Dense nonaqueous phase liquids (dnapls)

Treatment Technologies

In Situ Flushing:
Cosolvent/Alcohol Flooding, Surfactant Flushing

This page identifies general resources that contain detailed information on the design and implementation of in situ flushing technologies. Information on applications of in situ flushing technology specific to a chemical class can be found in the class subsections listed to the right. More resources on flushing technologies for a wide range of contaminants can be found in the In Situ Flushing pages of Technology Focus.

Soil flushing involves flooding a source area with an appropriate solution to remove the contaminant from the soil. Water or liquid solution is injected or infiltrated into the area of contamination. The contaminants are mobilized by solubilization, formation of emulsions, or a chemical reaction with the flushing solutions. After passing through the contamination zone, the contaminant-bearing fluid is collected by a groundwater extraction system and brought to the surface for disposal, recirculation, or on-site treatment and reinjection. Application of soil flushing is based on delivery of the flushing fluid, control of the fluid flow, and fluid recovery.

Flushing solutions may be water, acidic aqueous solutions, basic solutions, chelating or complexing agents, reducing agents, cosolvents, or surfactants. For example, water-soluble (hydrophilic) or water-mobile constituents can be flushed with water, and different metals can be removed with acidic solutions, basic solutions, and/or chelating, complexing, and reducing agents. Cosolvents are usually miscible and are effective for some organics, and surfactants can assist in the removal of hydrophobic organics (U.S. EPA 1991).

The techniques most frequently employed in soil flushing are surfactant and cosolvent flooding for fuels and chlorinated solvents. Many types of surfactants (cationic, anionic, nonionic) are available, but anionic or nonionic surfactants are generally used because their negative or neutral charge reduces the possibility of their sorption to negatively charged clay particles. They also are generally less toxic than cationic surfactants. Surfactant/cosolvent flushing has been shown to be effective for several DNAPL types, including spent degreasing solvents (TCE and TCA), dry cleaning solvents (PCE), heavy fuel oils, and coal tar/creosote. Laboratory work has also demonstrated applicability to PCB-containing mineral oils (ITRC 2003).

Surfactants are commonly constructed with hydrophobic and hydrophilic chemical components, meaning that one end of the molecule is attracted to oil (or organic compounds) and the other to water. Surfactants chosen primarily to increase the contaminant (generally a NAPL) solubility are used in a solubilization flood. Surfactants chosen to produce ultra-low interfacial tensions are employed in a mobilization flood (Kueper et al. 1997). Mobilization flooding should only be considered when there is a high degree of certainty that the solution can be recovered, such as with a competent bedrock or capillary barrier underlying the treatment zone.

A typical surfactant solution also may contain additives, such as electrolytes and a cosolvent. In addition to being effective with the target contaminant, the surfactant solution should be compatible with the site-specific soil, soil pore water, and groundwater (if applicable). A cosolvent, such as isopropanol, can be used to improve the surfactant solubility in solution and provide the surfactant/contaminant solution with an acceptable viscosity. A side effect of adding chemicals to the surfactant solution is that they need to be treated along with the contaminant at the recovery end (NAVFAC 2002).

Cosolvents, usually alcohols, are chemicals that dissolve in both water and NAPL. In an alcohol flood, the alcohol may partition into both the NAPL and water phases. Partitioning affects the viscosity, density, solubility, and interfacial tension of the NAPL (Kueper et al. 1997). The physical properties of the NAPL vary with the amount of alcohol available for interaction, and whether the alcohol preferentially dissolves into the NAPL or into the water. Complete miscibility is achievable and results in a pumpable solution that, depending upon the density of the NAPL and the proportions of alcohol and water in the solution, may be more or less dense than water.

Before implementing surfactant and/or cosolvent flushing, laboratory and bench-scale treatability testing should be done to ensure the selection of one or more agents best suited for the contaminant and the site-specific soil and geochemical conditions. Modeling of subsurface conditions is commonly done to identify the best delivery system. Flushing is most efficient in relatively homogeneous and permeable (K ≥ 10^-3 cm/sec) soil (NAVFAC 2002). Heterogeneous soil reduces the efficiency of the flood sweep and may prevent optimum contact between the agent(s) and the target contaminant. Flushing of relatively homogeneous but lower permeability (10^-4 to 10^-5 cm/sec) units is possible, but it requires a high induced gradient to move the agent, while greatly increasing the remediation time (NAVFAC 2002).

Other soil factors that may adversely affect efficiency are high cation exchange capacity, high buffering capacity, high organic soil content, and pH. Land disposal restrictions and underground injection control regulations also may limit selection of the flushing solution. At a former drycleaner, ethanol was substituted for isopropanol because of regulatory concern about the toxicity and persistence of isopropanol. Most states allow in situ flushing of saturated or unsaturated soil, with a permit, if the aquifer in the area is already contaminated. When applying for a permit, all chemicals involved, including unreacted compounds and impurities, must be listed (NAVFAC 2002).

Due to its use for decades in oil field applications, soil flushing is considered a mature technology; however, it has found limited application in the environmental arena. ITRC (2003) estimates the cost of surfactant/cosolvent flushing of a DNAPL source zone to range between $65 and $200 per cubic yard, whereas the NAVFAC website gives cost estimates of $100 to $300 per cubic yard for flushing. The variability stems from the waste type and the quantity to be treated. The NAVFAC figures do not include design and engineering costs, which can be considerable. Cost per cubic yard can be misleading, and the cost per gallon recovered or destroyed should also be evaluated. Overall costs can be lowered if the flushing agent is recovered and recycled (U.S. EPA 2006).

Technology Advantages

Elimination of the need to excavate, handle, and transport large quantities of the original contaminant;
Enhancement to pump and treat may speed site remediation and closure;
Applicable to a wide range of contaminants in both vadose and saturated zones; and,
May be used in conjunction with other technologies or in stages for complex cases (Roote 1997).

Technology Limitations

Lengthy remediation times due to the slow rate of diffusion processes in the liquid phase);
Potential for spreading contaminants beyond the capture zone, laterally or vertically, if the extraction system is not properly designed or constructed, hydraulic control is not maintained, or a groundwater discharge zone captures flow from the treatment zone;
Limited regulatory acceptance due to the potential for spreading contaminants, and concern with introducing flushing solutions into the subsurface that may remain in residual quantities;
Uncertainties involved in prediction of performance and duration to achieve clean up goals;
Limitations on effectiveness resulting from man-made obstructions, such as pipes/utilities, especially at underground storage tank sites;
Geologic setting conditions, e.g., low permeability, high clay or organic content, high degree of heterogeneity or secondary permeability, and close proximity to sensitive recharge areas or potable aquifers;
Selection of flushing solutions that reduce effective soil porosity by adhering to soil, accelerating biogrowth, or causing precipitation or other reactions with ambient soil or groundwater; and,
Inability to separate flushing additive from elutriate, resulting in high consumption and prohibitive expense of flushing additive (Roote 1997).

Additional research is needed to advance good sweep efficiency, to optimize the implementation of surfactant/cosolvent technologies in karst and fractured bedrock formations, to evaluate the combination of flushing technologies with other source zone and/or plume remedial technologies, and to evaluate the long-term impact of the mass removal on post-flushing water flooding and natural attenuation.

Primary Source: U.S. EPA. 2006. In Situ Treatment Technologies for Contaminated Soil: Engineering Forum Issue Paper. EPA 542-F-06-013.

ITRC. 2003. Technical and Regulatory Guidance for Surfactant/Cosolvent Flushing of DNAPL Source Zones.

Kueper, B. et al. 1997. Technology Practices Manual for Surfactants and Cosolvents (TR-97-2). Advanced Applied Technology Demonstration Facility Program, Rice University.

NAVFAC. 2002. Surfactant-Enhanced Aquifer Remediation (SEAR) Design Manual, NFESC Technical Report TR-2206-ENV.

Roote, D.S. 1997. In Situ Flushing: Technology Overview Report. Ground-Water Remediation Technologies Analysis Center, TO-97-02.

U.S. EPA. 1991. Engineering Bulletin: In Situ Soil Flushing. EPA 540-2-91-021.

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General Resources | Abstracts | Performance Monitoring for In Situ Flushing

General Resources

AATDF Technology Practices Manual for Surfactants and Cosolvents

Advanced Applied Technology Demonstration Facility for Environmental Technology (AATDF) Program, TR-97-2, 1997

Improved Monitoring Methods for Performance Assessment During Remediation of DNAPL Source Zones
R. Siegrist, R. Oesterreich, L. Woods, and M. Crimi.
Strategic Environmental Research and Development Program (SERDP), Project ER-1490, 116 pp, 2010

Investigators evaluated (1) the effects that sampling methods can have on the accuracy of measurements made for chlorinated solvents in samples of porous media collected from intact cores, and (2) the effects that remediation agents can have on the ability to infer CVOC mass levels in the subsurface based on groundwater concentration data. The accuracy of VOC measurements was investigated using an experimental apparatus packed with sandy porous media and contaminated with known levels of VOCs (PCE, TCE, TCA) sampled using different methods under variable, but controlled, conditions. Five sampling methods were examined representing different degrees of porous media disaggregation and duration of atmospheric exposure that can occur during sample acquisition and preservation in the field. CVOCs were studied at dissolved, sorbed, and nonaqueous phases. Five porous media temperatures were examined ranging from 5 to 80 degrees C to represent ambient or thermal remediation conditions, and two water saturation levels were used to mimic vadose zone and groundwater zone conditions. Results show that sampling method attributes can impact the accuracy of VOC measurements in porous media by causing negative bias in VOC concentration data ranging from near 0 to 90% or more. In situ remediation technologies, such as thermal treatment, ISCO, and flushing, have the potential to alter subsurface properties, which can affect the behavior of CVOCs, including DNAPLs.

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 Overview Report
D.S. Roote.
Ground-Water Remediation Technologies Analysis Center (GWRTAC). TO-97-02, 24 pp, 1997

INDOT Guidance Document for In-Situ Soil Flushing
L.S. Lee, X. Zhai, and J. Lee.
SPR-2335; FHWA/IN/JTRP-2006/28, 49 pp, Jan 2007

Contains information ranging from the basic chemistry and mechanisms of cosolvent and surfactant flushing to the key factors that need to be considered during the selection, design, and implementation of this technology. Also provides information on several categories of contaminants subject to in situ flushing. This text should be used as a general guidance rather than as a design manual.

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

Surfactant-Enhanced Aquifer Remediation (SEAR) Design Manual
Naval Facilities Engineering Service Center. NFESC Technical Report TR-2206-ENV, 110 pp, 2002

Surfactant-Enhanced Aquifer Remediation (SEAR) Implementation Manual
Naval Facilities Engineering Service Center. NFESC Technical Report TR-2219-ENV54, 54 pp, 2003

Surfactant-Enhanced DNAPL Remediation: Surfactant Selection, Hydraulic Efficiency, and Economic Factors
D.A. Sabatini, R.C. Knox, J.H. Harwell.
EPA 600-S-96-002, 15 pp, 1996

Surfactant Enhanced DNAPL Removal: ESTCP Cost and Performance Report
Environmental Security Technology Certification Program (ESTCP), 216 pp, 2001

Surfactants/Cosolvents: Technology Evaluation Report
C.T. Jafvert.
Ground-Water Remediation Technologies Analysis Center, TE-96-02, 50 pp, 1996

Technical and Regulatory Guidance for Surfactant/Cosolvent Flushing of DNAPL Source Zones
Interstate Technology & Regulatory Council (ITRC). DNAPLs-3, 151 pp, 2003

Abstracts

Modeling Field-Scale Cosolvent Flooding for DNAPL Source Zone Remediation
H. Liang and R.W. Falta. Journal of Contaminant Hydrology, Vol 96 Nos 1-4, p 1-16, 29 Sep 2007

When a 3-D, compositional, multiphase flow simulator was used to model a field-scale test of PCE DNAPL removal by cosolvent flooding, the effectiveness of DNAPL source zone remediation was affected mainly by characteristics of the spatial heterogeneity of porous media and the variable (and unknown) DNAPL distribution. The inherent uncertainty in the DNAPL distribution at real field sites means that some form of calibration of the initial contaminant distribution will almost always be required to match contaminant effluent breakthrough curves.

Simultaneous Optimization of Dense Non-Aqueous Phase Liquid (DNAPL) Source and Contaminant Plume Remediation
A. Mayer and K.L. Endres. Journal of Contaminant Hydrology, Vol 91 Nos 3-4, p 288-311, 2007

A framework developed for simultaneous, optimal design of ground-water contaminant source removal and plume remediation strategies allows for varying degrees of effort and cost to be dedicated to source removal versus plume remediation. High and low estimates of capital and operating costs for chemical flushing removal of the source are considered.

Performance Monitoring for In Situ Flushing

In situ soil flushing involves flooding a zone of contamination with an appropriate solution to remove the contaminant from the soil. The techniques most often employed in soil flushing are surfactant and cosolvent (usually an alcohol) flooding for fuels and chlorinated solvents (EPA 2006). The table below provides a comprehensive menu of performance monitoring parameters for surfactant and cosolvent flushing. Most of the table addresses surfactant flushing, which requires a greater amount of monitoring compared with cosolvent flushing alone due to its greater capacity to mobilize DNAPL. The type and amount of data needed is site specific and will be affected by the site hydrogeology and size and architecture of the source area.

Surfactant flooding involves the preparation of low-viscosity surfactant solutions that are pumped through the DNAPL-contaminated zone by introduction at injection points and removal from extraction points. Polymer amendments that will increase the viscosity of the surfactant solution might be required for higher viscosity contaminants (e.g., creosote) when temperature augmentation for viscosity reduction is not feasible. The surfactant flooding wellfield generally will be composed of dedicated surfactant injection and extraction points, and 'water' injection points for hydraulic control (NFESC 2003).

Discussions of the different sampling and analysis methods appropriate for this technology can be found in NFESC 2003 and ITRC 2003.

The performance of a surfactant/cosolvent flushing system can be measured by the following metrics: (1) the final average DNAPL saturation (i.e., the volume percent of the pore space that still contains DNAPL); (2) the percentage of the initial contaminant mass removed; (3) the source strength or mass flux of contaminants emanating from the source; (4) the percentage of the injected chemicals recovered (a measure of the efficiency of hydraulic control); and (5) the risk associated with any DNAPL remaining after treatment, as well as the risk reduction accomplished with the DNAPL removal action (ITRC 2003).

A variety of indirect techniques can be used to measure the success of a surfactant flood: tracers, such as the partitioning interwell tracer test, where the measurement is performed before and after the flood; contaminant flux measurements, also performed before and after the flood; and geophysical techniques, such as electrical resistivity tomography, performed during the flood. Descriptions of other general techniques that might be useful can be found in Remediation Measurement Tools.

Performance Monitoring Parameters for In Situ Flushing of DNAPLs

Sampling Location	Performance Parameter	Method	Data Use	Recommended Frequency of Analysis
Fresh Surfactant Tank Batches	Surfactant	Potentiometric Titration, High Performance Liquid Chromatography, Evaporative Light Scattering, and UV or Fluorescence (NFESC 2003).	Determine if concentrations of the flush are within specifications for all three components. Note that for some cases small fluctuations in electrolyte concentrations can have profound effects on the phase performance of the injectant (ITRC 2004).	Before injection from tank begins. In batch mixing, samples to be taken from top and bottom of tank to verify uniform mixing (NFESC 2003).
	Electrolyte¹	Specific conductance by surrogate (hand-held meter), SW-846: 6010C for confirmation of Ca⁺² or Na⁺¹ concentrations (NFESC 2003). Ion Selective Electrode (ISE)³ for field measurement of Ca⁺² or Na⁺¹
	Cosolvent, if present²	If Alcohol, SW-846: 8015C (GC) or SW-846: 8260B (preferably field for either).
	Overall Quality	Phase behavior test (NFESC 2003).	To determine if injectant mixing with site NAPL will yield phase results comparable to the laboratory phase behavior standards.
	Temperature, pH, Specific Conductance	Hand-held meter	Provide baseline indicator parameters.
Injection Wells	Water Levels	Manual water/air interface meter, Pressure transducer	Provides warning of potential plugging of soil pore space	Baseline and frequently during injection. Note that NFESC 2003 recommends the pressure transducer as it can provide near-continuous readings.
Source Area Monitoring Wells	Free-phase NAPL levels	Oil/water interface probe.	Identify mobilization of free phase NAPL. Note that NFESC 2003 recommends to the extent possible that identified free phase NAPL be removed from a site before surfactant flushing begins.	Periodically during injection. Exact number of times is site specific (ITRC 2003).
	Dissolved Contaminants of Concern (COCs) and degradation products²	Non-halogenated VOCs, EPA SW-846: 8015C (GC) Aromatic and halogenated VOCs, 8021B (GC), or VOCs, 8260B (GC/MS)(preferably field) SVOCs, 8270D (GC/MS) (preferably field). Note that for some less common NAPLs, there might be specific tests for them that yield better detection limits, if needed.	Monitors cleanup progress at that sampling point. Note that NFESC 2003 recommends multi-level sampling wells instead of single-screen wells to determine if uniform cleanup is occurring.	Baseline, periodically during injection process, and after flush is over. Exact number of times is site specific (ITRC 2003).
	Injectant Concentrations: Surfactant	Potentiometric Titration, High Performance Liquid Chromatography, Evaporative Light Scattering, and Ultraviolet or Fluorescence (NFESC 2003) ISE for field measurement	Provides information on whether flushing fluid is reaching the sampling point (fluid dispersion). After complete flushing is over, including final water flush, provides information on whether any surfactants are left.	Periodically during injection process, and after flush is over. Exact number of times is site specific (ITRC 2003).
	Electrolyte¹	Specific conductance by surrogate (hand held meter), SW-846: 6010C for confirmation of Ca⁺² or Na⁺¹ concentrations (NFESC 2003) ISEs for field measurement of Ca⁺², Na⁺¹.
	Cosolvent, if present²	If Alcohol, SW-846: 8015C (GC) or SW-846: 8260B (preferably field for either). Note for GC or GC/MS methods NFESC 2003 recommends using a packed column rather than the capillary column usually deployed with these methods because of potential clogging issues.
	Temperature, pH, Specific Conductance	Hand held probes, in-line cells.	Provides information on potential changes in subsurface and injectant chemistry (NFESC 2003).
	Groundwater Levels	Water/air interface probes, pressure transducers.	Provides information on whether hydraulic control is being maintained. Provides information in conjunction with the injection well water levels on whether there may be a loss in permeability due to the injection NFESC 2003).
Perimeter Monitoring Wells	Dissolved COCs and degradation products	Non-halogenated VOCs, SW-846: 8015C (GC) Aromatic and halogenated VOCs, 8021B (GC), or VOCs, 8260B (GC/MS) (preferably field) SVOCs, SW-846: 8270D (GC/MS) (preferably field). Note that there might be specific tests for less common NAPLs that yield better detection limits, if needed.	Used to verify hydraulic control. A steep rise in concentrations would mean it is not in control (NFESC 2003).	Frequency is site specific (NFESC 2003, ITRC 2004).
	Injectant Concentrations¹ Surfactant	Potentiometric Titration, High Performance Liquid Chromatography, Evaporative Light Scattering, and Ultraviolet or Fluorescence (NFESC 2003) ISE for field measurement	Used to verify hydraulic control. There should not be any injectant materials in these wells during the flushing operation (NFESC 2003).
	Electrolyte¹	Specific conductance by surrogate (hand held meter), SW-846: 6010C for confirmation of Ca⁺² or Na⁺¹ concentrations (NFESC 2003). ISEs for field measurement of Ca⁺², Na⁺¹.
	Cosolvent, if present	If Alcohol, SW-846: 8015C (GC) or SW-846: 8260B (preferably field for either).
	Temperature, pH, Specific Conductance	Hand-held probe, in-line cell.	Provides information on potential changes in subsurface and injectant chemistry (NFESC 2003).
	Groundwater Levels	Water/air interface probes, pressure transducers.	Used to verify hydraulic control (NFESC 2003).
Extraction Well Effluents	Dissolved COCs and degradation products²	Non-halogenated VOCs, SW-846: 8015C (GC) Aromatic and halogenated VOCs, 8021B (GC), or VOCs, SW-846: 8260B (GC/MS) VOCs (preferably field) SVOCs, 8270D (GC/MS) (preferably field). There might be specific tests for the less common NAPLs that yield better detection limits, if needed.	Used to measure cleanup progress. Also used to calculate the amount of contaminants removed (NFESC 2003 and ITRC 2003).	Site specific; however, to ensure an adequate amount of certainty in the contaminant removal mass, estimating at least 20 to 30 samples from each extraction well is recommended (NFESC 2003 and ITRC 2003). NFESC 2003 also suggests considering in-line auto sampling and GC analysis for COC recovery calculations.
	Injectant Concentrations: Surfactant	Potentiometric Titration, High Performance Liquid Chromatography, Evaporative Light Scattering, and UV or Fluorescence (NFESC 2003). ISE for field measurement.	Used to determine injectant recovery rates (NFESC 2003).	Site specific (ITRC 2003).
	Electrolyte¹	Specific conductance by surrogate (hand held meter), SW-846 6010C for confirmation of Ca⁺² or Na⁺¹ concentrations (NFESC 2003). ISEs for field measurement of Ca⁺², Na⁺¹.
	Cosolvent, if present²	If Alcohol, SW-846: 8015C (GC) or SW-846: 8260B (preferably field for either).
	Temperature, pH, Specific Conductance	Hand-held probe, in-line cell.	Provides information on potential changes in subsurface and injectant chemistry (NFESC 2003).	As needed for process monitoring. Taken at the same rate as COC sampling is done (NFESC 2003).
	Flow Rates	Flow meters, bucket tests (NFESC 2003).	For performance monitoring the flow rate is associated with the COC contaminant concentration to develop a contaminant mass removal rate.
Oil-Water Separator Tank	NAPL	Volumetric.	Determines NAPL mass removal for use in calculating total mass removal.	Site specific (NFESC 2003).
Statistically Determined, Random Soil Cores in the Source Zone Area	COCs, degradation products, and NAPL	Non-halogenated VOCs, SW-846: 8015C (GC) Aromatic and halogenated VOCs, 8021B (GC), or VOCs, 8260B (GC/MS) (preferably field) SVOCs, 8270D (GC/MS) (preferably field). There might be specific tests for the less common NAPLs that yield better detection limits, if needed. For DNAPL, visual observation or indicator dye, such as Sudan IV or Red Oil O (Kram et al. 2001).	Used to estimate cleanup success.	At the end of the final water flush (NFESC 2003).

¹ Note: Some commercial-grade salts (NaCl, CaCl₂) can contain low levels of metal/metalloid contaminants of concern. For example, at the Camp Lejeune surfactant demonstration (ESTCP 2001), arsenic was monitored.

² Note: For GC or GC/MS methods, NFESC 2003 recommends using a packed column rather than the capillary column usually deployed with these methods because of potential clogging issues. Also, for COC effluent measurements in source area wells and extraction wells the sample may have to be diluted to keep the concentration within the linear range of the instrument.

³ Note: ISE methods can be used for field measurements of Ca⁺², Na⁺¹, and surfactant. The instrument manufacturer should be consulted to determine whether a site-specific condition might affect use.

Performance parameters and locations are those suggested in NFESC 2003 and ITRC 2004.

References

DNAPL Characterization Methods and Approaches, Part 1: Performance Comparisons
M. Kram, A.A. Keller, J. Rossabi, and L.G. Everett.
Ground Water Monitoring and Remediation, Vol 21 No 1, p 67-76, 2001

In Situ Treatment Technologies for Contaminated Soil: Engineering Forum Issue Paper
EPA, EPA 542-F-06-013, 35 pp, 2006.

Strategies for Monitoring the Performance of DNAPL Source Zone Remedies
Interstate Technology & Regulatory Council, 205 pp, 2004

Surfactant-Enhanced Aquifer Remediation (SEAR) Design Manual
Naval Facilities Engineering Service Center. NFESC Technical Report TR-2206-ENV, 110 pp, 2002

Surfactant-Enhanced Aquifer Remediation (SEAR) Implementation Manual
Naval Facilities Engineering Service Center. NFESC Technical Report TR-2219-ENV54, 54 pp, 2003

Surfactant Enhanced DNAPL Removal: ESTCP Cost and Performance Report
Environmental Security Technology Certification Program (ESTCP), 216 pp, 2001a

SW-846 On-Line: Test Methods for Evaluating Solid Waste, Physical/Chemical Methods
U.S. EPA, Office of Resource Conservation and Recovery.

Technical and Regulatory Guidance for Surfactant/Cosolvent Flushing of DNAPL Source Zones
Interstate Technology & Regulatory Council (ITRC). DNAPLs-3, 151 pp, 2003

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, 2001b

Technology Practices Manual for Surfactants and Cosolvents (TR-97-2)
Kueper, B. et al. Advanced Applied Technology Demonstration Facility Program, Rice University, 1997

Abstracts

Benefits of Partial DNAPL Source Removal: Measuring Contaminant Flux Change

View Abstract

Tracer Techniques for DNAPL Source Delineation and In Situ Flushing Techniques for Enhanced Source Removal: Pilot Scale Demonstrations at the Dover National Test Site