Abstract:
Two field tests at Hill Air Force Base Operational Unit 2 were completed in May and
September of 1996 to demonstrate surfactant remediation of an alluvial aquifer
contaminated with DNAPL (dense nonaqueous phase liquid). The DNAPL at Hill OU2 consists
primarily of trichloroethene (TCE), 1,1,1-trichloroethane (1,1,1-TCA) and tetrachloroethene
(PCE). Sheet piling or other artificial barriers were not installed to isolate the
6.1 x 5.4 m test area from the surrounding aquifer. Hydraulic confinement was achieved by:
(1) injecting water into a hydraulic control well south of the surfactant injectors (2)
designing the well pattern to take advantage of the alluvial channel confined below and to
the east and west by a thick clay aquiclude and (3) extracting at a rate higher than the
injection rate within the well pattern. An extensive program of laboratory experimentation,
hydrogeological characterization, effluent treatment and predictive modeling was critical in
the design of these tests and the success of the project. Simulations were conducted to
determine test design variables such as well rates, injected chemical amounts and test
duration, and to predict the recovery of contaminants and injected chemicals, degree of
hydraulic confinement and pore volume of the aquifer swept by the injected fluids.
Partitioning interwell tracer tests were used to estimate the volume and saturation of DNAPL
in the swept volume and to assess the performance of the surfactant remediation. Analysis
of the Phase I and Phase II results showed high recoveries of all injected chemicals,
indicating that hydraulic confinement was achieved without sheet pile boundaries.
Approximately 99% of the DNAPL within the swept volume was removed by the surfactant in less
than two weeks, leaving a residual DNAPL saturation of about 0.0003. The concentration of
dissolved contaminants was reduced from 1100 mg/l to 8 mg/l in the central monitoring well
during the same time period.
Reference:
C.L. Brown, M. Delshad, V. Dwarakanath, D.M. McKinney, G.A. Pope, R.E. Jackson, J.T.
Londergan, H.W. Meinardus, W.H. Wade, "Demonstration of Surfactant Flooding of an Alluvial
Aquifer Contaminated with DNAPL," in Innovative Subsurface Remediation: Field Testing of
Physical, Chemical, and Characterization Technologies, M. Brusseau, M. Annable, and J.
Gierke (eds.) ACS Symposium Series 725, American Chemical Society, Washington, DC, 1999.
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Last updated: April 25, 2002