5
Testing Remediation Technologies

Many major U.S. industries, such as the pharmaceutical and automotive industries, have standard protocols for testing new product performance. Such protocols are lacking in the hazardous waste site remediation industry. This lack of protocols contributes to the difficulties that remediation technology developers face in trying to convince potential clients that an innovative technology will work. Lacking performance data collected according to a standard protocol, clients may hesitate to choose an innovative remediation technology because of the uncertainty in how the innovative technology will perform in comparison to a conventional technology. The types of data collected for evaluating remediation technology performance vary widely and are typically determined by the preferences of the consultant responsible for selecting the technology, the client, and the regulators overseeing remediation at the contaminated site. From the perspective of the client and the service providers who are interested in solving the immediate problem in a cost-effective manner, such a site-specific strategy is justified. However, from the broader perspective required for remediation technology development and testing, the performance and cost data needed to meet site-specific objectives are often insufficient to extrapolate the results from one site to another.

As a result of the lack of standard procedures for remediation process testing, many of the early attempts at soil and ground water cleanup, especially at complex sites, served as poorly planned and very costly national experiments. Expensive remediation systems were installed to clean up sites with very little understanding of the mechanisms controlling their performance. The results of these efforts were evaluated to try to gain a better understanding of mechanisms governing remediation, but such evaluations were complicated by the lack of stan-



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Innovations in Ground Water and Soil Cleanup: From Concept to Commercialization 5 Testing Remediation Technologies Many major U.S. industries, such as the pharmaceutical and automotive industries, have standard protocols for testing new product performance. Such protocols are lacking in the hazardous waste site remediation industry. This lack of protocols contributes to the difficulties that remediation technology developers face in trying to convince potential clients that an innovative technology will work. Lacking performance data collected according to a standard protocol, clients may hesitate to choose an innovative remediation technology because of the uncertainty in how the innovative technology will perform in comparison to a conventional technology. The types of data collected for evaluating remediation technology performance vary widely and are typically determined by the preferences of the consultant responsible for selecting the technology, the client, and the regulators overseeing remediation at the contaminated site. From the perspective of the client and the service providers who are interested in solving the immediate problem in a cost-effective manner, such a site-specific strategy is justified. However, from the broader perspective required for remediation technology development and testing, the performance and cost data needed to meet site-specific objectives are often insufficient to extrapolate the results from one site to another. As a result of the lack of standard procedures for remediation process testing, many of the early attempts at soil and ground water cleanup, especially at complex sites, served as poorly planned and very costly national experiments. Expensive remediation systems were installed to clean up sites with very little understanding of the mechanisms controlling their performance. The results of these efforts were evaluated to try to gain a better understanding of mechanisms governing remediation, but such evaluations were complicated by the lack of stan-

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Innovations in Ground Water and Soil Cleanup: From Concept to Commercialization dardized data sets (National Research Council, 1994; EPA, 1992). In some cases, remediation systems, such as soil vapor extraction (SVE), proved successful despite the limited understanding. In other cases, however, such as with pump-and-treat systems, tens of millions of dollars were spent at individual sites to install systems that later proved unable to meet cleanup goals (National Research Council, 1994; EPA, 1992). Since the early 1990s, the Environmental Protection Agency (EPA) and other federal agencies have increasingly recognized the limitations of existing data on remediation systems and have taken steps to improve the consistency of data collection at contaminated federal sites. In 1995, the Federal Remediation Technologies Roundtable, a group of lead agency representatives involved in site remediation, issued guidelines for the collection of remediation cost and performance data at federal facilities (Federal Remediation Technologies Roundtable, 1995). Nevertheless, no standard process exists for data collection and reporting at privately owned contaminated sites, and the degree to which the Federal Remediation Technologies Roundtable guidelines are applied at federal facilities is unclear. The challenge for remediation technology development is to provide a framework and an infrastructure so that the individual benefits accruing to service providers and clients at specific sites, both federal and private, are gradually aggregated. Aggregation and critical review of data gathered according to standard protocols at numerous sites are essential for ensuring that the data are widely accessible to other technology developers and users, so that the success stories are not derived solely from anecdotes or unpublished reports. This chapter describes a set of general principles that should be applied when testing performance of remediation technologies. It outlines the types of data needed to prove the performance of different classes of technologies, how to choose an appropriate test site for a remediation technology, and how to determine the amount of additional testing required to evaluate whether a technology tested at one site is applicable at another site. It also recommends ways that policymakers and others can encourage standardization in the collection of data on remediation technology performance. DATA FOR PROVING TECHNOLOGY PERFORMANCE Commercialization is the process of increasing use of a technology to solve a particular problem. Those who are considering use of an innovative remediation technology early in the commercialization process must decide whether the benefit (performance) of the technology is commensurate with its risk (failure to attain regulatory requirements). Generally, the user's greatest concern is having to do more: apply the technology over a longer period, implement an additional technology, or abandon the innovative technology and apply a conventional one. Therefore, to commercialize a remediation technology, the technology developer

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Innovations in Ground Water and Soil Cleanup: From Concept to Commercialization must convince prospective users that the innovative technology will cost effectively solve their problems with minimal risk (cost) of failure. There are two approaches to minimizing the risk of using an innovative technology. The first is to guarantee performance. Such a guarantee requires assumption of financial risks or of residual liability. If the technology fails, the seller of the technology assumes the cost of meeting the remedial goals or the liability for noncompliance. To be able to offer the guarantee, the seller must have sufficient assets to make the guarantee credible. Given their limited financial resources, this is not possible for many technology developers. The second approach to minimizing the risk of using an innovative technology is to provide enough data so that the user is confident in the ability of the technology to provide the desired result. The data must be sufficient to verify the technology—that is, to prove its performance under a specific set of conditions with assurance of data quality. The data required to verify performance include proof that the technology works under field conditions and proof that the technology will be accepted by regulators. In order to prove that the technology works to the satisfaction of potential clients and regulators, the technology developer will need evidence to answer two fundamental questions: Does the technology reduce risks posed by ground water or soil contamination? That is, what are the levels of risk reduction achieved by implementing the technology? How does the technology work in reducing these risks? That is, what is the evidence proving that the technology was the cause of the observed risk reduction? As described in Chapter 4, remediation technologies reduce risk by decreasing the mass, concentration, mobility, and/or toxicity of contaminants in the subsurface. Direct measurements showing decreases in one or more of these parameters are essential for proving technology performance, but they are not sufficient to prove that the technology was responsible for the observed decrease in contamination. For example, contaminant concentrations in ground water may decrease for a variety of reasons, including sorption of contaminants by soil or aquifer solids, dilution due to natural mixing with uncontaminated ground water, biodegradation by native soil microbes, or chemical reactions with substances naturally present in the subsurface. A cause-and-effect relationship between application of the remediation technology and observed decreases in contamination must be established by collecting data to answer the second question, how does the technology work? Without answering this question and understanding the mechanisms responsible for performance of the technology, the technology design cannot be optimized, and the technology cannot be reliably transferred to other sites. In the past, technology tests have rarely been performed using protocols that answer this second question. This failure to gather evidence to explicitly

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Innovations in Ground Water and Soil Cleanup: From Concept to Commercialization link performance to remedial process has slowed regulatory acceptance and site-to-site transfer of innovative remediation technologies. Demonstrating Risk Reduction Achieved by the Technology To answer the question of whether the remediation technology works in reducing health and environmental risks, field tests are required to determine the reductions in contaminant mass, concentration, toxicity, and/or mobility achieved after application of the technology. Demonstrating reductions in all four risk measures—mass, concentration, toxicity, and mobility—is not necessary. Rather, the technology evaluation should provide two or more types of data leading to the conclusion that the technology has succeeded in decreasing one or more of the four risk measures. Which measure is appropriate depends on the remediation end points that the technology is designed to achieve. Contaminant concentrations in the field following application of a remediation technology are readily determined by analyzing ground water samples from monitoring wells and soil samples from soil cores according to standard procedures. Likewise, decreases in contaminant mobility can be documented through standard tests that analyze contaminant leachability (although these tests are sometimes misapplied). However, documenting reductions in contaminant mass and toxicity is more challenging. Quantifying contaminant mass in the subsurface, both before and after remediation, can present a significant challenge due to the complex distribution of contaminants among different phases (dissolved, sorbed, nonaqueous liquid, or solid) in both the horizontal and vertical directions. Contaminant mass is typically estimated based on concentration data from monitoring wells and soil core samples and on an estimation of the volume of contaminated material (mass equals concentration multiplied by volume). For example, in a field experiment to evaluate intrinsic remediation of petroleum hydrocarbons, the mass of hydrocarbons remaining in the subsurface at any given time was estimated by integrating concentration data from a network of monitoring wells over the contaminated area (Barker et al., 1987). However, although contaminant concentration and contaminant mass are closely linked and although contaminant mass is usually estimated based on measures of concentration, a reduction in contaminant concentration does not always signal a reduction in contaminant mass. Contaminant concentrations may decrease due to a manifestation of rate-limiting mass transfer phenomena or due to dilution with uncontaminated waters, while the total mass of contaminants remains essentially the same. The uncertainties associated with estimating total contaminant mass based on concentration data from discrete sampling locations at a heterogeneous site are often not reported. Determining the toxicity of contaminants in the field is likewise difficult because of the cost and complexity of the studies required to link contaminant exposure to human health and ecological damage. The actual toxicity of contami-

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Innovations in Ground Water and Soil Cleanup: From Concept to Commercialization nants to both human health and ecosystems can be measured only through long-term studies that assess the health and ecological impacts of contaminants. Such studies exist for some contaminants but not for others (see Chapter 4). An alternative for contaminated material that has been solidified or stabilized is to use leaching tests that analyze for toxic compounds in water that might leach through the solidified or stabilized material. Test methods for assessing the toxicity of leaching water include the extraction procedure toxicity test and the toxicity characteristic leaching procedure (EPA, 1989). Methods for measuring decreases in contaminant mass and concentration differ somewhat depending on whether the remediation technology is designed to stabilize or contain contaminants, or to extract or destroy them. For stabilization and containment technologies, decreases in mobile contaminant mass should be determined by analyzing the amount of contamination available for transport to zones of natural ground water flow; for all other types of technologies, decreases in mass should be determined by analyzing the amount of mass remaining within the zone of remediation. For stabilization and containment technologies, effects on contaminant concentration should be determined by analyzing concentrations outside the zone of remediation, while for other types of technologies concentration or mass decreases should be measured inside the zone of remediation. Demonstrating How the Technology Works The second type of evidence needed to prove innovative remediation technologies—the cause-and-effect evidence—comes from data that link the basic risk reduction criteria with the technology being tested. The goal of collecting these data is to show that the physical, chemical, and biological characteristics of the site change in ways that are consistent with the processes initiated by the technology. Table 5-1 outlines, for each remediation technology subgroup identified in Chapter 3, the environmental conditions that can be monitored to establish the cause-and-effect linkage between remediation and the applied technology. Carrying out many of the tests summarized in Table 5-1 will require the use of experimental controls. Experimental controls compare the differences in various site characteristics with and without application of the technology. The selection and use of controls in remediation technology testing are perhaps the most important factors in determining the success or failure of the experiment. Without good controls, it will be impossible to determine whether changes in site characteristics were a result of the technology application or of some other cause. Table 5-2 describes several control strategies that can be used to help determine which observed changes are a result of the remediation technology and which are not. Box 5-1 provides an example of experimental controls used to test a bioventing process. The complexities of the subsurface and remediation technologies make computer models a useful tool for analyzing and generalizing results of remediation

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Innovations in Ground Water and Soil Cleanup: From Concept to Commercialization TABLE 5-1 Data to Establish Cause-and-Effect Relationship Between Technology and Remediation Stabilization/Solidification/Containment Technologies Biological Reaction Technologiesa • Mechanism for decreased leachability - Formation of insoluble precipitate - Strong sorption/bonding to solids - Vitrification, cementing, encapsulation • Stoichiometry and mass balance between reactants and products • Increased concentrations of intermediate-stage and final products • Integrity of stabilized material - Completeness of processes throughout treated region - Compressive strength of solidified material - Reaction to weathering (e.g., wet/dry and freeze/thaw tests) - Reaction to changes in ground water chemistry - Microstructural analyses of composition • Increased ratio of transformation product to reactant • Decreased ratio of reactant to inert tracer (or, in general, decreased ratio of transformable to nontransformable substances) • Increased ratio of transformation product to inert tracer (or, in general, increased ratio of transformation product to nontransformable substances) • Geochemical conditions that affect leachability of stabilized materials (pH, Eh, competing ions, complexing agents, organic liquids, etc.) • Relative rates of transformation for different contaminants consistent with laboratory data • Increased number of bacteria in treatment zone • Increased number of protozoa in treatment zone • Increased ratio of immobile- to mobile-phase contaminants • Increased inorganic carbon concentration • Changes in carbon isotope ratios (or, in general, in stable isotopes consistent with the biological process) • Fluid transport properties of solidified material - Permeability - Porosity - Hydraulic gradient across monolith - Rate of water flow through monolith • Decreased electron acceptor concentration • Increased rates of bacterial activity in treatment zone • Bacterial adaptation to contaminant in treatment zone • Indicators of liquid/gas flow field consistent with technology (i.e., indication that treatment fluids have been stabilized or contained region is blocked) • Indicators of liquid/gas flow field consistent with technology (i.e., indication that flow through the successfully delivered to the contaminated area a For further details about proving performance of biological reaction technologies, see National Research Council, 1993. experiments. Whenever possible, computer simulation models should be used to plan and evaluate experiments to establish the link between observed remediation and the technology. Computer simulation models use mathematical equations to track the mass of contaminants in the subsurface. They describe how the contaminant mass is partitioned among aqueous and nonaqueous phases; how much is transported with the ground water, as a non aqueous-phase liquid (NAPL), or as a gas; how much reacts with other chemicals and with aquifer materials; how much degrades by biological or chemical reactions; and how each of these processes is affected by the introduction of a remediation technology. Simulations can be used in many ways in remediation technology evaluation. One approach is to use models to predict the behavior of contaminants under natural conditions and compare it with contaminant behavior during and following application of the remediation technology. A second approach is to use models to evaluate the sensitivity of soil or ground water quality variables to introduction of the remediation technology by simulating how those variables differ under natural and remediation conditions. A third approach is to use the model to quantify the uncertainty in various types of data, allowing the user to evaluate the trade-offs between information, cost, and uncertainty when using different types of data. A final approach is to use models to determine the optimal experimental design to maximize information content of data while minimizing cost and uncertainty.

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Innovations in Ground Water and Soil Cleanup: From Concept to Commercialization Chemical Reaction Technologies Separation/Mobilization/Extraction Technologies • Stoichiometry and mass balance between reactants and products • Increased concentration (mass) of contaminant in outflow stream • Increased concentrations of transformation products • Decreasing mass of contaminants remaining in subsurface consistent with mass extracted in outflow stream • Increased concentrations of intermediate-stage products • Increased mass removal per unit volume of transport or carrier fluid • Increased ratio of transformation product to reactant • Increased ratio of contaminants in carrier fluid to aqueous-phase contaminants • Decreased ratio of reactant to inert tracer (or, in general, decreased ratio of transformable to nontransformable substances) • Increased ratio of contaminants in carrier fluid to non-aqueous-phase contaminants • Increased ratio of transformation product to inert tracer (or, in general, increased ratio of transformation product to nontransformable substances) • Observed movement of injected carrier fluids (flushing amendments or injected gases) or tracers in carrier fluids• • Relative rates of transformation for different contaminants consistent with laboratory data Changes in geochemical conditions, consistent with treatment reactions (pH,Eh,etc.) • Spatial distribution of contaminants prior to, during, and after remediation • Indicators of liquid/gas flow field consistent with technology (i.e., indication that treatment products have been successfully delivered to the contaminated material) • Indicatiors of liquid / gas flow field consistent with technology affected by the introduction of a remediation technology. Simulations can be used in many ways in remediation technology evaluation. One approach is to use models to predict the behavior of contaminants under natural conditions and compare it with containment behaviour during and following application of the remediation technology. A second approach is to use models to evaluate the sensitivity of soil or ground water quality variables to introduction of the remediation technology by simulating how those variables differ under natural and remediation conditions. A third approach is to use the model to quantify the uncertainty in various

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Innovations in Ground Water and Soil Cleanup: From Concept to Commercialization Table 5-2 Experimental Controls for Improving Technology Evaluation Method Purpose Collection of baseline data Collection of accurate baseline data is the most basic type of experimental control and is essential to the success of the technology test. Without excellent baseline data, it will not be possible to develop an accurate comparison of conditions before and after application of the technology. Controlled contaminant injection In controlled contaminant injection, ground water from the site is spiked with the contaminants under consideration and re-injected into the aquifer. Therefore, the initial makeup, mass, location, and distribution of contaminants in the subsurface are known. Under these controlled conditions, the contaminant can be more easily and accurately tracked and monitored to determine the effect of the remediation technology. Conservative tracers Conservative tracers do not undergo the reactions associated with in situ reactive technologies. However, they are subject to a number of nonreactive processes that flow paths, flow rates, mixing, affect and retention of contaminants. Therefore, conservative tracers can be used to distinguish remediation resulting from the treatment process from that which occurs naturally. Partitioning tracers Partitioning tracers provide an indication of the total mass and spatial distribution of nonaqueous-phase liquids (NAPLs). They can be used to compare NAPL mass and spatial distribution prior to technology application with NAPL mass and distribution after remediation. Thus, they allow evaluation of NAPL removal and spatial patterns using a nondestructive technique. Sequential start-and-stop testing By alternating technology application and resting periods, the contaminant's fate can be observed under both natural conditions and remedial conditions. In this way the effects of the technology can be separated from remediation caused by naturally occurring processes. In addition, the start-and-stop approach can be used to distinguish between dynamic and equilibrium processes. Side-by-side and sequential application of technologies Side-by-side testing of two or more technologies at one site can be used to compare the capabilities of different technologies for the same hydrogeologic and contaminant setting. As an alternative, technologies can be applied sequentially at the same site to determine the marginal effectiveness of one technology over another. Untreated controls Untreated controls can help distinguish between technology-enhanced remediation and intrinsic remediation that occurs as a result of naturally occurring processes. The use of untreated controls is analogous to side-by-side testing with one of the remediation technologies being intrinsic remediation. Systematic variation of technology's control parameters The effect of changes in a technology's operating conditions on remediation can be determined by systematically changing control parameters. Ideally, this approach would be used to identify a technology's optimal operating conditions.

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Innovations in Ground Water and Soil Cleanup: From Concept to Commercialization BOX 5-1 Use of Experimental Controls: Evaluating Bioventing at Hill and Tyndall Air Force Bases At Hill Air Force Base in Utah and Tyndall Air Force Base in Florida, spills of JP-4 jet fuel have caused soil and ground water contamination. To demonstrate the capabilities of bioventing, the U.S. Air Force Center for Environmental Excellence sponsored field tests to evaluate the technology, which delivers oxygen to contaminated soils to stimulate contaminant biodegradation (Hinchee and Arthur, 1991; Hinchee et al., 1992). Prior to the field tests at Hill and Tyndall, laboratory tests had shown that the addition of both moisture and nutrients may be needed to support continued contaminant biodegradation in bioventing systems. The field tests at both sites used experimental controls to quantify the effects of moisture and nutrient additions. At Hill, the bioventing system's parameters were sequentially varied to determine bioventing's effectiveness under different operating conditions. By operating the bioventing system first with no added moisture or nutrients, then adding moisture, then adding nutrients, researchers found that moisture addition stimulated biodegradation, but nutrient addition did not. At Tyndall, researchers used two side-by-side test cells to analyze the effects of moisture and nutrients. One cell received moisture and nutrients for the duration of the study. The other cell received neither moisture nor nutrients at the outset, then moisture only, then moisture and nutrients. In this case, no significant effect of either moisture or nutrients was observed. Researchers surmise that the different results at the two field sites were most likely due to contrasting climatic and hydrogeologic conditions. The fact that the two sites reacted differently indicates the need for additional controlled experiments to better gauge the effects of moisture and nutrients on bioventing. types of data, allowing the user to evaluate the trade-offs between information, cost, and uncertainty when using different types of data. A final approach is to use models to determine the optimal experimental design to maximize information content of data while minimizing cost and uncertainty. In proving that a technology is responsible for documented remediation and establishing the extent and rate of remediation attributable to the technology, a single type of evidence alone will usually not be sufficient. The larger the body of evidence used, and the more varied the converging lines of evidence, the stronger the case for the performance of the remediation technology.

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Innovations in Ground Water and Soil Cleanup: From Concept to Commercialization Stabilization, Solidification, and Containment Technologies When evaluating the performance of stabilization and solidification technologies, the most important data are those documenting immobilization of the contaminants. Thus, as indicated in Table 5-1, samples that document the mechanisms for decreased leachability (such as formation of an insoluble precipitate or cemented monolith) provide evidence that the stabilization technology has worked. Related to this will be data documenting the integrity of the stabilized material, such as data that demonstrate that the stabilization process is complete throughout the treated region or, for solidified material, data that document the permeability, porosity, and rate of fluid flow through the solidified monolith. Other data, such as the solidified material's compressive strength or its reaction to weathering tests, are an indication of the materials' long-term stability. Stabilization, solidification, and containment technologies sometimes require certain environmental conditions to succeed. Properties such as pH, Eh, and concentrations of competing ions should be documented to show that geochemical conditions favor the stabilization processes at work. In addition, data can be collected to document changes in fluid flow fields that are consistent with the technology design. Box 5-2 provides a case example of the types of data gathered to document performance of one type of solidification/stabilization process in a successful field test. This example provides a useful model for tests of solidification, stabilization, and containment technologies at other sites. Biological and Chemical Reaction Technologies In the process of transforming or immobilizing contaminants, biological and chemical reactions alter the soil and ground water chemistry in ways that can be documented to prove that the reaction processes are taking place. The observed chemical changes should follow directly from the chemical equations that define reactants and products and their ratios. Thus, many cause-and-effect data for biological and chemical reaction processes are derived from mass balance relationships defined by governing chemical equations. Increased concentrations of transformation products, concentrations of intermediate and final products, and ratios of reactants to products all can be used to demonstrate performance of biological and chemical reaction technologies. Geochemical conditions should also change in ways that can be predicted from the governing chemical equations. For example, ignoring microbial growth, the stoichiometric relationship used to relate oxygen (O2) consumption and carbon dioxide (CO2) production to biodegradation of petroleum hydrocarbons is Cn Hm+ (n + 0.25m)O2→­nCO2 + (0.5m)H2O

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Innovations in Ground Water and Soil Cleanup: From Concept to Commercialization BOX 5-2 Proving In Situ Stabilization/Solidification of Polychlorinated Biphenyls (PCBs) at the General Electric Co. Electric Service Shop, Florida International Waste Technologies (IWT)/Geo-Con conducted a field study to demonstrate the ability of their stabilization/solidification process to treat PCB-contaminated soils (EPA, 1990). The IWT in situ process mixes water and a cement-based proprietary additive with the contaminated soil to immobilize and contain PCB contaminants in a solidified, leach-resistant monolith. A series of analyses was performed on samples from the demonstration site to document stabilization/solidification of the PCBs in the soil. The table below describes the types of data that were collected to (1) document immobilization of PCBs and (2) establish the cause-and-effect relationship between the stabilization/solidification process and the documented remediation. A careful comparison of treated and untreated soils, along with a careful analysis of baseline conditions, provided the experimental controls for this evaluation. Data Objective Type of Data Document PCB stabilization • Leach tests showing immobilization of PCBs   • Stabilized contaminant content of solidified soil Link PCB immobilization to cementation • Decrease in permeability of solidified material as compared to untreated soil   • High unconfined compressive strength of solidified material   • Documented integrity of solidified material under wet/dry weathering tests   • Microstructural analyses—optical microscopy, scanning electron microscopy, and X-ray diffraction—showing that the solidified mass is dense, homogeneous, and of low porosity, with no compositional variations in the horizontal and vertical directions. where CnHm represents a particular petroleum hydrocarbon. This equation can be used to determine how much O2 will be consumed and how much CO2 produced from the degradation of 1 mole (or 1 gram) of hydrocarbon or, conversely, how much hydrocarbon is degraded per mole of O2 consumed or CO2 produced. In other words, for every mole of O2 consumed per minute, 1/(n+0.25m) mole of

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Innovations in Ground Water and Soil Cleanup: From Concept to Commercialization The fact that lack of credible performance data limits selection of innovative remediation technologies is now well recognized. Several efforts to develop protocols to standardize the testing, data collection, and regulatory approval process for remediation technologies are under way. Box 5-12 summarizes current programs in three categories: those for standardizing data reporting procedures, those for creating a more uniform regulatory approval process, and those for verifying technology performance. In the first category is the Federal Remediation Technologies Roundtable guide that federal agencies are to use in documenting cost and performance of remediation technologies. In the second category are programs by the western states, southern states, a six-state consortium, and Massachusetts to increase the level of regulator confidence in data on innovative remediation technology performance. In the third category are the SITE program (the oldest program for remediation technology verification) and the California Environmental Protection Agency Technology Certification Program. Although the programs listed in Box 5-12 offer opportunities to report remediation technology performance data, independently verify these data, and specify steps necessary for regulatory approval of innovative remediation technologies, the existence of such a wide variety of programs in itself creates confusion for remediation technology developers and purchasers. Limited efforts to standardize the format for reporting cost and performance data under these various programs are under way, but nevertheless the different programs have different procedures for participation. Thus, the existence of these programs can exacerbate the problems faced by technology vendors in deciding which types of performance data to collect. Furthermore, the programs are voluntary and are not always accepted by agencies other than the ones participating in the program. Having a technology included in one of these programs may not provide a sales advantage except in the limited universe of sites under the jurisdiction of the agencies involved in the program. The costs of collecting all the data necessary for participation can be high, and technology developers may have to disclose company "secrets" in the process. Without the promise of a large market to make up for these costs, it is likely that very few companies will participate in the programs, except perhaps California's, which has a relatively large, well-defined market. A uniform, widely used national program for testing and verifying the performance of new subsurface cleanup technologies is needed to provide a clear path for technology vendors to follow in planning how to prepare their technologies for the marketplace. The program should focus on verification of technology performance, meaning proving performance under specific conditions and providing assurance of data quality, rather than on certification, meaning guaranteeing technology performance. Because of the wide variation in contaminated sites, no technology can be guaranteed to achieve a given performance level at every site, and some degree of site-specific testing will always be required. However, having a uniform national protocol for reporting performance data and a mecha-

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Innovations in Ground Water and Soil Cleanup: From Concept to Commercialization BOX 5-12 Testing, Verification, and Regulatory Approval Programs for Remediation Technologies Data Collection and Reporting Protocols Federal Remediation Technologies Roundtable Guide to Documenting Cost and Performance for Remediation Projects: The Federal Remediation Technologies Roundtable, a consortium of federal agencies involved in cleaning up hazardous waste sites, in 1995 published a guide specifying standard formats for documenting the performance of site cleanup technologies (Federal Remediation Technologies Roundtable, 1995). Agencies are required to use the guide to prepare cost and performance reports for Superfund sites on federal lands (Luftig, 1996). For information, contact the EPA's Technology Innovation Office, (703) 308-9910. Regulatory Approval Protocols Interstate Technology and Regulatory Cooperation (ITRC) Working Group: The ITRC, a group initiated by the Western Governors Association, is developing regulatory approval protocols for several classes of hazardous waste remediation technologies. Most of the 27 states participating in the ITRC work group have agreed to accept remediation technology test results from other states if the tests are conducted according to the protocols the ITRC is developing. For information, contact the Western Governors Association, (303) 623-9378, or the ITRC's World Wide Web site, http://www.gnet.org/gnet/gov/interstate/itrcindex.htm. Southern States Energy Board Interstate Regulatory Cooperation Project for Environmental Technologies: The Southern States Energy Board is working to develop compatible regulations for environmental technologies in southern states. The project began with a pilot demonstration of data management and integration technologies in South Carolina and Georgia. For information, contact the Southern States Energy Board, (770) 242-7712. Six-State Partnership for Environmental Technology: Six states (California, Illinois, Massachusetts, New Jersey, New York, and Pennsylvania) in 1995 signed a memorandum to develop a process for the reciprocal evaluation, acceptance, and approval of environmental technologies. The partnership has begun this effort with pilot projects to review 12 different environmental technologies, including several for use in contaminated site remediation. For information, contact the New Jersey Office of Innovative Technology and Market Development at (609) 984-5418.

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Innovations in Ground Water and Soil Cleanup: From Concept to Commercialization Massachusetts Strategic Envirotechnology Partnership (STEP): STEP is a recently initiated program to promote use of new environmental and energy-efficient technologies in Massachusetts. Under the program, the state provides opportunities to pilot test technologies on state properties or at state facilities. The STEP program also helps expedite regulatory review and permitting of new environmental technologies using a team of innovative technology coordinators. In addition, it provides all technology developers in the program with a business plan review, including assistance in identifying potential markets and sources of funding. For information, call the Massachusetts Office of Business Development, (617) 727-3206. Technology Performance Verification Protocols Superfund Innovative Technology Evaluation (SITE) Program: The first program for testing the performance of ground water and soil cleanup technologies, SITE was established in 1986 in response to a congressional mandate in the Superfund Reauthorization Act and Amendments (SARA) of 1986. SARA called for an "alternative or innovative treatment technology research and demonstration program." SITE is run by the EPA's National Risk Management Research Laboratory in Cincinnati. Under the program, EPA funds a select number of technology demonstrations each year. Technology developers can apply to have their technology tested under the SITE program by responding to an annual request for proposals. Developers pay for technology installation and operation costs; EPA pays for data collection and analysis. The SITE program, which has been criticized for failing to provide a market advantage to technologies that pass through it, received no funding in 1996, but funding was reinstated at $6 million in 1997. For information, contact the SITE program, (513) 569-7697. California Environmental Protection Agency (CalEPA) Technology Certification Program: In 1994, CalEPA established an environmental technology certification program in response to a mandate from the state legislature, specified in Assembly Bill 2060. The program will eventually provide mechanisms to certify all types of environmental technologies used in the state. The state's goal is to streamline the regulatory acceptance process for new environmental technologies and to increase customer confidence in performance data. The program began with a series of pilot tests to certify performance of a range of pollution prevention and environmental monitoring technologies. For information, contact CalEPA's Department of Toxic Substances Control, Office of Pollution Prevention and Technology Development, (916) 324-3823.

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Innovations in Ground Water and Soil Cleanup: From Concept to Commercialization nism for reviewing the validity of the data would increase client and regulatory acceptance of credible performance data and would enable credible defense of the choice of an innovative remedy in courts of law. It would also facilitate the extrapolation of data from one site to another. The SITE Program, the only national program available for verifying remediation technology performance, has inadequate breadth, funding, and recognition to provide the needed level of remediation technology performance validation. Verification of remediation technology performance should require reporting of data in the two categories described earlier in this chapter: (1) data showing that the technology works in reducing risks posed by specific contaminants under specific site conditions and (2) data linking the observed risk reduction with the technology. At least two types of evidence should be provided for each of these categories. The application for verification should provide a data summary sheet similar to the reports shown in Boxes 5-2, 5-3, 5-4, and 5–5. It should also specify the range of contaminant types and hydrogeologic conditions for which the technology is appropriate, and separate performance data should be provided for each different type of condition. Performance data should be entered in the coordinated remediation technologies data bases recommended in Chapter 3. Three possible types of organizations could serve as the center of the verification program: EPA: The EPA SITE Program could be greatly expanded to allow for verification of a wide range of remediation technologies. Verification could be provided by EPA staff or contractors at EPA laboratories. Third-party franchise: A third-party center (under the direction of a private testing organization or professional association) could work with technology developers to establish test plans and conduct tests in the field or at a test facility, as appropriate. Staff of the center would evaluate the results and submit a verification report to the EPA. Nonprofit research institute: A nonprofit research institute affiliated with a university could establish technology evaluation protocols, either independently or based on guidelines from the EPA and other agencies. It could franchise other laboratories to assist with the testing and to evaluate results. These laboratories would then submit results to the institute for verification. Regardless of which type of entity is responsible for verification, establishing a credible, widely used testing process will be essential. Questions regarding data acquisition, quality assurance and control, and appropriate measures of success would all need to be addressed. Whether data provided by the technology developer would be allowed in the verification process, or whether the data would need to be generated by an independent organization, would need to be established. The relative value of retrospectively and prospectively acquired data would need to be established. Roles of stakeholders (see Chapter 4) in the verification

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Innovations in Ground Water and Soil Cleanup: From Concept to Commercialization process would need to be defined. Incentives would need to be developed to participate in and use data produced by the program. The verification program should be launched with a series of small pilot projects involving a variety of technology types, environmental media, and technology developers. The pilot programs would assist in checking whether the test protocols are adequate and in determining quality assurance and control procedures. In the pilot programs, technology vendors would draft a technology test plan in conjunction with the verification entity, which would either test the technology directly or oversee tests conducted by others. Verification of the results (or a decision not to verify the results) by the verification entity would follow. DATA SHARING THROUGH GOVERNMENT AND INDUSTRY PARTNERSHIPS Private industries and government agencies "own" similar subsurface contamination problems. Yet, as discussed in this chapter, companies and agencies can be reluctant to accept remediation technology performance data generated by another company or agency. In addition to encouraging data acceptance through a verification program, sharing of data could be encouraged by forming technology testing and development partnerships including government agencies and a number of private companies. Such partnerships would, in the long run, provide cost savings to participating companies and agencies because they would leverage technology testing costs across a group of organizations so that no one organization would bear the entire cost. One such partnership, the Remediation Technologies Development Forum (RTDF) already exists. The RTDF is an EPA-facilitated umbrella organization established in 1992. Through the RTDF, government and industry problem "owners" meet periodically to share information about problems of mutual concern and work together to find solutions (EPA, 1996b). The RTDF is currently supporting $20 million in work effort. Several formal RTDF teams are in place to develop innovative remediation technologies, and the RTDF is considering establishing more such teams (Kratch, 1997). The first RTDF team formed is known as the Lasagna Consortium(TM). Through this partnership, Monsanto, DuPont, General Electric, the EPA, and the Department of Energy (DOE) are cooperating to develop a process that uses electroosmosis (see Box 3-3 in Chapter 3) to move contaminated ground water from low-permeability formations to in situ treatment zones. The EPA is supplying research capabilities, and the DOE is supplying funding and a test site at its Paducah, Kentucky, facility. The industrial partners are supplying program management, basic laboratory development, and design and construction capabilities. A successful pilot test to prove the principles underlying the technology's performance was completed in 1996, and a much-refined scaleup using zero-valent iron

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Innovations in Ground Water and Soil Cleanup: From Concept to Commercialization reaction zones (see Chapter 3 and Box 5-6) to destroy trichloroethylene is in progress. A second RTDF team is investigating bioremediation of chlorinated solvents. The team consists of a consortium of six companies (DuPont, General Electric, Monsanto, Dow Chemical, ICI Zeneca, and Beak Consultants) working in partnership with the EPA, DOE, and Air Force. The consortium is investigating three different types of bioremediation: accelerated dechlorination, cometabolic bioventing, and intrinsic bioremediation. The DOE and Chlorine Chemical Council are providing funding, and the Air Force is providing test sites at the Dover, Delaware, Air Force Base. EPA is providing research in bioventing. The industrial partners are providing program management, laboratory studies, and design of the accelerated and intrinsic bioremediation protocols. Two pilot tests are under way, and work is being completed to select additional sites for a parallel series of pilot tests. Recently established RTDF teams are demonstrating passive-reactive barriers for treatment of chlorinated solvents, in situ technologies for treating metals, and in situ techniques for cleaning up contaminated sediment. The RTDF is also establishing additional teams to investigate surfactant flushing systems for the treatment of DNAPLs in ground water and phytoremediation for the treatment of organic contaminants in soils. The major driver behind the RTDF consortia is the desire to develop sound technologies that will reduce remediation costs to government and industry users. The close collaboration of those involved is leading to a shared understanding of the technologies. Participants hope that the effort will lead to early acceptance and application of the technologies, because three of the major stakeholders (technology users, developers, and regulators) are a party to the process. The EPA's participation has helped remove regulatory barriers to pilot testing. It is too early to determine whether the RTDF arrangement will lead to rapid commercialization of the technologies being tested under the program. However, many elements are in place to speed the technologies through the pilot testing phase. For example, if the lasagna process proves successful, it is scheduled for full-scale implementation at Paducah, meaning there is a guaranteed first client for the technology. While such industry and government partnerships may not solve all the problems associated with testing and commercialization of remediation technologies, they should be encouraged as a potentially effective means for involving major stakeholders in mustering national resources to find solutions. CONCLUSIONS The wide variation in protocols used to assess the performance of innovative technologies for ground water and soil remediation has interfered with comparisons of different technologies and evaluation of performance data. In part because of the lack of standard performance reporting procedures, owners of con-

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Innovations in Ground Water and Soil Cleanup: From Concept to Commercialization taminated sites and environmental regulators may hesitate to consider data from other sites in assessing whether an innovative remediation technology may be appropriate for their site. While a technology developer may invest large sums in conducting a field test to prove technology performance, potential clients may be hesitant to accept data from the field test if it was not carried out on the client's site and under the client's supervision. The problem of variability in remediation technology performance data is now well recognized by environmental regulators, and various federal and state agencies have made efforts to standardize data collection and reporting procedures. However, the efforts of these agencies have not been coordinated. They thus provide little assurance to technology developers that following the procedures will provide a net benefit to the developer. The developer may expend large sums on testing a technology according to one agency's procedures, only to learn that the procedures will not be accepted by another agency. Some degree of national standardization in processes used to evaluate the performance of innovative remediation technologies is needed to allow for greater sharing of information, so that experiences gained in remediation at one site can be applied at other sites. In addition, more opportunities need to be created for cooperative technology development partnerships including government, industry, academia, and other interested stakeholders to encourage sharing and acceptance of data. Recommendations To standardize performance testing protocols and improve the transferability of performance data for innovative remediation technologies, the committee recommends the following: In proving performance of an innovative remediation technology, technology developers should provide data from field tests to answer the following two questions: Does the technology reduce risks posed by the soil or ground water contamination? How does the technology work in reducing these risks? That is, what is the evidence proving that the technology was the cause of the observed risk reduction? To answer the first question, the developer should provide two or more types of data leading to the conclusion that contaminant mass and concentration, or contaminant toxicity, or contaminant mobility decrease following application of the technology. To answer the second question, the developer should provide two or more types of evidence showing that the physical, chemical, or biological characteristics of the contaminated site change in ways that are consistent with the pro-

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Innovations in Ground Water and Soil Cleanup: From Concept to Commercialization cesses initiated by the technology, using evaluation procedures such as those shown in Table 5-1. In deciding how much site-specific testing to require before approving an innovative remediation technology, clients and environmental regulators should divide sites into the four categories shown in Figure 5-3: (I) highly treatable, (II) moderately difficult to treat, (III) difficult to treat, and (IV) extremely difficult to treat. For category I sites, site-specific testing of innovative remediation technologies should be required only to develop design specifications; efficacy can be determined without testing based on a review of fundamental principles of the remediation process, properties of the contaminant and site, and prior experience with the technology. For category II sites, field pilot testing should be required to identify conditions that may limit the applicability of the technology to the site; testing requirements can be decreased as the data base of prior applications of the technology increases. For category III sites, laboratory and pilot tests will be necessary to prove efficacy and applicability of the technology at the specific site. For category IV sites, laboratory tests and pilot tests will be needed, and multiple pilot tests may be necessary to prove that the technology can perform under the full range of site conditions. All tests of innovative remediation technology performance should include one or more experimental controls. Controls such as those summarized in Table 5-2 are essential for establishing that observed changes in the zone targeted for remediation are due to the implemented technology. Failure to include appropriate controls in the remediation technology performance testing protocol can lead to failure of the test to prove performance. The EPA should establish a coordinated national program for testing and verifying the performance of new remediation technologies. The program should be administered by the EPA and implemented by either EPA laboratories, a private testing organization, a professional association, or a nonprofit research institute. It should receive adequate funding to include the full range of ground water and soil remediation technologies and to test a wide variety of technologies each year. A successful test under the program should result in a guaranteed contract to use the technology at a federally owned contaminated site if the technology is cost competitive. The program should be coordinated with state agencies so that a technology verified under the program does not require additional state approvals. Applications for remediation technology verification under the new verification program should include a summary sheet in standard format. The summary sheet should contain information similar to that presented in Boxes 5-2, 5-3, 5-4, and 5-5. It should include a description of the site at which the technology was tested, the evaluation methods used to prove technology performance, and the results of these tests. It should also include a table showing the types of data used to answer each of the two questions needed to prove technology performance.

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Innovations in Ground Water and Soil Cleanup: From Concept to Commercialization Applications for remediation technology verification should specify the range of contaminant types and hydrogeologic conditions for which the technology is appropriate. Separate performance data should be provided for each different major class of contaminant and hydrogeologic setting for which performance verification is being sought. Data gathered from technology performance tests under the verification program should be entered in the coordinated national remediation technologies data bases recommended in Chapter 3. Data should be included for technologies that were successfully verified and for those that failed the verification process. Technology development partnerships involving government, industry, academia, and other interested stakeholders should be encouraged. Such partnerships can leverage resources to speed innovative technologies through the pilot testing phase to commercial application. REFERENCES Annable, M. D., P. S. C. Rao, W. D. Graham, K. Hatfield, and A. L. Wood. In press. Use of partitioning tracers for measuring residual NAPLs: Results from a field-scale test. Journal of Environmental Engineering. Barker, J. F., G. C. Patrick, and D. Major. 1987. Natural attenuation of aromatic hydrocarbons in a shallow sand aquifer. Ground Water Monitoring Review (Winter):64–71. Benson, R. C., and J. Scaife. 1987. Assessment of flow in fractured rock and karst environments. Pp. 237–245 in Karst Hydrogeology: Engineering and Environmental Applications, B. F. Beck and W. L. Wilson, eds. Boston: A. A. Balkema. Cochran, W. G., and G. M. Cox. 1957. Experimental Design. New York: John Wiley & Sons. EPA (Environmental Protection Agency). 1989. Evaluation of Ground-Water Extraction Remedies, Volume 2: Case Studies. EPA/540/2–89/054b. Washington, D.C.: EPA. EPA. 1990. International Waste Technologies/Geo-Con In Situ Stabilization/Solidification, Applications Analysis Report. EPA/540/A5–89/004. Cincinnati, Ohio: EPA, National Risk Management Research Laboratory. EPA. 1992. Evaluation of Ground-Water Extraction Remedies: Phase II, Volume I-Summary Report. Publication 9355.4– 05. Washington, D.C.: EPA, Office of Solid Waste and Emergency Response. EPA. 1996a. Accessing the Federal Government: Site Remediation Technology Programs and Initiatives. EPA/542/B-95/006. Washington, D.C.: EPA. EPA. 1996b. Remediation Technologies Development Forum. 542-F-96-010. Washington, D.C.: EPA. EPA. 1996c. State Policies Concerning the Use of Surfactants for In Situ Ground Water Remediation. EPA-542-R-96-001. Washington, D.C.: EPA. ETI (EnviroMetal Technologies, Inc.). 1995. Performance History of the EnviroMetal Process. Internal Document. Guelph, Ont.: ETI. Federal Remediation Technologies Roundtable. 1995. Guide to Documenting Cost and Performance for Remediation Projects. EPA-542-B-95-002. Washington, D.C.: EPA. Feenstra, S., and J. A. Cherry. 1996. Diagnosis and assessment of DNAPL sites. In DNAPLs in Ground Water: History, Behavior, and Remediation, J. H. Pankow and J. A Cherry, eds. Portland, Ore.: Waterloo Press.

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Innovations in Ground Water and Soil Cleanup: From Concept to Commercialization Gillham, R. W. 1995. Resurgence in research concerning organic transformations enhanced by zero-valent metals and potential application in remediation of contaminated groundwater. In Preprints of Papers Presented at the 209th American Chemical Society National Meeting, Anaheim, Calif., April 2–7, 1995. Washington, D.C.: American Chemical Society, Division of Environmental Chemistry. Gillham, R. W., and S. F. O'Hannesin. 1994. Enhanced degradation of halogenated aliphatics by zero-valent iron. Ground Water 32:958–967. Gillham, R. W., D. W. Blowes, C. J. Ptacek, and S. F. O'Hannesin. 1994. Use of zero-valent metals in in-situ remediation of contaminated groundwater. Pp. 913–930 in In situ Remediation: Scientific Basis for Current and Future Technologies, W. G. Gee and N. R. Wing, eds. Columbus: Battelle Press. Hinchee, R. E., and M. Arthur. 1991. Bench-scale studies of the soil aeration process for bioremediation of petroleum hydrocarbons. Journal of Applied Biochemistry and Biotechnology 28/29:901–906. Hinchee, R. E., S. K. Ong, R. N. Miller, D. C. Downey, and R. Frandt. 1992. Test plan and technical protocol for a field treatability test for bioventing. Brooks Air Force Base, Texas: U.S. Air Force Center for Environmental Excellence. Jin, M., M. Delshad, V. Dwarakanath, D. C. McKinney, G. A. Pope, K. Seperhnoori, C. Tilburg, and R. E. Jackson. 1995. Partitioning tracer test for detection, estimation, and remediation performance assessment of subsurface nonaqueous phase liquids. Water Resources Research 31(5):1201–1211. Johnson, P. C., R. L., Johnson, D. Neaville, E. Hansen, S. M. Stearns, and I. J. Dortch. 1997. Do conventional monitoring practices indicate in situ air sparging performance? Pp. 1–20 in In Situ and On-Site Bioreclamation, 3rd Symposium. Washington, D.C.: American Chemical Society. Kratch, K. 1997. Consortium researches technologies to solve priority problems. Water Environment and Technology 9(2):32. Lahvis, M. A., and A. L. Baehr. 1996. Estimation of rates of aerobic hydrocarbon biodegradation by simulation of gas transport in the unsaturated zone. Water Resources Research 32(7):2231–2249. Laws, E. P. 1996. Letter to Superfund, RCRA, UST, and CEPP national policy managers, Federal Facilities Leadership Council, and brownfields coordinators on EPA initiatives to promote innovative technology in waste management programs. April 29. Washington, D.C.: EPA. Luftig, S. D. 1996. Documenting Cost and Performance Data for Site Remediation Projects: January 17 Memorandum. Washington, D.C.: EPA, Office of Solid Waste and Emergency Response. National Research Council. 1993. In Situ Bioremediation: When Does It Work? Washington, D.C.: National Academy Press. National Research Council. 1994. Alternatives for Ground Water Cleanup. Washington, D.C.: National Academy Press. Orth, W. S., and R. W. Gillham. 1996. Dechlorination of trichloroethene in aqueous solution using Fe. Environmental Science & Technology 30: 660–71. Rao, P. S. C., M. D. Annable, R. K. Sillan, D. P. Dai, K. Hatfield, W. D. Graham, A. L. Wood, and C. G. Enfield. In review. Field-scale evaluation of in situ cosolvent flushing for remediation of an unconfined aquifer contaminated with a complex NAPL. Water Resources Research. Roberts, P. V., G. D. Hopkins, D. M. Mackay, and L. Semprini. 1990. A field evaluation of in situ biodegradation of chlorinated ethenes: Part 1-Methodology and field site characterization. Groundwater 28:591–604. Semprini, L., P. V. Roberts, G. D. Hopkins, P. L. McCarty. 1990. A field evaluation of in situ biodegration of chlorinated ethenes: Part 2-Results of biostimulation and biotransformation experiments, Groundwater 28:715–727. Siegrist, R. L., O. R. West, M. I. Morris, D. A. Pickering, D. W. Greene, C. A. Muhr, D. D. Davenport, and J. S. Gierke. 1995. In situ mixed region vapor stripping in low-permeability media. 2. Full-scale field experiments. Environmental Science & Technology 29:2198–2207.

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Innovations in Ground Water and Soil Cleanup: From Concept to Commercialization Starr, R. C., J. A. Cherry, and E. S. Vales. 1993. Sealable joint sheet pile putoff walls for preventing and remediating groundwater contamination . In Proceedings of the Technology Transfer Conference. Toronto: Ontario Ministry of the Environment. Steinberg, D. M., and W. G. Hunter. 1984. Experimental design: Review and comment. Technometrics 26(2):71–97. Thomas, A. O., D. M. Drury, G. Norris, S. F. O'Hannesin, and J. L. Vogan. 1995. The in situ treatment of trichloroethene-contaminated groundwater using a reactive barrier—results of laboratory feasibility studies and preliminary design considerations. In Contaminated Soil '95, W. J. van den Brink, R. Bosman, and F. Arendt, eds. Amsterdam: Kluwer Academic Publishers. West, O. R., R. L. Siegrist, J. S. Gierke, S. W. Schmunk, A. J. Lucero, and H. L. Jennings. 1995. In situ mixed region stripping in low-permeability media. 1. Process features and laboratory experiments. Environmental Science & Technology 29:2191–2197.