Technology Status Report: In Situ Flushing - CLU-IN

In Situ Flushing Project Summaries
GWRTAC Case Study Database
2,500 gallons per cell. The hydraulic conductivity of the saturated potion of the upper sand and
gravel unit at OU1 is 10-1 to 10-2 cm/sec based on aquifer test data, and 10-2 to 10-5 cm/sec
based on slug test data. For all of the flushing experiments (those with surfactants, cosolvents,
and cyclodexdrin), the flushing rate will be approximately one pore volume per day. Prior to and
after treatment of each cell, a partitioning tracer test has or will be performed. The mix of tracers
will be designed according to the expected volume of NAPL within the cell before and after
treatment. Among the tracers, hexanol and dimethylpentanol may be included.
For the test at Cell 3, OU 1, tert-butanol mixed with n-hexanol was used as the flushing solution.
The 3 m x 5 m test cell contains approximately 1,500 gallons of water (i.e., the PV). A partitioning
tracer test was performed on the cell with bromide, ethanol, methanol, tert-butanol, methylhexanol,
and dimethyl pentanol as tracers. From this test, the estimated amount of NAPL in the
cell is 60 gal. The LNAPL originated from petroleum hydrocarbons and spent solvents, and is a
complex mixture of aromatic and aliphatic hydrocarbons, chlorinated solvents, and other
compounds. The bulk of the NAPL composition consists of low solubility, low vapor pressure
compounds, and the NAPL not soluble in pure methanol, ethanol, acetone, or isopropanol.
The test involved the injection and extraction of 7,000 gallons of a mixture of tert-butanol and nhexanol.
Specifically, the following chemical system was delivered in sequence:
0.85 pore volume of 95 vol% tert-butanol/hexanol (1 pore volume is approximately 1,500 gal)
1.33 pore volumes of 81 vol% tert-butanol/hexanol, 16 vol% n-hexanol
2.33 pore volumes of 95 vol% tert-butanol
0.33 pore volume of 47.5 vol% tert-butanol
30 pore volumes of waterflood
It was anticipated that most of the NAPL will be removed before the total volume of alcohol is
pumped. The earlier cosolvent test at Hill AFB performed by The University of Florida group (Test
1, Operational Unit 1) was designed to solubilize the NAPL. The intent in this test is to mobilize the
NAPL to basically remove it in a plug. Formulating a cosolvent mixture that will mobilize this
specific complex NAPL has required extensive laboratory work. Fluids produced during the effort
were stored on site with plans for eventual discharge to the onsite wastewater treatment plant.
The results of post flood soil coring indicate better than 90% removal of the more soluble
contaminants (TCA, toluene, ethylbenzene, xylenes, trimethylbenzene, naphthalene) and 70% to
80% removal of less soluble compounds such as decane and undecane. The results of pre-flood
and post-flood NAPL partitioning tracer tests show about 80% removal of the total NAPL content
from the test cell.
Report(s)/Publication(s) (Additional Information Sources):
Falta, et. al., 1997: Abstract "Field Evaluation of Cosolvent-Enhanced In-Situ Remediation",
CRADA CR-821992-01-0 between R.S. Kerr Environmental Research Lab and Clemson University,
July 28, 1997.
Ground-Water Remediation Technologies Analysis Center
Operated by Concurrent Technologies Corporation
Appendix - Page 30 of 164
Copyright GWRTAC 1998
Revision 1
Tuesday, November 17, 1998