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

The Hanford Site (also known as the Hanford Reservation) occupies approximately 1,450 km² (560 square miles) along the Columbia River in south-central Washington, north of the city of Richland. The site was established by the federal government in 1943 to produce plutonium for nuclear weapons. Currently, the mission of the site, under the responsibility of the U.S. Department of Energy (DOE), is management of wastes generated by the weapons program and remediation of the environment contaminated by that waste. As part of that mission, DOE and the State of Washington Department of Ecology prepared the Hanford Site Tank Waste Remediation System Draft Environmental Impact Statement (DEIS).

The DEIS evaluates alternative strategies for managing and disposing of radioactive, hazardous, and mixed wastes from Hanford underground storage tanks (large single- and double-shell tanks and miscellaneous small tanks), as well as the elements cesium and strontium in capsules currently stored on the site. Within the DEIS are descriptions and analyses of the potential enviromental consequences and the impact on public and worker health and safety related to various alternatives for waste management and remediation of the facilities. These alternatives range from no waste retrieval and treatment actions to extensive retrieval, with varying levels of treatment, and disposal of portions of the treated waste on and off site. The DEIS provides a source of information for decision makers to consider when selecting remediation actions.

At the request of the DOE Office of Waste Management, the Committee on Remediation of Buried and Tank Wastes conducted a general review of the DEIS. Its findings and recommendations are the subject of this report. Selection of a disposition plan for these wastes is a decision of national importance, involving potential environmental and health risks, technical challenges, and costs of tens to hundreds of billions of dollars. The last comprehensive analysis of these issues was completed 10 years ago, and several major changes in plans have occurred since. Therefore, the current reevaluation is timely and prudent. The committee endorses the decision to prepare this new environmental impact statement, and in particular the decision to evaluate a wide range of alternatives not restricted to those encouraged by current regulatory policies.

The committee's principal findings identified during this review, as discussed briefly below, are: (1) significant uncertainties exist that limit the ability of DOE to define and characterize disposal alternatives and, hence, to select a final disposal alternative for all of the tanks' wastes; (2) in light of these uncertainties, a phased decision strategy that considers multiple alternatives involving both ex situ and in situ disposal is needed, rather than a phased implementation plan for a single alternative as DOE and the Washington State Department of Ecology propose in the DEIS; and (3) analyses in the final environmental impact statement should be broadened and improved to support such a phased decision strategy.

Uncertainties, both stated and unstated, concerning the Hanford wastes, the environment, and the remediation processes are found throughout the DEIS. Not enough is known at this time to choose a final, long-term strategy for management of all of the Hanford Site tank wastes. Furthermore, such a decision is neither required nor prudent at this time. Significant 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 in practice of technologies to remove and treat waste from tanks,

• costs of operations and off-site waste disposal,

• future policy and regulatory environment,

• characterization of tank wastes,

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

• long-term risks associated with various alternatives for treating and processing the tank wastes, both in relation to residues left on site and risks transferred off site when processed wastes are moved to a repository.

The scope of the DEIS also has significant limitations. Because the DEIS does not address remediation of the tanks themselves and associated environmental contamination, the alternatives it considers for tank waste remediation are not defined well enough. In addition, the connections between tank remediation alternatives and other cleanup activities at the Hanford Site are not taken into account. Because tank waste remediation alternatives are analyzed and evaluated in isolation from other geographically-related contamination at the Hanford Site, information about risks and costs in the DEIS is difficult to place in a proper perspective.

The DEIS surveyed a wide range of remediation options, including strategies in which tanks with varying contents are treated differently. However, the committee believes that additional alternatives for management of the tank wastes need to be explored in parallel, using a phased decision strategy like the one outlined in this report. Such a strategy would provide flexibility in the event that specific, preferred technologies or management approaches do not perform as anticipated or that innovative waste management and remediation technologies emerge. Among additional options that should be analyzed are (1) in-tank waste stabilization methods that are intermediate between in situ vitrification and filling of the tanks with gravel, (2) subsurface barriers that could contain leakage from tanks, and (3) selective partial removal of wastes from tanks, with subsequent stabilization of residues, using the same range of treatment technologies as in the alternatives involving complete removal of wastes.

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

The preferred Phased Implementation Alternative presented in the DEIS does not adequately address all of the uncertainties that make it difficult to decide how to complete remediation of the tanks. During Phase 1, cesium and technetium, the most troublesome elements in a vitrifier, are to be removed from the high-level waste that is sent to the pilot vitrification plant, potentially

limiting the value of information obtained from the pilot plant operations. This may also delay a decision on the final waste form for these elements. In addition, the plan for this phase does not consider promising ancillary technologies (some of which may already be under development in other parts of the DOE Environmental Management program) such as subsurface containment barriers, other materials and processes for stabilizing wastes left in the tanks, and a range of waste forms for the low-activity materials separated from the wastes removed from the tanks, all of which could play important roles in the remediation approach ultimately selected.

Decisions regarding tank remediation must consider risk, cost, and technical feasibility. Where risks are involved, care should be taken to present a range of potential risks, including expected or most likely estimates as well as the upper-bound estimates presented in the DEIS. While upper-bound estimates may give confidence that actual impacts will not exceed those presented in the DEIS from a worst-case perspective, the inherent uncertainties in risk assessments can distort the comparison of alternatives. This is of particular concern when the upper-bound estimates are derived from a cascade of parameters, each of which was also derived on an upper-bound basis.

While the committee recognizes the utility of quantitative risk assessment in the comparison of remedial alternatives, the limitations of analysis must be underscored. Given the complexity of the Hanford tank farms, many of the potential uncertainties cannot be measured, quantified, or expressed through statistically derived estimates. According to the 1996 National Research Council report Understanding Risk, the 1996 U.S. Environmental Protection Agency report Proposed Guidelines for Carcinogen Risk Assessment, and a recent draft report by the Commission on Risk Assessment and Risk Management, characterization of risks should be both qualitative and quantitative. In this case, qualitative information should include a range of informed views on the risks and the evidence that supports them, the risk likelihood, and the magnitude of uncertainty. Such evaluations of risk should be based on deliberative scientific processes that clarify the concerns of interested and affected parties to prevent avoidable errors, provide a balanced understanding of the state of knowledge, and ensure broad participation in the decision-making process.

It should be expected that the environmental regulations governing the tank wastes, and the Hanford Site in general, will change over the time during

which waste management and environmental remediation occur. DOE should work with the appropriate entities to ensure that future regulatory changes and the future selection of tank remediation approaches are on convergent paths.

The preferred alternative for tank remediation that is identified, analyzed, and evaluated in the DEIS is phased implementation of a particular action plan. This alternative includes first a demonstration phase, up to 10 years in duration, during which a portion of the double-shell tank waste would be retrieved, treated, and stored. Using the experience of the demonstration phase, a second phase, lasting approximately 40 years, would complete the task of retrieval, treatment, and storage of the remaining tank wastes.

The committee shares the preference for a phased approach as stated in the DEIS. The committee believes that a phased approach should be a strategy for guiding decision making as information is developed, not merely a plan for implementing decisions made during a single point in time by scaling-up a single, preselected technological approach. Realistically, it is not timely to choose remediation technologies for the less tractable single-shell tanks. The important action now is to select the most promising technologies to be developed, tested, and evaluated for performance. DOE should undertake a program of research, development, and pilot testing and demonstrations to resolve the major process and technical uncertainties concerning single-shell tanks, while pursuing its plans to build a pilot treatment plant for double-shell tank supernatant. In the initial phase of this program, technologies should be selected for evaluation based on technical merit and the environmental consequences, and current regulatory policies should not rule out additional study of otherwise attractive options.

Decisions regarding final disposition of single-shell tank wastes should be deferred until the outcome of this evaluation phase is known. This could take as long as 10 years. The extensive base of information, including what is presented in the DEIS, that is now available for planning should be used to support future decisions. Valuable experience should be gained while retrieving and treating wastes from two single-shell tanks, which the committee understands will be accomplished under the upcoming Hanford Tank Initiative.

This initiative could serve as a good starting point for the DEIS Phase 1 single-shell tank investigation.

A prudent approach to the first phase of the decision-making process requires identification of alternative strategies for the entire remediation process. Each remediation approach selected for analysis should include a plan for research on gaps in technical knowledge, environmental impacts, and other important uncertainties. Results of this research should inform those responsible for making subsequent decisions while scaling up from bench scale, to pilot plant, to full-scale operation. When the applicability and maturity of proposed technologies are uncertain, fallback options should be pursued in parallel. To provide a genuine choice, several phased alternatives should be fully developed for consideration by DOE management, regulators, and the public. Until a range of phased alternatives is compared, it will not be clear whether the one presented in the DEIS will emerge as the best.

Concerning the management and disposal of the cesium and strontium capsules and of the miscellaneous underground storage tanks, the committee found that the DEIS lacks enough substantive information for an evaluation of the proposed remediation strategies. Over 99 percent of the tank wastes is in the single-shell and double-shell tanks, and that is where the greatest potential for health and environmental risks exists. However, the extremely high concentration of radioactivity and the nature of the materials in the capsules necessitate a more thorough discussion of their treatment, disposal, and environmental impact. There are serious deficiencies in the attention given to the long-term changes in the chemical and isotopic composition of the cesium and strontium capsules. The large number and wide distribution of the miscellaneous underground storage tanks make a more complete discussion of their management necessary.

1. The proper approach to decision making for tank farm cleanup is to use a phased decision strategy in which some cleanup activities would proceed in the first phase while important information gaps are filled concurrently to define identified remediation alternatives more clearly, and possibly to identify new and better ones. As part of this strategy, periodic independent scientific and technical expert reviews should be conducted so that deficiences may be recognized and midcourse corrections be made in the operational program.

2. A comprehensive strategy of enviromental 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.

3. Plans for building a pilot plant should proceed, but in the context of a phased decision strategy that does not preclude processing of wastes other than the double-shell tank supernatant or producing waste forms other than the glass currently planned.

4. The first phase of such an approach should also include gathering crucial information necessary to support selection from a broad range of well-defined alternatives to be made several years hence. Goals of the first phase should be to (a) reduce uncertainties concerning technology performance, cost, and risks, (b) address policy and regulatory uncertainties, (c) adequately reduce uncertainties associated with the characteristics of wastes inside and outside the tanks, (d) evaluate environmental and public health consequences, (e) explore a range of technology options, as needed, and (f) analyze interrelationships with other site cleanup decisions.

5. The development, testing, and analysis of alternatives during the first phase should continue unconstrained by current regulatory requirements and should examine currently untested technologies.

6. A comprehensive plan should be developed to define the programs for waste management, site-wide remediation, and future land use for the entire Hanford Site.

7. The final environmental impact statement should be as useful as possible to the public and decision makers outside DOE. It should go beyond

merely providing a description of alternatives and a comparative evaluation of their impacts by discussing the critical elements that constituted the basis for the selection of the preferred alternative. In addition, to the extent possible, the relationship between the tank waste remediation alternatives and other contamination and anticipated cleanup actions at the Hanford Site should be analyzed.