Evaluation of DNAPL Distribution in South Carolina (Florence)

Morwick G360 PROJECT TEAM: Dr. Beth Parker, Dr. Philipp Wanner, Steven Chapman, Maria Gorecka, Rashmi Jadeja, Ryan Kroeker, Dr. Glaucia Lima, Adam Gilmore & Nathan Glas (MASc Candidate)

A detailed research study sponsored by NSERC, DuPont, Chemours, and the University Consortium with support from the University of Waterloo and University of Neuchâtel (UNINE) has been ongoing since 2008 to evaluate the contaminant distribution from mixed solvent DNAPL releases into a surficial heterogeneous sandy aquifer underlain by an organic-rich clayey aquitard. The impetus of the study was to evaluate effects of mass storage and release from low permeability zones on plume persistence following treatment of the DNAPL source zone as well as to assess integrity of the aquitard. The mixed chlorinated solvent DNAPL source zone was treated in-situ by soil mixing with ZVI/bentonite in late 2007, with the goal of reducing mass discharge from the source zone via abiotic degradation and permeability reduction. Several high resolution site characterization techniques have been employed including: (1) membrane interface probe (MIP), (2) continuous coring for assessing small-scale heterogeneity with detailed subsampling to quantify contaminant distributions in the aquifer and aquitard, and (3) microbial characterization and application of compound-specific isotope analyses (CSIA) for assessment of degradation. Early time conditions were established via major field episodes in 2008, including installation of a detailed groundwater monitoring network of multilevel systems (MLS) installed along transects, which have been sampled episodically over the past decade for target VOCs, hydrochemistry and CSIA.

In March 2018, a major field episode was conducted to evaluate conditions ten years post-treatment including multifaceted sampling of cores for target VOCs, degradation products, CSIA, microbial characterization, etc. as well as application of more recent techniques including Geoprobe MIP integrated with the Hydraulic Profiling Tool (MiHPT). Investigations of conditions within the treated source were also examined, including use of magnetic susceptibility screening of cores for evaluation of reactive media (ZVI) distributions. This study is unique in the long time frame for post-treatment monitoring as well as the high resolution characterization efforts to provide clear performance data and insights on controlling processes.

Pictured Left: Sample selection during coring.
Pictured Right: Researchers working at the Florence Site.

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