Fractured Cary Mills Limestone. This is a very complex system with the presence of three different fracture systems as well as several faults. Fracturing within the treatment zone, however, was sparse. Ground-water flow is believed to be controlled by bedding plane fractures.
Targeted Environmental Media:
 Dense Non-aqueous Phase Liquids (DNAPLs) - Fractured Bedrock
- Light Non-aqueous Phase Liquids (LNAPLs)
The nonaqueous phase liquids (NAPLs) were distributed in inclined bedding plane fractures. Initially, a technical impracticability (TI) waiver was granted for the ground-water cleanup due to the complexities associated with the site.
Major Contaminants and Maximum Concentrations:
- Tetrachloroethene (DNAPL)
- Trichloroethene (var)
- Carbon tetrachloride (var)
- Benzene-toluene-ethylbenzene-xylene (BTEX) (LNAPL)
- Borehole Geophysics
- Caliper
- Acoustic Televiewer
- Fluid Loggings
- Temperature
- Conductivity/Resistivity
- Vertical Chemical Profiling
- Coring
- Other (Electrical Resistivity Tomography and Radar Tomography)
Comments:
This was a research project to determine if steam can heat fractured rock and remove dense nonaqueous phase liquid (DNAPL) mass. Geophysical tools (electrical resistance tomography and borehole radar tomography) were tested to determine if they could track heat and/or steam movement in fractured rock.
During the summer of 2001, boreholes were drilled based on the contaminant distribution in the subsurface. Cores from these boreholes were used to obtain rock chip samples that were analyzed for volatile organic solvents. Transmissivity measurements were made in each of the boreholes on 10 foot intervals. Ground-water samples were obtained from selected intervals.
During the summer of 2002 interconnectivity testing was performed between the boreholes. The hydraulic testing was conducted using straddle packers having a variable packer spacing ranging from 3 meters to greater than 10 meters. The results of the single well tests were used to direct an interwell testing program in which more than 100 pulse interference tests were conducted. The pulse interference tests were conducted by measuring the pressure response between two boreholes in which specific permeable features had been isolated. Straddle packers having a spacing of 3 meters were used to isolate the features in each borehole. Based on the results of the pulse interference testing and hydraulic head measurements, the site was separated into three areas having poor interconnection between each.
This information was used to design the specific injection and extraction points for the steam enhanced remediation (SER) program.
- Thermal Treatment (In Situ)
- Steam Enhanced Extraction
Comments:
Steam injection was initiated in September 2002 and continued for 83 days. Temperature distribution and the extraction rate were monitored. After funding for the research was exhausted and the injection terminated, extraction continued for an additional 7 days, and periodic temperature monitoring was continued for an additional 3 months. During the Summer of 2003, post treatment ground-water and rock core samples were obtained and analysed.
During the steam injection temperature was monitored in 27 boreholes around the site. The results of the heat transport were compares to the results of the pulse interference tests to assess the value of hydraulic characterization. Based on the comparison, it was determined that the pulse interference testing identified the major hot water carrying fracture features and was invaluable in determining the location of specific steam injection and water extraction zones.
Data is being compiled to describe the heat flow as well as the flow and transport of contaminants. The final report can be downloaded from: http://www.epa.gov/ORD/NRMRL/pubs/540r05010/540r05010.htm
This was a research project with the intent of removing contaminant mass.
Final report is completed.
Detailed information on lessons learned on fractured rock characterization and the application of steam enhanced remediation to fractured rock is available in the final report which can be downloaded from http:www.epa.govORDNRMRLpubs540r05010540r05010.htm
Additional References:
Davis, Eva L.; Gorm Heron; Steve Carroll. 2004. Steam Injection into Fractured Bedrock at Loring AFB. The Fourth International Remediation of Chlorinated and Recalcitrant Compounds Conference, Monterey, California. May 24-27.
Novakowski, K.S.; E.L. Davis; S. Carroll; G. Heron. 2004. Hydraulic Characterization for Steam Enhanced Remediation Conducted in Fractured Rock. The Fourth International Remediation of Chlorinated and Recalcitrant Compounds Conference, Monterey, California. May 24-27.
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