Subcommittee on Landfills

Overview and Summary of Preliminary Recommendations

Overview of Subcommittee Activities and Approach

Because of its brief exposure to DOE landfill technology-development efforts during its two meetings in 1995, the subcommittee feels that both its findings and recommendations must be considered preliminary. In addition, the subcommittee accepted as its charge for 1995 to make only constructive recommendations that can be implemented by the Landfills Focus Area in the short term. Preliminary observations and recommendations presented in this overview and summary have been selected from the body of this report, which contains the rationale and more detailed discussion of each observation and recommendation.

Observations and Preliminary Recommendations
  1. Reorganization of DOE technology development into focus areas is a positive development. The Landfills Focus Area has moved aggressively to implement departmental guidance, and there is clear evidence that initial efforts have been successful. The focus area technical team demonstrates a high-level of esprit de corps and willingness to engage in cooperative R&D between laboratories and sites.
  2. Greater effort in long-term performance testing and monitoring of engineered containment techniques and systems, including covers, caps, barrier walls, and floors, is encouraged.
  3. If the Landfills Focus Area receives adequate and stable funding, it is probable that DOE will be able to meet its needs to develop better technology.
  4. A problem-solving orientation in technology development is advocated.
  5. A ranking/categorization for landfill-related problems based on relative risk would be useful to drive technology development in DOE. These analyses need not use sophisticated models and may already exist to some degree in DOE literature. Technology needs determined by this risk prioritization process would establish technical tasks. These technical tasks would then be organized into technology-based


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--> Subcommittee on Landfills Overview and Summary of Preliminary Recommendations Overview of Subcommittee Activities and Approach Because of its brief exposure to DOE landfill technology-development efforts during its two meetings in 1995, the subcommittee feels that both its findings and recommendations must be considered preliminary. In addition, the subcommittee accepted as its charge for 1995 to make only constructive recommendations that can be implemented by the Landfills Focus Area in the short term. Preliminary observations and recommendations presented in this overview and summary have been selected from the body of this report, which contains the rationale and more detailed discussion of each observation and recommendation. Observations and Preliminary Recommendations Reorganization of DOE technology development into focus areas is a positive development. The Landfills Focus Area has moved aggressively to implement departmental guidance, and there is clear evidence that initial efforts have been successful. The focus area technical team demonstrates a high-level of esprit de corps and willingness to engage in cooperative R&D between laboratories and sites. Greater effort in long-term performance testing and monitoring of engineered containment techniques and systems, including covers, caps, barrier walls, and floors, is encouraged. If the Landfills Focus Area receives adequate and stable funding, it is probable that DOE will be able to meet its needs to develop better technology. A problem-solving orientation in technology development is advocated. A ranking/categorization for landfill-related problems based on relative risk would be useful to drive technology development in DOE. These analyses need not use sophisticated models and may already exist to some degree in DOE literature. Technology needs determined by this risk prioritization process would establish technical tasks. These technical tasks would then be organized into technology-based

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--> product lines, rather than the waste-type and climate-based product lines as they are organized currently. The proposed technology grouping would include five product lines: (1)   characterization, (2)   retrieval, (3)   treatment (including both in-and ex-situ methods), (4)   containment and monitoring, and (5)   systems integration and design. The technology-development program in the Landfills Focus Area would benefit greatly from a critical ongoing assessment of the efficacy and efficiency of technologies already developed both inside and outside DOE. Recent work in assessing the state-of-the-art in relevant technical areas addressing DOE's priority needs is supported, and an increased level of effort in this area is needed. The desired goal is to establish DOE's niche in environmental technology development by focusing DOE-EM's efforts in technology development into areas of need not well supported outside of the department. Each technical project would benefit from clearly established goals and a strategic plan to guide development. An action plan describing how strategic goals are to be met should be part of an assessment of field applications. The subcommittee is strongly supportive of ''gate'' reviews and believes that the gate-review concept would be helpful in R&D planning (see discussion of gate reviews in Chapter 3, page 19). The Landfills Focus Area should be proactive in working with regulatory agencies to establish criteria that will promote regulatory acceptance of appropriate landfill remediation technologies. Also, agreed-upon means for establishing targeted cleanup levels would serve as useful guides to technology-development activities. The subcommittee does not challenge the notion that cleanup levels should be site specific. Increased effort in performing project peer reviews (for example, the EM-50 Project Review [TTP No. SF201101] of In-Situ Microbial Filter Project by the Plumes Focus Area, June 6-7, 1995) by external technical experts who have been rigorously screened for conflict of interest is strongly encouraged. Such peer review could take place at a particular "gate" of the DOE-EM technology maturation model, or at highly focused workshops where related technology projects are assessed. Preliminary Findings, Observations, and Recommendations Scope of DOE Landfills Focus Area The Landfills Focus Area has defined its scope as that of technology development appropriate for DOE landfill needs. Improvements in technical methods

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--> are sought in each aspect of remediation. The stages of remediation include assessment (or characterization of both sites and buried waste), selection of one or more treatment options, design of the remediation system, implementation of the remediation plan, and post-monitoring (as appropriate) to confirm risk abatement. Remediation options for landfills include excavation (or retrieval), with the generation of a waste stream destined for above-ground storage and/or ex-situ treatment; containment, as with barriers; in-situ stabilization, as with an injected grout or in-situ vitrification; and in-situ remediation, using physical, chemical, and/or biological techniques. Because of the magnitude and variety of DOE landfill problems (with an estimated three million cubic meters of buried waste in landfills nationwide, in a variety of climates and hydrogeological settings), it is anticipated that each of the above-mentioned remediation options will find application somewhere in the DOE complex. The Landfills Focus Area, with an annual budget between $30 and $50 million, has supported work in Fiscal Years (FY) 1995 and 1996 in the areas of assessment, retrieval, containment, in-situ stabilization, in-situ remediation, and ex-situ treatment. Overview of DOE Landfills Program and Focus Area The Landfills Focus Area has begun an ambitious program of facilitating technology development. Several clearly defined roles or program elements can be identified. The focus area awards funding to R&D projects that have technical merit and contribute to program goals. For organizational purposes, these projects have been grouped into four areas, called product lines, each overseen and coordinated by a separate program manager. Based on strategic plans developed within DOE-EM, the Landfills Focus Area has undertaken strategic planning activity (USDOE, 1994). Assessment of state-of-the-art practices in relevant technical areas. Examples of information gathering activities include the International Containment Technology Workshop (August 29-31, 1995, in Baltimore, Md.), the TRU (transuranic), TRU Mixed, and Mixed Low-Level Waste Treatment Technologies Technical Peer Review meeting (November 13-15, 1995, in Dallas, Tex.), and the Non-Destructive Assay and Non-Destructive Evaluation (NDA/NDE) workshop (January 25-26, 1996, in Pittsburgh, Pa.). Another example is the technical "bakeoff" demonstrations, such as the Very Early Time ElectroMagnetic (VETEM) demonstration planned at Idaho National Engineering Laboratory (INEL), where

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--> competing technical methods and systems can be compared by their performance on a common test bed. Interaction with technology customers within DOE. Interactions with stakeholders and EM-40 site managers have occurred through the Site Technology Coordination Groups (STCGs) and through the efforts of the External Integration Team. An end user is required of all projects funded beyond "gate four" of the R&D technology maturation model developed within EM-50. Interactions of the focus area's industrial team with commercial and industrial organizations to assess what to buy outside of DOE versus what to develop in-house. This work includes market assessment and the development of commercialization or business plans for DOE-developed technologies. Performance of technology demonstrations on DOE sites. Interaction with technology developers and a site selection process are involved. The Subcommittee on Landfills endorses the new approach to DOE technology development begun in 1994 with formation of the focus area structure, and the work of the Landfills Focus Area in their efforts to implement this new approach. Strategic Planning, Programmatic Goals, and Performance Measures A problem-solving orientation for technology development is advocated. The development, demonstration, and implementation of environmental remediation technologies should be focused on the problems of the DOE sites. Implementing a problem-oriented technology-development plan encompasses the following: problem identification and prioritization; identification of the technology needs to control, eliminate, and/or minimize the risk that established the problem; establishment of goals tied to a strategic plan to track technical progress toward problem solution; and restructuring of the organizational product lines to focus on problem solving, with the establishment of an additional Systems Integration and Design Group. A problem-solving orientation requires that the problems be ranked according to risk, forcing the earliest attention on the problems whose solutions yield the greatest benefit. It also avoids the criticism that the easiest, least important problems are the first ones examined and solved. However, the time required to solve the problem also should be considered when determining technologies appropriate for the solution. Ranking the problems according to risk requires the definition of risk, the human or environmental component at risk, and the time frames of concern for the risk. For example, the risk measure may be 100 mrem/yr to critical members of the population after 300 years of site control. The risk measure also may be inferred

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--> by indirect criteria such as the drinking-water limiting concentrations to potential potable water sources off-site. The data needed for a risk determination may not be available, highlighting the need for proper characterization of each problem, particularly the inventory and contaminant characteristics. However, sufficient data on the critical parameters should be available for a preliminary evaluation of risk sufficient for ranking. A complete characterization is not required to evaluate reasonably the risk ranking for landfills. The next step involves determining the contaminant inventory and characteristics, the potential pathways for contact, and the critical pathways for the potential exposures. These pathways then must be characterized, and the appropriate models for the risk must be selected. The model need not be sophisticated for the purpose of ranking the problems. Regulatory Aspects Impacting the Landfills Focus Area One way to view landfill-remediation needs is to understand the regulatory requirements for legal closure at a landfill site. Any existing or potential releases of hazardous chemicals and/or radioactive waste to the environment makes a site eligible for consideration in the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA)/Superfund Amendments and Reauthorization Act (1986) (SARA) process, among other Applicable or Relevant and Appropriate Requirements, (ARARs). These ARARs, including CERCLA/SARA legislation, allow for Removal Actions. Where there is a threat to public health or welfare or the environment, Removal Actions, whether Time or Non-Time Critical, can be implemented. Removal Actions shall, to the extent practical, contribute to the efficient performance of the anticipated long-term remedial action. For some landfills of interest here, this categorization is possible and currently is practiced by another federal agency (the Department of Defense) to expedite site remediation. If Removal Actions are not appropriate, the full CERCLA process on a relevant Operable Unit is then invoked, involving a period of investigation that results in a Remedial Investigation/Feasibility Study (RI/FS), followed by the signed Record of Decision (ROD), containing the legally agreed upon remediation method. Flexibility is built into some RODs, allowing attempts at alternate solutions for trial periods typically lasting approximately one year (see, for example, Soelberg et al., 1995). However, the schedule of ROD signings dictates the end of the period during which various remediation scenarios are debated most fully. The use of a new technical method would have to be advocated prior to the ROD signing. The bulk of technology development is then necessary prior to the ROD. The schedule of RODs acts as a significant time constraint on the implementation and use of results of R&D work products. For other regulatory processes, similar considerations apply. For landfills under local regulation, a new technology advocated for use would have to gain

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--> acceptance by local regulators. Those technical methods that have achieved a greater level of maturity, testing, and history of successful application would naturally be favored. Recommendations The Landfills Focus Area should be proactive in working with regulators on landfill remediation. Consultations to date with the EPA are supported, and it is hoped that such continued interactions with representatives of regulatory agencies can produce remediation choices and designs that enjoy widespread acceptance7. Field demonstrations of appropriate technologies can enable the granting of Removal Actions and garner local regulatory support. The focus area should try to ensure that demonstrations affect this process in a positive manner. CERCLA Removal Actions are less costly than the full RI/FS process that involves more extensive characterization studies. Regulatory acceptance is an important issue. A regulator or regulatory body's yes/no (go/no go) decision to try an emerging remediation technique can translate directly into the worthiness of the requisite technology development. In general, only technologies at a sufficiently mature level of development will be able to undergo a credible field test demonstration and be considered seriously for regulatory approval. Because this maturity occurs at the end of development, the development costs are undertaken with some risk. Regulators have been described as reluctant to participate in technology development, or to endorse a technical method, prior to its full development, and such caution is understandable. Technology developers can be frustrated not knowing whether technical progress will translate into the regulatory acceptance required for deployment. Technology seminars with state and local regulators would help expand their knowledge of the applicability of new and existing remedial technologies. Presenters at these seminars should include experts from within as well as outside DOE. The straightforward answer to this situation is to have technical criteria established that serve both state and local regulators. The Landfills Focus Area should establish criteria that satisfy the relevant regulations and serve as guidelines for technology development. To help facilitate interactions of the focus area with regulators and developers, the focus area should disseminate the criteria broadly, especially within DOE, EPA, and state regulatory agencies. 7   Briefings to the Subcommittee on Landfills by DOE-EM 50 personnel and Subijoy Dutta of the U. S. EPA

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--> Status of Current DOE Environmental-Technology Projects The Digface characterization project being developed by the Idaho National Engineering Laboratory (INEL), Ecology International, and Rust Geotech Inc., is an integrated demonstration of multiple sensors that can be used as part of a retrieval effort. The Digface characterization technology will allow continuous and continually improving monitoring and characterization of the site being remediated. The Digface characterization excavation system is useful and fills a needed role of providing characterization information beyond the limitations of present nonintrusive techniques. (For a list of FY 1995 projects, see USDOE [1995 a, b]). The issue here is the adequacy of existing information (from historical records and from characterization studies done with current methods) in providing a sufficient waste and site assessment for remediation planning purposes. The question is raised whether present technical methods can supply this information adequately, without costly drilling and sampling. An example of a significant omission with present techniques is an underground storage tank at Fernald that was not discovered during site characterization; its later discovery required adjustments to the remediation strategy. The Digface system seems to provide a technical approach to proceed with available information, and with the flexibility to acquire more information and make decisions as the excavation proceeds. The projects cited below are examples of work whose rationale for development does not seem to be on a sufficiently firm basis to be treated as priorities. Items 1, 2, 4, and 6 are developed technologies and item 3 has a doubtful success probability in the short (2–5 years) term. Success is needed for containment in situ, which should remain a development priority along with monitoring methods. Item 5 is a temporary fix in an arid environment. The short-term benefit from air drying of a coarse-grained cover layer does not outweigh the cost of the technology. Alternative Landfill Cover Demonstration (LLW/Arid). The proposed project area generally is considered to be a developed technology, and facilities currently are using the ideas. One example is the radon barrier and cover field test at Grand Junction, Colorado, multiyear field test conducted over several years. Another example is the multilayer earthen cover system planned for the Low-Level Waste Disposal Facility in North Carolina. Although the program is currently conducted in an arid environment, it should take place in a humid environment, which is the more critical use for multilayer covers. This project also needs mass balance data (supporting a relation such as In(precipitation) = Out(evapotranspiration + capture/collection) at an appropriate site to evaluate effectiveness. Design of Capillary Barriers (LLW/Arid). This project area is well developed, including computer codes to predict capillary performance. Capillary barriers are being used in covers, and they have also been designed and proposed in covers over

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--> commercial LLW disposal facilities. An example is the multilayer earthen cover system planned for the California Low-Level Waste Disposal System. It has a capillary barrier that also functions as a biointrusion barrier. Again, the capillary barrier program should be conducted in a humid environment. Subsurface Barrier Emplacement (Grouts) (LLW/Arid; LLW/Non-Arid). DOE sites have worked on this project area for decades. In-situ grouting has met with limited success and is not used commercially because integral barriers have not been achieved. It is also difficult to determine in the short run if a grout barrier under a landfill maintains full integrity. Short-run success is doubtful for this area. The technology is not in the technology-development stage, but is in the research stage. Better testing methods to evaluate barrier performance are also needed. Radon Mitigation and Monitoring at Fernald. Techniques have been developed for mitigation and monitoring of radon in the environment. This project sounds more like a site application test than a technology-development test. Dry Barriers for Covers (LLW/Arid). This project may reduce moisture in earth covers in arid environments. However, it is an active process that is a temporary solution at best. Tracers to Determine Transport Processes in the Vadose Zone. Tracers have been used to determine water and gaseous flow in geologic media for several years. Most geohydrologists believe that transport processes are well understood but are not easy to monitor quantitatively. Field experience, modeling, and testing of vadose zone transport have established a suitable technical basis for design and implementation. Thermal Enhanced Soil Vapor Extraction. This technique has been demonstrated (Cox et al., 1995; Gopinath and Germar, 1995; Strzempka et al., 1995) commercially using more cost-effective methods than DOE's electrode-type heating probes. State-of-the-Art Assessment of Environmental Technologies The Landfills Focus Area should identify clearly those technologies needed to address specific site-related problems, including an assessment of the state-of-the-art technologies that have found application to similar problems both inside and outside of DOE. This assessment involves locating and referencing relevant resources and centers of expertise, with a goal of establishing the unique niche or role of DOE in technology development. Projects included in the 1995 technology-development program (USDOE, 1995a) focus on the demonstration of a wide variety of technologies, not all of which are uniquely attributable to DOE research and development. Indeed, DOE has not played a significant role in the development of some of the technologies counted as "successes" or work products. In other instances, technology development has not

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--> been clearly focused on the technology needs for solving specific problems. Past program plans sometimes have neglected critical assessment of state-of-knowledge in project-related areas and do not show evidence of leveraging DOE efforts with existing centers of expertise. Specifically, DOE technology-program plans do not establish clearly DOE's niche in contributing to the development of those technologies that are already the subject of broad-based research and development efforts elsewhere. Implementing technology demonstrations is a significant part of the Landfills Focus Area activity, and such demonstrations need not necessarily come from in-house development. In briefings to the subcommittee at the Savannah River Laboratory, the FY 1996 program for technology development in the Plumes and Landfills focus areas demonstrated greater knowledge and outreach. It is hoped that a technology-based focus area approach for problem solution will help foster further development of the context in which the DOE technology program exists. To this end, the focus area should engage in outreach activities that seek out the best in each technical field. One aim of this effort is to provide the rationale for the technology-development activity that is sponsored within the agency. Another aim is to engage peer review input. DOE headquarters has made efforts to work with other agencies and private sector vendors, such as the recent co-sponsoring of the August 1995 International Containment Technology Workshop in Baltimore, Md., by DOE, EPA, and DuPont (USDOE et al., 1996). The invited speakers included representatives from abroad and from a host of institutions, including industry, the USNRC, and universities. This effort of soliciting broad-based input for technical issues in barrier technology is the kind of activity required to develop the rationale for the DOE program in barriers. Input on state-of-the-art practice, a sense of technical needs, and ideas for what methods are most suitable for deployment in DOE are the kinds of information that are needed to establish an understanding of the technical-development program. Specifically, the policy-related findings of this workshop should be established and recorded. The plan to convene a more rigorous follow-up public conference in the near future (early 1997) is supported. Similar information-seeking efforts conducted by the Landfills Focus Area in late 1995 also are supported. These include the transuranic (TRU), TRU Mixed, and Mixed Low-Level Waste Treatment Technology Technical Peer Review meeting (November 13-15, 1995, in Dallas, Tex.), the Non-Destructive Assay and Non-Destructive Evaluation workshop (NDA/NDE) (January 25-26, 1996, in Pittsburgh, Pa.), and the Very Early Time Electromagnetic (VETEM) technical demonstration (scheduled for late 1995 at INEL). This approach for key technical areas of importance in landfill remediation strategy is endorsed. A key decision emerging from this process is the determination of the technical areas in which DOE wants to have in-house, first-rate expertise. This process involves deselecting some technical areas in ER where external expertise can then be called in, perhaps in a subcontractor role, and in which DOE can view itself as a customer.

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--> Barrier and Cap Technology The integrity and long-term performance of cap and barrier walls are issues worthy of further work that is focused in certain areas of need. These issues are discussed below. Although caps can be successful (as shown by archaeological analogs in burial mounds) present designs have exhibited shortcomings, mainly through biointrusion of both animals and plants. However, little is known at present about long-term performance of presently engineered barrier walls and caps. Arguably, the most long-term data on present cap design are on vegetated caps, installed in the mid-1980's (Schulz et al., 1995); the DOE Hanford Site Permanent Isolation Surface Barrier work (Cadwell et al., 1993); and the DOE Uranium Mill Tailings Remedial Action Program (UMTRAP) work (Zellmer, 1981; Simmons and Gee, 1981; Gee et al., 1984; Mayer et al., 1981a; Cline et al., 1982; Voorhees et al., 1983; Beedlow, 1984; and Mayer et al., 1981b) done in the late 1970's and early 1980's. The subcommittee heard from several researchers and practitioners that long-term data on barrier wall performance are also a significant need8 (USDOE et al., 1996; ER'95, in press). To collect such data, a limited program of long-term performance assessment of barrier walls and caps is recommended, because these are key components of present DOE Environmental Restoration (ER) strategy9. It can be argued that every barrier wall, or a representative sample of them, should be monitored over the design lifetime. A program for monitoring long-term performance is suggested, in part because of current limitations of verification and monitoring techniques (Heiser, 1994). For an example of a testing and monitoring plan, see Gee et al. (1993). The work should not repeat previous studies of this type; rather it should have a clear objective with specific outcomes, and it should be focused on humid, not arid sites. The reason for such a monitoring effort is that caps and barrier walls are not a proven permanent isolation technique. Their failure depends upon imperfections and nonidealities in installation and on material properties. For a discussion of failure mechanisms and construction quality assurance and control, see Rumer and Ryan (1995). The subcommittee has heard from practitioners that present field installation methods make guaranteeing integrity difficult. Pathways for leaks can be produced by mechanical stresses at interfaces, during installation or due to underlying strata. Present materials (grout, slurry, and plastics) possess finite leachability and conductivity parameters that do not guarantee long-term environmental isolation. One suggestion is to perform field studies on existing DOE-UMTRAP caps, which were designed to last 1000 years, in compliance with regulations. The Cannonsburg, Pa., site is a candidate for humid-area studies. 8   Briefing to the Subcommittee on Landfills by Professor David Daniel of the University of Texas at Austin, July 20, 1995, Washington, D.C. 9   Remarks of John Lehr at Barriers for Long-Term Isolation Workshop , on in-place actions envisioned within the Office of Environmental Restoration (EM-40) throughout the DOE-EM complex; ER'95, 1996.

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--> Technical-Needs Assessment Studies An ongoing and more extensive system of needs assessment is encouraged. Part of this assessment involves dialogue with EM-40 customers, which the focus area has begun and which should continue. Another component of this assessment involves a comparison between the results of expected environmental transport mechanisms (including the ultimate fate of the contaminants) and the proposed plans to assess the long-term adequacy of the proposed remediation methods. Such comparisons also should be continued. One way to do this is to compare two technical studies. The first is a study to assess the leachability of materials in present DOE landfills, and the methods used to assess long-term leachability characteristics. This work would be useful for establishing DOE "waste acceptance criteria" for future waste designated for landfill disposal. Long-term leachability characterization also should assess differing climate conditions. The second is a study (see, for example, Siskind and Heiser, 1993; Heiser and Milian, 1994) to assess the materials used in stabilization and containment methods. Such a study should include information on hydraulic conductivity, permeability, long-term integrity, and application considerations under varying source conditions. Work that tracks the progress of technical work in this area can be used as a reference to establish DOE criteria for selecting both the material and the method of application. The results of these two studies should establish knowledgeable estimates on the relevant time scale and degree of containment achieved by containment and stabilization methods. Performance Measure Modification Program performance measures (USDOE, 1994), a management tool designed to facilitate a problem-solving approach, should be modified as necessary to measure factors that reflect desirable working relationships. Specifically, a record should be kept of the number of challenging technical and environmental problems that are solved, and such a count should be given greater weight in assessing the program than the presently used performance measures for EM-40 and EM-50. Higher-risk problems should be given correspondingly higher weighting factors. General Guidance and Subcommittee Perspective The preliminary recommendations outlined above have been given with the intention of

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--> retaining the practice of sound environmental science and technology in DOE's landfill remediation work, establishing implementation techniques that provide long-term protection, and developing methods to monitor the long-term effectiveness of landfills, to the extent possible. To guide its work in technology development, DOE's program should interact with, draw from, and support the best of research and application activity in appropriate disciplines. References Beedlow, P. A. 1984. Designing Vegetation Covers for Long-Term Stabilization of Uranium Mill Tailings, prepared by Pacific Northwest Laboratory Operated for the U.S. Nuclear Regulatory Commission by Battelle Memorial Institute under Contract DE-AC06-76RLO 1830, NUREG/CR-3674, PNL-4986. March. Cadwell, L. L., S. O. Link, and G. W. Gee (eds). 1993. Hanford Site Permanent Isolation Surface Barrier Development Program: Fiscal Year 1992 and 1993 Highlights, prepared by Pacific Northwest Laboratory Operated for the U.S. Department of Energy by Battelle Memorial Institute under Contract DE-AC06-76RLO 1830, PNL-8741, UC-702. September. Cline, J. F., et al. 1982. Long-Term Biobarriers to Plant and Animal Intrusions of Uranium Tailings, prepared by Pacific Northwest Laboratory Operated for the U. S. Department of Energy by Battelle Memorial Institute under Contract DE-AC06-76RLO 1830, DOE/UMT-0209, PNL-4340, UC-70. September. Cox, R.E., J.A. Karachewski, and A. Gopinath. 1995. Integrated Geological and Process Engineering Approach to Remediation of Brun Pits, Sacramento Army Depot, California, Proceedings of the Ninth National Outdoor Action Conference and Exposition. May 2-4, Las Vegas, Nev. ER'95. In press. Proceedings of Barriers for Long-Term Isolation Workshop at ER'95 co-sponsored by DOE and by the National Academy of Sciences, August 13, 1995, in Denver, Colo.

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--> Gee, G. W., K. K. Nielson, and V. C. Rogers. 1984. Predicting Long-Term Moisture Contents of Earthen Covers at Uranium Mill Tailings Sites, prepared by Pacific Northwest Laboratory Operated for the U.S. Department of Energy by Battelle Memorial Institute under Contract DE-AC06-76RLO 1830, PNL-5047, DOE/UMT-0220, UC-70. September. Gee, G. W., L. L. Cadwell, H. D. Freeman, M. W. Ligotke, S. O. Link, R. A. Romine, and W. H. Walters, Jr., 1993. Testing and Monitoring Plan for the Permanent Isolation Surface Barrier Prototype, prepared by Pacific Northwest Laboratory Operated for the U. S. Department of Energy by Battelle Memorial Institute under Contract DE-AC06-76RLO 1830, PNL-8391, UC-702. June. Gopinath, A. and D. Germar. 1995. Steam Injection Vacuum Extraction Technology Demonstration, Naval Air Station, Lemoore, California. Paper presented at the Superfund XVI Conference, Washington, D.C. November 8. Heiser, John H. 1994. Subsurface Barrier Verification Technologies, Environmental and Waste Technology Center, Brookhaven National Laboratory, BNL-61127. June. Heiser, John H. and Lawrence W. Milian. 1994. Laboratory Evaluation of Performance and Durability of Polymer Grouts for Subsurface Hydraulic/Diffusion Barriers, Environmental and Waste Technology Center, Brookhaven National Laboratory, BNL-61292. May. Mayer, D. W., P. A. Beedlow, and L. L. Cadwell. 1981a. Moisture Content Analysis of Covered Uranium Mill Tailings, prepared by Pacific Northwest Laboratory Operated for the U.S. Department of Energy by Battelle Memorial Institute under Contract DE-AC06-76RLO 1830, UMT-0207, PNL-4132, UC-70. December. Mayer, D. W., et al. 1981b. Radon Diffusion Through Multilayer Earthen Covers: Models and Simulations, prepared by Pacific Northwest Laboratory Operated for the U.S. Department of Energy by Battelle Memorial Institute under Contract DE-AC06-76RLO 1830, UMT-0204, PNL-3989, UC-70. September. Rumer, Ralph R. and Michael E. Ryan (eds.), 1995. Barrier Containment Technologies for Environmental Remediation Applications. John Wiley and Sons, Inc., New York, pp. 4-5, 51-58, 80-82, 130-138. Schulz, R. K., R. W. Ridky, and E. O'Donnell, 1995. Control of Water Infiltration Into Near Surface LLW Disposal Units, Progress Report on Field

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--> Experiments at a Humid Region Site, Beltsville, Md. (NUREG/CR-4918, Vol. 8). Simmons, C. S., and G. W. Gee. 1981. Simulation of Water Flow and Retention in Earthen Cover Materials Overlying Uranium Mill Tailings, prepared by Pacific Northwest Laboratory Operated for the U.S. Department of Energy by Battelle Memorial Institute under Contract DE-AC06-76RLO 1830, DE82000239, PNL-3877. September. Siskind, Barry, and John Heiser. 1993. Regulatory Issues and Assumptions Associated with Barriers in the Vadose Zone Surrounding Buried Waste, Environmental and Waste Technology Center, Brookhaven National Laboratory, BNL-48749. February. Soelberg, N.R, R. A. Montgomery, N. R. Jensen, and R. A. Bessent 1995. Nitric Acid Extraction of Chromium, Cobalt-60, and Cesium-137 from Disposal Pond Sediments, in Proceedings of the American Nuclear Society Decommissioning, Decontamination and Reutilization Technology Workshop, June 1995. Pp. 363-370. Strzempka, C.P., R.E. Cox, R.E. Freasier, and J.W. Critzer. 1995. Thermally Enhanced Fluid Injection with Vacuum Extraction at a Colorado Superfund Site in Proceedings of the Ninth National Outdoor Action Conference and Exposition. Las Vegas, Nev. May 2-4. U.S. Department of Energy (USDOE). 1994. Environmental Management Program Strategic Plan, M917 Version #1 Draft. October 21, 1994. U.S. Department of Energy (USDOE). 1995a. Landfill Stabilization Focus Area Technology Summary , DOE/EM-0251. June. U.S. Department of Energy (USDOE). 1995b. FY-95 Technology Catalog: Technology Development for Buried Waste Remediation. Office of Technology Development. DOE/ID-10513. U.S. Department of Energy (USDOE), Environmental Protection Agency, and DuPont In press. International Containment Technology Workshop (co-sponsored by DOE, EPA, and DuPont, Aug. 29-31, 1995, in Baltimore, Md.), and Follow-Up Review meeting (Nov. 8-9, 1995, in Dover, Del.). Voorhees, L. D., et al. 1983. Guidance for Disposal of Uranium Mill Tailings: Long-Term Stabilization of Earthen Cover Materials, prepared by the Oak Ridge National Laboratory for the U.S. Nuclear Regulatory Commission, NUREG/CR-3199, ORNL/TM-8685. October.

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