Remediating TCE-contaminated groundwater in low-permeability media using hydraulic fracturing to emplace zero-valent iron/organic carbon amendment



A field pilot test in which hydraulic fracturing was used to emplace granular remediation amendment (a mixture of zero-valent iron [ZVI] and organic carbon) into fine-grained sandstone to remediate dissolved trichloroethene (TCE)-contaminated groundwater was performed at a former intercontinental ballistic missile site in Colorado. Hydraulic fracturing was used to enhance the permeability of the aquifer with concurrent emplacement of amendment that facilitates TCE degradation. Geophysical monitoring and inverse modeling show that the network of amendment-filled fractures extends throughout the aquifer volume targeted in the pilot test zone. Two years of subsequent groundwater monitoring demonstrate that amendment addition resulted in development of geochemical conditions favorable to both abiotic and biological TCE degradation, that TCE concentrations were substantially reduced (i.e., greater than 90 percent reduction in TCE mass), and that the primary degradation processes are likely abiotic. The pilot-test data aided in re-evaluating the conceptual site model and in designing the full-scale remedy to address a larger portion of the TCE-contaminated groundwater plume. © 2012 Wiley Periodicals, Inc.