A field study of the vertical immiscible displacement of LNAPL associated with a fluctuating water table
A variety of field techniques were utilized to study the immiscible displacement of LNAPL (gasoline) above a fluctuating shallow water table. Hydrophobic and hydrophillic tensiometer measurements were compared to a dual-well monitoring system that measured the potentiometric head of groundwater and the LNAPL-water interface in a fully screened well. This combination of techniques successfully monitored the changing water and LNAPL heads as the potentiometric surface fluctuated. Tensiometric measurements revealed that as the potentiometric surface fluctuated, there were proportional changes in water pressures, whereas the LNAPL pressures responded to its changing saturation and redistribution due to the release and entrapment of LNAPL. The strongly seasonal water table fluctuation caused a temporal forcing whereby the thickness of LNAPL in a well was not always in equilibrium with the difference in LNAPL and water heads. Therefore, theories for predicting the amount of mobile LNAPL in an aquifer based on static conditions and the measured LNAPL thickness in a well will not necessarily be valid. Cores revealed that the LNAPL distribution above a falling potentiometric surface increased with depth and reached a maximum saturation of 20% at the level of the air-LNAPL interface in an observation well. In contrast, the LNAPL distribution above a rising surface was uniform at a saturation of 6-8 %.
International Association of Hydrological Sciences Publication Number 225 ISBN 0-947571-29-9 Once a groundwater system becomes contaminated, it is often a formidable task to clean it up. Many contaminants are persistent and remain hazardous even at low concentrations. This publication comprises the proceedings of the International Conference on Groundwater Quality: Remediation and Protection (GQ’95) held at Prague in May 1995. The major objective of the conference was to discuss the full range of issues involved in groundwater remediation and protection. The conference focused on practical approaches to assess groundwater quality, viable solutions to contamination problems, and methods for protection. The volume contains 54 papers spread over the following topics : Field and laboratory investigations, monitoring (6 papers) Physical, chemical and biological processes (14 papers) Stochastics, variability and uncertainty (5 papers) Modelling (10 papers) Contamination sources: waste disposal, mining, industry and agriculture (9 papers) Remediation (6 papers) Protection and regulatory issues (4 papers)
Record created on 2005-12-09, modified on 2016-08-08