Development of an Integrated High-Resolution Site Characterization Program and Innovative Laboratory Methods to Evaluate NAPL Migration in Shallow Sediments to Support Remedy Design and Implementation.
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Background/Objectives: Dense non-aqueous phase liquid (DNAPL) distribution in shallow sediments is controlled by pore-scale processes, which demand detailed site characterization and laboratory testing to select, design, and implement effective and cost-efficient remedies.

The combination of scale-appropriate tools that are selected to delineate DNAPL in the subsurface is termed High Resolution Site Characterization (HRSC). Successful deployment of HRSC is an emerging multidisciplinary science that continues to metamorphose as new tools become available, as interpretative algorithms are developed, and as research efforts and site remediation projects are advanced.

Approach/Activities: A detailed investigation of the potential migration of DNAPLs in deep (native) sediments was undertaken to support the selection, design, and implementation of an in situ stabilization and capping remedy. A methodology was developed to i) advance understanding of pore-scale processes that control DNAPL migration in shallow sediments, ii) deploy detailed site characterization methods for delineating DNAPL distribution, and iii) an establish innovative laboratory testing program to determine conditions that lead to DNAPL migration. Recent advances in real-time tools for DNAPL delineation has focused on the calibration of measurement tools such as laser induced fluorescence probes; thereby, allowing indirect measurements to be translated with more certainty to quantitative measures of DNAPL saturation and hence DNAPL mass and volume. The outcomes of this evaluation are discussed and a methodology is presented for determining the value of large data sets using predictive analytics to extract statistical information from measured data and predict trends in future data.

Results/Lessons Learned: Here we illustrate the concepts that underpin HRSC and demonstrate advances in the emerging science that supports the evaluation of DNAPL migration within sediments. The case study discussed will be supported by reference to relevant research and in the context of current and emerging best-practice guidance.