Chlorinated solvents pose significant environmental problems to the Department of Defense (DoD). A large amount of money and effort is invested annually by DoD on remedial efforts. In many cases, it is not clear how successful investments in innovative in-situ technologies are because of the difficulty associated with measuring and quantifying remedial performance. The objective of this project was to evaluate the success of in-situ remedial systems at three hydrogeologically distinct sites employing a range of innovative in-situ treatment technologies. The diagnostic procedures applied included technology- and geology-specific tools for real-time diagnosis of remedial technology success as well as those that can be used widely irrespective of the type of technology or site conditions. Mass flux measurement was used as a technology-wide metric of overall system performance since it can clearly demonstrate a reduction in the rate of contaminant mass release from the treated zone.
Three demonstration sites were chosen for this study including (1) Watervliet Arsenal, New York, (2) Vandenberg Air Force Base (VAFB), California and (3) Fort Lewis Logistics Center, Washington. The sites illustrate some of the types of remedial challenges faced at a number of DoD sites nationwide, and are located in distinctly different hydrogeologic environments. In situ chemical and biological remediation technologies were implemented at two of these sites to address soil and groundwater impacted by chlorinated solvents and other volatile organic compounds (VOCs), providing the opportunity to evaluate a variety of conventional and innovative diagnostic tools for a range of data objectives.
At Watervliet Arsenal, the effectiveness of in situ chemical oxidation using permanganate for treating both fracture water and contamination within the rock matrix was evaluated. Technology- and geology-specific diagnostic tools included isotopic fractionation and rock core sampling. Mass flux analysis also was used to assess overall system performance. At Fort Lewis, the effectiveness of in situ bioremediation with enhanced mass transfer was evaluated in the source area under different electron donor conditions. Technology- and geology-specific diagnostic tools included isotopic fractionation, molecular techniques, integrated conventional techniques, and mass flux analyses. At VAFB, the effectiveness of six-phase heating was evaluated with various field methods that estimate contaminant mass discharge. Mass flux measurements were used as a diagnostic tool to evaluate overall remedial system performance.
A summary of recommendations for each of the tools studied is provided in the Guidance Document. When implemented according to these recommendations, the tools evaluated in this project can provide sufficient value of information for decision-making to justify the additional investment beyond conventional characterization and performance assessment.
Also provided is a summary of the applicability of innovative diagnostic tools for various stages of the remedial decision-making process, based on the value of information provided by the tool for each decision-making point. There are many factors to consider in the selection of the most appropriate and informative tools. These factors are discussed throughout the report. In each case, therefore, the selection and use of diagnostic tools will be site-specific. However, this report provides relevant criteria to consider during the selection decision, as well as evaluation of the criteria for each tool.
The results provide technical guidance regarding the application of diagnostic tools for both source zone and dissolved plume remediation. The practical benefits and limitations of each method, including costs, are presented to help practitioners assess which approach is most applicable under different conditions.