much can be learned by looking at collective data from the integration of laboratory aquifer model and a field site. This has been done with a 3-D intermediate scale tropical sand tank model and a leaking underground petroleum pipeline site in south-western Nigeria. Numerical modelling and computer simulations were conducted for the physical laboratory model and the field site. Soil particle size and hydraulic conductivity data has been used to establish a correlation between the hydrodynamic transport parameters for the laboratory and field porous media soils. A Retardation factor R = 2.5, and biodegradation rate of 0.0004/day (half life of 5 years) were obtained from the model calibration for BTEX. A clean-up time for BTEX of about 48 years was estimated by natural attenuation from model predictions.

The paper reviews Phase I, II, III Environmental Site Assessment for contaminated sites as practised in Canada. It focuses on hydrocarbon contaminated sites and various methods of site remediation. A typical case study of a leaking petrol station close to a harbour with a highly sensitive water body in the Vancouver Island, British Columbia, Canada is presented. Site remediation carried out at the site included soil characterization, delineation of the contaminant plume, and construction of a drainage trench cutoff. Ground water remediation included aeration, setting up a biopile, soil vapour extraction by soil venting, and biodegradation. About 1,420 tonnes of contaminated soils and the entire ground water at the site were remediated.

The parking problems and traffic congestion in the central business district (CBD) of Akure metropolis is already assuming a disturbing dimension. The reduced level of service of the roads within the CBD and the congestion hazards for both motorists and pedestrian, will definitely adversely affect the economic and social life of the community. This study has revealed that increased volume of traffic, ribbon development/street trading, improper structural layout/land use pattern, within the CBD are factors responsible for these problems. The superimposition of a radial traffic movement pattern on a morphologically linear road network in Akure, has however further compounded the problem. From the results of the data collected and the analysis of the traffic volume, spot speed and the number of weekly trips per capita for the CBD, the solution to the parking problems have been recommended. This includes, provision of adequate off-street parking facilities, abolition of all unauthorized terminals, adjustment of the structural layout/ land use pattern in the CBD and the provision of an inner ring road around the Akure CBD.