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Evaluating Long-Term Impacts of Soil-Mixing Source-Zone Treatment using Cryogenic Core Collection

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Technical Report,01 Dec 2015,01 Jun 2017

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Trihydro Corporation Laramie United States

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A former source zone containing TCE DNAPL was remediated using soil mixing with zero valent iron and bentonite, a technology referred to as ZVI-Clay Soil Mixing. Four years of remediation performance data suggest that peak groundwater and soil concentrations have been reduced by 4 orders of magnitude, and groundwater TCE concentrations have approached MCLs. This project assessed the long-term impacts of ZVI-Clay Soil Mixing, in terms of rebound potential and effects on natural processes. Existing soil and groundwater data were supplemented with high-resolution data, generated using cryogenic core collection, for several parameters including chlorinated ethylenes, gaseous products, inorganic parameters, and soil properties. The evaluation suggested that contaminant concentration rebound appears unlikely within the treated source zone, due to the low contaminant mass remaining, ongoing apparent reactivity of ZVI toward TCE, and lack of heterogeneity within the mixed-soil zone. Down gradient of the treated zone, the concentration distribution suggests that long-term site management may be strongly affected by chlorinated ethylene mass in low-k zones. However, the presence of degradation products, including ethylene and acetylene, suggest ongoing degradation is occurring outside of the mixed-soil zone, and degradation may be occurring within low-k zones. Down gradient treatment may also be affected by uncertain groundwater flow patterns.

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  • Industrial Chemistry and Chemical Processing

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