S93: Site characterization for monitored natural attenuation of chlorinated solvent contamination in ground water

This presentation discusses the site characterization data needed for successful assessment of monitored natural attenuation (MNA) for remediating chlorinated solvent contamination in ground water.  Anaerobic biodegradation is a major component of MNA.  Collection of microbiological field data and understanding the microbiological processes that occur during MNA is critical.  However, it is also critical to integrate physical and chemical data from a contaminated site with the microbiological data into a complete conceptual site model to place the microbiological data into context and to evaluate MNA as a potential clean-up remedy.  The necessary data are physical (geological and hydrogeological), anthropogenic, chemical (contaminant and geochemical), and biological/microbiological.  Specific data needed describe the site hydrogeology, contaminant concentrations, degradation products, potential non-aqueous phase liquids, terminal electron-accepting processes, and microbiological populations.  Critical data needs address confirmation of ground-water and contaminant flow paths, indicators of contaminant loss, ensuring that no errors occur in estimating contaminant degradation rates and disappearance, and confirming microbial attenuation processes.

The subsurface processes and data needs at chlorinated solvent MNA sites involve a number of scientific disciplines.  This presentation focuses on site characterization to provide a framework and overview for practitioners in the various disciplines to enhance their understanding of what is needed for successful evaluation of MNA.  Development of a site conceptual model to integrate the data, issues to be considered in assessing MNA, other degradation mechanisms, and the use of the site characterization data for potential enhanced bioremediation will also be briefly discussed.