Natural attenuation was first demonstrated at sites with hydrocarbon contamination, but recent studies at sites contaminated by chlorinated compounds have shown that this approach often has merit for these more challenging contamination problems. This volume covers natural attenuation in media ranging from deep aquifers to shallow soils, and for contaminants ranging from fuels to solvents to herbicides, and offers the reader a comprehensive overview of case studies that represent the state of the art in natural attenuation approaches to site remediation.

In the past decade, officials responsible for clean-up of contaminated groundwater have increasingly turned to natural attenuation-essentially allowing naturally occurring processes to reduce the toxic potential of contaminants-versus engineered solutions. This saves both money and headaches. To the people in surrounding communities, though, it can appear that clean-up officials are simply walking away from contaminated sites. When is natural attenuation the appropriate approach to a clean-up? This book presents the consensus of a diverse committee, informed by the views of researchers, regulators, and community activists. The committee reviews the likely effectiveness of natural attenuation with different classes of contaminants-and describes how to evaluate the "footprints" of natural attenuation at a site to determine whether natural processes will provide adequate clean-up. Included are recommendations for regulatory change. The committee emphasizes the importance of the public's belief and attitudes toward remediation and provides guidance on involving community stakeholders throughout the clean-up process. The book explores how contamination occurs, explaining concepts and terms, and includes case studies from the Hanford nuclear site, military bases, as well as other sites. It provides historical background and important data on clean-up processes and goes on to offer critical reviews of 14 published protocols for evaluating natural attenuation.

The first comprehensive guide to one of today's most innovative approaches to environmental contamination Natural attenuation is gaining increasing attention as a nonintrusive, cost-effective alternative to standard remediation techniques for environmental contamination. This landmark work presents the first in-depth examination of the theory, mechanisms, and application of natural attenuation. Written by four internationally recognized leaders in this approach, the book describes both biotic and abiotic natural attenuation processes, focusing on two of the environmental contaminants most frequently encountered in groundwater--fuels and chlorinated solvents. The authors draw on a wealth of combined experience to detail successful techniques for simulating natural attenuation processes and predicting their effectiveness in the field. They also show how natural attenuation works in the real world, using numerous examples and case studies from a wide range of leading-edge projects nationwide involving fuel hydrocarbons and chlorinated solvents. Finally, they discuss the evaluation and assessment of natural attenuation and explore the design of long-term monitoring programs. An indispensable reference for anyone working in environmental remediation, Natural Attenuation of Fuels and Chlorinated Solvents in the Subsurface is essential reading for scientists and engineers in a range of industries, as well as state and federal environmental regulators, and professors and graduate students in environmental or chemical engineering.

Studies at numerous sites have shown high variability in the degradation rates of chlorinated solvents as measured by microcosm studies with 14C labeled contaminants. The ability of nutrient and carbon additions to stimulate degradation can vary widely. Although some of these variations can be related to the structure of the extant microbial community, the presence of other less refractory contaminants may be critical fctors impacting the rate of chlorocarbon mineralization. Relaatively highe rates of TCE degradation have been observed in the DOE K-25 burial grounds with diverse organic loadings as well as in areas that show evidence for hydrocarbon contamination. Similarly, at other sites where there was TCE in the absence of hydrocarbons or other contaminants, the measured degradation rates have often been found to be very low. At various other sites, the intrasite variability in degradation rates appeared to be related to the presence of hydrocarbon contamination. The highest rates were observed at sites with evidence of hydrocarbons. These observations indicated that the viability of natural attenuation as a remediation option for chlorinated solvents might depend in part on the presence co-contaminants such as hydrocarbons or natural matter.

Sponsored by the Natural Attenuation Task Committee of the Environmental and Multi-Media Council of the Environmental and Water Resources Institute of ASCE. This report provides the regulatory framework, scientific and engineering principles, and applications of natural attenuation for the remediation of contaminated sites. Natural attenuation is a process that relies on the natural assimilative capacity of a site to reduce or stabilize contaminates to desirable levels. It is becoming an increasingly popular, cost-effective remedial alternative for many contaminated sites. The report describes in detail sites contaminated with petroleum hydrocarbons and MTBE, chlorinated solvents, polycyclic aromatic hydrocarbons, metals, and radioactive wastes. Topics include: Ømajor pollutants; Øextensive review of literature; Øexamples of applications of natural attenuation; Øsite characterization and monitoring requirements and procedures; and Øbasic scientific principles on physical, chemical, and biological processes. Environmental engineers and scientists will find this book full of information on basic principles to summaries of natural attenuation applications.

Natural Attenuation: CERCLA, RBCAs, and the Future of Environmental Remediation presents the concept of "natural attenuation"-the tendency of soils to severly limit the toxicity of many types of hazardous waste. It reviews and updates the most recent findings from the field and lab and shows how natural attenuation is rapidly changing the direction and focus of environmental remediation. Outlining the legal and regulatory framework that has made waste remediation so costly, this book shows how applying an understanding of natural attenuation can decrease cleanup outlays while lowering risks to human health. Natural Attenuation: CERCLA, RBCAs, and the Future of Environmental Remediation makes it clear why natural attenuation will be relied upon more and more in the future.

- Natural Attenuation Considerations- Natural Attenuation Case Studies I: Chloroethenes- Natural Attenuation Case Studies II: Other Organics and Metals.