U.S. EPA Contaminated Site Cleanup Information (CLU-IN)

U.S. Environmental Protection Agency
U.S. EPA Technology Innovation and Field Services Division

Dense Nonaqueous Phase Liquids (DNAPLs)

Treatment Technologies

In Situ Flushing

Case Studies: Multi-Component Waste

The literature indicates ongoing laboratory work in the investigation and development of in situ flushing of DNAPL mixtures from soil; however, few descriptions of field applications of the technology to coal tar, creosote, or heavy oils are available. In addition to chemical flushing, water alone, both heated and at ambient temperature, has been applied in a flushing process called waterflooding to the mobilization of DNAPL mixtures from the subsurface.

For Further Information

Adobe PDF LogoWestern Research Institute, Contained Recovery of Oily Waste (CROW) Process: Innovative Technology Evaluation Report
EPA 540-R-00-500, 112 pp, 2000

The technology demonstration at the Brodhead Creek Superfund site in Stroudsburg, PA, was a full-scale remediation effort lasting about 20 months. The system used for the demonstration included six hot water injection wells, two recovery wells, an aboveground water treatment system, and a data acquisition and control system. The injection and recovery wells targeted an accumulation of free-phase coal tar within a 40-ft by 80-ft treatment area. The CROW process was successful in removing coal tar from the subsurface; however, it was unable to reduce coal tar concentrations to residual immobile levels. No significant change was observed in the concentration of coal tar in the soil outside the treatment area except for measurements of the amount of coal tar in the layer under the treatment zone, which suggest that some coal tar was pushed down into the underlying confining unit. See also the project cost and performance report.

Adobe PDF LogoCROW™ Field Demonstration with Bell Lumber and Pole
L.A. Johnson Jr. and L.J. Fahy.
WRI-02-R005, 25 pp, 2002

The Bell Pole Phase 1 CROW demonstration began in mid-1995 and was operated until January 2001. The operation of the demonstration was satisfactory, though at less than the design conditions. During the demonstration, 25,502,902 gal of hot water were injected and 83,155 gal of organics were transferred to the storage tank. More than 65% of the produced organic material was used in Bell Pole's treating operation. Recycling the produced organic material partially offset the cost of remediation.

Adobe PDF LogoIn Situ Flushing: Technology Status Report
D.S. Roote.
Ground-Water Remediation Technologies Analysis Center (GWRTAC). TS-98-01, 212 pp, 1998

  • At the Koppers Co. Inc., Seaboard Plant, Kearny, NJ, waterflooding (i.e, the use of hydraulic pressure achieved via groundwater injection and recirculation) was used to mobilize coal tar and creosote toward collection trenches.
  • In a small-scale field demonstration at a private wood treating site in Laramie, WY, 144,000 gallons (28 pore volumes [pv]) of water were cycled between the delivery and recovery drain lines to displace mobile free-phase oil, followed by a second soil flushing step consisting of delivery of 30,000 gallons of flushing solution (alkaline agents, polymer, and surfactants) into the test cell. As part of the soil flushing step, 10,000 gallons (2 pv) of Polystep A-7R were used to produce reusable wood-preserving oil, followed by 10,000 gallons (2 pv) of Makon-10R to achieve lower cleanup levels. After the first 20,000 gallons of flushing solution delivery, 10,000 gallons (2 pv) of water were delivered to continue fluid movement while waiting for the arrival of additional flushing solution. An additional 10,000 gallons (2 pv) of Makon-10R were then delivered to the cell to complete the soil flushing step. In a reconditioning step, the cell was flooded with 150,000 gallons (30 pv) of water to displace mobilized oil and soil-washing solution remaining in the aquifer.
  • At a Fredricksburg, VA, wood treating site, flushing with a combination of an alkaline agent, surfactant, and polymer was used to recover creosote-based wood-treating oils from soil.

Abstracts of Journal Articles

In-Situ Biosurfactant Flushing, Coupled with a Highly Pressurized Air Injection, to Remediate the Bunker Oil Contaminated Site
Lee, M., J. Kim, and I. Kim.
Geosciences Journal, Vol 15 No 3, p 313-321, Sep 2011

A pilot-scale test of in situ biosurfactant flushing coupled with highly pressurized air injection (HPAI) was performed to remediate a site contaminated with A and C bunker oil in Ulsan, Korea. Twelve injection wells and 2 extraction wells were installed in a 17 m x 12 m x 4 m contaminated area. Addition of a 2% biosurfactant flushing solution into each injection well at 2 L/min was followed by HPAI (20 kgf/sq cm) to accelerate solution mobility in pore spaces. The process was repeated until about 1.9 pore volumes of biosurfactant solution (350 tons) had been flushed, removing ~2.2 tons of TPH (82% of the initial TPH) from the site. The resultant average residual TPH concentration in soil was <500 mg/kg. Longer abstract

In Situ Remediation of Coal Tar-Impacted Soil by Polymer-Surfactant Flooding
C.M. Young, V. Dwarakanath, T. Malik, L. Milner, J. Chittet, A. Jazdanian, N. Huston, and V. Weerasooriya.
Proceedings of the Third International Conference on Remediation of Chlorinated and Recalcitrant Compounds (Monterey, CA; May 2002).
Battelle Press, Paper 2C-33, 8 pp, 2002

In a thermally enhanced polymer/surfactant pilot field test conducted in 2001 at a former manufactured gas plant in Bloomington, IL, 80% of the coal tar DNAPL was removed (10% solubilized, 90% mobilized). Heating the injection solution lowered the viscosity of the coal tar by 50% (from 65 cps to 34 cps) when the temperature was increased from 24 to 38 degrees C. The surfactant— Alfoterra™ 123-8 PO Sulfate (branched propoxylated alcohol sulfates)—was designed for recovery of bunker fuel. Batch and column experiments were conducted to optimize the in situ flushing design for site DNAPL, soil, and temperature. Three pore volumes of surfactant solution were injected. The solution consisted of 4% surfactant, 8% secondary butyl alcohol, 0.13% polymer, and 0.08% CaCl2. The initial saturation of the coal tar was around 35%.

Additional data from this field test are available in slides from a presentation by D. Jackson, "Mobility Control in Surfactant Floods: Improving NAPL Recovery by In-Situ Control of Viscosity."