This page provides links to case studies of in situ flushing applications, beginning with resources documenting multiple case studies. The next section identifies a small number of projects conducted to remediate inorganic contaminants, followed by the organization of organic contaminants under headings for dense nonaqueous-phase liquids and light nonaqueous-phase liquids.

Case Study Compilations

Federal Remediation Technologies Roundtable Cost and Performance Database

Cyclodextrin-Enhanced In Situ Removal of Organic Contaminants from Groundwater at Site 11, Naval Amphibious Base Little Creek, Virginia Beach, Virginia (2005)

In Situ Treatment Using Cosolvent Flushing, Thermal Desorption, or In-Well Air Stripping at Four Drycleaner Sites (2001)

Surfactant-Enhanced DNAPL Flushing at Marine Corps Base Camp Lejeune, Site 88, Building 25, NC (2001)

Well Injection Depth Extraction (WIDE) Soil and Groundwater Flushing at RMI Titanium Plant, Ashtabula, Ohio (2001)

In Situ Flushing Site Profiles

EPA has developed a searchable database that contains information about ongoing and completed applications of in situ flushing technologies to treat chlorinated solvents, petroleum products, metals, explosives, and PCBs in groundwater and soil. The project profiles provide summary information about each application, including site information, contaminants and media treated, technology design and operation, cost information, and performance results, as well as points of contact and references.

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

This report provides brief summaries of 84 in situ flushing projects conducted between 1988 and 1998. Examples:

• At the Koppers Co. Inc., Seaboard Plant, Kearny, NJ, water flooding (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 pv) of water were cycled between the delivery and recovery drain lines to displace mobile free-phase oil, followed by delivery of 30,000 gallons of flushing solution (alkaline agents, polymer, and surfactants) into the test cell. Next, 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. An additional 10,000 gallons (2 pv) of Makon-10R then were delivered to the cell, followed by 150,000 gallons (30 pv) of water to displace mobilized oil and flushing 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.

Synthesis Report on Five Dense, Nonaqueous-Phase Liquid (DNAPL) Remediation Projects
U.S. EPA, National Risk Management Research Laboratory, Cincinnati, OH.
EPA 600-R-07-066, 94 pp, 2007

Summarizes the performance and results of demonstration projects for the remediation of DNAPL contamination at five sites: (1) thermally enhanced remediation with resistive heating and with steam injection/extraction for TCE DNAPL at Launch Complex 34, Cape Canaveral, FL; (2) cosolvent flushing, surfactant flushing, cosolvent DNAPL mobilization, complex sugar flushing, and AS/SVE for PCE at Dover AFB, DE; (3) surfactant-enhanced aquifer remediation for chlorinated solvent contamination (primarily TCE) at Hill AFB, UT; (4) thermally enhanced remediation of fractured bedrock with steam injection for multiple contaminants, primarily PCE and TCE in the quarry site at Loring AFB, Limestone, ME; and (5) cosolvent flushing and enhanced bioremediation for PCE at Sages Drycleaners in Jacksonville, FL.

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Inorganic Contaminants

(Fourth) Five Year Review Report for United Chrome Products, Corvallis, Oregon
U.S. EPA Region 10, 76 pp, 2011

Soil flushing from 1988 to 2004 addressed Cr(VI) concentrations as high as 60,000 mg/kg in soil and 19,000 mg/L in groundwater. Two infiltration basins delivered water to the contaminated soil to mobilize the water-soluble Cr(VI) into the aqueous phase. The groundwater extraction network converted soluble Cr(VI) to an insoluble Cr(III) precipitate via chemical reduction and precipitation and recharged treated water. Groundwater extraction largely ended in December 2004 except for ongoing extraction and treatment from one well to maintain hydraulic containment at the site, as the MCL of 0.1 mg/L Cr has not yet been attained in the deep aquifer. During the flushing period, 32,100 lbs of Cr were recovered from 84.1 million gallons of extracted groundwater. Additional information: Oregon DEQ Site Summary Report; Superfund Information System

Chemical Extraction of Uranium and Molybdenum from Vadose-Zone Soils and Aquifer Materials: Dam-to-Ditch Area, Cotter Uranium Mill, Canyon City, Colorado
AMEC Earth & Environmental, Inc. for Cotter Corp., 23 pp, 2011

As part of the ongoing remedial investigations for the dam-to-ditch area (DDA), Cotter considered implementing in situ soil flushing for U and Mo removal from the soil; however, a study designed to provide reagent recommendations for use in future field-scale pilot tests for removal of U and Mo from DDA soils found no significant source of the contaminants there. The study was completed in anticipation that the results could be useful in the design of future soil flushing systems elsewhere at the site. This report (1) provides a literature summary of chemical reagents that have been used effectively to mobilize U from contaminated soil and (2) identifies chemical reagents that can be used to extract U and Mo from soil and aquifer materials at the Cotter site.

Mobilization, Extraction, and Removal of Radionuclides
U.S. DOE, Office of Environmental Management.
DOE-EM-0559, 32 pp, 2001

This flushing of radionuclides demonstration was conducted from September 2, 1998, to September 2, 1999, at the Fernald Environmental Management Project, Cincinnati, OH. Groundwater was extracted from 15 wells located up and down gradient of the injection wells, treated to remove uranium, and re-injected (1,000 gpm) into the aquifer.

PG&E Topock Compressor Station, Needles, California: Revised Groundwater Corrective Measures Implementation/Remedial Design Work Plan for SWMU 1/AOC 1 and AOC 10
Pacific Gas and Electric Company, 312 pp, Nov 2011

The selected remedy for Cr(VI) in groundwater at SWMU 1/AOC 1 and AOC 10 near the Compressor Station combines in situ reduction with fresh-water flushing in an in situ reactive zone with injection of an organic carbon source to promote biological reduction of Cr(VI) to Cr(III). Fresh and carbon-amended water will be injected alternately upgradient of the plume to mobilize Cr from soil and provide nutrients to the treatment zone. MNA will provide a long-term component for any residual Cr. This well-documented project has a large dedicated website.

Recent Developments for In Situ Treatment of Metal Contaminated Soils
EPA 542-R-97-004, 1997

This report assists the remedy selection process by providing information on four in situ technologies for treating soil contaminated with metals: electrokinetic remediation, phytoremediation, soil flushing, and solidification/stabilization. The section on flushing includes 2 brief case studies.

Smalley Piper NPL Site
Annual Legislative Report for July 1, 2012 - June 30, 2013. Tennessee Department of Environment and Conservation, Division of Remediation, p 7, 2013

Industrial activities conducted at the Smalley-Piper site (~9 acres in size) included the manufacture of magnesium battery casings utilizing caustic soda, acetic acid, and chromium acid, which contaminated soil, surface water pathways, and groundwater with Cr(VI). All on-site operations ceased in 2007. An amended Superfund State Contract (SSC) addresses the previously performed soil remedy of excavation and ex situ stabilization/solidification as specified in the 2008 ROD and adds a soil flushing component. The original SSC addressing soil remedial action was performed at a cost of $1,982,915. The amended SSC has a total current estimated cost of $7,781,970, with a state 10% match of $778,197. The intent of the in situ flushing remedy is to reduce remaining Cr(VI) subsurface soil concentrations that might leach into groundwater. Water will be extracted by on-site recovery wells; treated by chemical reduction, precipitation, and ion-exchange treatment modules; and then re-injected into the former source area via an infiltration gallery. The system is expected to operate for one year. Construction of the treatment plant building is scheduled for December 2014, followed by the installation of the treatment equipment in January 2015 and system startup in March 2015. Additional information: EPA Region 4.

Soil Flushing through a Thick Vadose Zone: Perchlorate Removal Documented at Edwards AFB, California
Battey, T.F., A.J. Shepard, and R.J. Tait.
American Geophysical Union, Fall Meeting 2007, Abstract H33E-1685, 2007

A soil flushing treatability study was conducted to address a 129-ft thick vadose zone consisting primarily of perchlorate-contaminated clayey sand. An infiltration gallery consisting of slotted PVC pipes was installed within a highly permeable engineered bed of washed gravel. The introduced water reached the 125-ft bottom of the access tubes 14 weeks after the water was introduced into the gallery. The perchlorate groundwater concentration of 4,500 µg/L below the gallery spiked to 72,400 µg/L 18 weeks after the start of infiltration, indicating perchlorate transfer from the vadose zone to the saturated zone, where it was captured by an adjacent groundwater extraction well. Continued flushing of treated water through the vadose and saturated zones resulted in a rapid decline in perchlorate groundwater concentrations. Longer abstract; Presentation slides

The Use of Soil-Flushing to Remediate Metal Contamination in a Smelting Slag Dumping Area: Column and Pilot-Scale Experiments
Navarro, A. and F. Martinez.
Engineering Geology 115(1-2):16-27(2010)

A pilot-scale in situ soil flushing test and a column experiment were carried out to evaluate the efficiency of flushing to remove metals from an old mining area heavily contaminated by uncontrolled dumping of base-metal smelting slags. The volume of water injected and pumped in the pilot-scale site (0.9 ha) reached ~1.2 and 2.3 pore volumes, respectively. Results showed removal of Al (43.1 to 81.1%), Co (24.5 to 82.4%), Cu (0 to 55%), Fe (0 to 84.7%), Mn (66.2 to 85.8%), Mo (0 to 51.7%), Ni (0 to 46.4%), and Zn (0 to 83.4%), although considerable differences between control wells were observed. Other metals, such as As, Se, Sb, Cd, and Pb, were mobilized or removed from the groundwater in negligible amounts. This work suggests that soil flushing could be used as an effective remediation technique in areas contaminated by mining and metallurgical activities in suitably porous media and with negligible contaminant-related reaction. Longer abstract

Treatability Study Work Plan: In Situ Soil Flushing Pilot, Nevada Environmental Response Trust Site, Henderson, Nevada. Revision 2
Nevada Division of Environmental Protection (NDEP), 190 pp, 2014

A groundwater extraction and treatment system (GWETS) has removed chromate since 1986 and perchlorate since 1998 from the site's groundwater under NDEP oversight. Collected groundwater is first treated to reduce chromate to Cr( III ) through a ferrous sulfate treatment system, and then the perchlorate is addressed in a series of fluidized bed reactors that contain perchlorate-reducing bacteria. Following treatment, groundwater is discharged to the Las Vegas Wash. This Work Plan details the pilot test conceptual design, preliminary lab-scale evaluations, and preliminary field work necessary for conducting an in situ soil flushing pilot test at the site. The proposed pilot testing continues and builds on a preliminary evaluation of soil flushing technology conducted in 2010. The testing program will evaluate the performance of alternative flushing liquids ( Lake Mead water versus GWETS effluent) and the potential for the technology to stimulate biodegradation of perchlorate in situ, prior to implementation at the field scale. Additional information: Other Reports.

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Dense Nonaqueous-Phase Liquid Contaminants

Aquifer Washing by Micellar Solutions: 3. Field Test at the Thouin Sand Pit (L'Assomption, Quebec, Canada)
Martel, R., P.J. Gelinas, and L. Saumure.
Journal of Contaminant Hydrology 30:(1-2)33-48(1998)

At the Thouin Sand Pit near Montreal, a field test was performed to study in situ recovery of DNAPL using surfactant solutions, evaluate an injection-pumping strategy, and test the use of polymer solutions to control the mobility of a washing solution slug and improve the vertical sweep efficiency throughout the sand unit. The test was performed in contaminated zones both saturated (17 cu m) and unsaturated in a shallow medium sand aquifer. Solutions were injected through a central well and pumped into four wells arranged in a five-point square pattern. In the zone swept by solution, 86% of residual DNAPL was recovered using only 0.9 pore volume of a surfactant solution. The use of a polymer solution before and after injection of the washing solution helped the washing solution to sweep all the sand layers in spite of soil heterogeneities. The rinsing cycles were not completed because of problems with freezing weather, and small but significant amounts of the washing solution remained in the aquifer at the end of the test. Longer abstract

Bachman Road Site, Oscoda, MI

A July 2000 pilot-scale demonstration of surfactant-enhanced aquifer remediation at the Bachman Road site involved source-zone flushing with a 6% solution of Tween 80, a nonionic, food-grade surfactant. The surfactant was flushed through an identified source region in a relatively homogeneous, unconfined aquifer formation to remove trapped PCE. Post-treatment monitoring 450 days later showed a decrease in PCE concentrations by two orders of magnitude within the source zone, and acetate and formate were detected at measurable levels (> 0.1 mM). These volatile fatty acids, undetectable prior to surfactant treatment, likely are products of Tween 80 fermentation and are known to support reductively dechlorinating populations present in the Bachman Road site aquifer. Concentrations of PCE dechlorination products (TCE, cis-DCE) rose by more than 2 orders of magnitude beyond pre-treatment levels within the treatment zone and downgradient, which suggests that Tween 80 can provide reducing equivalents to the oligotrophic aquifer and stimulate microbial reductive dechlorination. Additional information on work conducted at the Bachman Road site.

CROW™ Field Demonstration with Bell Lumber and Pole
Johnson, L.A. 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.

Case Study: In-Situ Surfactant Enhanced DNAPL Recovery Pilot Project, Refinery Site, Montreal Canada
Ivey, G.A. and M. Beaudoin.
FCS 2010: Federal Contaminated Sites National Workshop, Montreal, Quebec, Canada, May 10-13, 2010. Poster, 2010

Pilot-scale surfactant flushing was implemented September 11-24, 2007, at an active refinery to improve the mass recovery of chlorobenzene and dichlorobenzenes from the soil and groundwater. DNAPL and BTEX impacts noted in an area of 8-plus acres posed a significant risk to a nearby municipal groundwater aquifer. Over the course of the pilot application. The pilot-scale flushing system increased the rate of contaminant recovered by 800-1200%, permitting rapid and cost-effective reclamation. The case study provides an overview of site conditions; source and extents of contaminant plumes; and design, installation, and application of an Ivey-Sol® in situ flushing system. Additional information: 2008 project paper

Cosolvent Flushing Pilot Test Report: Former Sages Dry Cleaner
Florida Department of Environmental Protection, 58 pp, 1998

A pilot-scale field test of in situ alcohol flushing for enhanced solubilization and extraction of a PCE source zone was conducted at the former Sages Dry Cleaner site located in Jacksonville, FL. Alcohol flushing successfully removed a substantial volume (62-65%) of the DNAPL, although evidence indicated that continued alcohol flushing would have resulted in a greater NAPL removal effectiveness. Additional information on work conducted at the Sages site.

Cyclodextrin-Enhanced In Situ Removal of Organic Contaminants From Groundwater at Department of Defense Sites. Cost and Performance Report
Environmental Security Technology Certification Program (ESTCP) Project CU-0113, 101 pp, 2004

Cyclodextrins are nontoxic, modified sugars that form complexes with hydrophobic pollutants. During the 4-month flushing demonstration at Naval Amphibious Base Little Creek, Virginia Beach, VA, about 32.5 kg TCE and 1,1,1-TCA plus an estimated 3 kg of 1,1-DCE and an unknown amount of other contaminants were removed, a total DNAPL volume of ~30 liters. This demonstration also compared the performance of a conventional air stripper and a pervaporation system. Additional information

Cyclodextrin-Enhanced Vertical Flushing of a Trichloroethene Contaminated Aquifer
Blanford, W.J., M. Barackman, T.B. Boving, E. Klingel, and M. Brusseau.
Ground Water Monitoring and Remediation 21(1):58-66(2001)

In Tucson, AZ, a pilot-scale test of a groundwater flushing remediation technology was conducted in a source zone of a TCE-contaminated Superfund site. The pilot test involved injecting a 20% HPCE (hydroxypropylbeta-cyclodextrin, a complexing sugar) solution into the upper screened interval of a dual-screened vertical circulation well and extracting it from the lower screened interval. TCE concentrations increased by a factor of three in the presence of the cyclodextrin pulse compared to concentrations obtained during previous water flushing.

Design of a Field Scale Project for Surfactant Enhanced Remediation of a DNAPL Contaminated Aquifer
Brown, Chrissi Lynn, Ph.D. dissertation, University of Texas, 471 pp, 2004

The primary objective was to develop and apply engineering methods, especially flow and transport modeling using UTCHEM, the University of Texas CHEMical flood simulator, to optimize the removal of contaminants (TCE, PCE, 1,1,1-TCA) using surfactant-enhanced aquifer remediation (SEAR). Field surfactant floods and tracer tests were conducted at OU2 in Hill AFB, which allowed validation of the test design methodology, including the value of simulation in this process. The simulations accurately predicted tracer breakthrough times, tracer peak times and concentrations, and performance of the tracer 'tail' or concentration decline critical for moment analysis and DNAPL volume determination. The simulations also were critical in determining the appropriate injection and extraction rates, injection concentrations, and time required for each segment of the test. Surfactant was injected successfully in the field. The field test resulted in 98.5% DNAPL recovery and a reduction in TCE concentration in the produced water from 900 mg/L down to 10 mg/L at the end of the test.

First Five-Year Review Report for Jennison-Wright Corporation Site, Granite City, Madison County, Illinois
U.S. EPA Region 5, 61 pp, June 2009

For NAPL removal, hot water flushing was the selected alternative rather than surfactant flushing because it was a more proven technology. Illinois EPA and U.S. EPA will be funding the current remedial activities. This work includes (1) excavation and disposal of the remaining on-site contaminated soil and waste; and (2) additional groundwater remediation consisting of the current biological treatment, in addition to using a hot water and steam flushing system. MNA will be used where the groundwater contamination is much lower. Once constructed, the hot water and steam flushing system is expected to continue operation from 2009 until 2017. The estimated remaining cost to complete the remedial action at the site is $10.7 million, plus an additional $1.2 million for O&M of the flushing system. Additional information: Superfund Site Progress Profile

First Use in the UK of Full-Scale In Situ Surfactant-Enhanced Recovery within an Aquifer Impacted by Trichlorobenzene
Baldock, J., P. Crowcroft, A. Peacock, Z. Gillingham, A. Sykes, A. Thomas, J. Teer, M. Klabun, and R. Timson.
Seventh International Conference on Remediation of Chlorinated and Recalcitrant Compounds (Monterey, CA; May 2010). Battelle Press, Columbus, OH. ISBN 978-0-9819730-2-9, Paper E-042, 4 pp, 2010

Potential trichlorobenzene DNAPL source zones were identified at a dye works site within the underlying heterogeneous clay, silt, sand, and gravel aquifer. A full-scale surfactant-enhanced recovery system was installed to address DNAPL and dissolved-phase constituents in groundwater. The system is believed to be the first full-scale surfactant-enhanced recovery project undertaken within an aquifer in the United Kingdom. Twenty-three injection/extraction wells installed across an area of ~800 sq m delivered a combination of 2 surfactants either under pressure or via gravity drainage, depending on subsurface permeability. Extraction for aboveground treatment took place after 7 days of equilibration and mobilization of the chlorinated benzenes. This process was repeated for 3 months with surfactant recycling until TCB concentrations reached baseline within each well. Aboveground treatment involved groundwater influent tanks, sediment filters, a photocatalytic UV reactor, and liquid-phase carbon filters. The system recovered ~2,650 kg of contaminants. Afterward, emulsified vegetable oil was injected to encourage further reduction of residual contamination via anaerobic degradation. Longer abstract

Full-Scale In Situ PAH (Creosote Oil) Removal Using Surfactant Washing
Sykora, L., J. Jurak, M. Stavelova, and V. Kinkor. AECOM CZ, Czech Republic.
Seventh International Conference on Remediation of Chlorinated and Recalcitrant Compounds (Monterey, CA; May 2010). Battelle Press, Columbus, OH. ISBN 978-0-9819730-2-9, Paper E-044, 4 pp, 2010

Full-scale implementation of surfactant flushing was carried out to remediate PAH (creosote oil) contamination on the Wood Impregnation Company site, South Bohemia, Czech Republic. In situ remediation via infiltration and extraction of a biodegradable anion-active surfactant was carried out in three periods from May 2005 to April 2009 in the remedial area E1 West when conventional cleanup pumping was no longer effective. Flushing efficiency was increased significantly by heating. This remedial activity removed a total of 3.56 tons of PAHs mostly in free phase during 23 months (including a 6-month pilot test) of treatment.

In Situ Remediation of Coal Tar-Impacted Soil by Polymer-Surfactant Flooding
Young, C.M., 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 Richard Jackson.

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 15(3):313-321(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 Decontamination of Sand and Gravel Aquifers by Chemically Enhanced Solubilization of Multiple-Compound DNAPLs with Surfactant Solutions: Phase 1-Laboratory and Pilot Field-Scale Testing and Phase 2-Solubilization Test and Partitioning and Interwell Tracer Tests
U.S. DOE, Washington, DC. DOE/MC/29111-01, 625 pp, 1997

This report describes lab and field feasibility testing of in situ flushing at DOE's Paducah Gaseous Diffusion Plant using a 1% micellar-surfactant solution, sorbitan monooleate (approved by the FDA as a food-grade additive), to solubilize TCE DNAPL.

Innovative Green Treatment of Former Manufactured Gas Plant Dense Non Aqueous Phase Liquids using Surfactant-Enhanced In-Situ Chemical Oxidation (S-ISCO™)
Hoag, G.E. and J.B. Collins.
International Gas Union Research Conference, 2008, Paris. 18 pp, 2009

Surfactants and cosolvent/surfactant mixtures can increase the apparent solubility of VOCs and SVOCs in MGP soils for subsequent oxidation using activated persulfate. This process does not require separate mobile-phase NAPL recovery as the purpose of the surfactant/cosolvent is to increase the apparent solubility of the NAPL in the aqueous phase and not to mobilize the NAPL phase. This presentation illustrates the progress of an S-ISCO pilot test at the Bay Shore MGP site, Bay Shore, NY. The S-ISCO™ process underwent a successful large-scale field trial in Long Island, New York, in 2006 at a 125-yr-old former MGP site for coal tar DNAPL in residually saturated soils.

NAPL Removal: Surfactants, Foams, and Microemulsions
Ward, C.H., Lewis Publishers, Boca Raton, FL. ISBN: 1566704677, 592 pp, 2000

This text contains detailed discussions of the planning, design, implementation, and results of two technology field demonstrations at Hill AFB in 1997: a surfactant/foam process and a single-phase microemulsion in situ flushing process for surfactant-enhanced aquifer remediation. Additional information is available online on flushing projects conducted at Hill AFB.

Optimization Evaluation: Lee Chemical Superfund Site, City of Liberty, Clay County, Missouri
U.S. EPA, Office of Solid Waste and Emergency Response, Washington, DC.
EPA 542-R-11-013, 69 pp, Jan 2012

The current remedy, in place since March 26, 1994, consists of the operation of an in situ flushing system (referred to in the site documents as an in situ aqueous soil washing system) to address a source of TCE contamination, extraction of groundwater from 2 extraction wells, and discharge of the extracted groundwater to a single permitted outfall to Town Branch Creek. Soil contamination readily mobilized by soil flushing has been removed long since, but soil contamination remains that might be mobilized when the water table rises to historically high levels and/or remedy pumping decreases substantially. This report provides recommendations to improve remedy effectiveness, provide technical improvement, and gain site closure. Additional information: Superfund Site Information System

Polychlorinated Biphenyl (PCB) Recovery under a Building with an In Situ Technology Using Micellar Solutions
Martel, R., S. Foy, L. Saumure, A. Roy, R. Lefebvre, R. Therrien, U. Gabriel, P.J. Gelinas.
Canadian Geotechnical Journal 42(3):932-948(2005)

In a source zone of soil contaminated with Aroclor 1248 beneath an industrial building, the PCB was almost immobile due to its high viscosity. In the lab, a solution composed of an anionic surfactant and an alcohol recovered 99% of initial PCBs by dissolution after the injection of 10 pv of solution, but field recovery rates reached only 25%. The low recovery was explained by the presence in the soil of a surfactant previously spilled in a production accident. Those remnants modified the ratio of alcohol to surfactant of the injected solution in the soil and caused the formation of a viscous gel that partially plugged the porous media. Ethanol was used to dissolve the gel, and following the injection of three pore volumes of solution, 99% of the initial PCB contained in the soil was recovered. Longer abstract

RCRA Corrective Measures Implementation (CMI) Report for the Lawrence Berkeley National Laboratory
Lawrence Berkeley National Laboratory (LBNL), Univ. of California, 183 pp, 2007

Measures to address four areas of soil contamination and 11 areas of groundwater contamination at LBNL are designed to reduce residual concentrations of chlorinated VOCs to levels at or below the California media cleanup standards. The measures include excavation of contaminated soil, installation and operation of soil-flushing systems, and injection into the subsurface of HRC® or use of dual-phase extraction, followed by MNA. This report provides a consolidated record of the construction and implementation of these measures. Additional Information: 2014 Semiannual Progress Report

Remediation of Groundwater Contamination by Combined Flushing and MPPE Water Treatment: Summary and Conclusions
Ramsay, L. and J.B. Jorgensen.
Danish Environmental Protection Agency, Denmark. Environmental Project No 725, p 7-8, 2002

Macro porous polymer extraction (MPPE) technology makes use of small hydrophobic particles of plastic placed in a column through which contaminated water is pumped for treatment. A liquid immobilized in the pore structure of the particles removes the contaminants by liquid-liquid extraction. When the column is saturated with contamination, the particles can be regenerated by steam treatment. This summary briefly presents two case studies of flushing (a cosolvent and a chemically treated tenside mixture of rape seed oil, fatty acids, and glycerol, respectively) and MPPE used together to address PCE contamination at former drycleaner sites. Longer abstract

Remediation of NAPL Source Zones: Lessons Learned from Field Studies at Hill and Dover AFB
McCray, J.E., G.R. Tick, J.W. Jawitz, J.S. Gierke, M.L. Brusseau, R.W. Falta, R.C. Knox, D.A. Sabatini, M.D. Annable, J.H. Harwell, and A.L. Wood.
Ground Water 49(5):727-744(2011)

Studies of innovative remediation technologies--surfactant flushing, cosolvent flooding, flushing with a complexing sugar solution, and air sparging--were conducted between 1994 and 2004 at NAPL-contaminated sites at the Hill and Dover Air Force bases. The field tests proved that aggressive remedial efforts tailored to the contaminant can remove more than 90% of the NAPL-phase contaminant mass. Despite incomplete removal of the source, technology implementation achieved a significant reduction in the groundwater contaminant mass flux. The studies illuminated the importance of small-scale heterogeneities on remediation effectiveness and encouraged research on enhanced delivery methods. Most contaminant removal occurred in hydraulically accessible zones, and complete removal was limited by contaminant mass stored in inaccessible zones. The work at these sites also emphasized the importance and feasibility of recycling and reusing chemical agents and enabled the implementation of successful follow-on efforts at full scale. Additional information: Longer abstract; Field Demonstration of Surfactant-Enhanced Solubilization of DNAPL at Dover Air Force Base, Delaware (Abstract); Childs, J. et al. Journal of Contaminant Hydrology 82(1-2):1-22(2006)

Revised Work Plan And Trial Management Plan: Surfactant Enhanced In Situ Chemical Oxidation (S-ISCO®) & Surfactant Enhanced Product Recovery (SEPR™), Block 5 and Hickson Road, Barangaroo, Pilot Trial
New South Wales Office of Environment and Heritage, Australia. 355 pp, 2011

From 1840 to 1921, sections of the Barangaroo site were used to manufacture gas, and portions of the former gas-works infrastructure remain in place beneath the current slab surface and adjacent roadway. This revised work plan provides detailed descriptions of the S-ISCO® and SEPR™ processes and the system design for their pilot tests. S-ISCO® is designed to solubilize contaminants rather than mobilize them. The co-eluted surfactant/co-solvent and oxidant fronts move through the subsurface together, and solubilization and oxidation occur simultaneously, such that the contaminants (in this case, TPH, BTEX, PAHs, and coal tar) are destroyed in place. The system incorporates water, activator (Fe-TAML and/or sodium hydroxide), VeruSOL® surfactant, and oxidant (hydrogen peroxide and/or sodium persulfate).

Solvent Release into a Sandy Aquifer 3: Enhanced Dissolution by Methanol Injection
Broholm, K.
Environmental Technology 28(1):11-18(2007)

A field experiment involving a release of 5 liters of a mixture of chlorinated solvents (0.5 L chloroform, 2.0 L TCE, and 2.5 L PCE) was carried out in a sandy, unconfined, shallow aquifer at Canadian Forces Base Borden, Ontario, Canada. The dissolution of the chlorinated solvents into the groundwater was studied in detail for 220 days, and then a methanol/water mixture was injected to study the possible enhancement of the dissolution. Effects were observed only at a few sampling points, likely due to the distribution of the solvent as a laterally extensive, thin pool. This investigation shows that it is crucial to know the exact location of the DNAPL in the subsurface when designing and performing remedial techniques at contaminated sites. Longer abstract

Surfactant Remediation Field Demonstration Using a Vertical Circulation Well
Knox, R.C., D.A. Sabatini, J.H. Harwell, R.E. Brown, C.C. West, F. Blaha, and C. Griffin.
Ground Water 35(6):948-953(1997)

A field demonstration of surfactant-enhanced solubilization was completed in a shallow unconfined aquifer located at a Coast Guard Station in Traverse City, MI. The main goals were to assess the control of chemical extractants in the circulation well system and the behavior of the surfactant solution in the subsurface, with a goal of maximum surfactant recovery. A secondary goal was to demonstrate enhanced removal of PCE and recalcitrant components of a jet fuel. The surfactant increased the contaminant mass extracted by 40- and 90-fold for the PCE and jet fuel constituents, respectively. The well system captured >95% of the injected surfactant solution. Demonstration design information is provided in Sabatini, D.A. et al., "Design of a Surfactant Remediation Field Demonstration Based on Laboratory and Modeling Studies," Ground Water 35(6):954-963(1997).

Technical Report for Surfactant-Enhanced DNAPL Removal at Site 88, Marine Corps Base Camp Lejeune, North Carolina
Environmental Security Technology Certification Program (ESTCP), 114 pp, 2001

Prior to surfactant flooding, free-phase PCE DNAPL removal operations were conducted over a period of about 60 days. During this period, an estimated 30-60 gallons of free-phase DNAPL were removed. Later, during the 143-day SEAR demonstration, approximately 76 gallons of PCE DNAPL were removed from this site as a result of both enhanced solubilization and enhanced mobilization of DNAPL. A custom surfactant, Alfoterra 145-4-PO sulfate™, was manufactured by Condea Vista Company for the demonstration. Additional information: Cost & Performance Report

The DNAPL Remediation Challenge: Is There a Case for Source Depletion?
EPA 600-R-03-143, 2003

The Bachman Road and Sages sites, summarized in Appendix A, are examples of removing substantial amounts of DNAPL, with subsequent changes to the geochemical environment that enhance biodegradation of the remaining mass of DNAPL. These technologies are not likely to be effective at removing DNAPL present in low permeability source zones, such as fractured systems. At the time this report was written, neither field-scale demonstrations nor full-scale applications of in situ flushing were known to have achieved site closure at a DNAPL source zone.

Well Injection Depth Extraction (Wide) Soil Flushing. Innovative Technology Summary Report
U.S. DOE, Ohio Field Office, Ashtabula Environmental Management Project, Ashtabula, OH. DOE/EM-0577, 30 pp, 2001

The WIDE system utilizes prefabricated vertical wells (PVWs) in lieu of conventional wells or sumps to extract groundwater and inject liquid flushing agents. The WIDE field-scale demonstration at Ashtabula, OH, measured 70 ft by 70 ft with a grid of over 480 PVWs installed to a depth of 15 ft. A vacuum extraction unit removed the groundwater, simultaneously volatilized the TCE, and delivered the TCE-contaminated groundwater and soil gas to an aboveground treatment system. The system extracted TCE, U, and Tc-99 from the subsurface and reduced their concentrations in the groundwater. Additional information: 2002 Ph.D. dissertation by K.A. Warren

Western Research Institute: Contained Recovery of Oily Wastes (CROW) Process. Innovative Technology Evaluation Report
EPA 540-R-00-500, 112 pp, 2000

The CROW hot-water injection technology was demonstrated at the Brodhead Creek Superfund site in Stroudsburg, PA, over a 20-month period. The injection and recovery wells targeted an accumulation of free-phase coal tar. See also the project cost and performance report.

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Light Nonaqueous-Phase Liquid Contaminants

2010 Summary Report and Risk Evaluation: Former Unocal Seattle Marketing Terminal, 3001 Elliott Avenue, Seattle, Washington
Washington Department of Ecology, 157 pp, Feb 2011

The soil at a former bulk fuel distribution facility is affected by leaded and unleaded gasoline, diesel, lube oil, motor oils, and petroleum-based solvents (non-chlorinated). In a surfactant-enhanced pilot test completed in July 2010 to remediate LNAPL in well MW-61A-R, ~200 gals of 4% solution of Gold Crew Release® surfactant were gravity fed into the well and allowed to remain in the formation for 24 hrs prior to extraction. The work plan called for removal of 3 times the injection volume of surfactant solution, but after extraction of 600 gals, monitoring via mason jar shake tests still showed suds, indicating the presence of surfactants. The vacuum truck removed an additional 300 gals of groundwater/surfactant solution, and the sample obtained following the extraction of 900 gallons contained no visible surfactant or LNAPL. A detailed discussion of the pilot test procedure and results is given on pages 26-30.

Advancements in Use of Surfactant for LNAPL Remediation
Hayward, J., T. Porter, F. Barranco, and J, Harwell.
Seventh International Conference on Remediation of Chlorinated and Recalcitrant Compounds (Monterey, CA; May 2010). Battelle Press, Columbus, OH. ISBN 978-0-9819730-2-9, Paper E-050, 8 pp & 19 slides, 2010

At the Oasis Fuel Point site, Fort Drum, New York, a field pilot study was performed to evaluate the potential for full-scale use of surfactant-enhanced aquifer remediation (SEAR) for removal of free-phase and residual JP-8 LNAPL from subsurface soil. A proprietary blend of anionic surfactants was mixed in a biodegradable formulation to mobilize the LNAPL and allow it to be pumped to the surface. The SEAR pilot study was performed within a 15.2 m x 30.5 m recirculation cell using an array of 13 injection wells and 2 extraction wells. The estimated pretreatment volume of free-phase LNAPL present in the pilot cell was recovered completely, and LNAPL thicknesses observed in the majority of monitoring wells within the cell decreased from several feet to non-detect. Based on the successful results, full-scale SEAR is being designed for the site. Longer abstract

Chester River Hospital Center Pilot Test Evaluation Report and Proposed 2015 Action Plan
Maryland Department of the Environment (MDE), 128 pp, 2015

The Chester River Hospital Center (CRHC) Technical Team implemented a pilot study in August 2014 to demonstrate the viability and effectiveness of the Ivey-sol® surfactant flushing push-pull process to safely liberate sorbed residual hydrocarbons from soils. CRHC has used pump and treat (P&T) for over 20 years to remove liquid petroleum hydrocarbons (free product) and remediate the groundwater. Based on the evidence of monitoring data, the project moved into a closure status/process during 2012/2013; almost a year later, however, subsequent monitoring results led to the restart of P&T, and investigations revealed that a seasonal high water table contacted sorbed residual hydrocarbons in a smear zone in soils near the original spill. In July 2014, MDE approved the proposed Ivey-sol® pilot study under a set of specific conditions. The push-pull flushing process was completed successfully, and CRHC proposed its use at full scale to complete the cleanup. [MDE approved the revised action plan (with modifications) in July 2015.] Follow up on this project at MDE's Oil Control Program Remediation Sites page. Additional information: A report describing successful implementation of the flushing technology at full scale was posted in June 2016.

Cyclodextrins in Bioremediation of Contaminated Soil
Fenyvesi, E.
Cyclodextrin News 25(5):1-7(2011)

During an in situ field experiment at a transformer station in Hungary to address transformer oil, a combined technology (ventilation, nitrogen, and phosphorus) was implemented with randomly methylated beta-cyclodextrin (RAMEB) addition, continuous removal of groundwater, continuous flushing by slow infiltration of the treated water, and ex situ treatment on activated carbon. The soil was flushed with a RAMEB solution periodically through the injection well, and after a few days' acclimation, the groundwater was pumped continuously from the extractor wells on the other side of the transformer. Continuous groundwater removal reduced the risk of spreading the RAMEB-solubilized contaminants. The period of acclimation after flushing allowed adsorption of RAMEB on the soil, providing for long-term biodegradation. After RAMEB addition, the carbon dioxide content of the soil gas increased suddenly, indicating improved microbial activity. By the end of treatment, the hydrocarbon content of the soil decreased from ~25,000 mg/kg to <300 mg/kg. A similar technology combination was used at a former tank station on an agricultural site in Hungary contaminated with aged diesel and engine oil from leaking USTs.

Ethanol Flushing of Gasoline Residuals: Microscale and Field Scale Experiments
De Oliveira, Everton, Ph.D.
Dissertation, University of Waterloo, ON, Canada. 331 pp, 1997

This work included an evaluation of ethanol flushing of gasoline in a field test cell at Canadian Forces Base Borden.

Field Application of Modified In Situ Soil Flushing in Combination with Air Sparging at a Military Site Polluted by Diesel and Gasoline in Korea
Lee, H., Y. Lee, J. Kim, and C. Kim.
International Journal of Environmental Research & Public Health 11(9):8806-8824(2014)

A modified soil flushing procedure with surfactants and air sparging was applied to a full-scale operation at a fuel-contaminated military site. The objective was to improve removal efficiency at depths >7 m. Slurping and soil flushing operations were conducted for 10 months in the first stage, and a modified process of soil flushing serially operated with air sparging was used in the second stage. TPH removal efficiencies were 52.8%, 57.4%, and 61.8% for the soil layers at 6-7, 7-8, and 8-9 m, respectively. Total TPH and BTEX mass removed during the full-scale operation was 5,109 and 752 kg, respectively. Crucial factors identified from a serial pilot study and during unit process operation provide meaningful information for operations of more than 12 months that use surfactant-aided soil flushing at sites affected by gasoline and diesel. The findings also provide information regarding the scale-up process for modifying technology from a column test to a pilot study and then to full-scale application. This paper is Open Access.

Fourth Five-Year Review Report for Havertown PCP Superfund Site, Haverford Township, Delaware County, PA
U.S. EPA Region 3, 82 pp, 2010

National Wood Preservers operated on this site from 1947 to 1991. The company reportedly disposed of liquid waste—mostly diesel oil contaminated with PCP—in a well leading to groundwater under the plant. Liquid waste spills also contaminated soil in the area. The remedy includes excavation and removal of contaminated soils, pump and treat, and in situ flushing in the source area using water from the groundwater treatment facility mixed with an emulsifier to enhance mobilization of the principal threat waste. Source area wells contain the highest levels of PCP, ranging from an average of 5,000 ug/L to 10,000 ug/L. These high levels of PCP continue to act as a source of contamination to the aquifer. Continued capture of the contamination plume through groundwater extraction is the priority for this site. Source area flushing to enhance recovery of highly contaminated groundwater started in July 2010. Additional information: 2011 Interim Remedial Action Report

In Situ Flushing of Contaminated Soils from a Refinery: Organic Compounds and Metal Removals
Iturbe, R., C. Flores, C. Chavez, A. Ramirez, and L.G. Torres.
Remediation Journal 14(2):141-152(2004)

A field demonstration of in situ flushing for the remediation of soil contaminated with petroleum hydrocarbons was conducted at a Mexican refinery. After 6 weeks of in situ flushing with alternate periods of water and water/surfactant, the initial average TPH concentration of 55,156 mg/kg had fallen to 1,407 mg/kg, a total removal efficiency of 98%. At the end of the process, no fuel constituents or PAHs were found. The removal efficiency for iron was 70%, and 94.4% for vanadium. The volume of soil treated was 41.6 cu m, equivalent to 69.5 tons of soil. A rough calculation of the process costs estimated a total cost of $104.20 per cubic meter. Longer abstract

Performance Optimization of LNAPL Three Phases Extraction by Prefabricated Vertical Wells (PVWs)
Sharmin, Nadia. Ph.D. dissertation, North Carolina State University, 269 pp, 2009

The Well Injection Depth Extraction (WIDE) system incorporates prefabricated vertical wells as the mechanism for pressurized injection of a flushing solution into the soil concurrent with vacuum extraction for removal of the contaminated solution. In a field study conducted at a former Air Force base in Ohio, system performance was monitored in terms of extracted liquid and gas phases over 185 operating hours on 38 separate days. Results from the study document field data on system performance for extraction of LNAPLs in a subsurface with lenticular morphology. Field results were used to calibrate the models used in the analytical studies.

Pester Refinery Site, El Dorado, Kansas: Third Five-Year Review Report
U.S. EPA Region 7, 54 pp, 2009

The design document for the soil portion of OU 1 established the organization and technical basis for the in situ flushing and bioremediation of pond soils contaminated with BTEX and PAHs. After removal of sludge in 1994, the ponds were refilled with water to mobilize soil contaminants to a subsurface interceptor trench for collection, treatment, and reintroduction to the ponds. The trench extracted seepage from the ponds and maintained hydraulic control, simultaneously preventing contaminant discharge into the adjacent river while maintaining the water level in the aqueous bioremediation system. Initially, water was pumped from below the oil/water interface in the interceptor trench. Mechanical filtration removed suspended contaminants and then the water was discharged back into the pond cavities. Surface aerators in the northern half of the stormwater pond augmented biodegradation of organic contaminants in the pond water. The efficacy of the bioremediation and soil flushing remedy declined after 2000, and a ROD amendment in 2005 specified in situ solidification of residual contaminated soils, followed by placement of a final soil cover.

Petroleum Storage Tank Trust Fund: Summary of Activities and Statements of Costs Incurred during Remediation of UST/AST Sites
Arkansas Department of Environmental Quality, 2011

Successful free-product removal operations utilizing surfactant flushing and mobile dual-phase extraction (a vacuum truck) were conducted in 2009-2010 to remove diesel at Tyson Feed Mill, Springdale, AR, and gasoline at Downen Oil Company, Little Rock.

Recent Development of Low Concentration Surfactant Flushing for NAPL-Impacted Site Remediation and Pollution Prevention
Shiau, B.J.B., J.M. Brammer, D.A. Sabatini, J.H. Harwell, and R.C. Knox.
Prevention, Assessment, and Remediation, 20th Conference and Exposition, August 19-22, 2003, Costa Mesa, California. National Ground Water Association, p 92-106, 2003

This paper presents 3 brief case studies of LNAPL remediation or pollution prevention using a low surfactant flushing approach for fuel hydrocarbon contamination. In one case, Fenton's reagent was implemented after flushing.

Retrospective Evaluation of a Surfactant Flush to Remove Gasoline Contamination from an Aquifer in Golden, Oklahoma
U.S. EPA, Science Inventory Record Report, 2005

A surfactant flush was conducted in June 2002 at a gasoline spill in Golden, OK. The remediation was designed to meet three cleanup goals: in Phase 1, remove as much of the free-phase gasoline as possible, and in Phase 2, decrease the soil and groundwater concentrations by 1-2 orders of magnitude, and approach, if not reach, drinking water standards for BTEX. Phase 2 followed the Phase 1 flush with in situ bioremediation to reduce concentrations of BTEX compounds and TPH in groundwater to meet the last two goals. For more information on this project, see Lin et al., "Influence of Subsurface Geochemistry on Surfactant Enhanced Aquifer Remediation (SEAR) Design," IPEC 2007, slides 13 thru 21. For follow-up monitoring, see Halihan, T. et al., "Post-Remediation Evaluation of a LNAPL Site Using Electrical Resistivity Imaging (Abstract)," Journal of Environmental Monitoring 7(4):283-287(2005).

Soil Washing with a Micellar Solution: Field Test at a Gas Station (Laval, Quebec, Canada)
Grenier, M., R. Martel, U. Gabriel, L. Trepanier, C.D.-Rancourt, T. Robert, and J.-M. Lauzon.
REMTECH 2010: The Remediation Technologies Symposium, Banff, AB, Canada, 20-22 Oct 2010. Environmental Services Association of Alberta, Edmonton, AB (Canada), 32 slides, 2010

A pilot-scale field test of soil washing with a micellar solution to recover petroleum hydrocarbons at residual saturation was launched after vacuum extraction of free-phase product. The polymer/micellar solution solubilized the remaining gasoline adsorbed on soil particles or trapped in the porous media, sweeping 40 cu m of contaminated aquifer. Lab and field methodology and results are presented. Longer abstract

Solar-Powered In Situ Soil Washing with Surfactant to Collect LNAPL
Miller, C., S. Ruffing, and R. Kline.
Remediation Journal 22(2):69-79(2012)

An in situ flushing pilot study of surfactant-enhanced product recovery was completed between January 2010 and May 2010 at the Hydrocarbon Burn Facility, John F. Kennedy Space Center, FL. The goal was to implement a simple and sustainable LNAPL recovery process, evaluate site-specific volumes and rates of LNAPL collection, and assess the achievable degree of soil and groundwater cleanup. The petroleum-contaminated groundwater was extracted, mixed with a biodegradable surfactant (ECOSURF(tm) SA-15), and injected upgradient of the extraction site. The product then was recovered using an electronic product recovery skimmer in the extraction well. All the system equipment (submersible pump, LNAPL skimmer, surfactant feed pump, controls, and various other equipment) was powered by a solar panel array. The system collected ~60 gals (429 lbs) of LNAPL at the recirculation site over a period of three months at a maximum rate of ~1 gal free product per day.

Surfactant Enhanced HVDPE Remediation of Petroleum Contaminated Soil, Bedrock, and Groundwater, Northern California, USA
Kenoyer, G., C. D'Sa, G. McLinn, and G.B. Ivey.
WATERtech 2011, Banff, Alberta, Canada, 13-15 April. Environmental Services Association of Alberta (ESAA). 65 slides, 2011

A site located in Northern California experienced a leak of diesel fuel in 1991. The diesel hydrocarbons migrated through near-surface sandy soils into the underlying fractured bedrock, and ultimately to groundwater. The diesel constituents have persisted in the groundwater at high concentrations for 18 years, despite periodic multiphase extraction (MPE). In a pilot study conducted to evaluate the effect of coupling the use of non-ionic surfactants with MPE, multiple applications of a non-ionic surfactant blend were injected in a central monitoring well while vacuum-enhanced MPE of groundwater was conducted at downgradient monitoring wells. Maintaining capture of injected solutions was essential to achieve regulatory acceptance. The pilot showed immediate substantial changes in the concentrations of diesel constituents, and the mass removal rate increased sharply over previous results without surfactants. The approach and findings are discussed. Longer abstract

Surfactant Enhanced LNAPL Recovery and Attenuation
Tworkowski, R.J. and J.L. Baer.
IPEC 2004: The 11th Annual International Petroleum Environmental Conference, 11-15 October 2004, Albuquerque, NM. Integrated Petroleum Environmental Consortium, Univ. of Tulsa, OK. 9 pp, 2004

For residual LNAPL at an operational retail gasoline service station located in Maryland, the approach involved the in situ application of a surfactant mixture, under pressure, into the site subsurface, followed by high-vacuum-induced, multi-phase recovery from an extraction well via a mobile vacuum truck.

Surfactant Flush Pilot Study Work Plan: Gasoline Fueling Station — Royal Farms #96, 500 Mechanics Valley Road, North East, Cecil County, Maryland 21901

During an underground storage tank system upgrade in June 2011, a site groundwater monitoring well at the Royal Farms #96 convenience store/gasoline fueling station showed ~2 inches of liquid-phase hydrocarbon (LPH). The primary objective of this work plan is to evaluate the effectiveness of surfactant flushing assisted by multi-phase enhanced fluid recovery extraction for LPH removal. This approach will augment current groundwater remediation efforts by promoting increased solubility and mobility of the residual and mobile LPH within the release area. This work plan describes the surfactant injection/extraction means and methods, and pre- and post-flushing groundwater monitoring activities.

Technical and Economic Feasibility of Soil Flushing with Non-Ionic Surfactant to Remediate Gas Well Condensate
Felske, D. and P.R. Morton.
RemTech 2005: Remediation Technologies Symposium, 19-21 October 2005, Banff, Alberta, Canada. 33 slides, 2005

In a pilot-scale field feasibility study, a commercially available non-ionic surfactant (Ivey-sol) was evaluated for its solubility-increasing properties as an economic means of solubilizing soil-bonded condensate inaccessible to ex situ remediation. Results showed that over the projected time for remediation attainment, surfactant flushing achieved significant solubilization and soil remediation of condensate at economical rates compared to bioventing, biosparging, or SVE. Longer abstract

Two Rapid Enhanced Flushing NAPL Recovery Methods
Jacobs, J.A., N. Nelson, and J. Begley.
Sixth International Conference on Remediation of Chlorinated and Recalcitrant Compounds, May 19-22, 2008, Monterey, CA. Battelle Press, Columbus, OH. Abstract only, 2008

Two different enhanced flushing were developed for rapid removal of gasoline free product from within an aquifer. Method 1: At a field trial in Ontario, Canada, water supersaturated with CO(2) in a patented gas-liquid mass-transfer system was injected into an aquifer test cell where a 200-L hydrocarbon mixture formed a residual NAPL zone. The rising bubbles contacted VOC NAPL ganglia in the saturated zone, mobilizing NAPL trapped in pores and volatilizing the VOCs into the vapor phase for removal via SVE. Method 2: A former tank pit contained used hydraulic oil that was trapped beneath the saturated zone. The 2-step flushing process used high-pressure air injection and biosolvent injection to thin and mobilize the heavy oil. High-pressure air injection and biosolvents were used with high-vacuum extraction to recover both the used hydraulic oil and the biosolvent. The final stage separated the heavy oil from the unspent biosolvent and groundwater. Over 11 55-gal barrels of free product were removed and a similar volume of biosolvent was recovered during the 1-week process. Additional information: Poster

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