Abstract

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 products. The approaches require a detailed knowledge of both site hydrogeology and the phsicochemical 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 products. The first case history describes an investigation of an oil product leak including delineation of the are 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 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 plume was determined by drilling. Oil recovery was carried out by two - stage skimmer units located in 10 strategically place boreholes. place 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 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 reduce concentrations of petroleum hydrocarbons below a clean-up target of 100 mg/kg over an area of 3600 m. The main advantage of the in-situ treatment system is that soil contamination was removed without disrupting above-ground operational activities.

Introduction

Contamination of groundwater by oil and petroleum products has been identified as a significant environmental issue in a number of regions of the world. Although most of the groundwater contamination detected to date has been associated with commercial and retail oil industry activities, there is and increasing focus on groundwater contamination resulting from oil and gas exploration and production operations.

Significant advance have been made in recant years in developing approaches and technologies for the investigation and remediation of soil and groundwater contaminated by oil products. Increasingly sophisticated methods have been products. Increasingly sophisticated methods have been required because of the necessity to minimise environmental impacts by quickly locating and cleaning up oil product leaks and spills. Much of this development work has been carried out by, or on behalf of, the major oil companies. Recent developments have included field portable detection equipment, computer models and sophisticated soil and groundwater cleanup technologies.

This paper describes some of the complexities that need to be considered when evaluating subsurface oil product contamination and used recent case histories to illustrate particular technologies and approaches. particular technologies and approaches. P. 1

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