Limitations of Monitoring Wells for the Detection and Quantification of Petroleum Products in Soils and Aquifers |
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| Authors: | Abdul S. Abdul Sheila F. Kia Thomas L. Gibson |
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| Affiliation: | Abdul S. Abdul received his Ph.D. in contaminant hydrogeology from the Institute of Ground Water Research, Department of Earth Sciences, University of Waterloo in 1985. He has been a member of the Environmental Science Department in General Motors Research Laboratories (Warren, MI 48090-9055) since 1985. His major interests include the movement of immiscible fluids and reactive solutes through hydrogeologic materials, and the development of technologies based on physical, chemical, and biological processes to clean up contaminated soil and aquifer systems.;Thomas L. Gibson received his Ph.D. in chemistry from the University of Texas at Austin in 1972. A professional staff member of the Environmental Science Department in General Motors Research Laboratories (Warren, MI48090-9055) since 1979, his primary research interests are in the investigation and remediation of toxic contaminants in the environment. Dr. Gibson is a member of the American Chemical Society, the American Geophysical Union, and the Association of Ground Water Scientists and Engineers. His research has included publications in areas of contaminant migration through hydrogeologic systems, measurement of toxic and mutagenic pollutants, and atmospheric chemistry.;Sheila F. Kia is a staff research engineer in the Department of Environmental Science at the General Motors Research Laboratories (Warren, MI 48090-9055). She received a Ph.D. from Cambridge University and pursued post-doctoral research at the University of Michigan, Ann Arbor. Her current research interests include multiphase flow of immiscible fluids, physical processes and heterogeneities in porous media, contaminant recovery, and colloidal chemistry. |
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| Abstract: | Theoretical analysis and laboratory column experiments were carried out to investigate the conditions required for petroleum products (oil) to flow into a well installed through a sandy porous medium contaminated with the oil. The results indicated that oil would flow into a well only after a layer of "free oil" is formed in the adjacent porous medium. Because significant quantities of oil could be stored in the porous medium under the influence of capillary suction prior to the formation of the zone of free oil, the presence of oil in a well would indicate an advanced stage of oil contamination of the subsurface. While monitoring wells could be used to delineate the extent of the free-oil plume and the plume of dissolved petroleum constituents, they are not useful for delineating the extent of capillary held oil.
The experimental results also indicated that the ratio of the oil-layer thickness in the well to that in the porous medium is not a constant as is sometimes assumed in practice. Further, estimates of the oil thickness in the medium based on the oil thickness in wells and on capillary properties measured in the laboratory were sensitive to the values of the parameters used in these estimates. The measured thickness of the oil layer in a monitoring well alone may not yield reliable estimates of the amount of oil in the subsurface, and assuming that the oil-thickness ratio is a constant can lead to inadequate site assessments and inappropriate remedial plans. |
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