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Final Progress Reports: University of North Carolina-Chapel Hill: Enhanced Remediation of Heterogeneous Subsurface

Superfund Research Program

Enhanced Remediation of Heterogeneous Subsurface

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

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Final Progress Reports

Year:   2005  1999 

The focus of Project 6 is on the development of improved fundamental understanding of multiphase porous medium systems and the application of this understanding to evolve improved methods for the remediation of subsurface systems contaminated with dense nonaqueous phase liquids (DNAPL). During this past year important advancements have been made on the following aspects of this project: (1) maturation of surfactant-brine methods for remediation of DNAPL source-zone areas; (2) preparatory work for an important field evaluation of the projects brine-based technology; and (3) several fundamental advancements in modeling of porous medium systems. These are detailed briefly below.

A major thrust of Dr. Miller and his research team’s work is on the development of improved methods to remediate porous medium systems contaminated with DNAPLs, which are among the most common and difficult to remediate of all Superfund contaminants. The project investigators have examined several open issues related to these methods, including the rate of removal of the brine after remediation has been accomplished, the effects of brine on clay stability, and a screening of surfactant, alcohol, and salt solutions to evaluate phase behavior and stability properties. The net result of these advances is a continuing and growing confidence in the ability of brine-based remediation methods to provide a means to substantially remediate DNAPL source zones.

Given project researcher’s encouraging laboratory results, many public and private concerns have expressed an interest in advancing their work to the field evaluation stage. Such an evaluation has been in the planning stage for the last year and is currently in the initial stage of field implementation. This experiment will be completed by March of 2006, and the results of this experiment will be a detailed comparison with other DNAPL technologies in a controlled natural setting. A substantial amount of planning has gone into this aspect of the team’s work, and they have worked in collaboration with a national consulting firm (RETEC) and an international supplier of brine (Dead Sea Bromine Group), both of whom have contributed funding for this project, along with the Department of Defense’s contribution of the use of a field site and local support for sampling and analytical work. The researchers will evaluate source zone remediation effects as well as fractional mass recovery in this experiment as a function of three distinct stages of the technology. They feel certain that if this field study approaches the results they have obtained in the laboratory, then significant applications of their methods would soon follow at a full field scale.

Work is underway to evolve a new class of porous medium models based upon a careful multiscale approach to describing fluid flow and contaminant transport. The new class of models responds to many deficiencies with current approaches, which have resulted in the near universal use of inadequate, ad hoc closure schemes. In addition to model formulation work, the researchers have also made progress on improved numerical methods schemes to model the multiphase systems of concern in this project.

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