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STEAM ENHANCED REMEDIATION RESEARCH FOR DNAPL IN FRACTURED ROCK, LORING AIR FORCE BASE, LIMESTONE, MAINE
Citation:
DAVIS, E. L., N. AKLADISS, B. BRANDON, S. CARROLL, G. HERON, R. HOEY, M. NALIPINSKI, K. NOVAKOWSKI, AND K. UDELL. STEAM ENHANCED REMEDIATION RESEARCH FOR DNAPL IN FRACTURED ROCK, LORING AIR FORCE BASE, LIMESTONE, MAINE. U.S. Environmental Protection Agency, Washington, DC, EPA/540/R-05/010, 2005.
Impact/Purpose:
Inform the public.
Description:
This report details a research project on Steam Enhanced Remediation (SER) for the recovery of volatile organic compounds from fractured limestone that was carried out at the Quarry at the former Loring Air Force Base in Limestone, Maine. This project was carried out by USEPA, Maine Department of Environmental Protection (DEP), SteamTech Environmental Services, and the US Air Force. Experts from acedemia provided technical input on fractured rock characterization and steam injection remediation.
The Quarry at Loring AFB was historically used for disposal of drums of spent solvents. Leakage from the drums allowed chlorinated solvents (mainly tetrachloroethylene) and fuel components to enter the subsurface. Groundwater concentrations in the fractured limestone indicated the likely presence of dense nonaqueous phase liquids. An agreement was made between the Air Force, Maine DEP, and EPA to use the site for research on the recovery of DNAPL from fractured rock. SER was chosen as the technology to be tested, and the objectives of the research included determining if steam injection could heat the target area, the contaminant recovery rate as the subsurface was heated, changes in ground water and rock chip concentrations of contaminants, and operating parameters for steam injection in fractured rock.
Pre-steam injection characterization was carried out in Summer 2001 and 2002, and included logging rock cores, collection of rock chip samples for chemical analysis, borehole geophysics, transmissivity and interconnectivity testing, and discrete interval ground water sampling. Operation of the system was carried out in Fall 2002, with 83 days of steam injection. Post-treatment ground water and rock chip sampling was performed in 2003 and 2004.
Although sufficient funding was not available to continue to operate the steam injection long enough to heat the entire target area, and the subsurface remained relatively cool, significant enhancements in the recovery of contaminants were documented after approximately 3 weeks of steam injection. Because the subsurface was not heated adequately, ground water concentrations do not show a reliable reduction in contaminant concentrations; however, rock chip samples showed a possible reduction in concentrations. Three deep monitoring wells around the treatment area did not indicate that contaminants had been moved horizontally or vertically outside of the treatment area. Operating parameters needed for steam injection in fractured rock were found to differ from those commonly used in unconsolidated media.
Thus, SER appears to be capable of enhancing the recovery of volatile contaminants from fractured rock. Based on the results of this research project and a treatability study on SER in fractured rock at another site, recommendations are made on characterization necessary for the application of SER in fractured rock, on deployment of SER to other fractured rock sites, and the application of other thermal technologies to fractured rock.