Remediation of NAPL Source Zones: Lessons Learned from Field Studies at Hill and Dover AFB

Authors

John E. McCray, Colorado School of MinesFollow
Geoffrey R. Tick, University of AlabamaFollow
James W. Jawitz, University of FloridaFollow
John S. Gierke, Michigan Technological UniversityFollow
Mark L. Brusseau, University of ArizonaFollow
Ronald W. Falta, Clemson UniversityFollow
Robert C. Knox, University of Oklahoma Norman CampusFollow
David A. Sabatini, University of Oklahoma Norman CampusFollow
Michael D. Annable, University of FloridaFollow
Jeffrey H. Harwell, University of Oklahoma Norman CampusFollow
A. Lynn Wood, U.S. Environmental Protection AgencyFollow

Document Type

Article

Date of this Version

2011

Comments

Published in Ground Water (2011) 49(5): 727-744; doi:10.1111/j.1745-6584.2010.00783.x

Abstract

Innovative remediation studies were conducted between 1994 and 2004 at sites contaminated by nonaqueous phase liquids (NAPLs) at Hill and Dover AFB, and included technologies that mobilize, solubilize, and volatilize NAPL: air sparging (AS), surfactant flushing, cosolvent flooding, and flushing with a complexingsugar solution. The experiments proved that aggressive remedial efforts tailored to the contaminant can remove more than 90% of the NAPL-phase contaminant mass. Site-characterization methods were tested as part of these field efforts, including partitioning tracer tests, biotracer tests, and mass-flux measurements. A significant reduction in the groundwater contaminant mass flux was achieved despite incomplete removal of the source. The effectiveness of soil, groundwater, and tracer based characterization methods may be site and technology specific. Employing multiple methods can improve characterization. The studies elucidated the importance of smallscale heterogeneities on remediation effectiveness, and fomented research on enhanced-delivery methods. Most contaminant removal occurs in hydraulically accessible zones, and complete removal is limited by contaminant mass stored in inaccessible zones. These studies illustrated the importance of understanding the fluid dynamics and interfacial behavior of injected fluids on remediation design and implementation. The importance of understanding the dynamics of NAPL-mixture dissolution and removal was highlighted. The results from these studies helped researchers better understand what processes and scales are most important to include in mathematical models used for design and data analysis. Finally, the work at these sites emphasized the importance and feasibility of recycling and reusing chemical agents, and enabled the implementation and success of follow-on full-scale efforts.