The Hanford Tanks: Environmental Impacts and Policy Choices (1996)

The committee concludes that not enough is currently known to support any final decision on tank farm cleanup. Major uncertainties exist in the areas of technology, costs, performance, regulatory environment, future land use, and health and environmental risks. Among the issues that remain uncertain are:

• effectiveness and feasibility in practice of technologies to remove and treat waste from tanks,

• costs of operations and off-site waste disposal,

• future policy and regulatory environment for managing waste at the Hanford Site,

• characterization of tank wastes, and

• relationship between tank waste removal, remediation of the surrounding environment, and ultimate land use at the site.

These are in agreement with DOE's own conclusion in its Systems Requirements Review (U.S. Department of Energy, 1995). The analysis in the DEIS reveals that there are crucial gaps in the scientific and technical knowledge that make it imprudent to decide now on a multidecade plan. Furthermore, there is no need to make such a sweeping decision now.

In view of such uncertainties, the committee recommends that the proper approach to decision making for tank cleanup is a phased decision strategy in which some cleanup activities would proceed in the first phase,

while the important information gaps are filled, in parallel, by focused research, technology and engineering development, and pilot-test and demonstration programs. The major programmatic decisions in such a phased decision strategy should be deferred, possibly for as long as 10 years, while the information needed to provide a more complete basis for sound decisions is developed. Such a phased decision strategy is compatible with the view, expressed in other National Research Council reports, that the DOE environmental remediation activities throughout the DOE Defense Waste Complex should be viewed as an experimental program rather than a straightforward cleanup effort (National Research Council, 1995b, 1996b).

The committee applauds the choice by the U.S. Department of Energy and the Washington State Department of Ecology of a phased approach as the preferred option in the DEIS. However, the phased option in the DEIS is narrowly drawn, representing two stages of scale-up of a single selected technological approach. In the phased approach described in the DEIS, the first phase is more like a demonstration project in which two pilot plants provide operating experience that will allow optimization of the relevant processes associated with a single technology before the construction of full-scale facilities. In the phased decision strategy recommended in this report, the first phase should provide information about backup technologies and overall strategies to leave open the option of selecting a different alternative for full-scale operation.

The phased decision strategy involves moving forward on two tracks. Concerning the supernatant in the double-shell tanks, uncertainties regarding characterization, removal, and treatment technology are much less significant than for other wastes in both the single- and double-shell tanks. The committee concurs with the view expressed in the DEIS that a pilot treatment plant should be built now, and it recommends that such a plant be part of Phase 1 of the phased decision strategy. However, the committee is not aware of an adequate analysis to support the choice of glass in the DEIS (and the Tri-Party Agreement) over grout, the previous solidifier, as the low-level waste form to be produced by this plant, and it believes that the choice of waste form to be produced by this plant should be reevaluated based on present knowledge before plans for the pilot plant are made final.

As for the other tank wastes, the first phase should be used to gather all of the crucial information necessary to support a selection from among a range of alternatives several years hence. In the first phase, DOE should explore technical options and overall strategies that may be realistically considered candidates for a role in the long-range tank cleanup effort. For each such option explored, the gaps in technical knowledge should be identified and analyzed. In the committee's view the first phase should be dedicated to providing the technical data on required processes and analyses of costs and impacts needed to support informed decisions.

After the first phase in the strategy recommended by the committee, DOE and the State of Washington would supplement the final TWRS Environmental Impact Statement and issue a new record of decision selecting a preferred alternative based on the new information and understanding of the feasibility and impacts of several alternative strategies developed during the first phase. The reality is that a multidecade commitment to a particular course of action for remediating all of the Hanford tanks cannot be made at this time. Unlike a record of decision to implement a typical RCRA closure or Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) remediation action for a site, whatever course is chosen now cannot be implemented very quickly, and changes will have to be made as circumstances warrant. The preferred option, estimated to cost as much as $42 billion, represents a significant commitment of national resources. A program of this magnitude will undoubtedly be subject to intense scrutiny as it is implemented and will be subject to “midcourse corrections” based on experience and external policy changes (e.g., possible changes in the controlling environmental laws and regulations).

A comprehensive strategy of environmental monitoring and risk surveillance should be an essential component of the phased approach. The goal of this strategy should be to assure that public health and the environment are adequately protected during implementation of the overall remediation program.

The phased decision strategy is similar to the CERCLA process for remediation, which involves a sequence of (1) treatability studies on the remediation target, (2) a record of decision that establishes the preferred remediation approach based on the results of the treatability studies, and

then (3) large-scale remediation using this preferred approach. This strategy is being used to remediate underground waste storage tanks at Oak Ridge National Laboratory (U.S. Department of Energy, 1994).

In making this recommendation, the committee concurs fully with the conclusion of the DOE System Requirements Review (U.S. Department of Energy, 1995).⁷ That review recommended a similar course of action, involving development of a baseline and testing of both the baseline and backups (U.S. Department of Energy, 1995).⁸

The committee recommends that DOE and the Washington State Department of Ecology not restrict their decision to choosing one among the nine alternatives identified in the DEIS. Such a restriction will limit the range of alternatives by driving the decision inexorably toward the phased alternative currently described in the DEIS because this is the only alternative that benefits from phasing. The best decisions will result if DOE compares a range of different phased alternatives and chooses the best one.

The DOE TWRS System Requirements Review observed the need for development of better alternatives.⁹ The committee agrees with the conclusion that in the absence of substantive data, estimates of the cost and performance of first-of-a-kind alternatives “are so uncertain that they can

only be used for crude screening of alternatives to define limited sets of alternatives for further testing” (U.S. Department of Energy, 1995, p. 2-26). It is not possible at this stage to support a conclusion that any alternative is clearly preferable, and the current emphasis should be placed on identifying a set of alternatives that are worthy of further technical exploration. The DOE should use its existing understanding of the uncertainties to identify a reasonable set of alternatives for examination that, taken together, provide confidence that workable and environmentally acceptable options will be available when the time comes to commit to full-scale remediation.

Backup approaches are needed because the technologies projected to meet current requirements might not work or might cost far more than anticipated. Costly options designed to meet regulatory requirements may fail to provide significant additional health benefits or environmental protection, thereby focusing attention on the need for regulatory change. Further, if funding for the Hanford Site cleanup is constrained, as it almost surely will be in an era of increasingly tight federal budgets, it will become more important to be able to optimize the cost/risk reduction ratio across the entire site.

DOE should develop fallback options and promising alternatives that might achieve most of the projected benefits of current options at a substantially reduced cost. For example, the additional $14 billion cost of the preferred Phased Implementation Alternative compared to the Ex Situ/In Situ Combination Alternative (DEIS, Table S.7.6) reduces the projected long-term health effects from 88 to 15 fatalities (DEIS, Table S.7.3). Although, as pointed out earlier in this report, the values of costs and risks in the DEIS are uncertain, one could calculate from the above a projected cost-per-avoided-cancer-fatality of nearly $200 million, an exceedingly large number, especially given the speculative and highly conservative nature of the health risk estimates in the DEIS. At the very least, this suggests that improved versions of the ex situ/in situ alternatives are worth further development and evaluation.

When funding is constrained, it is more difficult to devote resources to continued development of backup options. However, considering the great uncertainty in the cost and performance of the technologies required for the preferred alternative, the period during which

funding is constrained is precisely the wrong time to drop work on alternatives that might achieve satisfactory results at a significantly lower cost. Having such alternatives available could allow remediation to proceed expeditiously, even if funding constraints prevent timely implementation of the currently preferred alternative.

A phased decision process is inevitable, and the decisions concerning what to do in the second phase will necessarily be driven by what has been learned and accomplished in the first phase. DOE and the Washington State Department of Ecology should deliberately adopt a phased decision strategy that recognizes the uncertainties affecting the TWRS effort at this time and is aimed at reducing the uncertainties and keeping options open so that a more informed choice among better-defined alternatives is possible later. This involves pursuing a wide enough range of phased alternatives to provide adequate confidence that at least one workable option will be available for full-scale deployment in the second phase. Indeed, a single alternative will probably not be applicable to all of the tanks.

The first phase should include gathering the information needed to support a broad programmatic decision concerning disposition of the tank wastes and to implement the decision. As discussed earlier, important uncertainties are found in several key areas; cost and performance of necessary technologies, regulatory requirements, characteristics of the tank contents and the environment, and analysis of health and safety risks associated with the alternatives.

The first phase should have the following goals:

• reduce uncertainties about technology, performance, cost, and risks;

• address policy and regulatory uncertainties;

• reduce uncertainties associated with the characteristics of the waste inside and outside of the tanks;

• explore a broader range of technologies; and

• analyze interrelationships with other site cleanup decisions.

The phased option in the DEIS focuses only on pilot-scale tests for waste retrieval, separations, and vitrification activities using waste from double-shell tanks. The first phase should include activities to acquire more information about the methods for removal of wastes from the single-shell tanks to meet the 99 percent removal objective for full-scale operation in the second phase. The committee concurs with DOE's earlier recommendation that the TWRS program should “determine the methods of waste removal that will meet requirements for the extent of tank decontamination and other requirements such as allowable leakage to the ground” (U.S. Department of Energy, 1995, p. viii). The committee also concurs with the DOE recommendation for early sluicing demonstrations of representative waste to obtain performance data on retrieval of “hard pan” material using past-practice sluicing and/or enhanced sluicing (U.S. Department of Energy, 1995, p. xiv).

The recently announced Hanford Tank Initiative appears to be designed to address these and other issues associated with removal of waste from the single-shell tanks to the double-shell tanks and the ultimate closure process for the evacuated tanks after as much waste as possible has been removed (U.S. Department of Energy, 1996b). This effort will attempt to take two single-shell tanks, one low-risk tank and one presenting substantial safety risks, all the way from removal of the waste through closure. The process, which will involve close interaction with a range of stakeholder groups, will provide a better basis of information for the second phase retrieval activities. The committee endorses the decision by DOE and the Washington State Department of Ecology to undertake an effort of this type and recommends that the effort be included in the final Hanford TWRS environmental impact statement as an important part of the first-phase activities. This is consistent with NEPA requirements.

It should be noted that useful testing of alternatives need not be limited to the Hanford Site; the TWRS program should also take into account the results of related work at other DOE sites. For example, the experience of vitrifying high-level waste streams at the Defense Waste Processing Plant at the Savannah River Site, S.C., and at the West Valley (N.Y.) Demonstration Project, as well as the experience of several foreign countries, should provide useful input to the decision about full-scale vitrification at the Hanford Site. Valuable information on the scientific and technological aspects and operational experience of vitrification was presented at an international workshop conducted by the National Research Council, May 13-15, 1996, in Washington, D.C.

There is a need for ongoing coordination and discussion among DOE, the Washington State Department of Ecology, and other regulatory agencies to address and resolve regulatory and policy uncertainties. The magnitude of the proposed action requires prudent consideration of potential regulatory changes. This should include long-term interactions with the DOE Office of Civilian Radioactive Waste Management and USNRC to resolve issues concerning the acceptability of high-level waste from Hanford tanks for off-site disposal. As noted earlier, what constitutes “incidental waste” may prove critical to decisions on both waste treatment and tank closure. The committee understands that the objective of the developing Hanford Tank Initiative is to help reduce the uncertainty about the regulatory requirements for waste left in the tanks by attempting to develop a legally acceptable tank closure process. Suggestions for other initiatives to reduce regulatory uncertainties are needed. For example, DOE might petition EPA for an alternative disposal standard for waste left in the tanks, under 40 CFR Part 191.

Adequate characterization of the tank wastes and surrounding contaminated environment will be required for processing of waste that is

removed for treatment and for in situ disposition of wastes not removed from the tanks (either by choice or by necessity). A better understanding of what has already leaked and how rapidly it is moving toward the ground water is needed for assessing risks. Significant uncertainty currently exists concerning the sources and migration paths of cesium and technetium that have been found at some depth beneath the tank farms. Leakage from the tanks caused by sluicing, as well as the risk associated with waste left in the tanks, must be analyzed during the first phase in the context of the overall risks. The mechanisms and rates of migration of cesium and other radionuclides originating from the tank farms and from other waste disposal facilities at the Hanford Site also need to be better understood.

DOE and the Washington State Department of Ecology are to be commended for considering in the DEIS technologies that do not or may not meet current regulatory requirements. The development, testing, and analysis of technology alternatives during the first phase should continue unconstrained. The committee has identified several technology options that were not included in any of the DEIS alternatives and recommends that they be considered for inclusion in the first phase.

Consideration of the use of appropriately designed subsurface barriers (vertical and subsurface horizontal) could be an integral part of many of the alternative approaches evaluated in the final environmental impact statement. Such barriers could not only contain releases to the subsurface during sluicing operations, but they could also provide an effective containment of the tanks when the radioactive contents cannot be completely removed, as is the case for many of the DEIS alternatives. Thus, pilot studies on barriers are desirable in the first phase in the search for promising methods of containment (National Research Council, 1996c).

Another key issue in isolating the single-shell tanks at the Hanford Site is the manner in which the wastes remaining in the tanks are stabilized. Several alternatives in the DEIS state that the tanks would be filled with gravel, either with or without the retrieval of tank contents, depending on the alternative. While gravel may be effective in keeping the tanks from

collapsing, it would do little to reduce the possibility of human intrusion or to supplement the effectiveness of the Hanford barrier to reduce the infiltration of precipitation.

Other approaches for stabilizing tanks should be evaluated in a broadened first phase through appropriately designed bench, pilot, and demonstration studies. For example, the residue left after retrieval, or the contents without retrieval, could be covered with large cobbles that would impede drilling into the radioactive residue. Furthermore, the voids in such a very coarse sediment mass could be filled with bentonite clay, which may result in further resistance and perhaps minimize infiltration of precipitation.

The final environmental impact statement should consider additional options that appear worthy of further examination, including:

• Use of a stabilization and protection technology for the in situ residuals left in the tanks that is intermediate between the less effective gravel fill and the more complex (and less feasible) in situ vitrification. While the two extreme cases presented in the DEIS may bound the impacts from wastes left in the tanks, they may give a very distorted picture of what is reasonably achievable.

• Removal options of less than 99 percent to examine more thoroughly the tradeoffs between cost and risk reduction in removing the last fraction of the waste residue. Such an examination might be applied during the Hanford Tank Initiative.

• A deferred-action option in which tanks containing significant quantities of relatively short-lived radionuclides (90Sr and 137Cs) would be stabilized and contained by temporary physical barriers for perhaps 100 to 150 years to allow them to decay by an order of magnitude before remediation is undertaken.

It is particularly important that the first tank cleanup phase be used to assess the interactions and interdependencies among the remediation actions described in this DEIS and the other related waste management and environmental remediation activities at the Hanford Site.

For example, a decision to proceed with any full-scale remediation effort for the tanks must be based on a much better understanding of the relationship between the remediation of tank wastes and remediation of the tanks themselves and of associated contamination than is presented in this DEIS. DOE and the Washington State Department of Ecology should not make a final decision on a remediation approach for the tanks without considering the ultimate disposition of the tanks and associated contamination, but they should proceed with the first phase to gather the necessary information. The DOE TWRS System Requirements Review clearly recognizes the problems that could potentially result from a lack of integration of waste retrieval, decontamination, and final closure of the tanks (U.S. Department of Energy, 1995, pp. 2-22 to 2-23).

While the necessary technology development activities are underway, DOE should prepare a comprehensive plan for site-wide cleanup and future land use to provide the needed context for decisions concerning specific projects such as environmental remediation of the tanks and related contaminated soils and ground water. To the extent that the Tri-Party Agreement is the programmatic environmental management framework, it should be subject to a systematic analysis of costs and impacts that takes into account the interrelationships among component projects on a site-wide basis.

In its 1994 letter report to DOE (National Research Council, 1994), the committee stressed the importance of considering the tank remediation actions in a broader context. Based on its review of the DEIS, the committee believes that these comments continue to be valid. In this

context, the attempt in the DOE Hanford Tank Initiative to address closure issues on an accelerated basis is a welcome step forward. ¹⁰