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University of North Carolina-Chapel Hill

Superfund Research Program

Enhanced Remediation of Heterogeneous Subsurface

Project Leader: Cass T. Miller
Grant Number: P42ES005948
Funding Period: 1995- 2011

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Project Summary (2000-2006)

The overall goal of this project is to develop improved methods for quantifying and remediating dense non-aqueous phase liquids (DNAPL)-contaminated porous medium systems. Researchers are investigating the mechanisms and extent of density-motivated DNAPL mobilization in two- and three-fluid-phase, heterogeneous porous media systems. The range of applicability and accuracy of partitioning tracer methods for the measurement of DNAPL volumes is being analyzed, and approaches for removing DNAPL residual are being evaluated. Project investigators are also considering the effects of geochemical conditions on density-motivated remediation methods. High-resolution numerical models are being developed to design, describe, and predict results from laboratory experiments of density-motivated remediation. Two basic conceptual approaches are being used. In the first approach, the resident aqueous phase is displaced by a dense brine solution, such that the DNAPL becomes less dense than the brine solution and is motivated by buoyancy forces to move upward toward the unsaturated zone. The second approach is to float a layer of brine between an impermeable layer and a DNAPL contaminated region and then remove the fresh water from the DNAPL contaminated region, leaving the DNAPL-contaminated region unsaturated. This approach results in DNAPL being an intermediate wetting phase in most cases and a significant increase in gravity forces, which will result in a relatively high and rapid rate of DNAPL removal down to the brine layer. The brine layer is then controlled and used to capture the DNAPL.

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