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FIELD-SCALE EVALUATION OF IN SITU COSOLVENT FLUSHING FOR ENCHANCED AQUIFER REMEDIATION
Citation:
Rao, P. C., M. D. Annable, R. K. Sillan, D. Dai, K. Hatfield, W. D. Graham, A L. Wood*, AND C G. Enfield*. FIELD-SCALE EVALUATION OF IN SITU COSOLVENT FLUSHING FOR ENCHANCED AQUIFER REMEDIATION. WATER RESOURCES RESEARCH. American Geophysical Union, Washington, DC, 33(12):2673-2686, (1997).
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Description:
A comprehensive, field-scale evaluation of in situ cosolvent flushing for enhanced remediation of nonaqueous phase liquid (NAPL)-contaminated aquifers was performed in a hydraulically isolated test cell (about 4.3 m x 3.6 m) constructed at a field site at Hill Air Force Base, Utah. This sand-gravel-cobble surficial aquifer, underlain by a deep clay confining unit at about 6 m below ground surface, was contaminated with a multicomponent NAPL as a result of jet fuel and chlorinated solvent disposal during the 1940s and 1950s. The water table within the test cell was raised to create a 1.5 m saturated flow zone that contained the NAPL smear zone. The cosolvent flushing test consisted of pumping about 40,000 L (approximately nine pore volumes) of a ternary cosolvent mixture (70% ethanol, 12% n-pentanol, and 18% water) through the test cell over a period of 10 days, followed by flushing with water for another 20 days. Several methods for assessing site remediation yielded consistent results, indicating that on the average >85% mass of the several target contaminants was removed as a result of the cosolvent flushing; NAPL constituent removal effectiveness was greater (90-99+%) in the upper 1-m zone, in comparison to about 70-80% in the bottom 0.5-m zone near the clay confining unit. Various interacting factors that control the hydrodynamic sweep efficiency, and the NAPL removal effectiveness during cosolvent flushing in this unconfined aquifer are discussed.
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FIELD-SCALE EVALUATION OF IN SITU COSOLVENT FLUSHING FOR ENHANCED AQUIFER REMEDIATION
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