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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants Executive Summary Cleaning up contamination at installations that were part of the former nuclear weapons production complex is the most costly environmental restoration project in U.S. history. The Department of Energy (DOE), which is responsible for these installations, has spent between $5.6 billion and $7.2 billion per year on environmental management over the past several years. Despite these expenditures, progress has been limited. Although management and institutional problems have slowed the cleanup effort, technical limitations also have played a role. Effective technologies do not exist for treating many of the common groundwater and soil contaminants at DOE facilities. This report advises DOE on technologies and strategies for cleaning up three types of contaminants in groundwater and soil: (1) metals, (2) radionuclides, and (3) dense nonaqueous-phase liquids (DNAPLs), such as solvents used in manufacturing nuclear weapons components.1 Metals and DNAPLs are common not only in the weapons complex but also at contaminated sites nationwide owned by other federal agencies and private companies. They have proven especially challenging to clean up, not just for DOE but also for others responsible for contaminated sites. Although the recommendations in this report are designed for DOE, the bulk of the report will 1 As used in this report, ''cleanup'' means removing contaminant mass from groundwater or soil, immobilizing the contaminant in the ground to keep it from spreading, or containing the contamination in place
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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants be useful to anyone involved in the cleanup of contaminated sites. The report contains reviews of regulations applicable to contaminated sites, the state of the art in remediation technology development, and obstacles to technology development that apply well beyond sites in the DOE weapons complex. Within DOE, the Subsurface Contaminants Focus Area (SCFA) in the Office of Science and Technology is responsible for developing technologies to clean up metals, radionuclides, and DNAPLs in groundwater and soil. SCFA, like others involved in developing technologies to solve these problems, has encountered major obstacles. This report recommends where SCFA should direct its technology development program to achieve the most progress. This report was prepared by the National Research Council's (NRC's) Committee on Technologies for Cleanup of Subsurface Contaminants in the DOE Weapons Complex. The NRC appointed this committee in 1997 at DOE's request. The committee included experts in hydrogeology, environmental engineering, geochemistry, soil science, and public health. Members were selected from academia, consulting firms, private industries, and public interest groups to represent a range of perspectives on DOE contamination problems. The committee's conclusions are based on a review of relevant technical literature, briefings by staff from DOE and environmental regulatory agencies, visits to several DOE installations, consultations with other experts, and the knowledge and experiences of committee members. DOE'S PROGRESS IN GROUNDWATER AND SOIL REMEDIATION In total, DOE is responsible for cleanup of 113 installations in 30 states. To date, DOE has identified approximately 10,000 individual contaminant release sites within these installations that contain groundwater and/or soil contamination; continuing investigations may uncover further contamination. Current estimates indicate that some 1.8 × 109 m3 of groundwater and 75 × 106 m3 of soil are affected. These contamination problems date from the start in 1942 of the Manhattan Project to develop nuclear weapons. Assessing DOE's progress in cleaning up contaminated groundwater and soil is difficult because of data limitations, conflicting terminology, and lack of an agreed-upon metric for measuring success (see Chapter 1 for details). DOE's Office of Environmental Restoration reported that, as of 1998, remedies had been selected for 27 of 92 active groundwater cleanup projects and for 163 of 221 soil cleanup projects. Some of these projects include multiple contaminated sites,
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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants so it is unclear what percentage of the 10,000 contaminant release sites are being cleaned up. However, it appears that the number is small, and progress has been minimal. DOE's attempts to clean up contaminated groundwater and soil have been limited in part by technological difficulties. Conventional pump-and-treat systems for contaminated groundwater, which are slated for use at the bulk of DOE sites where groundwater restoration is under way, often cannot achieve cleanup goals for many of the types of contamination scenarios encountered at DOE installations. For example, a 1994 NRC survey of 77 contaminated sites showed that pump-and-treat systems had achieved cleanup goals at just 8 of the sites. Excavation, the most common remedy for contaminated soil at DOE installations, can increase the risk of exposure to contamination (exactly the problem remediation is supposed to avoid) and destroy native ecosystems, and in many circumstances it is costly. Because of such limitations, new technologies are needed to enable DOE to achieve remediation requirements for groundwater and soil at reasonable cost. THE CHANGING REGULATORY ENVIRONMENT An essential part of planning SCFA's program to develop new remediation technologies is an understanding of what cleanup requirements DOE must achieve, because these determine the desired technology performance goals. Groundwater and soil restoration goals have not yet been specified for many DOE sites, making it difficult to establish technology performance goals. Nonetheless, when these goals are established they must satisfy the requirements of applicable regulations: generally the Resource Conservation and Recovery Act (RCRA); Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA); Uranium Mill Tailings Remediation Control Act (UMTRCA); or a combination of these. Historically, regulations under these laws have required that at most sites DOE restore contaminated groundwater to drinking water standards, known as maximum contaminant levels (MCLs), or to special standards designed specifically for UMTRCA sites. Regulators at DOE sites usually require that soil cleanup meet specifications outlined in a soil screening guidance document developed by the Environmental Protection Agency (EPA). In general, DOE must achieve groundwater and soil cleanup standards across the full site, except in specially designated waste management areas where remaining contaminants will be contained in place. In the past few years, changes in baseline cleanup standards for
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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants groundwater and soil and in the overall process of site cleanup have become increasingly common, in part due to technical limitations and costs. Changes include increases in the number of waivers to baseline cleanup standards and to original site remedies, increasing use of natural attenuation in place of engineered remedies, emergence of brownfields programs with less stringent cleanup standards, and emergence of new risk-based methods for priority setting (all described in detail in Chapter 2). These new paradigms may affect the selection of cleanup goals for DOE sites and, correspondingly, the suite of possible remediation technologies for achieving those goals. Nonetheless, SCFA will have to continue developing technologies capable of cleaning up difficult sites with long-term liability concerns and of meeting baseline standards at the many sites where these will remain as cleanup goals. TECHNOLOGIES FOR METALS AND RADIONUCLIDES Cleanup of metals and radionuclides in the subsurface is complicated by a number of factors. Metals and radionuclides have multiple possible oxidation states with different mobilities, can partition to organic matter present in soil, can sorb to other soil components, and can precipitate. All of these factors can affect the performance of remediation technologies. Few well-established technologies are available for treating these types of contaminants, but a number of promising technologies are in the development stage. Because metal and radionuclide contaminants are generally nondegradable, treatment technologies must involve some form of mobilization of the contaminant (in order to move it to a location where it can be treated) or immobilization (in order to stabilize it in place and prevent further spreading). Table ES-1 lists established and emerging technologies for mobilization, followed by treatment, or immobilization of metals and radionuclides (see Chapter 3 for details). As is clear from the table, additional work is needed to increase the range of proven options for treating metals and radionuclides in situ and for extracting them (without excavation) for ex situ treatment; most of the technologies listed in the table are still in the development stage. TECHNOLOGIES FOR DNAPLS Conventional technologies are generally ineffective at restoring DNAPL-contaminated sites, as has been well documented in previous studies by the NRC and others. Chlorinated solvents are the
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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants Table ES-1 Technologies for Remediation of Metals and Radionuclides in Groundwater and Soil Technology Applicability Subsurface barriers Well-established method for preventing the spread of metal and radionuclide contaminants in groundwater. Vertical barriers are widely available; methods are being developed for installation of horizontal barriers beneath existing waste. In situ vitrification Developing technology for immobilizing metal and radionuclide contaminants in the subsurface. It is particularly suitable for sites with high concentrations of long-lived radioisotopes within 6 to 9 m of the soil surface (depending on water table depth and soil moisture). This technology may be able to treat mixtures of organic and inorganic contaminants. However, it is among the most expensive of treatment options. Solidification and stabilization Mature technologies for ex situ immobilization of contaminated soil. Less well developed for use in situ because of the difficulty of ensuring sufficient mixing. Improved mixing methods are being tested. Permeable reactive barriers Among the most promising and rapidly developing treatment technologies for treating metals, radionuclides, and mixtures of organic and inorganic contaminants. These barriers either intercept the flow of contaminated groundwater with a subsurface zone in which reactive materials have been installed to treat the contaminants or direct water flow through such a zone; a variety of reactive materials have been tested successfully. Operation and maintenance costs are relatively low because little or no energy input is required to maintain the system. Because the technology is relatively new, the longevity of reactive materials is a major uncertainty. In situ redox manipulation A developing method for treating metals and radionuclides at depths at which digging the trenches required for barrier technologies is impractical. The technology involves injection of chemical reductants into the ground to create reducing conditions that lead to immobilization of certain metals and radionuclides. It is especially well suited for elements (such as chromium) that can be reduced to solids that are resistant to reoxidation by ambient oxygen. It is less suitable for elements (such as technetium) that reoxidize easily. As with reactive barriers, the longevity of the treated zone is unknown.
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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants Technology Applicability Bioremediation Developing method using subsurface microorganisms to mobilize or immobilize metals and radionuclides. If further developed, the technology may be able to treat combinations of organic and inorganic contaminants at relatively low cost and with relatively little disruption to the site. Electrokinetic systems Developing technologies in which an electric field is applied to soil either to stabilize the contaminants in situ or to mobilize them for extraction near the electrodes. Extensive field tests of electrokinetic systems for the remediation of metal and radionuclide contamination have yet to be conducted in the United States. If better developed, the method would be appropriate for treating media with very low hydraulic conductivities. Soil washing Established technology for the ex situ separation of fine-grained soils, which generally harbor most of the contamination, from coarser soils. Because this is an ex situ process, it requires excavation of the soils and has all the limitations imposed by excavation. Soil flushing Developing technology for treating metals and radionuclides in situ by flushing contaminated soils with solutions designed to recover the contaminants. This technology is derived from the mining industry but has not yet been widely applied for environmental remediation of metals and radionuclides. Phytoremediation Developing technology in which specially selected or engineered plant species are grown and harvested after taking up metals and radionuclides through their roots. Phytoremediation has been field tested for treating a range of metals and radionuclides. It is most applicable to large areas of surface soils with low to moderate levels of contamination. Costs are low, and implementation is relatively easy, but mobilization of contaminants and transport to the groundwater is a risk when certain soil amendments are used to facilitate plant uptake of the contaminants.
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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants predominant DNAPL contaminants at DOE sites. These solvents have low solubilities in water and are denser than water. They tend to remain as a separate organic liquid in the subsurface, rather than mixing with water. A portion of a DNAPL contaminant will become entrapped in soil pores, while the rest sinks beneath the water table. Small amounts of separate-phase solvent can then dissolve in the flowing groundwater at levels high enough to make the water unsafe for drinking. Solutions to DNAPL contamination problems are best approached by dividing the problem into two distinct elements: (1) the DNAPL source zone, consisting of areas of the subsurface containing undissolved solvents entrapped in soil pores or traveling separately from the water, and (2) the dissolved plume, consisting of water that has been contaminated by components of DNAPLs that have dissolved. Several emerging technologies have shown the ability to remove mass relatively rapidly from DNAPL source zones. Other innovative technologies have demonstrated the ability to clean up plumes of dissolved contaminants. Table ES-2 summarizes technologies for treating DNAPL source zones and dissolved plumes emanating from DNAPL sources (see Chapter 4 for details). Although these technologies show promise, determining the ultimate level of cleanup attainable for each is not possible because of the lack of carefully controlled field tests. Each of the technologies is based on well-established chemical and physical principles and thus is more likely to be limited by hydrogeologic conditions (especially geological heterogeneities, which can interfere with circulation of treatment fluids and water or can limit access to the subsurface) than by limitations of the processes themselves. Nonetheless, more field tests are needed to demonstrate performance levels under a variety of hydrogeologic conditions. DOE REMEDIATION TECHNOLOGY DEVELOPMENT SCFA has helped to develop a number of innovative technologies for remediation of metals, radionuclides, and DNAPLs, but use of these technologies in actual DOE cleanups has been limited (see Chapter 5). For example, the Office of Environmental Restoration reported that the predominant remedies for groundwater contamination are conventional pump-and-treat systems (used at 41 percent of sites) and natural attenuation (used at 22 percent of sites). Further, no-action alternatives are being used more often than any one innovative technology. The environmental restoration office reported two uses each of air sparging and free product recovery systems and one use each of
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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants Table ES-2 Technologies for Remediation of DNAPLs in Groundwater and Soil Technology Applicability Soil vapor extraction Effective at cleaning up source zones containing volatile compounds in homogeneous, permeable soils; with addition of thermal processes, the technology can be extended to semivolatile compounds. Thorough removal of DNAPLs requires sufficient flow through the entire source zone, which may be difficult to achieve. Steam Demonstrated ability to clean up DNAPL source areas in permeable soil in both the saturated and the unsaturated zones. It may be combined with electrical heating when finer-grained layers are present. Heterogeneities in geologic materials in the subsurface may limit efficiency of this process. Surfactant flooding Demonstrated to effectively remove large masses of nonaqueous-phase liquids from source zones in permeable aquifers. Geologic heterogeneities and nonuniform contaminant distribution may reduce the efficiency of this process. Cosolvent flooding Has shown potential for solubilizing large masses of nonaqueous-phase liquids. Geologic heterogeneities and nonuniform contaminant distribution may reduce process efficiency. In situ oxidation Proven to be effective at destruction of specific chlorinated DNAPL compounds in source zones in permeable, relatively homogeneous soils. Geologic heterogeneities may reduce the efficiency of these processes, and mass transfer limitations may limit the volume of DNAPL that can be treated efficiently. Electrical heating and electrokinetic methods Have shown potential for remediation of dissolved contaminants from DNAPLs in low-permeability units. Significant data are available from field trials of electrical heating systems, but data are inadequate to verify the effectiveness of electrokinetic methods for treating DNAPL source zones. Bioremediation Demonstrated method for stimulating microorganisms in the subsurface to degrade chlorinated compounds. Degradation takes place primarily in the dissolved phase. Treatment of DNAPL source zones using biodegradation methods probably is not practical because of the long time required for dissolution.
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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants Technology Applicability Phytoremediation Emerging method that uses plants to enhance microbial degradation of contaminants, take up contaminants, or provide hydraulic containment. Results are not yet conclusive for application to dissolved contaminants from DNAPLs, but field tests are under way. In situ vitrification Demonstrated as effective for converting soil to a molten material that solidifies upon cooling and for producing temperatures that should lead to the destruction or mobilization of DNAPL compounds. However, data on the performance of this technology at DNAPL sites are insufficient to provide a meaningful evaluation at this time. Reactive barrier walls Have shown great promise for treatment of dissolved plumes of contamination from chlorinated solvents. Although these technologies do not directly clean the DNAPL source zones, they limit the migration of plumes of contamination emanating from these zones. Uncertainties over the longevity of barrier walls are among the main limitations of this technology. thermally enhanced vapor extraction systems and passive reactive barriers. Excavation, followed by ex situ treatment or disposal, is still the predominant remedy for contaminated soil. The major barrier to deployment of SCFA's technologies is lack of demand from individual DOE cleanup operations (the end users of SCFA technologies). Other factors that have interfered with deployment of SCFA's technologies include regulatory requirements that favor conventional technologies, inconsistencies in technology selection processes and cleanup goals, and SCFA budget limitations. The demand for innovative remediation technologies at DOE installations is lagging. In part, demand is lacking because incentives for rapid, cost-effective cleanup of DOE installations are inadequate. On the contrary, rapid cleanup of DOE sites can lead to loss of revenue for the contractor responsible for managing cleanup at the site and loss of local jobs once the cleanup is completed and the site closed. Further, DOE site managers can hesitate to approve the use of innovative remediation technologies due to the risk that if the technology fails, they will still be liable for paying for the cleanup. Also limiting demand for SCFA technologies is insufficient in-
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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants volvement of technology end users in setting SCFA's technology development priorities. End users have to be involved in determining whether to continue funding for specific projects and in ensuring that the technologies being developed meet site needs. SCFA also must provide these end users with adequate technical support for implementing new technologies. Unless SCFA can better connect its R&D effort with technology end users to first set the R&D direction and then work cooperatively with them to employ the technologies in specific applications, SCFA expenditures will continue to show modest results. SCFA has initiated strategies to increase end user involvement, but in fiscal year 1998 it was unable to implement these new strategies because the entire SCFA budget went to paying for projects that began before SCFA was formed. Regulatory problems have also interfered with deployment of innovative remediation technologies at DOE installations. Especially problematic are the slow, linear nature of the regulatory process and inconsistencies in the way the process is applied from site to site. These regulatory problems can delay the selection of remediation technologies (which further reduces demand) and result in the use of outdated technologies chosen years before site cleanup begins (although at some sites regulators allow changes to the original cleanup plans). Regulatory inconsistencies create uncertainties about whether a technology proven at one location will meet the regulatory requirements at another location, making contractors hesitant to take the risk of using an innovative technology. The U.S. General Accounting Office (GAO) has, in past reports, pointed to management problems in the Office of Science and Technology as another reason for the limited success of DOE's technology development programs. For instance, in reviews in 1992 through 1994, the GAO determined that the Office of Science and Technology lacked sufficient mechanisms for eliminating poorly performing projects, performing comprehensive assessments of technology needs, and preventing overlap in technology development work. The Office of Science and Technology has instituted several management reforms to address these problems. Large budget swings are a final factor that has contributed to the difficulties of SCFA's program. SCFA's budget has been cut substantially: from a high of $82.1 million in 1994 to a level of $14.7 million in fiscal year 1998, of which $5 million was earmarked by Congress, leaving SCFA with a budget of $9.7 million. The fiscal year 1999 budget of $25 million, although an increase over the 1998 level, is approximately equal to the average price of cleaning up a single CERCLA site. The current budget allows only a limited number of technology
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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants development projects to go forward and may not be sufficient for the large field demonstrations needed to advance new technologies. Despite the slow progress in deploying innovative remediation technologies at DOE installations, SCFA has helped to develop a number of technologies that have shown considerable promise. Notable SCFA accomplishments in developing systems for remediation of metals and radionuclides include work on in situ redox manipulation for chromium contamination at Hanford, horizontal barriers for waste containment at the Idaho National Engineering and Environmental Laboratory, and penetrometer systems for characterizing metals and radionuclides in the subsurface. Achievements in the development of systems for remediation of DNAPLs include work on steam technologies at Lawrence Livermore National Laboratory, electrical resistance heating to enhance recovery of DNAPLs by soil vapor extraction in low-permeability soils at several DOE installations, and collaborative work with private industries to develop and field test electrokinetic systems for DNAPL remediation. These successful projects, described in detail in Chapter 5, can provide models for future SCFA work. RECOMMENDATIONS SCFA has an important mission to fulfill in developing technologies for cleanup of metals, radionuclides, and DNAPLs in the subsurface. SCFA's past success in developing technologies that are later deployed in the field has been limited by a number of factors, including lack of customer demand, inadequate involvement of technology users in setting SCFA program priorities, regulatory obstacles, and budget limitations. Although some of these problems must be addressed by higher levels of DOE management, SCFA can take steps to increase the likelihood that the new technologies it helps develop will be deployed and to focus its financial resources on the most promising technologies. The committee developed recommendations to help improve the SCFA program in a variety of areas. Chapter 6 describes all of the recommendations in detail. Following are the highest priorities: Setting Technology Development Priorities In situ remediation technologies should receive a higher priority in SCFA because of their potential to reduce exposure risks and costs. SCFA should fund tests designed to develop and determine performance limits for technologies capable of treating the types of contaminant mixtures that occur at DOE sites.
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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants SCFA should focus a portion of the program's work on development of remedial alternatives (including containment systems) that prevent migration of contaminants at sites where contaminant source areas cannot be treated. Methods for monitoring long-term performance of these systems should be included in this work. Improving Overall Program Direction SCFA should continue its efforts to work more closely with technology end users in setting its overall program direction. Working with end users, SCFA should identify key technical gaps and prepare a national plan for developing technologies to fill these gaps. Although SCFA consulted with end users and developed a prioritized list of problem areas (known as work packages) for funding in fiscal year 1998, it was unable to use this list to guide its program because the entire SCFA budget went to supporting multiyear projects that began before SCFA was formed. SCFA should strive to increase the involvement of technology end users in planning the technology demonstrations it funds. End users should be involved in planning every demonstration that SCFA funds, as in the Accelerated Site Technology Deployment Program. SCFA should significantly increase use of peer review for (1) determining technology needs and (2) evaluating projects proposed for funding (see NRC, 1998, for guidelines on peer review). Peer reviews should carry sufficient weight to affect program funding. SCFA should improve the accuracy of its reporting of technology deployments. SCFA should use a consistent definition of deployment and should work with the Office of Environmental Restoration to verify the accuracy of its deployment report. Overcoming Barriers to Deployment SCFA should sponsor more field demonstrations, such as those funded under the Accelerated Site Technology Deployment Program, to obtain credible performance and cost data. SCFA should consider whether sponsorship could include partial reimbursement for failed demonstrations, if an alternate remediation system has to be constructed to replace the failed one. SCFA should ensure that the project reports it provides contain enough technical information to evaluate potential technology performance and effectiveness relative to other technologies. The project descriptions contained in SCFA's periodic technology summary reports are
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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants not sufficiently detailed to serve this purpose. SCFA's project reports should follow the guidelines in the Federal Remediation Technologies Roundtable's Guide to Documenting and Managing Cost and Performance Information for Remediation Projects (FRTR, 1998). A key future role for the SCFA should be the development of design manuals for technologies that could be widely used across the weapons complex. Possible models include the Air Force Center for Environmental Excellence design manual for bioventing, the American Academy of Environmental Engineers WASTECH monograph series, and the Advanced Applied Technology Demonstration Facility surfactant-cosolvent manual. Appropriately qualified SCFA staff members (with in-depth knowledge of remediation technologies) should be available to serve as consultants on innovative technologies for DOE's environmental restoration program. These staff members also should develop periodic advisories for project managers on new, widely applicable technologies. Addressing Budget Limitations DOE managers should reassess the priority of subsurface cleanup relative to other problems and, if the risk is sufficiently high, should increase remediation technology development funding accordingly. SCFA should pursue a variety of strategies to leverage its funding. Strategies include (1) improving collaborations with external technology developers to avoid duplication of their work, (2) developing closer ties with the Environmental Management Science Program, and (3) continuing involvement with working groups of the Remediation Technologies Development Forum. In summary, DOE faces the challenge of cleaning up massive quantities of contaminated groundwater and soil with a suite of baseline technologies that are not adequate for the job. Although recent DOE budget projections have indicated that most groundwater at DOE installations will not be cleaned up, federal law requires groundwater cleanup, and political pressure to meet the federal requirements continues. DOE will thus have to continue to invest in developing groundwater and soil remediation technologies. As shown in Tables ES-1 and ES-2, a variety of emerging technologies for treating contaminated groundwater and soil are in the pipeline. DOE has to ensure that SCFA is adequately organized and supported to advance these types of technologies and to develop new technologies for contamination problems that still cannot be solved.
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Ground Water & Soil Cleanup: Improving Management of Persistent Contaminants REFERENCES FRTR (Federal Remediation Technologies Roundtable). 1998. Guide to Documenting and Managing Cost and Performance Information for Remediation Projects. Washington, D.C.: EPA. NRC. 1998. Peer Review in Environmental Technology Development Programs: The Department of Energy's Office of Science and Technology. Washington, D.C.: National Academy Press.
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