Monitored natural attenuation (MNA), while a remedy of choice for many sites, can be challenging when the contaminants are chlorinated solvents. Even with many high quality technical guidance references available there continue to be challenges implementing MNA at some chlorinated solvent sites. The U.S. Department of Energy, as one organization facing such challenges, is leading a project that will incorporate developing concepts and tools into the existing toolbox for selecting and implementing MNA as a remediation option at sites with chlorinated solvents contamination. The structure and goals of this project were introduced in an article in the Winter 2004 issue of Remediation (Sink et al.). This article is a summary of the three technical areas being developed through the project: mass balance, enhanced attenuation, and characterization and monitoring supporting the first two areas. These topics will be documented in separate reports available from the US Department of Energy Office of Scientific and Technical Information at www.osti.gov.

The Old Man in the Corner was one of the earliest armchair detectives, popping up with so many others in the wake of the huge popularity of the Sherlock Holmes stories. The Old Man relies mostly upon sensationalistic "penny dreadful" newspaper accounts, with the occasional courtroom visit for extra laughs. He narrates all this information (while tying complicated knots in a piece of string) to a Lady Journalist who frequents the same tea-shop.

Chlorinated solvents and their daughter products are the most common contaminants of groundwater at industrial and military facilities in the United States. Limitations of conventional technologies have intensified efforts to find alternative methods to remediate contaminated sites to regulatory goals set by CERCLA. Natural attenuation of chlorinated solvents is a promising alternative to traditional pump and treat methods but has not been well understood or widely accepted. This modeling study investigated the ability of TCE to completely degrade under various aquifer conditions and rate order constants. It also examined a case study of a former landfill site at Moody AFB. We found unusually high flow of ground water by advection or dispersion inhibits the complete degradation of TCE. High concentrations of sulfate or nitrate inhibit the creation of methanogenic conditions and therefore inhibit reductive dechlorination of TCE. We also found an electron donor co-contaminant a critical factor for the complete destruction of TCE because it creates anaerobic conditions. The model illustrated a possible explanation for the lack of down gradient contaminants at the landfill site may be the coupling of reductive dechlorination and cometabolism naturally attenuation the contaminants.

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.

Capstone objectives are: 1) Analyze the potential for monitored natural attenuation to achieve the site-specific risk-based clean up goals for 1,1,1-Trichloroethane (TCA) and 1,1-Dichloroethene(1,1-DCE). One expected degradation pathway for TCA is: TCA U+2026.. 1,1-DCEU+2026U+2026..Vinyl ChlorideU+2026..CO2. 2) Compare the cost difference between Monitored Natural Attenuation and Traditional Pump-and-treat remediation strategies.