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EVALUATIONS OF DNAPL REMEDIAL PERFORMANCE BASED ON FIELD MEASUREMENTS OF CONTAMINANT FLUX
Citation:
BROOKS, M., C. G. ENFIELD, M. D. ANNABLE, AND A. L. WOOD. EVALUATIONS OF DNAPL REMEDIAL PERFORMANCE BASED ON FIELD MEASUREMENTS OF CONTAMINANT FLUX. Presented at AGU Meeting, Beijing, CHINA, July 24 - 27, 2006.
Impact/Purpose:
To inform the public.
Description:
Under a concentration-based regulatory framework, the benefits of conducting dense nonaqueous phase liquid (DNAPL) source-zone remediation are questionable because of the impracticality of complete DNAPL elimination at most sites. Removing a sufficient mass of DNAPL to achieve concentration-based regulatory goals is often hampered primarily by site hydrogeologic heterogeneity and DNAPL characteristic uncertainty. Alternatively, flux reduction downgradient from source zone areas after DNAPL remediation has been proposed as a benefit, especially when source treatment is viewed as a component of a treatment train. In this framework, the goal then of DNAPL mass removal is to reduce the mass discharge to levels appropriate for the natural attenuation capacity of the down gradient system. Recent modeling work indicates a wide range of flux behavior may occur as a function of hydrogeological conditions and DNAPL distributions, however limited field-based evidence exist with which to evaluate mass removal-flux reduction relationships. The objective of this work is to assess DNAPL remedial performance using field measurements of mass discharge before and after source remediation. Mass discharge is being measured across control planes located down gradient from the source areas by two methods: passive flux meters and integral pumping tests. Measurements are being conducted at four test sites, three in the United States (Tacoma, Washington; Layton, Utah, and Jacksonville, Florida) and one in Canada (Borden, Ontario). Different source remedial technologies are being implemented at these sites and include in-situ resistive heating, surfactant flushing, in-situ chemical oxidation, and cosolvent flushing. Pre- and post-remedial flux measurements completed at three of the sites will be presented (work at the fourth is ongoing), and the results will be discussed in light of site characterization and measurement uncertainty.