Technology Status Report: In Situ Flushing - CLU-IN

In Situ Flushing Project Summaries
GWRTAC Case Study Database
Phase 2 PreTest Waterflood (1.2 PV)
Electrolyte flood (0.7 PV)
Intermediate Partitioning Interwell Tracer Test (2.9 PV)
Phase 2 Chemical Delivery (PV 2.4)
Phase 2 Water Flushing (PV 7.8)
Final Partitioning Interwell Tracer Test (PV 4.3)
Typical fluid delivery rates were on the order of 7.5 gpm, with flow split equally between the wells.
Typical recovery rates were slightly higher, on the order of 9.2 gpm, and again flow was split
equally between the wells. The water delivery rate to the hydraulic control well was approximately 7
gpm.
Fluids produced during the field demonstration were initially treated to approximately
10 mg/L TCE by an existing onsite steam stripping unit. Fluids from this system were subsequently
discharged to the AFB wastewater treatment system. This effort will develop data supporting the
potential use of this technology for larger scale applications. In addition, researchers at the U.S.
EPA Cincinnati Laboratory collected approximately 5,000 gallons of Phase II fluids to be used in
testing of membrane filtration technologies for reuse of surfactant. This effort is funded by the U.S.
Navy."
Approximately 800 gallons of DNAPL was present in the test section of the aquifer. However,
approximately 450 gallons of DNAPL was free-phase DNAPL and was removed by pumping prior
to the first PITT. During the solubilization test, with an 8% surfactant injection over 0.6 days (0.6
pore volumes), the TCE concentration in the central monitoring well rose from approximately 600
mg / L prior to the injection to 40,000 mg / L after. The maximum DNAPL solubilization capacity
was calculated to be 61,000 mg / L for this surfactant injection concentration. The concentrations
in the 3 extraction wells were lower, likely due to dilution caused by streamtube convergence on
these wells. Problems with surfactant foaming in the steam stripper occurred during this phase,
which the investigators attempted to remedy in Phase II.
The PITT indicated that there was a total of 346 gallons of residual DNAPL in the 4-ft thick test
zone with an average residual DNAPL saturation of 20% (i.e., Sr = 0.20) or approximately 4%
when measured over the whole, 20-ft thick, swept volume of the aquifer (i.e., Sr = 0.036). The
solubilization test showed the selected surfactant to be extremely effective, and that there was no
significant head loss due to mobilization of fines across the line-drive test zone. Furthermore, the
steam stripper at OU2 readily treated the surfactant-rich waste waters.
The results of the Phase I field operations were used to finalize the design of the Phase II
surfactant flood. The Phase II flood, the purpose of which was to remove all remaining DNAPL
from the test zone in the alluvium, was preceded and followed by PITTs so that the performance of
the flood could be assessed. The surfactant flood consisted of the injection of a solution of 8%
surfactant, 4% isopropyl alcohol and 0.7% NaCl, producing an interfacial tension of 0.02
dynes/cm. The Phase II field operations lasted for 30 days, of which surfactant injection at 7.5
Ground-Water Remediation Technologies Analysis Center
Operated by Concurrent Technologies Corporation
Appendix - Page 43 of 164
Copyright GWRTAC 1998
Revision 1
Tuesday, November 17, 1998