Ray Close Conference Room--Building 100
Hill Air Force Base, Utah
May 8-9, 1997

Dr. A. Lynn Wood, U.S. Environmental Protection Agency (EPA)
Mr. Stephen Shoemaker, E.I. Dupont DeNemours & Company, Inc.
Mr. Robert Elliott, Hill Air Force Base (AFB)

Dr. Wood and Mr. Shoemaker, the two co-chairs for this Remediation Technologies Development Forum (RTDF) In situ Flushing Action Team, opened the meeting by welcoming participants, thanking them for their attendance, and explaining that this meeting is a followup to one held with a precursor group. Both chairpeople were impressed to see how interest in in situ flushing technologies has grown, based on the number of participants present at the meeting (see Attachment A for a list of participants). The co-chairs identified four goals for the meeting:

Mr. Elliott welcomed participants to Hill AFB and talked about Hill AFB's nonaqueous phase liquid (NAPL) ground-water contamination. NAPL removal has posed a challenge, but Hill AFB is optimistic that in situ flushing technologies could provide a solution. A series of in situ flushing demonstration projects have been performed at Hill AFB; these demonstrations have been made possible by the cooperative relationship that exists between Hill AFB and regulatory agencies, namely EPA and the Utah Department of Environmental Quality.

Mr. Richard Steimle, Technology Innovation Office (TIO), Office of Solid Waste & Emergency Response, EPA

Mr. Steimle presented an overview of the RTDF program. EPA established the RTDF in 1992 when industry spokespeople expressed interest in identifying ways for the government and industry to work together to solve complex hazardous waste remediation problems. Today, a number of RTDF teams have been formed, all of which focus on a particular hazardous waste issue or a remedial technology. Updates on the progress of each RTDF team will soon be available on the RTDF Internet site, maintained by EPA.

The RTDF allows government and industry to work together to develop and improve environmental technologies so that hazardous waste cleanup goals are met in a safe and cost-effective manner. The RTDF fosters public- and private-sector partnerships to undertake research, development, demonstration, and evaluation efforts needed to achieve common cleanup goals. The RTDFs mission is three-fold:

RTDF teams:

No strict guidelines outline how RTDF action teams should be managed. In general, two co-chairs, one from industry and one from EPA, lead each team. Co-chairs from all RTDF teams convene once a year to discuss their respective team's progress. Beyond the co-chairs, the organizational structure of each team is unique. According to a 1996 fact sheet, 47 percent of RTDF members were from industry, 32 percent from government, and 21 percent from academia.

Membership for RTDF teams is unrestricted and all interested organizations are welcome to participate. Members should be dedicated to carrying out the RTDF mission rather than joining just as a means to stay up-to-date on the latest advancements in a particular field. Members also should be willing to donate time or money to further the development of the technology. (The RTDF originally required a cash downpayment from all members, but this requirement has been suspended.)

All of the RTDF programs are currently supported on a budget of $20 million. Government sources (e.g., EPA, Department of Energy, Department of Defense) provide 48 percent of this funding, while corporations contribute 43 percent and industrial associations contribute 9 percent. No strict guidelines describe how RTDF teams should bankroll projects, although teams are encouraged to find ways within each team to fund their projects. For large projects, proposals can be written to government agencies.

Mr. Richard Steimle, TIO, Office of Solid Waste & Emergency Response, EPA

Mr. Steimle presented information about GWRTAC, a large information center established in 1995 and operated by the National Environmental Technology Applications Center (NETAC) in association with the University of Pittsburgh's Environmental Engineering Program. GWRTAC's activities are overseen by a guidance committee consisting of 25 people. Its mission and role are to:

GWRTAC keeps up-to-date on the status of innovative ground-water remediation technologies. Several databases are accessible through GWRTAC, including the Technology Database, the Vendor Database, and others that link to various environmental remediation technology databases. Several types of technical reports are available through GWRTAC, including technology evaluation reports, information reports, technology overview reports, and status reports. GWRTAC advertises upcoming events (e.g., demonstrations, conferences, technical courses), and provides news briefs summarizing technological demonstrations, initiatives, and regulatory acceptance issues. Additionally, GWRTAC conducts a variety of customized information searches on a fee basis.

GWRTAC can be accessed at:

Address: 615 William Pitt Way
Pittsburgh, PA 15238
Phone: 800-373-1973 or 412-826-5512 (Ext. 215)
Fax: 412-826-5552

Mr. Richard Steimle, TIO, Office of Solid Waste & Emergency Response, EPA

Mr. Steimle explained that in situ flushing technologies reduce ground-water contaminant concentrations by injecting an aqueous solution into a zone of contaminated soil/ground water. Subsurface contaminants are solubilized or mobilized by the injected flushing agent and then brought to the surface via a downgradient extraction well. Flushing offers a variety of benefits over other ground-water remediation technologies:

A total of 40 in situ flushing demonstration projects have been completed or are currently underway in the United States. Attachment B lists these 40 sites as well as the contaminants located at each and the flushing agent utilized. Mr. Steimle presented a map that indicated how many projects had been conducted in each EPA region. Regions 5 and 8 lead the nation with ten and eight projects, respectively. No projects have been conducted in Region 1 or 9. Mr Steimle speculated that the lack of projects in Region 1 could reflect an unwillingness to use this technology in hard rock/fractured rock environments.

The success of in situ flushing is highly site-dependent and, as a result, requires a detailed site-specific predesign stage. Numerous geological factors can affect the outcome; for example, high clay content, high organic content, fractured rock, soils with large surface areas, and low hydraulic conductivity can hinder success. Soil pH and buffering capacity and contaminant properties may also affect the success of flushing systems. Properties that can affect outcome include degree of water solubility, soil sorption constants, octanol/water partitioning coefficients, vapor pressure, liquid viscosity, and liquid density.

A variety of agents can be utilized as flushing agents, with different degrees of success for different types of contaminants. Mr. Steimle offered a list of agents and the conditions where they are applicable:

Flushing Agents Contaminants Targeted
Clean Water High solubility organics, soluble inorganic salts
Surfactants Low solubility organics, petroleum products
Water/Surfactants Medium solubility organics
Cosolvents Hydrophobic contaminants
Acids Basic organic contaminants, metals
Bases Phenolics, metals
Reductants/Oxidants Metals

Of the 40 demonstration projects listed in Attachment B, 24 involve surfactants, 11 utilize water, 5 utilize cosolvents, and 10 use other flushing agents. Researchers are currently investigating the potential of alternative flushing agents such as cyclodextrins, humic acid, and food additives.

Many issues need to be resolved before in situ flushing can be considered for widespread use, including:

Mr. Steimle noted that state agencies are generally receptive to in situ flushing technologies, especially when the flushing agents are nontoxic. EPA contacted every state and found Nebraska to be the only state with policies that prohibited use of surfactants and other injectables. (One participant in the audience noted that some Nebraska regulators have shown interest in use of in situ flushing.) Mr. Steimle's comments prompted discussion among participants. Some have not found state regulatory agencies to be as agreeable as Mr. Steimle has indicated, although they did admit that the situation is improving. Members from industry note that states are more apt to be receptive when they are included early in the decision-making process and treated as valued team members.

Dr. P. Suresh Rao, University of Florida

Dr. Rao, a researcher from the University of Florida, discussed some issues pertaining to the health of the innovative technologies market. The National Research Council (NRC) is scheduled to release a report offering findings and recommendations related to this issue at the end of the summer.

Characteristics of the Remediation Market

Dr. Rao said the remediation market is amorphous and diverse. Problems associated with different sites are highly variable, with each site presenting different contamination issues and hydrogeologic characteristics. Because the problems are so diverse, solutions must be flexible; one technology will not have the same success at all sites. Clients served by remedial technologies are also diverse, with about two-thirds managed by private owners and one-third managed by the government.

Dr. Rao described the remediation market as fragmented and difficult to define or predict. Optimists claim that market potential has not yet been reached and the market is about to "take off." Pessimists, however, state that the market is on a steady decline.

Barriers to Utilization of Site Remediation Technologies

In the last 10 years, many companies in the remedial technology industry have had difficulty breaking into the market. As a result, many small companies have been forced to merge with larger ones. The current market is regarded as "mature," with only a few large companies providing the majority of services.

Many barriers restrict more widespread use of innovative remedial technologies. In the majority of cases, sites choose to delay remedial activities or to utilize conventional technologies (e.g., ex situ pump and treat remediation, soil vapor extraction [SVE]). Such choices are driven by economic, technical, and regulatory factors.

Technological Testing Issues

To convince site managers to use innovative technologies, vendors will need to prove that the technology will effectively solve site-specific problems in a cost-effective manner with minimal risk of failure. Claims of successful performance will need to be supported by convincing field testing and multiple lines of evidence. Controlled experiments will need to be performed to convince clients that the technologies are actually reducing contaminants rather than just displacing them. In an ideal situation, vendors visiting sites will be able to present performance data and automatically gain the confidence of clients at different sites. Dr. Rao asked the following questions:

Dr. Jon Ginn, Hill AFB

Dr. Ginn provided an overview of the operational activities and environmental issues at Hill AFB. The War Department established Ogden Arsenal (now known as Hill AFB) in the 1920s for use as a storage center for unused ordnance. Since its inception, Hill AFB has been used for a variety of functions, including manufacturing of explosives, bombs, artillery shells, and small munitions; handling and storing munitions; and storing, testing, and repairing missiles. Hill AFB was placed on the National Priorities List in 1987 and nine operable units (OUs) have been identified. For the purpose of this meeting, the NAPL ground-water plumes associated with OU-1 and OU-2 are of interest because several in situ flushing demonstrations have been conducted.

Ground water at OU-1 has been contaminated by petroleum products from activities at fire training areas and by oils, fuels, and solvents from disposal practices at chemical disposal pits #1 and #2. The OU-1 plume is characterized by light nonaqueous phase liquids (LNAPL). A Record of Decision (ROD) to determine remedial action for OU-1 will be signed in 1998.

Ground water at OU-2 has been impacted by disposal activities at chemical pit #3. Estimates suggest that 100,000 to 1 million gallons of wastes (consisting primarily of trichloroethylene [TCE], tetrachloroethylene [PCE], and 1,1,1-trichloroethane [1,1,1-TCA]) were disposed in these pits. The OU-2 plume is characterized by dense nonaqueous phase liquids (DNAPL). In 1993, a solvent recovery system was installed and about 30,000 gallons of DNAPL were removed. An ROD was recently signed for this OU and the AFB is planning to install an interceptor trench to prevent off-base migration. The base is open to suggestions to upgrade remedial efforts and will be analyzing the success of different demonstrations that have been conducted at this plume, namely surfactant flushing, surfactant/foam flushing, steam technologies, and SVE.

Mr. Robert Stites, EPA, Region 8

Mr. Stites, the EPA Region 8 project manager for Hill AFB, offered the group insight into regulatory concerns regarding in situ flushing technologies, including:

Mr. Stites discussed ways to gain regulatory approval, underscoring the importance of involving regulators early-on in the decision-making process. Mr. Stites also suggested concentrating efforts on better dissemination of information. (Comprehensive Environmental Response, Compensation, and Liability Act [CERCLA] training programs offer training in innovative technologies, but in situ flushing technologies are not presently included.) A report summarizing what has worked would be very helpful to regulators.


Project Description
Dr. Carl Enfield, EPA

Dr. Enfield, the technical point of contact for the SERDP project on enhanced source removal, defined SERDP's role and gave a brief overview of in situ flushing demonstrations conducted under SERDP. This SERDP project evaluates the effectiveness of emerging technologies by performing side-by-side field demonstrations and comparing them to each other and to conventional pump and treat technology. (Pump and treat is used as a comparison because this technology is currently being used at more than 90 percent of sites undergoing remedial activities.) Under the SERDP project, researchers characterize the sites, install and operate innovative technologies, evaluate the performance of the technology, and write manuals incorporating results from the different demonstration projects.

A number of in situ flushing demonstration projects have been performed under SERDP at Hill AFB. (The results of some of these projects will be summarized below.) The different demonstrations utilized different flushing agents but similar setups; for example, all the SERDP demonstrations at OU-1 were performed in cells isolated with physical barriers (sheet pilings). A preponderance of data will be required before people are convinced that in situ flushing technologies are effective. These SERDP demonstrations, therefore, evaluate performance in multiple ways, including:

The field work for the SERDP demonstrations at Hill AFB have been completed but investigators are still interpreting the data. SERDP is planning additional studies at Dover AFB in Delaware.

Cosolvent Mobilization--Cell 3 at Hill AFB's OU-1
Dr. Ronald Falta, Clemson University

Dr. Falta opened his discussion by explaining the two mechanisms involved in cosolvent NAPL removal. Flushing agents that solubilize NAPLs increase the total aqueous solubility of the contaminants. Agents that mobilize NAPLs reduce the interfacial tension. The degree of solubilization versus mobilization that occurs during a cosolvent flood can be controlled by choosing cosolvents that place emphasis on these different mechanisms.

The Cell 3 team's goal was to mobilize the NAPL. Analysis of the LNAPL, however, indicated that mobilization of this particular NAPL would be a challenge. As a result, the flushing agent chosen was nearly pure alcohol, with a small amount of added water to prevent it from freezing. The alcohol flood consisted of three phases: first, 1,000 gallons of tert-butanol were injected, followed by 2,000 gallons of a tert-butanol/hexanol mixture, and finishing with 4,000 gallons of tert-butanol. After the alcohol flood was complete, water was injected to remove any remaining cosolvent. Dr. Falta noted a few challenges that arose along the way:

A preliminary data analysis offers the following conclusions:

Cyclodextrin Solubilization--Cell 4 at Hill AFB's OU-1
Dr. Mark Brusseau, University of Arizona

Dr. Brusseau opened his discussion with a description of cyclodextrin, a reagent that differs markedly from alcohols and surfactants. Cyclodextrins, glucose based molecules, are used in many pharmaceutical, food processing, and chemical processes. Dr. Brusseau used a beta-cyclodextrin, consisting of seven glucose molecules, each of which has three alcohol (-OH) functional groups attached. The -OH groups, arranged on the outside of the molecule, make the outer portions of the molecule highly soluble in water. The inner "core is an area of low polarity. Cyclodextrins enhance the solubility of hydrophobic NAPL constituents by forming inclusion complexes. The NAPL constituents can partition into the cyclodextrin core, where they are shielded from surrounding water.

Cyclodextrins have several properties that make them excellent candidates for use in flushing technologies because they:

For the demonstration at Hill AFB, the Cell 4 team injected about 10 pore volumes (PVs) of 10 percent cyclodextrin into the subsurface. The team used two different methods to calculate the percent removal for several contaminants. Results obtained using the different methods differed by less than a factor of two for the majority of contaminants and ranged from 39 to 83 percent. For four contaminants (1,1,1-TCA, o-xylene, decane, and undecane) the results differed by more than a factor of three. The Cell 4 team is currently investigating this discrepancy.

The Cell 4 team was able to predict field behavior fairly well with laboratory data. Before performing the field experiment, the team calculated the amount of LNAPL that they expected to be extracted. For many contaminants, the predicted numbers were very similar (within a factor of two) to those actually measured in the field. In other cases, the values measured in the field were less than predicted, perhaps as a result of competition, complexation by the cyclodextrin in a multicomponent solution, or enhanced biodegradation of labile contaminants. The Cell 4 team will be investigating this matter further.

The Cell 4 team compared the solubility enhancement potential of cyclodextrins with water so that they could draw a comparison with conventional pump and treat systems utilizing water flushing. The results indicate that cyclodextrins offer superior solubility enhancement.

Dr. Brusseau noted that further investigation needs to be performed to determine the feasibility of recycling cyclodextrins. Recycling is a particularly important issue with cyclodextrins because they are more expensive than some surfactants.

Surfactant Solubilization--Cell 6 at Hill AFB's OU-1
Dr. Robert Knox, University of Oklahoma

According to Dr. Knox, this test cell is referred to as Hill AFB's "problem cell." Although the team installed sheet pilings, they experienced problems with leakage. Water level monitoring indicated that leakage rates exceeded 0.3 percent PVs per day; as a result, the team was forced to alter its original plan and inject surfactant into only three injection wells rather than four (the fourth well was used to pump water). The Cell 6 team used Dowfax 8390 (solutions of 4.3 weight percent) as its flushing agent, injecting two PVs of water, followed by 10 PVs of Dowfax solution, and then followed by another two PVs of water.

The Cell 6 team formulated preliminary conclusions based on the following evaluation methodologies:

Surfactant Mobilization--Cell 5 at Hill AFB's OU-1
Dr. David Sabatini, University of Oklahoma

The Cell 5 team mobilized NAPL using a middle phase microemulsion (MPM) surfactant system. Dr. Sabatini explained that the MPM phase appears when the hydrophilic-lipophilic balance (HLB) of a surfactant system is adjusted so that it is right at the interface between being water and oil soluble. MPM phases are characterized by ultra-low interfacial tension and can cause bulk oil displacement. Dr. Sabatini notes three ways that a surfactant can be manipulated to achieve the MPM phase:

Achieving MPM phases with a NAPL as complex as the one at Hill AFB was a challenge, but not impossible. Soil core data indicate that more than 90 percent of the analyzed contaminants were removed, except naphthalene (75 percent removed). Analysis of partitioning tracer tests indicate that 75 percent of the NAPL was removed, with NAPL saturation at 8.5 percent prior to flushing and 2.0 percent afterward.

Dr. Sabatini recommends further analysis of the following:

Dr. Gary Pope, University of Texas

Dr. Pope's team performed a solubilization flush on the DNAPL at Hill AFB's OU-2. The NAPL at OU-2 was less complex than the NAPL at OU-1 and consisted primarily of 1,1,1-TCA, TCE, and PCE. The field demonstration at OU-2 differed from those at OU-1 in that hydraulic controls were used rather than physical controls.

Dr. Pope's team used a flushing agent consisting of 8 percent Aerosol MA (also called sodium dihexyl sulfosuccinate) and 4 percent isopropyl cosolvent. The flushing agent was chosen based on successful performance in the laboratory. Aerosol MA is a particularly attractive choice for use at Hill AFB because it does not sorb to Hill AFB's soils. Budgetary restrictions prevented Dr. Pope from adding a polymer to the flushing agent, although he is certain that the addition of a polymer would have offered mobility control and would have reduced costs (by decreasing the amount of surfactant required), shortened remediation times, and mitigated heterogeneities.

Dr. Pope's demonstration was conducted in two phases. Phase I proved that partitioning tracer tests work well and provided insight for design of Phase II. Phase II involved injecting 2.5 PVs of the flushing solution into the subsurface. The flush resulted in a removal of 510 to 530 gallons of DNAPL. Estimates for the percent removal of contaminants ranged from 97 percent (calculated by comparing ground-water contaminant concentration in wells before and after flushing) to 99 percent (calculated by comparing DNAPL saturation provided by partitioning tracer tests).


Dr. Stephanie Fiorenza, Rice University

Dr. Fiorenza provided an overview of the AATDF program, which was formed in May 1993 and is scheduled for completion by October 1997. AATDF's funding ($19.3 million) supports projects investigating innovative remedial technologies.

Dr. Fiorenza described how AATDF determined which of the 170 proposals they received to fund. After narrowing the prospects to 38 projects, AATDF conducted "due diligence" to make its final selection. Over a course of 4 to 5 months, principal investigators and other related experts argued for certain projects. In the end, 12 projects were selected. Four of these projects will be discussed by presenters below.

AATDF identified two types of challenges that in situ flushing technologies face: technical challenges pertaining to subsurface heterogeneity and unintended migration, and economic challenges posed by the high cost of surfactants and cosolvents. AATDF hopes field-demonstration projects will provide insight on how to increase mobility control and improved sweep efficiency; achieve more efficient miscible displacement to reduce PVs; and recover and reuse surfactant.

Single-Phase Microemulsion (SPME)/Cosolvent Comparison--Hill AFB's OU-1
Dr. Michael Annable, University of Florida

Dr. Annable worked on two different projects at Hill AFB. Both projects focused on solubilization of NAPL rather than mobilization because the investigators did not want to address concerns regarding migration to previously uncontaminated areas. One of the demonstrations utilized SPME technology and the other used cosolvents. Both projects were conducted at Hill AFB's OU-1, but at different cells.

SPME Study

Dr. Annable opened his discussion by describing the basis of SPME technology. This technology utilizes a surfactant/cosurfactant combination that forms a water-continuous, low-viscosity, microemulsion when it comes into contact with NAPL. The microemulsion can be diluted in water and transported through porous media as a single-phase, low-viscosity fluid. Using SPME technology to solubilize agents is advantageous because it aims to remove all fractions of the oil phase rather than just specific components of the NAPL. Dr. Annable notes the difference between the SPME phase, which solubilizes NAPL, and Dr. Sabatini's MPM phase, which mobilizes NAPL via immiscible displacement. The flushing agent used in the demonstration consisted of 3 percent surfactant (Brij 97® [C18O(C2H4O)10H]) and 2.5 percent cosurfactant (n-pentanol). A total of nine PVs were used, but the majority of the contaminants were removed in the first one or two PVs.

Dr. Annable concludes that this technology effectively removes NAPL in a reasonable timeframe. Preliminary conclusions can be drawn based on the following evaluation methodologies:

Cosolvent Study

The flushing agent used in the cosolvent study consisted of 70 percent ethanol and 12 percent pentanol. When choosing the cosolvent, the team believed that ethanol was the only alcohol regulators deemed acceptable for injection into the ground. Many people are finding, however, that regulators are receptive to other cosolvents as well. Given this new development, Dr. Annable wanted to note that blending cosolvents may allow researchers to use solutions that contain only 20 to 30 percent of cosolvent.

The cosolvent study, which was completed about 2 years ago, is offering some interesting information on spatial issues, an area that requires further exploration. Different performance levels were observed between upper and lower layers of the cell. For example, the percent removal of 1,2-dichlorobenzene was 99 percent at 16.25 feet but only 49 percent at 20 feet. This difference in performance may be attributable to the fact that the low density flushing agents have difficulty reaching deeper layers. The team tried to mitigate this problem by using gradient injection. Dr. Annable stresses that the issues of density override (when trying to sink flushing agents) and underride (when trying to displace flushing agents) will have to be examined further.

Comparison of the SPME and Cosolvent Studies

Dr. Annable concluded that the efficacy between the two methods is comparable. In terms of efficiency:

Dr. Annable notes that the issue of recycling and reusing surfactants/cosolvents should be resolved if either of these technologies is going to be used in a full-scale field study.

Surfactant With Mobility Control--Hill AFB's OU-2
Dr. Clarence Miller, Rice University

Dr. Miller's team's demonstration was similar to that conducted by Dr.Pope's team, with one novel exception: it incorporated mobility control via foam. Laboratory experiments analyzing the ability of a surfactant (Aerosol MA) to extract a DNAPL (TCE) in a heterogeneous environment (high permeability upper layer and low permeability lower layer) indicate that the surfactant does not effectively extract TCE from low permeability areas. By adding air to the laboratory test cells, and thereby creating a foam, the TCE is extracted more effectively and at a more constant rate. Using such a technology is very beneficial for Hill AFB's OU-2 because characterization studies indicate that many of the contaminants are in areas of low permeability.

Based on promising laboratory results, Dr. Miller's team initiated a study in the field. Their flushing agent was composed of 4 percent Aerosol MA and 11,500 parts per million of sodium chloride (NaCl). The NaCl was added to promote the formation of a third phase (see Dr. Sabatini's discussion). Although Dr. Pope's team found that the efficacy of their surfactant was increased when combined with a cosolvent, alcohols could not be used for Dr. Miller's demonstration because alcohols degrade foam. The team simultaneously injected air and three PVs of surfactant into the subsurface. At one point, the rate of air injection was decreased because the researchers were unsure how substantial pressure increases would impact injection wells; later, this fear was deemed unfounded and air injection rates were increased again. A lot of the air escaped and never reached subsurface targets, foam was observed in two monitoring wells, however, and was present at a range of depths (even the bottom foot above the clay layer). Dr. Miller's team completed work at OU-2 in April 1997 and, like the other presenters at this conference, has not had a chance to fully evaluate its data. Preliminary analysis indicates that DNAPL recovery exceeded that which was initially present, reflecting that the cell was not completely isolated from incoming DNAPL sources.

Surfactant Recovery--HILL AFB's OU-2
Dr. Jeffrey Harwell, University of Oklahoma

As was noted by several participants, efforts to recover and reuse surfactants are vital if in situ flushing technologies are going to be cost effective. Dr. Harwell explained that this AATDF project attempted to determine optimal recovery schemes for surfactant recovery and to determine under what conditions the recovery systems can be economically employed. Recovery involves two processes: 1) decontamination (separating the surfactant from contaminants), and 2) reconcentration (removing excess water). Previous studies indicate that it is economically advantageous to decontaminate entire waste streams before reconcentrating them. For heavy surfactants (molecular weight > 1,000), monomers might be recoverable through ultrafiltration; lighter molecules generally require multistage foam recovery processes. Challenges facing researchers trying to recover surfactants from an in situ flush include:

Dr. Harwell's team analyzed four different recovery processes:

Recovery System Pluses and Minuses for Recovery System
Packed column vacuum air stripping Low volume vapor stream is easy to treat
Often leads to foaming, causing the column to stop working
It only works for contaminants with sufficient vapor pressure
The system becomes inefficient as concentrations decrease
Columns are more expensive than air stripping
Packed column air stripping Inexpensive
Often leads to foaming, causing the column to stop working
It only works for contaminants with sufficient vapor pressure
The system becomes inefficient as concentrations decrease
Hollow fiber membrane air stripping Does not cause foaming
Liquid can bleed through pores
Air rate can be very high to get good mass transfer
It only works for contaminants with sufficient vapor pressure
The system becomes inefficient as concentrations decrease
Membranes are very compact
Membranes are very expensive
Liquid/liquid extraction in a hollow fiber membrane module No emulsions form
Water rate can be very high to get good mass transfer
Works for all contaminants that go into micelles, not just volatile ones
For good solvent, concentration dependence is less
Membranes are very compact
Membranes are very expensive
Oil must be environmentally acceptable
Oil must not solubilize in surfactant solution

In the laboratory, each of these recovery systems was tested for its ability to recover nonionic and anionic surfactants from a stream that also contained isobutylbenzene (IBB), PCE, and oil (squalene). The vacuum stripper foamed under all conditions, even when antifoam agents were added; the packed column air stripper did not foam as long as the liquid loading or the air/water ratios were kept low; the hollow fiber air stripper did not foam as long as the air pressure exceeded water pressure by 1 to 2 pounds per square inch absolute (psia). The liquid/liquid extraction system did not produce an emulsion and was the only system that readily stripped the lowest IBB and PCE concentrations.

After the lab studies were completed, the team decided that design criteria for recovery systems should be based on 90 percent removal rather than 99 percent because achieving the latter doubles recovery costs and is unnecessary since the material is just going to be reinjected back into the most contaminated part of the aquifer. This decision allows air stripping to be considered as an option, even with low volatility contaminants. Use of air stripping is preferable if it can be designed so that foaming does not occur. Packed column air stripping is preferable over membrane stripping because the latter is 40 percent more expensive.

After completing all lab work, the team conducted field scale demonstrations for the packed column air stripper and the hollow fiber membrane module using surfactant wastestreams generated by Hill AFB in situ flushing teams. They concluded the following:

Technology Practices Manual for Surfactants and Cosolvents
Dr. Thomas Simpkin, CH2M Hill

Dr. Simpkin presented the "Technology Practices Manual for Surfactants and Cosolvents," a document that he coauthored. He explained that this manual is not a guidance manual, research summary, or textbook. It is to be used as a tool for informed decision-making. Two editions are planned for this manual; the first has been completed and is available at RICEMANUAL/TOC.htm. Dr. Simpkin welcomes any comments on this draft and encourages new data to be submitted by July so that they can be incorporated into the second edition (scheduled for release in fall 1997). The manual provides a technical description and update to the current status of in situ flushing technology, information on hydrogeology and the basic mechanisms involved with flushing technologies, a stepwise approach to implementation (not to be confused with a protocol), and information on cost considerations. The section on cost estimates analyzes several different site scenarios.

Mr. Stephen Shoemaker, E.I. Dupont DeNemours & Company, Inc.

Mr. Shoemaker presented the results of a report, presented in October 1996, entitled "Economic Study of Surfactant-Enhanced Pump and Treat Remediation." The goals of this study were to:

The study evaluated a variety of variables such as volumes of PCE contamination, affected aquifer volumes, type of surfactant, surfactant concentration, pumping rate, remediation time, and solubilization versus mobilization. The following conclusions were drawn:

Ms. Laura Yeh, Naval Facilities Engineering Service Center (NFESC)

Ms. Yeh opened her discussion by explaining that the Navy is very interested in technologies that utilize surfactants because approximately 100 Navy sites are contaminated with DNAPL (e.g., TCE), and no available technologies have been proven to effectively remove DNAPL.

Ms. Yeh is leading an effort to test surfactant recovery processes. Her team's objective is to prove that surfactants can be recovered and reused, and that use of such a recycling system can significantly reduce the overall cost of using surfactants for subsurface remediation. The recovery system involves a combination of pervaporation and micellar-enhanced ultrafiltration (MEUF).

Like other researchers interested in promoting in situ flushing technologies, Ms. Yeh's team has faced several barriers, the largest of which has been finding a site where they can perform a demonstration. She considers the following characteristics to represent conditions of an "ideal" testing site:

Recently, the team has altered its strategy for finding a site and hopes that it will soon be successful. Once it has completed its demonstration it will conduct an economic analysis.

Mr. Tohren Kibbey, University of Michigan

Mr. Kibbey discussed a project being conducted by the University of Michigan, Michigan State, and Georgia Tech to investigate surfactant-enhanced aquifer remediation at the Bachman Road site in Michigan. The team has just initiated work and plans to characterize the site within the next year, perform a pilot study in 1998, and complete a full-scale demonstration by 2001. The team has not decided which surfactant will be used, but is planning to initiate surfactant screening tests after the site characterization is complete.


Mission Statement

Meeting members formulated a mission statement for this RTDF group:

To facilitate the development and implementation of in situ flushing technology for site remediation.

Identification of Action Items and Future Activities

A list of action items that need to be addressed by this RTDF group was generated. It was generally agreed that the different action items should be tied together under one "umbrella" project and that a document focusing on designing a conceptual, generic, large in situ flushing study should be created. The group expressed the opinion that creating a manual will force the group to address the majority of issues/needs that were discussed during the 2-day meeting, and it will foster the conduct of consistent demonstration projects. Five action areas will need to be further pursued to compile this document:

It was agreed that it would be most effective to split the participants into subgroups to work on these different areas. The two co-chairs plan to find out who is interested in each action item and to identify subteam leaders. Dr. Wood suggested setting deadlines to achieve certain goals. Dr. Pope suggested setting up an e-mail group so that RTDF members can update each other on their activities without having to physically meet.

The co-chairs tentatively set a date for the next meeting in September/October 1997. The goals for the next meeting are to formalize the mission and action plans. Dr. Pope recommended that the co-chairs outline a list of specific elements to be addressed under each subteam, e-mail it to everyone, allow people to comment on the list, and then incorporate the comments before the next meeting.

Other Issues

Other action items identified by participants include:

Attachment A

In Situ Flushing Action Team Meeting

The Ray Close Conference Room - Building 100
Hill Air Force Base, UT
May 8-9, 1997

Final Attendee List


Michael Annable*
Assistant Professor
Department of Environmental Engineering Sciences
University of Florida
217 Black Hall
Gainesville, FL 32611-2013
Fax: 352-392-3076
Mark Hasegawa
Operations Manager
Surbec Environmental
3200 Marshall Avenue - Suite 200
Norman, OK 73072
Fax: 405-366-1798
David Sabatini*
Associate Professor
School of Civil Engineering & Environmental Science
University of Oklahoma
202 West Boyd - Room 334
Norman, OK 73019
Fax: 405-325-4217
Phil Bedient
Environmental Science
and Engineering
Rice University
P.O. Box 1829
Houston, TX 77005
Fax: 713-285-5203
Bronson Hawley
Division of Solid and
Hazardous Waste
Utah Department of
Environmental Quality
P.O. Box 144880
Salt Lake City, UT 84114-4880
Fax: 801-538-6715
Tom Sale
Research Assistant
Colorado State University
Engineering Research Center B-17
Foot Hills Campus
Fort Collins, CO 80523
Fax: 970-491-8224
Raymond Bilbo
Market Manager
Oleo Chemical and Derivatives
Witco Corporation
One American Lane
Greenwich, CT 06831
Fax: 203-552-2890
George Hirasaki
Department of
Chemical Engineering
Rice University
6100 Main Street (MS 362)
P.O. Box 1892
Houston, TX 77005-1892
Fax: 713-285-5478
Roberta Schlicher
Montgomery Watson
4525 South Wasatch Boulevard
Salt Lake City, UT 84124
Fax: 801-273-0430
Kevin Bourne
U.S. Air Force - OO-ALC/EMR
7274 Wardleigh Road
Hill AFB, UT 84056-5137
Fax: 801-777-4306
Colin Johnston
Centre for Groundwater Studies
Council for Scientific and Industrial Research
Land and Water
Floreat Park Laboratory
Private Bag, PO Wembley, 6014
Tel: 61-9-3870328
Fax: 61-9-3878211
E-mail: colin.johnston@per.
Stephen Shoemaker*
Solid Waste & Geological Engineer
Engineering Department
DuPont Engineering
140 Cypress Station Drive
Suite 135
Houston, TX 77090
Fax: 281-586-2504
E-mail: shoemash@a1.bmoa.
Steve Brown
CH2M Hill, Inc.
4001 South 700 East - Suite 700
Salt Lake City, UT 84107
Fax: 801-281-2427
Tohren Kibbey
Graduate Student
Department of Civil &
Environmental Engineering
The University of Michigan
EWRE Building - Room 281
1351 Beal Road
Ann Arbor, MI 48109-2125
Fax: 313-763-2275
Mike Shook
Advisory Scientist
Environmental Laboratory
Idaho National Engineering
P.O. Box 1625
Idaho Falls, ID 83415-2107
Fax: 208-526-0875
Mark Brusseau*
Associate Professor of
Subsurface Hydrology
Soil and Water Science Department
Hydrology and Water
Resources Department
University of Arizona
429 Shantz Building - #38
Tucson, AZ 85721
Fax: 602-621-1647
John Kilbane
Senior Environmental Scientist
Institute of Gas Technology
1700 South Mount Prospect Road
Des Plaines, IL 60018
Fax: 847-768-0546
Thomas Simpkin*
Environmental Engineer
CH2M Hill
P.O. Box 241325
Denver, CO 80224
Fax: 303-754-0196
Chi-Chung Chang
Project Manager
Radian International, LLC
9801 Westheimer - Suite 500
Houston, TX 77042
Fax: 713-789-8404
Robert Knox*
School of Civil Engineering
& Environmental Science
University of Oklahoma
202 West Boyd - Room 334
Norman, OK 73019
Fax: 405-325-4217
Muhammad Slam
Division of Environmental Response
Utah Department
of Environmental Quality
168 North 1950 West - 1st Floor
Salt Lake City, UT 84116
Fax: 801-536-4242
Greg Davis
Project Leader
Centre for Groundwater Studies
Council for Scientific and
Industrial Research
Land and Water
Floreat Park Laboratory
Private Bag, PO Wembley, 6014
Tel: 61-8-93330386
Fax: 61-8-93878211
Richard Landgraf
Hydrogeology Group Leader
Environmental Restoration
Lawrence Livermore
National Laboratory
P.O. Box 808 - L-544
Livermore, CA 94550
Fax: 510-422-9203
Duane Smith
Leader, Innovative Technologies
Environmental Science
and Technology
Federal Energy Technology Center
U.S. Department of Energy
P.O. Box 880
Morgantown, WV 26507-0880
Fax: 304-285-4469
Deb Drain
Montgomery Watson
4525 South Wasatch Boulevard
Suite 200
Salt Lake City, UT 84124
Fax: 804-273-0430
Stephen LaRoche
Vice President
The Westford Chemical Corporation
P.O. Box 798
Westford, MA 01886
Fax: 508-832-2468
Richard Steimle*
Technology Innovation Office
U.S. Environmental
Protection Agency
401 M Street, SW (5102G)
Washington, DC 20460
Fax: 703-603-9135
Thomas Early
Oak Ridge National Laboratory
Building 3504 (MS-6317)
P.O. Box 2008
Oak Ridge, TN 37831-6317
Fax: 423-574-7420
E-mail: eot@ornl.go
George Losonsky
Project Manager
IT Corporation
One Lakeshore Drive - Suite 1810
Lake Charles, LA 70629
Fax: 318-436-3244
Robert Stites*
U.S. Environmental
Protection Agency
999 18th Street - Suite 500
Denver, CO 80202-2405
Robert Elliott*
U.S. Air Force - OO-ALC/EMR
7274 Wardleigh Road
Hill AFB, UT 84056-5137
Fax: 801-777-4306
Donald Lowe
AATDF Assistant
Program Manager
Energy and Environmental
Systems Institute
Rice University
6100 Main Street (MS 316)
Houston, TX 77005-1892
Fax: 713-285-5948
Daniel Stone
U.S. Air Force - OO-ALC/EMR
7274 Wardleigh Road
Hill AFB, UT 84056-5137
Fax: 801-777-4306
Carl Enfield*
Senior Research Scientist
National Risk Management
Research Laboratory
U.S. Environmental
Protection Agency
P.O. Box 1198
Ada, OK 74820
Fax: 405-436-8582
Bill Mabey
240 Aptos Place
Danville, CA 94526
Fax: 510-643-2076
Leland Vane
Chemical Engineer
National Risk Management
Research Laboratory
U.S. Environmental
Protection Agency
26 West Martin Luther King Drive
Cincinnati, OH 45268
Fax: 513-569-7677
Carol English
Cytec Industries
Foot of Trembley Point Road
Linden, NJ 07036
908-862-6000, Ext. 434
Fax: 908-862-4163
Hans Meinardus
Senior Hydrogeologist
Intera, Inc.
9111 Research Boulevard
Austin, TX 78758
Fax: 512-425-2099
E-mail: hwmeinar@dpcmail.
Barry Weissert
Western States BioSolve
17151 Newhope Street - Suite 201
Fountain Valley, CA 92708
Fax: 714-438-2217
Ronald Falta*
Associate Professor
Geological Sciences
Clemson University
Brackett Hall - Room 340C
P.O. Box 341908
Clemson, SC 29634-1908
Fax: 864-656-1041
Clarence Miller*
Department of Chemical Engineering
Rice University
6100 Main Street
Houston, TX 77005-1892
Fax: 713- 285-5478
Bill Wade
Department of Chemistry
and Biochemistry
University of Texas
Austin, TX 78712
Stephanie Fiorenza*
Research Scientist
Energy & Environmental
Systems Institute
Rice University
P.O. Box 1892 (MS 316)
Houston, TX 77251-1892
713-527-4700, Ext. 3338Fax: 713- 285-5948
Randy Parker
Environmental Engineer
Remediation and
Containment Branch
U.S. Environmental
Protection Agency
26 West Martin Luther King Drive
Cincinnati, OH 45268
Fax: 513-569-7571
Lynn Wood*
Robert S. Kerr Environmental
Research Laboratory
U.S. Environmental
Protection Agency
P.O. Box 1198
Ada, OK 74821
Fax: 405-436-8582
John Fountain
Department of Geology
University of Buffalo - SUNY
722 National Sciences
& Math Complex
Buffalo, NY 14260
716-645-6800, Ext. 3796
Fax: 716-645-3999
Gary Pope*
Department of Petroleum
& Geosystems Engineering
University of Texas
Austin, TX 78712
Fax: 512-471-9678
K. Yegorov
Environmental Science and Technology
Federal Energy Technology Center
U.S. Department of Energy
P.O. Box 880
Morgantown, WV 26507-0880
Fax: 304-285-4469
Jon Ginn*
U.S. Air Force - OO-ALC/EMR
7274 Wardleigh Road
Hill AFB, UT 84056-5137
Fax: 801-777-4306
P. Suresh Rao*
Graduate Research Professor
Inter-Disciplinary Program in Hydrologic Sciences
Institute of Food and
Agriculatural Sciences
University of Florida
2169 McCarty Hall
P.O. Box 110290
Gainesville, FL 32611-0150
Fax: 352-392-3902
S. Laura Yeh
Chemical Engineer
Technology Development Branch
Naval Facilities Engineering
Service Center
1100 23rd Avenue (ESC 411)
Port Hueneme, CA 93043-4370
Fax: 805-982-4304
Jeff Harwell*
School of Chemical
Engineering & Materials Science
University of Oklahoma
100 East Boyd - Room T335
Norman, OK 73019-0628
Fax: 405-325-5813
William Rixey
Assistant Professor
Department of Civil & Environmental Engineering
University of Houston
Cullen Engineering Building
4800 Calhoun (N117)
Houston, TX 77204-4791
Fax: 713-743-4260


Attachment B

Table 2: In Situ Flushing Case Studies
Location PRP/Sponsor/
Technical Team
Contaminant Flushing
Project Date
36 Beazer East Inc., Kearny, NJ Kay Environmental Creosote/coal tar Treated Site Groundwater 2
12 Bog Creek Farm, Howell Township, NJ VOCs Treated Site Groundwater 1994- 2
20 Canadian AFB Borden, Alliston, Ontario, Canada Canada AFB; SUNY Buffalo PCE Surfactants Completed NA
35 Chem-Dyne, Hamilton, OH Conestoga Rovers Association; Waterloo, Ontario, Canada As, benzo(a)pyrene, chlordane, dieldrin, hexachlorobenzene, PCBs, priority pollutant acid compounds, VOCs Tested Site Groundwater January 1988-
October 1992
19 Corpus Christi Dupont, Corpus Christi, TX Dupont Corporate Remediation Group; SUNY Buffalo Carbon tetrachloride Surfactant Completed 6
11 Cross Brothers Pall, Pembroke, IL VOCs (BTEX, PCE, TCE), PCBs 5
15 DOE Gaseous Diffusion Site, Portsmouth, OH DOE Morgantown Energy Technology Center, Morgantown, WV; Intera, Inc.; SUNY Buffalo; Univ. of Texas at Austin DNAPLs, TCE with some PCBs and other chlorinated solvents Surfactant Fall 1996- 5
32 Dover AFB, Dover, DE USAF DNAPLs Cosolvent/Surfactant Projected July 1997 3
39 Estrie Region Machining Shop, Quebec, Canada Ecosite Inc., Quebec City, Quebec, Canada Hydrocarbons, LNAPLs Nonionic Biodegradable Surfactant Completed NA
21 General Motors NAO Research & Development Center, Warren, MI GM NAO R&D Center, Warren, MI PCBs, oils Surfactant Completed 5
4 Goose Farm, Plumsted Twp., NJ VOCs, SVOCs, TCE, PAH Treated Site Groundwater 1993- 2
Hill Air Force Base, UT (Cell 3, OU1) Clemson University NAPLs Alcohol/Water Mixture Summer 1996- 8
3 Hill Air Force Base, UT (Cell 5, OU1) Univ. of OK-Institute for Applied Surfactant Research; USAF LNAPLs, VOCs, naphthalene, PEST, PCBs, dioxins, JP4 Surfactant
(Dowfax 8390)
Summer 1995- 8
Hill Air Force Base, UT (Cell 6, OU1) Univ. of OK NAPLs Surfactant
Dow (8390)
Summer 1996 8
Hill Air Force Base, UT (Cell 8, OU1) Univ. of Florida; DoD/AATD; Rice University NAPLs Surfactant/Brij 97
Summer 1996- 8
2 Hill Air Force Base, UT (OU2) Intera, Inc., Montgomery Corp., SUNY Buffalo; USAF BTEX, PCBs Ethanol/Water Mix Summer 1995- 8
1 Hill Air Force Base, UT (Test 1, OU1) EPA (RSKERL), Univ. of Florida BTEX, JP4, PEST, VOCs, SVOCs Ethanol/Water Mix March 1995- 8
27 Hooker Chemical/Ruco Polymer, NY Vinyl chloride, TCE, VOCs, SVOCs, PCBs Pre-design 2
22 JADCO-Hughes, Belmont, NC Benzene, PC, TCE, toluene, xylenes, PCBs, phenols, As, Cr, Pb Treated Site Groundwater Installed 4
28 Lee Chemical, Liberty, MO City of Liberty, State of Missouri TCE Untreated Site Groundwater Operational 7
5 Lipari Landfill, Putman, NJ CDM Federal Programs Corp., New York, NY VOCs, TCE, SVOCs, PAHs, chlorinated ethers (bis-2-chloroethyl ether) Operational 2
29 Montana Pole & Treating, Butte, MT Metals, PAHs, PCB, dioxin/furans Being installed 8
16 New Jersey (operating facility of a major U.S. corporation) NJ program for collaboration between NJ firms and universities VOCs, SVOCs, BTEX Nonionic Surfactant Began April 1995 2
8 Ninth Avenue Dump, Gary, IN Fluor Daniel GTI, Chicago, IL BTEX, TCE, PAH, phenols, lead, PCBs, total metals Treated Site Groundwater Complete 5
25 Ornet Corp., Hannibal, OH PCE, cyanide, fluoride, As, Sb, Be 5
23 Peak Oil Co./Bay Drum Co., Tampa, FL DeMaximus, Inc., Knoxville, TN; Parsons Engineering, Winter Park, FL BTEX, PAHs, PCE, As, Cr, Pb Additives Under Consideration Pre-design 4
26 Pester Refinery Co., El Dorado, KS VOCs, other organics, metals Pre-design 7
18 Picatinny Arsenal, NJ U.S. EPA Office of Exploratory Research; USGS; Univ. of Virginia TCE Surfactants
(Triton X-100)
Summer 1995- 2
13 Private wood treating site, Laramie, WY CH2M Hill, Denver, CO PAH, carrier oils Alkaline Agents, Polymer/Surfactants 10
24 Rasmussen's Dump, Brighton, MI DeMaximus Inc. VOCs, benzene, TCE, toluene, xylene, ketones, chlorinated hydrocarbons, phenols, metals, Cd, Pb Operational 5
38 Serrener/Varisco Consortium, CA Varisco SPA BTEX, aliphatic hydrocarbons Surfactant/Cosolvent Operational NA
33 Sindelfingen, Germany TCE Operational NA
34 Spiegelberg Landfill, Brighton, MI Ford/GM SVOCs, inorganics, metals, VOCs Operational 5
37 Tallon Metal Inc., Quebec, Canada Environmental Technology, Tallon Metals Technology, Inc. As Treated Site Groundwater Pre-design NA
Thouin Sand Quarry, Quebec, Canada Laval Univ., Quebec; Ministry of Environment and Fauna; GW Division of Canada DNAPLs Water/Polymer/ Surfactant/Bacteria
and Nutrients
1995- NA
17 U.S. Coast Guard Base, Traverse City, MI Univ. of OK-Institute for Applied Surfactant Research PCE, TCE, BTEX Fall 1994
30 Umatilla Army Depot (Lagoons), Hermiston, OR Design-U.S. Army Corp. of Eng., Seattle District; Constr.-ICF Kaiser, Richland, WA Explosives-TNT, RDX, TNB, HMX Treated Site Groundwater (considering Nutrient Addition) January 1997- 10
10 United Chrome Products, Corvallis, OR United Chrome Products; CH2M Hill Max. 19,000 mg/L Cr+6 City-supplied water Operational 10
6 Vineland Chemical, Vineland, NJ As Treated Site Groundwater Design in progress 2
Volk Air National Guard Base, WI EPA; U.S. Air Force Hydrocarbons, chlorinated hydrocarbons Surfactant Completed 5