Potential for Solute Retardation on Monitoring Well Sand Packs and Its Effect on Purging Requirements for Ground Water Sampling |
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| Authors: | Carl D Palmer Joseph F Keely William Fish |
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| Institution: | Carl D. Palmer is an assistant professor in the Department of Environmental Science and Engineering at the Oregon Graduate Center (19600 N. W. von Neumann Dr., Beaverton, OR 97006-1999). He received his Ph. D. in hydrogeology from the Department of Earth Science at the University of Waterloo (Waterloo, Ontario). He was with the Department of Geological and Geophysical Sciences at the University of Wisconsin-Milwaukee before joining the Oregon Graduate Center. Dr. Palmer's research interests are in ground water monitoring, solute transport and hydrogeochemistry.;Joseph F. Keely received a B. S. in professional chemistry and an M. S. in hydrology from the University of Idaho, and a Ph. D. from Oklahoma State University. He is an assistant professor in the Department of Environmental Science andEngineering at the Oregon Graduate Center (19600 N. W. von Neumann Dr., Beaverton, OR 97006-1999). His research interests are focused on the improvement of field methods used to characterize sub-surface contaminant transport processes and the integration of technical issues into ground water policy. He is a certified professional hydrogeologist (AIH no. 483) and is a consultant to the U. S. Department of Justice for Superfund cases. He continues to collaborate with U. S. EPA's Office of Research and Development, where he worked for five years as hydrologist.;William Fish, Ph. D., is a research scientist in the Department of Environmental Science and Engineering at the Oregon Graduate Center (19600 N. W. von Neumann Dr., Beaverton, OR 97006-1999). He received his B. S. E. in environmental engineering from the University of Florida and holds a doctorate in aquatic sciences/civil engineering from the Massachusetts Institute of Technology. His research centers on trace metal geochemistry in both surface and subsurface waters, with special emphasis on complexation reactions, redox chemistry, and the influence of microbial organisms on these processes. |
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| Abstract: | Monitoring well sand packs are theoretically capable of retarding metal ions and organic contaminants. If this retardation does indeed occur it may have a significant effect on the purging requirements of newly installed monitoring wells. Calculations based on mass balance and retardation concepts demonstrate that if common guidelines for well purging are followed, contaminants may not be detected or may be detected in lower concentrations than are actually present in the ground water. This problem is greatest in relatively shallow wells installed in low to moderate permeability materials. In most cases, the effect of solute retardation in the sand pack can be avoided simply by additional purging prior to the first sampling of the monitoring well. Common purging guidelines can then be applied to subsequent samplings. The methodology outlined in this paper can be used to calculate the purging requirements of existing monitoring wells or it may be applied to alternative monitoring well designs to test which will require the smallest volume of purged water. |
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