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Allernatives for Ground Water Cleanup National Research Council Committee on Ground Water Cleanup Alternatives, Presented by Lynne Presto EXECUTIVE SUMMARY The United States currently faces a very large ground water contamination problem. Although the total number of contaminated sites is unknown, estimates of the total number of waste sites where ground water and soil may be contaminated range from approximately 300,000 to 400,000. Recent estimates of the total cost of cleaning up these sites over the next 30 years have ranged as high as $1 trillion. Several recent studies have raised troubling questions about whether existing technologies are capable of solving this large and costly problem. These studies focused on "pump-and-treat" systems, which involve installing wells at strategic locations to pump contaminated grouted water to the surface for treatment. Pump-and-treat systems are the most common technology for ground water cleanup in the United States. The studies indicated that pump-and-treat systems may be unable to remove enough contamination to restore the ground water to drinking water standards, or that removal may require a very long time, in some cases centuries. As a result of these studies, there is almost universal concern among groups with diverse interests in ground water contamination from government agencies overseeing contaminated sites to industries responsible for the cleanups, environmental groups representing affected citizens, and research scientists-that the nation might be wasting large amounts of money on ineffective remediation efforts. At the same time, many of these groups are concerned that the health of current or future generations may be at risk if contaminated ground water cannot be cleaned up to make it safe for drinking. To address these concerns, the National Research Council initiated a study of ground water cleanup systems. The goals of the study were to review the performance of existing pump-and-treat systems, to determine the performance capabilities of innovative cleanup technologies, to assess whether there are scientific and technological limits to restoring contaminated ground water, to consider the public health and economic consequences of contaminated ground water, and to provide advice on whether changes in national ground water policy are needed to reflect the limits of current technology. This report presents the findings of the National Research Council's study. The study was carried out by the Committee on Ground Water Cleanup Alternatives, appointed by the National Research Council to work under its Water Science and Technology Board and Board on Radioactive Waste Management. The committee consisted of recognized leaders in the fields of environmental engineering, hydrogeology, chemistry, epidemiology, environmental economics, and environmental law and policy. The findings of this report are based on the committee's review of original data from case studies, reports in scientific journals, presentations by experts outside the committee, evaluation of policy documents, and the extensive experience of committee members. D-101

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D-102 BARRIER TECHNOLOGIES FOR ENVIRONMENTAL MANAGEMENT COMPLEXITY OF TlIE CONTAMINATED SUBSURFACE Theoretically, restoration of contaminated ground water to Stinking water standards is possible. However, cleanup of contaminated ground water is inherently complex and will require large expenditures and long time periods, in some cases centuries. The key technical reasons for the difficulty of cleanup include the following: Physical heterogeneity: The subsurface environment is highly variable in its composition. Very often, a subsurface formation is composed of layers of materials with vastly different properties, such as sand and grave] over rock, and even within a layer the composition may vary over distances as small as a few centimeters. Because fluids can move only through the pore spaces between the grains of sand and grave! or through fractures in solid rock and because these openings are distributed nonuniformly, underground contaminant migration pathways are often extremely difficult to predict. Presence of nonaqueous-phase liquids (NAPL,s): Many common contaminants are liquids that, like oil, do not dissolve readily In water. Such liquids are known as NAPEs, of which there are two classes: light NAPEs (LNAPEs), such as gasoline, are less dense than water; dense NAPEs (DNAPLs), such as the common solvent trichioroethylene, are more dense than water. As a NAP L moves through the subsurface, a portion of the liquid will become trapped as small immobile globules, which cannot be removed by pumping but can dissolve in and contaminate the passing ground water. Removing DNAPEs is further complicated by their tendency, due to their high density, to migrate deep underground, where they are difficult to detect and where they may remain In pools that slowly dissolve in and contaminate the ground water. Migration of contaminants to inaccessible regions: Contaminants may migrate by molecular diffusion to regions Inaccessible to the flowing ground water. Such regions may be microscopic (for example, small pores within aggregated materials) or macroscopic (for example, clay layers). Once present within these regions, the contaminants can serve as long- term sources of pollution as they slowly diffuse back into the cleaner ground water. Sorption of contaminants to subsurface materials: Many common contaminants have a tendency to adhere to solid materials In the subsurface. These contaminants can remain underground for long periods of time and then be released when the contaminant concentration in the ground water decreases. Difficulties in characterizing the subsurface: The subsurface cannot be viewed in its entirety, but is usually observed only through a finite number of drilled holes. Because of the highly heterogeneous nature of subsurface properties and the spatial variability of contaminant concentrations, observations from sampling points cannot be easily extrapolated, and thus knowledge of subsurface characteristics is inevitably incomplete. Regardless of the remediation technology chosen, these inherent complexities pose major obstacles to ground water cleanup.

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APPENDIX~PAPERS PRESENTED PERFORMANCE OF CONVENTIONAL PUM:P-AND-TREAT SYSTEMS D-103 The committee found that at the majority of contaminated sites, the complex properties of the subsurface environment and the complex behavior of contaminants In the subsurface interfere with the ability of conventional pump-and-treat systems to achieve drinking water standards for contaminated ground water. The committee reviewed information from 77 sites where conventional pump-and-treat systems are operating. At 69 of the sites, cleanup goals have not yet been reached,~although it is possible that they will be reached at some of these sites In the future. The apparent success of remediation at the remaining eight sites suggests that In special circumstances, cleanup In a relatively short time period (less than a decade) may be possible. Capabilities of Pump-and-Treat Systems The performance of pump-and-treat systems depends directly on site conditions and contaminant chemistry. As the complexity of the site Increases, the likelihood that the pump- and-treat system will meet drinking water standards decreases. Table ES-1, developed by the committee and taken from Chapter 3 of this report, shows the relative ease of ground water cleanup as a fimction of contaminant chemistry and subsurface hydrogeology. The committee categorized the 77 sites listed In Appendix A according to the raking system shown in this table. The conditions categorized as 1 represent those that will be easiest to remediate, while those categorized as 4 will pose the greatest technical challenge, as shown by the committeets review ofthe77sites: Cleanup of sites in category 1: At sites with conditions categorized as 1 according to the table, well-designed pump-and-treat systems generally should be able to restore the ground water to drinking water standards. Such ideal site conditions are rare in the group shown In Appendix A. For example, of the 77 sites listed, only two are categorized as 1; the pump-and- treat system reached cleanup goals at one of these sites, a service station where gasoline leaked. Cleanup of sites in category 2: Cleanup of sites in category 2 to drinking water standards is also possible but is subject to greater uncertainties than at sites In category 1. For example, 14 of the sites in Appendix A are in category 2, but cleanup goals have yet to be achieved at 10 ofthese sites, although it is conceivable that goals will be reached in the future. Cleanup of sites in category 3: Cleanup of sites in category 3 to drinking water standards is possible but is subject to significant uncertainties; partial cleanup may be a more realistic scenario for many such sites. For example, of the 29 sites in Appendix A in category 3, cleanup goals have been achieved at only three All three sites were contaminated with gasoline, which biodegrades relatively rapidly, a characteristic that may have accelerated cleanup. Cleanup of sites in category 4: Cleanup of sites in category 4 to Linking water standards is unlikely. However, containing the contamination is likely to be possible at such sites. Cleanup goals have not been achieved at any of the 42 sites categorized as 4 In Appendix A.

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D-104 BARRIER TECHNOLOGIES FOR E~IRONMENTAL MANAGEMENT TABLE ES-1 Relative ease of cleaning up of contaminated groundwater as a function of hydrogeologic conditions and contaminant chemistry Contaminant Chemistry Strongly Mobile, Sorbed, Hydrogeology Dissolved Dissolved Strongly Separate Separate (degrades/ Mobile, (degrades/ Sorbed, Phase Phase volatilizes) Dissolved volatilizes) Dissolved LNAPL DNAPL Homogeneous, single layer 1a 1-2 2 2-3 2-3 3 Homogeneous, 1 1-2 2 2-3 2-3 3 multiple layers Heterogeneous, 2 2 3 3 3 4 single layer Heterogeneous, 2 2 3 3 3 4 multiple layers Fractured 3 3 3 3 4 4 aRelative ease of cleanup, where 1 is easiest and 4 is most difficult. Table ES-1 provides a useful framework for comparing the relative effectiveness of pump-and-treat systems for cleaning up sites with different hydrogeologic and contaminant characteristics. However, it is important to realize that the categories in the table are based on the experience of committee members and a review of preexisting data for sites shown in Appendix A, not on new quantitative analyses. Even more important, the feasibility of cleanup may vary across the site. A single site may contain some regions where difficult-to-extract contaminants remain and continue to dissolve into the ground water and other regions where chemicals are primarily dissolved and no significant long-term contaminant sources are present. The part of the site containing primarily dissolved contaminants might fit category 1 or 2 according to Table ES- 1, while the part of the site containing entrapped sources of contamination might fit category 3 or 4. Finally' when using a framework such as Table ES-1, it is important to realize that to some extent the feasibility of ground water cleanup depends on the cleanup goals. Returning the ground water to drinking water standards may not be possible at many sites. However, reaching less stringent goals such as cleaning up areas containing dissolved contaminants and installing ~ _ O . . ~ A. it- 1 _ ~ ~ it_ ~ u~ ~ ~;~1~ ~+ containment systems around areas with undissolvect contam~nams mat cannot oe-oe pOSSlUl~ dt most sites. Cleanup Times for Pump-and-Treat Systems Remediation by pump-and-treat systems is a slow process. Simple calculations for a variety of typical situations show that predicted cleanup times range from a few years to tens,

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APPENDIX~PAPERS PRESENTED D-105 hundreds, and even thousands of years. Some have advocated that ground water cleanup should be considered technically impracticable when the cleanup time is very long. Given the complex policy implications of this issue, the committee defers to the expert agencies in deciding what, if any, limits to set on cleanup time. However, the committee believes that it is important for regulators to recognize that to some extent, cleanup time can be influenced by system design. A system pumping at very low rates may have a very long predicted cleanup time, while one pumping at higher rates may have a shorter predicted cleanup time. In considering the issue of cleanup time, regulators must also be aware that estimating the cleanup time is difficult and is subject to a large number of uncertainties; typical methods used to calculate cleanup time often result in underestimates because they neglect processes that can add years, decades, or even centuries to the cleanup. CAPABILITIES OF ENTIANCED PUMP-AND-TREAT AND ALTERNATIVE TECHNOLOGIES Numerous innovative technologies exist that have the potential to improve significantly the efficiency of ground water cleanups, especially when technologies suited to specific types of contaminants or specific hydrogeologic environments are combined. While no known technology can ensure the achievement of health-based cleanup goals at complex sites, these innovations nevertheless have the potential to increase the effectiveness and reduce the costs of ground water cleanup. Some innovative technologies-including soil vapor extraction, air sparging, and in situ bioremediation of petroleum products-are already being implemented. However, the use of innovative cleanup methods has been limited by technical, institutional, and economic barriers. As a result, conventional pump-and-treat systems are used at approximately three-quarters of sites with contaminated ground water. For this report, the committee divided innovative technologies into two categories: enhanced pump-and-treat systems, which require the pumping of fluids, and alternative technologies, which do not require pumping. Enhanced Pump-and-Treat Systems Conventional pump-and-treat systems pump relatively large volumes of water with relatively low contaminant concentrations. Because of the slow rates of contaminant desorption and dissolution, these systems must displace many volumes of aquifer water to flush out contaminants. Conventional pump-and-treat systems are therefore an inherently inefficient method for removing contaminants, even if they are effective in some cases. The enhanced pump-and-treat systems listed in Table ES-2 improve the efficiency of contaminant removal and lessen pumping requirements under certain conditions. These technologies can enhance contaminant removal and destruction compared to conventional systems' but each requires pumping fluids (water, air, or water solutions) through the subsurface and will therefore have some of the same limitations as conventional pump-and-treat systems.

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D-108 BARRIER TECHNOLOGIES FOR ENVIRONMENTAL MANAGEMENT Alternative Technologies Conventional pump-and-treat systems and the enhancements listed in Table ES-2 require a continuous energy input for pumping water or air. The alternative approaches listed in Table ES-3 do not require a continuous energy input and therefore may be less costly. These methods show promise, but they are in the development stage, and their long-term effectiveness has not yet been demonstrated. in addition, some of these methods contain, rather than clean up, the contamination, and the methods that do result In cleanup may be much slower than the more energy-intensive approaches. Barriers to Implementing Enhancements and Alternatives A variety of barriers have discouraged those involved in ground water cleanup from assuming the risks associated with using innovative technologies that lack proven track records. The most significant barriers include the following: allocation of liability if a technology fails; inability to raise sufficient capital for successful commercialization; lack of vendors for some innovations, federal regulations specifying that any contractor involved in the selection or testing of a technology is ineligible for construction; lack of testing facilities; lack of cost and efficiency information; lack of adequate technical expertise among consultants and regulators; and the requirement to construct a pump-and-treat system if the innovative technology fails to achieve cleanup goals. While the Environmental Protection Agency (EPA), the Department of Energy, the Department of Defense, and others are implementing programs to remove these barriers, the cumulative effectiveness of these efforts is unknown. Mutual risk sharing between the government and private parties would encourage greater use of innovative technologies. CHARACTERIZING SITES FOR GROUND WATER CLEANUP The inability of pump-and-treat systems to reach drinking water standards at many sites to date is not just a function of site complexity and technical limitations; it is also a result of insufficient or inaccurate characterization of the problem prior to cleanup. At several sites the committee reviewed, the cleanup systems failed to contain the contamination (much less clean it up) because of poor characterization of the extent of contamination and the locations of contaminant sources. The lack of adequate characterization has often occurred even after huge sums have been spent and considerable time has elapsed in characterizing the site. Thus, whether the technology is conventional or innovative, the design of a strategy for characterizing the site is as important as the design of the cleanup system itself. In brief, site characterization studies must provide the following information:

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APPENDIX~PAPERS PRESENTED D-109 the extent of ground water contamination, both horizontal and vertical; approximate locations of long-term sources of contamination, including sources near the surface where the contamination originated and sources that developed along the path of contaminant migration (such as residual NAPLs, pools of NAPEs, and metal precipitates); characteristics of the hydrogeologic setting important to the design of the remediation system and to the prediction of contaminant migration; and data to estimate the site's restoration potential using a method such as that represented in Table ES- 1. In characterizing a site with contaminated ground water, it is important to realize that due to the complexity of the subsurface and the difficulty of observing it, perfection in site characterization is unachievable. The performance of the remediation system itself will provide additional, extremely valuable information on site characteristics that may not be possible to obtain in any other way. Data collection should continue throughout the life of the ground water cleanup system, and these data should be analyzed regularly to determine whether they are consistent with the current understanding of the site and, if not, whether changes In the remediation plan are necessary. SETTING GOALS FOR GROUND WATER CLEANUP This report documents that the ability of technology to restore contaminated ground water to drinking water standards is uncertain at many sites. Nevertheless' regulations under the Comprehensive tinv~ronmenta~ Kesponse, Compensation, and Liability Act (the SuperfiInd law), the Resource Conservation and Recovery Act (RCRA), and similar state laws require that the water be cleaned up, usually to drinking water standards. The use of drinking water standards as cleanup goals has been questioned by many in the regulated community and others. Critics have long contended that options such as containing the contamination can protect public health, as long as the water in the containment zone is either restricted for use or treated with appropriate technology prior to use. The criticism of using drinking water standards as cleanup goals has increased because of the technical evidence that reaching these standards may not be possible in reasonable time frames at many sites. On the other hand, some people contend that drinking water standards or stricter requirements should be maintained as cleanup goals regardless of the capabilities of technology for two reasons: to provide an incentive against further pollution and to encourage development of improved cleanup technologies. In the debate over ground water cleanup goals, many alternative cleanup goals have been suggested. ~ broad terms, these alternatives are the following: complete restoration, or removal of all traces of contamination; non degradation, or removal of contamination to natural background levels or to detection limits; healfth-based standards, such as the drinking water standards used as cleanup goals at most sites today; technology-based standards, which would require cleanup to the capabilities of the best available technology; irrigation; and partially restricted use standards, meaning cleanup to allow nonpotable uses such as

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D-110 BARRIER TECHNOLOGIES FOR ENVIRONMENTAL MANAGEMENT containment, meaning that contamination remains in place but systems are installed to nr~?v`?nt nnnt~minnnt migration off site and. if necessary. to treat the ground water at the noint of tJ~- ~ _14~ ~ ^~_~^ ~ ~ ~ ^- ^~___~W_J ~ ~_ use. Each of these options reduces the risk of deleterious impacts due to ground water contamination. However, the magnitude of this risk reduction and the associated economic benefits are difficult- if not impossible to quantify. The professional community does not agree on the magnitude of health impacts of ground water contamination from hazardous waste sites for many reasons, the most important of which are difficulties in determining the extent to which humans have been and will be exposed to contamination, limitations in extrapolating toxicological effects observed in animal studies to human populations, and uncertainties in the science of epidemiology. Likewise, the total economic value of restoring contaminated ground water is unknown. Thus, a high degree of uncertainty exists, making quantitative assessment of the risks and benefits of various ground water cleanup goals extremely difficult. Like society as a whole, the committee had diverse views about which of the various alternative cleanup goals is most appropriate and whether the current approach of requiring cleanup to drinking water standards at a large number of sites should be changed. However, the committee strongly believes that because existing ground water cleanup goals cannot be attained In reasonable time frames (decades) at a large number of sites with current technologies, regulators should set short-term objectives for these sites based on the capabilities of current technology. While the long-term goals need not necessarily change, interim objectives are needed to acknowledge current technological limitations. In the recommendations below, the committee outlines a scenario for dividing contaminated sites into three categories, some of which would require interim objectives and some of which would not. CONCLUSIONS AND POLICY RECOMMENDATIONS In summary, the committee found that at many sites requiring ground water cleanup, some areas will remain contaminated above drinking water standards for the foreseeable future even when the best available technologies are used. However, the committee also found that cleaning up large portions of these sites is possible, even if limited areas remain contaminated. In addition, a wide range of developing technologies has the potential to improve the effectiveness of ground water remediation. Nevertheless, there are limits to what technology can accomplish, and existing regulatory requirements for ground water cleanup do not adequately account for these limits. The following recommendations provide guidance for modifying policies to reflect the key technical conclusions of this report.

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APPENDIX DIAPERS PRESENTED D-111 Complexity of the Subsurface Conclusion. Subsurface environments and many common contaminants have properties that interfere with decontamination efforts regardless of the technology chosen. These properties make finding the contaminant sources difficult, increase contaminant spreading' and cause contaminants to accumulate in zones from which they are difficult to extract. The complex interactions occurring In the subsurface are not fully understood, and therefore the effect of subsurface and contaminant properties on the ability to clean up ground water is often difficult to quantify. Recommendation 1. The committee recommends that the EPA systematically evaluate its experience in cleaning up sites to improve understanding of factors that prevent achievement of health-based ground water cleanup goals. The committee suggests that the EPA undertake an annual review of selected pump-and-treat systems based on the experience of EPA project managers throughout the United States. The analysis would be similar to a study of pump-and-treat systems at 24 sites that the EPA conducted In 1992 but would incorporate some of the improvements in analysis suggested in this report (for example, evaluating the number of pore volumes extracted per year). Recommendation 2. The committee recommends that the EPA establish a standardized, centralized, broadly accessible repository for site information. Culrently, accessing the large amount of existing site data from completed and ongoing ground water remediation projects is extremely difficult. To increase the accessibility of data, the EPA could develop suggested formats for collection and analysis of site-specific information. The EPA could also establish art easily used, publicly accessible data base for sites where ground water cleanup is under way. Performance of Conventional Pump-and-Treat Systems Conclusion. The ability of conventional pump-and-treat systems to reach health-based cleanup goals for contaminated ground water is highly site specific. Although cleanup is possible at some sites, properties of the subsurface and the contaminants may make restoring contaminated ground water to Drinking water standards technically Infeasible with current technology in reasonable time frames (decades) at a large number of sites. Conclusion. Although restoring the total volume of contaminated ground water to health- based standards may not be feasible at many sites, properly designed pump-and-treat systems still provide important benefits, including containment of the contamination, retraction of the plume of dissolved contaminants, and removal of some contaminant mass from the subsurface. Most sites with contaminated ground water contain two types of problem areas: (~) source areas and (2) dissolved plume areas. Conventional pump-and-treat systems may be effective for cleaning up plumes of dissolved contamination. However, this technology alone will be ineffective for restoring source areas such as those with significant amounts of residual NAPEs, pools of NAPEs, or metals that have precipitated. 4 - Recommer~dation 1. The committee recommends that the EPAts policy for determining whether ground water cleanup is feasible provide for the categorization of contaminated

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D-112 BARRIER TECHNOLOGIES FOR ENVIRONMENTAL MANAGEMENT sites into three groupings corresponding to the complexity of the site. At one extreme is a group of sites generally represented by category 1 In Table ES- 1; cleaning up sites in this group to meet health-based goals should be possible with current technology. At the other extreme is a group of sites generally represented by category 4 in Table ES-1; current technology is highly unlikely to restore sites In this group to health-based standards In reasonable time frames (decades), and therefore these sites may warrant permanent Unfeasibility waivers with the concomitant selection of a new protective long-term goal. In the middle is a group of sites generally represented by categories 2 and 3 In Table ES-1; for sites In this group, attaining health-based ground water cleanup goals will be difficult or unlikely with current technology but not necessarily impossible over the long term as technology improves. The long-term cleanup goals for sites In this middle group should be temporarily superseded by interim objectives reflecting the capabilities of existing technologies. (The correlation of the three groupings with the categories of Table ES- 1 is only approximate.) Recommendation' 2. The committee recommends that the EPA assess and develop guidance on institutional strategies for preventing public exposure to contamination over the long term at sites where reaching health-based cleanup goals is infeasible with the best available technologies. An institutional structure capable of lasting for several generations will be needed to oversee the large number of sites at which complete cleanup is Infeasible with current technologies. Recommer'~ation 3. The committee recommends that the EPA and other agencies identify and eliminate disincentives to early implementation of ground water remedial actions. Ground water cleanup is more likely to be effective if initiated early. Allowing responsible parties to commit to only one phase of cleanup at a time instead of requiring them to agree to the entire remedy all at once might provide an incentive for early cleanup; the EPA should pilot test this concept to determine whether it results In faster cleanups or whether it slows the process because of the additional negotiations it would require. Capabilities of Innovative Technologies Conclusion'. Although innovative technologies for ground water cleanup are subject to many of the same limitations as conventional pump-and-treat systems, many of these technologies can improve the efficiency of ground water cleanup efforts. However, important technical, economic, and Institutional barriers have slowed their development. Recommendation. The committee recommends that Congress investigate the possibility of charging an annual "infeasibility fee" to public and private responsible parties at sites where attaining health-based standards is not presently feasible. Congress could investigate various options for appropriating the funds collected from this fee. The committee sees two options as having special merit. One possibility is to use part of the funds to create an applied ground water research Find to pay for a strong research program for improved ground water cleanup techniques. The other possibility is to use some of the funds to encourage use of Innovative cleanup technologies by reimbursing responsible parties for testing these technologies in certain circumstances. Under this scheme, an expert pane] would approve use of an innovative technology. In the event that the innovative technology fails to achieve its intended goal and the

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APPENDIX~PAPERS PRESENTED D-113 responsible party is required to construct a backup technology, the responsible party would be able to recoup some or all of its losses from the infeasibility fee fimd. If the innovative technology worked, the fund would not subsidize the project. Initially the fund might apply only to Superfund sites, but if successful it might be extended to other types of sites. Characterizing Sites Conclusion'. Optimization of the site characterization and management process could improve the effectiveness of ground water cleanups. The poor performance of ground water cleanup systems is not solely a function of site complexity and technical limitations; it can also result from insufficient or inaccurate characterization of the problem prior to cleanup, leading to flawed design of the cleanup system. Recommendation 1. The committee recommends establishment of expert panels to evaluate site characterization, remetly selection, and remedy performance at complex sites. As discussed in this report, a large fraction of contaminated sites fit category 2 or 3 in Table ES- 1' and thus design of cleanup systems for many sites will be subject to considerable uncertainties. At present, federal and state regulatory agencies have an insufficient number of technically trained staff members to address the multitude of complex sites. While not a substitute for hiring and retaining technically trained staff, expert panels could provide guidance in addressing the often difficult technical choices at these sites. The panels could also evaluate proposals for using innovative technologies that would be covered under the infeasiblity fee fund discussed above. The panels could be funded by the infeasibility fee and/or by charging those responsible for cleanup at sites where the panels provide advice. The EPA should assess the feasibility of such an expert pane! approach to resolving problems at complex sites. Recommendation 2. The committee recommends that the EPA prepare new guidance documents that will lead to improved optimization of the hazardous waste site characterization process and explicitly address factors that will determine whether health- based cleanup goals are practicable. The EPA should revise existing site characterization guidance for the Superintend and RCRA programs to link the collection of specific characterization Information with early action implementation steps. New guidance documents are needed to ensure that factors that may limit the ability to achieve health-based ground water cleanup goals are recognized as early as possible. Setting Cleanup Goals Conclusion. Existing procedures for setting ground water cleanup goals do not adequately account for the diversity of contaminated sites and the technical complexity of ground water cleanup. Whether goals established under existing procedures adequately protect public health and the environment, or whether they are overprotective or underprotective, is uncertain, as are the costs to society when these goals cannot be achieved. RecommendLation I. Although the committee recognizes that different agencies must operate under different authorities, all regulatory agencies should recognize that ground water

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D-114 BARRIER TECHNOLOGIES FOR ENVIRONMENTAL MANAGEMENT restoration to health-based goals is impracticable with existing technologies at a large number of sites. The complexities and limitations that this report describes are iOunctions of the nature of the contaminants and the hydrogeology of the site, not of the identity of the agency or private party attempting to address the problem or the statutory authority or regulatory agencies involved. The EPA and other regulatory agencies should establish consistent mechanisms for deciding the restoration potential of contaminated sites, as indicated by the approach outlined in this report. Recommendation 2. The committee recommends that the EPA expand its efforts to inform the public about limitations of existing technologies and capabilities of innovative technologies. From the perspective of the affected public, the Superfund program has had limited success In responding to community concerns at many sites. Although the ground water cleanup problem is technically complex, the implications of site complexities as well as the promise that innovative technologies hold to improve cleanup should be explained to the affected public. The committee recommends that the EPA include expanded efforts at community relations within the technical impracticability waiver process and revise its community relations guidance documents to include issues of technical impracticability.