Zero-valent iron may participate in the reductive dechlorination process by three different mechanisms: direct, electrolytic reduction; reduction by hydrogen produced during the corrosion process; and reduction by dissolved (ferrous) iron that is also produced by corroding iron. The first step of electrolytic reduction is presumably, the transfer of one electron from the metal surface to the organic molecule. This results in an organic anion radical that may then lose a halide anion to give a carbon-centered radical, and oxidized iron, which is eventually released to the solution as Fe(2+). The goal of our research is to provide a comprehensive survey of the mechanisms that affect the performance of this reactive barrier technology.

In the late 1970s and early 1980s, our nation began to grapple with the legacy of past disposal practices for toxic chemicals. With the passage in 1980 of the Comprehensive Envir- mental Response, Compensation, and Liability Act (CERCLA), commonly known as Sup- fund, it became the law of the land to remediate these sites. The U. S. Department of Defense (DoD), the nation’s largest industrial organization, also recognized that it too had a legacy of contaminated sites. Historic operations at Army, Navy, Air Force, and Marine Corps facilities, ranges, manufacturing sites, shipyards, and depots had resulted in widespread contamination of soil, groundwater, and sediment. While Superfund began in 1980 to focus on remediation of heavily contaminated sites largely abandoned or neglected by the private sector, the DoD had already initiated its Installation Restoration Program in the mid-1970s. In 1984, the DoD began the Defense Environmental Restoration Program (DERP) for contaminated site assessment and remediation. Two years later, the U. S. Congress codified the DERP and directed the Secretary of Defense to carry out a concurrent program of research, development, and demonstration of innovative remediation technologies. As chronicled in the 1994 National Research Council report, “Ranking Hazardous-Waste Sites for Remedial Action,” our early estimates on the cost and suitability of existing techn- ogies for cleaning up contaminated sites were wildly optimistic. Original estimates, in 1980, projected an average Superfund cleanup cost of a mere $3.

This introductory manual addresses environmental site restoration practices that both ensure compliance with federal statutes and prevent further contamination or expense. It also includes up-to-date information and several new features to enhance the process. Emphasizing environmental chemistry, soil science, microbiology, plant science, and the underlying chemical processes, author John Pichtel discusses relevant chemical principles as they apply to the cleanup and removal of hazardous chemicals from soil, geological strata, and groundwater. The first part of this book provides an overview of the recent history of environmental contamination and the formulation of relevant regulations, leading to regulations for hazardous waste site remediation. This part also provides a background for several salient aspects of site remediation. The second part of the book closely examines field remediation technologies, including phytoremediation, bioremediation, and electrokinetic remediation. Theory of operation, practical considerations, and possible environmental impacts and other consequences of use are also discussed. Readers of the first edition will discover two new chapters in this Second Edition covering permeable reactive walls and technology selection. This updated edition now also includes end-of-chapter questions and instructions for completing two web-based exercises, one for the chapter on environmental site assessments and one for the chapter on technology selection.

The purpose of this book is to help engineers and scientists better understand dense nonaqueous phase liquid (DNAPL) contamination of groundwater and the methods and technology used for characterization and remediation. Remediation of DNAPL source zones is very difficult and controversial and must be based on state-of-the-art knowledge of the behavior (transport and fate) of nonaqueous phase liquids in the subsurface and site specific geology, chemistry and hydrology. This volume is focused on the characterization and remediation of nonaqueous phase chlorinated solvents and it is hoped that mid-level engineers and scientists will find this book helpful in understanding the current state-of-practice of DNAPL source zone management and remediation.