Significant advances have been made in recent years in developing approaches and technologies for the investigation and remediation of soil and groundwater contaminated by oil products. The approaches require a detailed knowledge of both site hydrogeology and the physicochemical properties of the oil product This paper describes three case histories that illustrate state-of-the-art methods for investigation and remediation of soil and groundwater contaminated by oil products. The first case history describes an investigation of an oil product leak including delineation of the area of contaminated groundwater, the likely rate of movement of the oil products in the subsurface and the possible impacts on marine shellfish beds. The extent of contaminated groundwater was determined by a combination of soil vapour measurements and groundwater sampling. The investigation showed that oil contamination had not moved offshore but that offshore migration was likely to occur in the future. A computer contaminant migration model was used to show that significant adverse impacts on the shellfish beds were unlikely to occur if further oil was prevented from entering the groundwater system.

The second case history describes the investigation and remediation of a 500,000 litre oil leak from a subsurface pipeline. The oil was found to have pancaked out on the water table and had migrated only about 200 metres down-gradient after about 2.5 months. The extent of the oil plume was determined by drilling. Oil recovery was carried out by two – stage skimmer units located in 10 strategically placed boreholes.

The third case history describes the design and operation of an innovative system for remediation of soil contaminated by oil product residuals. A combined vapour extraction/bioremediation system was designed to treat the contaminated soil in-situ. The design of the system was based on laboratory and field trials carried out over a period of three months. After two years of operation the system had reduced concentrations of petroleum hydrocarbons below a clean-up target of 100 mg/kg over an area of 3600 m2. The main advantage of the in-situ treatment system is that soil contamination was removed without disrupting above-ground operational activities.

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