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--> 2 Making Better Decisions A Conceptual Management Approach To meet the challenges identified in Chapter 1, a consistent management approach is needed that systematically takes into account relevant considerations at the proper time. This chapter describes the conceptual basis of an approach that, in the committee's judgment, can be used as the foundation for improved decision making in the development and implementation of effective, comprehensive plans for managing contaminated sediments. The proposed approach is centered around risk management because contaminated sediments are only a problem to the extent that they pose risks to human health and the environment. The general approach is outlined in the first section of the chapter, which lays out a road map for the development of a management plan in the form of a flow diagram and supporting text. The remainder of the chapter examines the ways risk management comes into play during project planning and implementation. Various perspectives on risk and specific risk-based approaches that can be used to improve decision making are discussed. CONCEPTUAL VIEW OF THE MANAGEMENT OF CONTAMINATED SEDIMENTS To provide a framework for a systematic analysis, the committee developed a conceptual overview of the process for managing contaminated sediments (see Figure 2-1). Each element is discussed briefly in this section, and many of the topics are examined in more detail later in this report. It must be emphasized that the diagram appears similar to, but has a different purpose than, the formal decision-making frameworks available for managing contaminated sediments. USACE and the EPA worked together to develop a framework for evaluating alternatives for
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--> FIGURE 2-1 Conceptual overview of the management of contaminated sediments. Note: For more detail on preliminary site assessment, see Figure 4-1. For more detail on implementing the management plan, see Figure 5-1.
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--> the disposal of dredged material associated with navigation projects (Code of Federal Regulations, Title 33, Sections 230 to 250)1 and for obtaining disposal permits under Section 404 of CWA (EPA, 1994). Another framework was developed for evaluating alternatives for remediation in Superfund projects (EPA, 1994). The committee recognizes the utility of these formal decision-making approaches. Figure 2-1 is intended simply to provide a generic overview of the management process and a context for the various components of the committee's assessment. The forces that drive an effort to manage contaminated sediments may dictate certain courses of action. As discussed in Chapter 1, the two fundamental driving forces are dredging, which is required to meet port and harbor navigation requirements, and environmental cleanup, which is required to reduce contaminant levels to a specific value. The preliminary site assessment begins with defining the degree and distribution of contamination, as well as justifying the consideration of taking appropriate actions. The data are used to decide whether and what type of contamination is present, to define the sampling area and density needed to characterize the site more fully, and to identify gaps and uncertainties in the available information that need to be overcome through further surveys, sampling, or studies. This report does not dwell on the initial screening process, focusing instead on how to manage contamination once it has been identified. If a site is judged to be contaminated, then decision criteria, and the constraints within which actions must be taken, need to be identified. Decision criteria include technical, regulatory, and stakeholder considerations Technical criteria are related to site characteristics. For instance, some management strategies are more suited to handling small rather than large volumes of sediments; some strategies are appropriate for handling organic contaminants and others for metals; and some are limited to handling sediments with particular physical characteristics, including water content and grain size. The question of risk also needs to be addressed. What level of risk is acceptable? What levels of contamination are acceptable? Risk can never be eliminated completely, and all management strategies are designed to reduce risk to a certain level at a specific cost. Cleanup standards can be dictated by applicable laws and regulations, which impose a variety of constraints on the management of contaminated sediments. The interests of stakeholders also influence the choice of management strategies. Regulatory realities and stakeholder interests need to be kept in mind prior to and throughout the planning and implementation of a project. Based on the decision criteria and constraints, a problem statement and objectives need to be developed and the need for further data identified. Because it can be 1 References to the Code of federal Regulations will be abbreviated using the format 33 CFR §230 to §250.
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--> very expensive to fill critical data gaps, refine cleanup standards, and reduce uncertainties in the relevant site parameters, the purposes for which data are to be collected need to be delineated clearly at this stage, and justification needs to be provided for any proposed additional surveys and studies. The next step is making a detailed site-specific assessment. The volume, distribution, and degree of contamination need to be determined as precisely as necessary and affordable for a specific project. The level of effort required depends heavily on the survey technology and sampling approach. Ideally, the distribution of contamination in three dimensions would be determined so that all unacceptable contamination—and only that amount and no more—could be removed for appropriate treatment. However, in the committee's judgment this is neither technologically nor economically feasible at this time. Sufficient information needs to be gathered to assess the risks and hazards posed by the contamination, the degree of risk reduction required, and the projected rate of natural recovery if no action is taken. Risk assessment techniques are discussed later in this chapter. If the level of estimated risk calls for remedial action, then management options need to be identified and organized in order of their applicability. Approaches that cannot be used, because of constraints identified earlier, must be screened out and eliminated, and the remaining strategies ranked according to implementation costs and uncertainties. If the level of risk is very high, then interim controls, such as a ban on fishing, may be implemented immediately. Source control also needs to be considered to eliminate continuing contamination and to ensure that remedial measures will not have to be repeated at a later date. Once management strategies have been ranked, the most promising options can be compared based on an evaluation of risks, costs, and benefits. In some cases, the best choice is obvious, but in other cases additional data or analytical estimates may be needed. The fundamental issue to be addressed is how best to allocate scarce resources using an integrated set of tools. The latter part of this chapter examines analytical tools—risk analysis, cost-benefit analysis, and decision analysis—for examining trade-offs and arriving at a management plan. Based on the results of comparisons and evaluations, a comprehensive, long-term management plan needs to be developed that is reasonably certain to meet the remediation criteria and to have the least economic impact, in terms of direct costs and the impact on the local, regional, and national economy. The acceptability of the associated risks and costs is, at this stage, a matter of judgment. The relevant risks need to be communicated effectively to stakeholders, who need to be involved and invested in the decision-making process. The plan needs to be reviewed in light of the mandates of relevant agencies, commercial and business interests, and public concern for the environment and the economy. If the plan is not acceptable, then the objectionable elements need to be removed through reconsideration of the balance of risks, costs, and benefits. If the plan is acceptable,
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--> then the associated expenditure of time and money is justified, and the plan can be implemented. The final step is implementation of the management plan. Systems Approach to Risk-Based Management To implement a management plan, a systems framework is needed for the engineering feasibility studies, the design, and the optimization of selected remediation technologies Systems engineering is widely used in the design of complex technological processes to ensure that the various subsystems function together smoothly and achieve optimum overall effectiveness. A formalized approach and discipline are essential for defining potential solutions to the management of contaminated sediments. Systems analysis, at its simplest, includes the definition of a boundary that surrounds a problem, quantitative representation of how the components within the boundary interface and interact, the constraints imposed on the bounded problem, and an evaluation of alternative ways to meet the agreed goals. The analysis applied in systems engineering can be mathematical, with each goal and constraint specified by exact quantitative algorithms or with model parameters with probability distributions. Fundamentally, however, systems analysis represents a structured approach to developing and improving the design of a complex system and its subsystems, in light of overall project goals and objectives. The approach, which is discussed further in Chapter 5, involves trade-off studies addressing design alternatives, technical and operational considerations, system performance, risks, costs, and benefits. Finally, on completion of the steps identified in the management plan, the residual risks at the site need to be assessed to ensure that the goals have been met. If the residual risks are unacceptably high, then an iteration of the decision-making process may be necessary. It also can be useful to examine whether predictions made during the decision-making process proved to be accurate so as to inform future decision-making processes related to other contaminated sediment sites. TRADE-OFFS IN RISKS, COSTS, AND BENEFITS A central feature of the risk-based management approach within a systems framework is the delineation of trade-offs in risks, costs, and benefits that need to be made in choosing the best course of action among available alternatives. The fundamental difficulty involved in making decisions about how best to manage contaminated sediments lies in the measurement of the gains and losses to various stakeholders. For example, the well-being of ports and the general public is advanced by dredging, but the benefits must be weighed against the risks and
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--> costs of dredging and managing sediment. Similarly, the benefits of environmental cleanup to human health and ecosystems must be weighed against the costs. The chances of identifying and implementing the best possible solution are enhanced when stakeholders have a solid understanding of all the gains and losses associated with various alternatives. A number of decision-making tools can be used to determine trade-offs in risks, costs, and benefits. These tools include risk analysis, cost-benefit analysis, and decision analysis. Risk analysis involves the extended application of risk assessment techniques, which typically are used only to assess the severity of inplace contamination. Cost-benefit analysis examines the costs associated with the reduction in risk to acceptable levels as established by risk assessments. Decision analysis incorporates the data from cost-benefit analysis into a computational framework that estimates the outcome of selected management approaches and evaluates the relative merits of alternative courses of action. Risk Analysis Risk analysis encompasses risk assessment and risk management, concepts defined in Chapter 1, as well as risk communication (USACE, 1991; EPA, 1996, and references therein). Risk communication is a dialogue that takes place on two levels, first when the risk assessor communicates technical findings to the risk manager, and later when the risk manager conveys the results to the public and other stakeholders (see Chapter 3). All three aspects of risk analysis—assessment, management, and communication—are essential to the cost-effective management of problems in general (NRC, 1996) and to the management of contaminated sediments in particular. Currently, however, they are not incorporated into the contaminated sediment management process. In fact, all three aspects of risk analysis are seldom included in any single project. As noted in Chapter 1, risk assessment typically is used only to determine the hazard posed by the initial contamination. Various methods, some more rational than others, have been used to conduct risk assessments. After the initial risk assessment, however, risk may not be addressed again directly in the sediment management process. There is little direct regard for the risks associated with sediment removal or relocation or for post-project residual risks. Although risk reduction capability is a consideration in the selection and evaluation of sediment management strategies, this capability typically is only predicted or estimated, not measured. For example, the efficacy of remediation technologies is usually monitored by measuring physicochemical parameters rather than by assessing residual risks (see Chapter 5). The absence of quantitative data on risk reduction capabilities complicates attempts to evaluate strategies for the disposal, remediation, and beneficial use of sediments.
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--> But the fundamental reason for not using risk analysis more lies in the uncertainties inherent in current risk assessment techniques,2 which are subject to debate and have several limitations: They provide only approximations of effects on human health and the environment; they provide evidence of acute, not chronic (such as on reproduction or growth), effects; and they do not take into account all conditions at a test site. Without a quantitative link between accepted measures of sediment quality and corresponding risks to the ecosystem and human beings, there will continue to be disagreements concerning the magnitude of the original problem and the efficacy of various remediation strategies (see Box 2-1). Although the resolution of these issues is outside the scope of the present report, it seems clear that improved end-points must be developed and interpreted constructively. In the meantime, however, decisions need to be made, and risk analysis can be used to improve these decisions despite the inherent uncertainties. Improved techniques for measuring risk would help conserve scarce resources by ensuring that money is not wasted on unnecessary remediation and by providing end-points for the quantitative evaluation of strategies for the disposal, remediation, and beneficial use of sediments. Thus, there are significant opportunities for improving and extending the application of risk analysis in the contaminated sediment context. The importance of risk analysis reaches beyond the issues just discussed because the results of risk assessments are essential elements in the cost-benefit analysis and the decision analysis. Cost-Benefit Analysis To make decisions about contaminated sediments, decision makers need to weigh the relevant factors, including costs and benefits, and make trade-offs. Risk assessment can provide information about the exposure, toxicity, and other aspects of the contamination, but relying on this approach alone can result in the less-than-optimum allocation of resources unless additional information is considered. For example, even though the concentration of contaminants at a particular site could be toxic enough to induce mortality in a test species, this fact, by 2 The risk assessment paradigm applied by the EPA to human health issues includes source and release assessment (hazard identification), exposure assessment, dose-response (or effects) assessment, and risk characterization When this fundamental paradigm was reviewed and reevaluated for applicability and efficacy from the standpoint of ecological assessment, a fifth step was needed consideration of simultaneous or alternate potential sources of environmental perturbation The EPA framework for ecological risk assessment (see EPA, 1996) includes the following steps problem formulation (planning, site characterization. stressor characterization, end-point characterization), analysis (exposure assessment, effects assessment), and risk characterization (exposure and effects comparison, determination of uncertainty and limitations, evaluation of ecological significance).
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--> itself, does not indicate the spending level that would be justified for cleanup. The decision must be a determination of the most efficient way to allocate resources based on information, risks, and costs. Cost-benefit analysis, which makes use of information provided in risk assessments, is a widely used tool that can provide a comprehensive understanding of the trade-offs implicit in choices among dredging or disposal alternatives. (Costs and benefits are defined more completely in Appendix D.) Benefits are the public's willingness to pay for all aspects of the project. Costs are the ''opportunity costs," including all the production factors used in construction of the project. Benefits include direct services, such as transportation, as well as indirect services, such as the value of ecological protection. The nature of the choice is illustrated in Figure 2-2. For purposes of this example, the objective is to relate the amount of contaminant removed from the sediment to the costs and benefits associated with its removal. It is assumed that the magnitude of costs and benefits related to various dredging strategies are known. The vertical axis measures the costs and benefits of removing contaminants; the horizontal axis measures the percentage removed. As the percentage of contaminants removed increases, the costs increase at an escalating rate because it becomes more and more difficult to locate and eliminate the remaining contaminants. At the same time, the benefits of contaminant removal accrue at a decreasing rate, so that additional removal continues to provide benefits but in smaller and smaller increments. The best decision is point A, at which the difference between costs and benefits is the greatest. A poor decision would be point C. at which the costs are greater than the benefits. At point B, the benefits just offset the costs. The important thing is that there are trade-offs associated with every course of action, regardless of the approach used to select that alternative. Many federal agencies use cost-benefit analyses extensively and have guidelines that explain how costs and benefits are to be computed and used (Water Resources Council, 1983). These concepts can be readily applied to decisions about environmental issues but have not been used systematically in the contaminated sediments context, except when new-construction dredging is involved, in which case cost-benefit analysis is required. Cost-benefit analyses can be useful for evaluating proposed management strategies. The basic principle is that activities should be pursued as long as the overall gain to society, correctly measured, exceeds the social cost. The difficulty lies in measuring the benefits and costs, or, more to the point, in projecting what they will be before a strategy is implemented. The method of computing cost-benefit ratios depends, in part, on how costs and benefits are defined. Three types of costs are involved in contaminated sediments cases: dollar costs of remediation and cleanup, dollar costs of foregone port services, and environmental costs. None of these costs can be measured precisely. The benefits of an action are simply the costs of not taking that action. Uncertainties concerning the costs of remediation, a major focus of this report, are addressed in Chapter 5. The difficulties involved
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--> BOX 2-1 Evaluating Sediment Contamination: Effects-Based Testing and Sediment Quality Criteria Three specific situations or reasons exist for evaluating sediments (Brannon and McFarland, 1996). The first is to determine what unacceptable adverse effects, if any, navigation channel sediments will pose in a particular placement environment. EPA regulations 40 CFR §220 to §228 and 40 CFR §230 provide guidance on the aquatic placement of dredged material. The second reason is to determine what effects on aquatic ecosystems sediments may have if they are left undisturbed or if they are removed for environmental purposes. If sediments are determined to have unacceptable environmental effects, consideration may then be given to some type of remediation, which may or may not include removal. If sediments are to be removed, then the potential effects they will have at the placement site must be considered. The third reason, recently advanced by the EPA, is for the source control of contaminants. Determination of locations where sediments, as sinks for contaminants, have unacceptable environmental or human health impacts could lead to identification of the source of the contamination, Effects-based testing is currently the primary means of sediment evaluation and is a basic tool for estimating the risk of various sediment management techniques (dredging, cleanup, etc.) to the aquatic environment. The assessment of sediment quality is a hazard assessment intended to determine whether the exposure of aquatic biota to a sediment will cause an increase in the incidence of adverse, unacceptable effects. To supplement effects-based testing, the EPA also is developing sediment quality criteria (SQC) as a way of determining the potential biological impacts of contaminants in sediments (DiToro et al., 1991) and has published proposed numerical SQC in the Federal Register for public comment (Federal Register, vol. 59, no. 11, January 18, 1994, p. 2652). Effects-based testing involves the use of organisms to determine the biological effects of sediments. In general, test species are exposed in the laboratory to sediments being evaluated, and their response is compared with that of reference organisms with regard to specific biological end-points, such as mortality. Effects-based testing inherently accounts for all of the contaminants present in a sediment and the potential interactions among contaminants because the approach relies on the exposure of test species to whole sediment. Therefore, the precise chemical composition of the sediment need not be known. Potential interactive effects of multiple contaminants are integrated based on the response of the test organism. Much of the criticism of the effects-based approach for evaluating dredged material centers on the lack of chronic, sublethal test end-points
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--> (i.e., growth and reproduction) in the current regulatory program. However, several chronic, sublethal sediment toxicity tests are in the late stages of development. (Dillon et al., 1995; Emery and Moore 1996; Liber et al., 1996) and may now be used as part of a dredged material evaluation. In addition, bioaccumulation tests account for the uptake of contaminants over long-term exposures (28 days, and if necessary steady state can be estimated) and may be used to infer the potential for chronic, sublethal effects. The EPA is developing SQC pursuant to the CWA, §304(a)(1) and §118(c)(7)(c) which are aimed at protecting benthic organisms from chronic sediment toxicity. The SQC approach advocated by the EPA for estimating the potential risk posed by contaminated sediment uses equilibrium partitioning modeling to predict pore water concentrations of non-polar organic compounds. These predicted pore water concentrations are then compared to chronic water quality criteria as an effects threshold. The EPA has proposed that SQC be used both in preventing sediment contamination and in establishing cleanup targets. SQC are single contaminant criteria, yet sediments typically contain a complex mixture of contaminants. Regulatory assessments, such as dredged material evaluations, require that the interactive effects of sediment contaminants be evaluated. Sediments are likely to contain contaminants for which SQC do not exist, which means that effects-based testing will still be required to determine whether exposure of aquatic biota to a sediment will cause an increase in the incidence of adverse, unacceptable effects. Government agencies embrace effects-based testing as a basis for making decisions concerning the placement of sediments and are moving to develop chronic effects-based testing protocols and applying more formalized risk assessment to bioaccumulation test results. Further development of chronic tests will provide improved end-points. There would still be a need to understand and interpret these end-points in a regulatory context to determine what constitutes an unacceptable adverse effect. in quantifying the value (costs) of economic services provided by ports and the environmental costs of remediating (or not remediating) contaminated sediments are discussed in Appendix D. Although the measurement of costs and benefits can be laborious, it is worth the effort in projects where the stakes are very large. Even for small projects for which detailed measurements may seem impractical, a consideration of economic issues can be useful for making qualitative judgments about management strategies. For example, remediation technologies can be evaluated on the basis of cost
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--> FIGURE 2-2 Conceptual illustration of the trade-offs involved in cost-benefit analysis. A = best decision point; B = benefits equal costs, C = worst decision point. effectiveness, at least in a qualitative sense (quantitative comparisons are precluded because of insufficient data on both cost and effectiveness [see Chapter 5]). Also, basic economic principles suggest some guidelines for decision making in general. (The derivation of these guidelines is explained in Appendix D.) For example, certain initial measures to reduce contamination may be relatively inexpensive, whereas the corresponding social returns can be quite high. However, the extensive cleanup of contaminated sediments tends to become increasingly costly as the concentration of contaminants declines. Furthermore, the social gains from cleanup tend to increase more slowly as the contaminant concentration declines. Decision makers are cautioned against seeking extreme solutions without first measuring social benefits and costs. The appropriate use of cost-benefit analyses could be encouraged through changes in federal policies and practices. For example, although cost-benefit analysis is currently required only for new-construction dredging, it might also improve decision making in situations that require major or continuing maintenance dredging where, even though the need to dredge has been established, decisions still need to be made concerning many other variables. Unfortunately, USACE guidelines for cost-benefit analyses are not complete and are not followed in all cases. The guidelines discuss, for example, how to account for situations in which additional traffic is encouraged at one port at the expense of another port, but these provisions are not employed in practice. The guidelines do not even address the possibility of price changes in navigation services as a result of
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--> changes in national policies. Although a detailed analysis of these issues is outside the scope of this report, it is clear that efforts to improve the precision, completeness, and ease of use of cost-benefit analyses could improve decision making. Decision Analysis Decision makers need to know how to use information about risks, costs, and benefits that may be controversial and difficult to evaluate, compare, or reconcile. The committee devoted considerable attention to finding ways to meet this need, which was identified in an earlier NRC report (NRC, 1989). Indeed, the demand is becoming increasingly urgent as the number of proposals for the remediation of contaminated sediments grows and as costs and controversies multiply. One tool that can help resolve problems with many variables is decision analysis, a computational technique for estimating the outcomes of management approaches. Decision analysis does not provide absolute solutions but can offer valuable insights. It can integrate the results of key management tasks (e.g., risk assessment, site assessment, economic assessment, technical feasibility studies) into models of the problem as it appears from the perspectives of various stakeholders. The modeling approach allows stakeholders to explore disagreements about subjective elements of the problem, thereby expediting problem solving. The process also formally accounts for uncertainties The output is the identification of the optimum approach, that is, the strategy that offers the best odds for successful risk management. Although decision analysis is not a new technique, it apparently has yet to be used in managing contaminated sediments. The committee's assessment, including its application of decision analysis to a hypothetical test case involving remediation of a hot-spot contamination site (see Appendix E), suggests that this approach may be valuable for sorting out management options when more conventional methods fail. Decision analysis is applicable in highly complex, contentious situations because it can accommodate more variables (including uncertainty) and perspectives than other analyses, such as cost-benefit analysis, that measures a single outcome, and because the methodology of decision analysis is explicit and rigorous and the analytical pathways are reproducible. However, because decision analysis is technical in design and involves complex computations, it will take some time and effort for stakeholders to gain confidence in the approach. Remediation of contaminated sediments tends to be expensive and arduous, so any approach that helps expedite corrective action and resolves environmental controversies fairly and cost effectively could prove valuable. Decision analysis appears to be such an approach. Its use may be particularly timely now because recent advances in computer hardware and software now make it possible to perform user-friendly, interactive analyses.
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--> SUMMARY The risk-based approach outlined in this chapter provides a rational strategy for the cost-effective management of contaminated sediments. This discussion also highlighted opportunities for improving management through the use of risk analysis, cost-benefit analysis, and decision analysis. Risk analysis is essential to the cost-effective management of contaminated sediments but has not been applied as often as it might be. At present, risks typically are assessed only for the initial contamination, and little or no consideration is given to the risks of sediment removal or relocation or the risks remaining after remediation. This approach limits the capabilities of evaluating strategies for sediment disposal or remediation, and opportunities for the beneficial use of sediments. The scientific underpinning of risk analysis also requires attention. Various types of sediment quality criteria are under development, but these approaches have not been linked quantitatively to ecological or human health risks. Environmentally acceptable end-points are needed for sediment contamination. In the contaminated sediments context, cost-benefit analysis usually is used only for major new navigation dredging projects and tends to be narrow in scope. The use of cost-benefit analysis could be extended to help identify the optimum solution for managing contaminated sediments. From an economic standpoint, the best strategy is the one in which benefits outweigh the costs by as much as possible. The costs involved are difficult to calculate and uncertain, but comprehensive cost-benefit analysis can still be worth the effort in very expensive or extensive projects. Informal estimates or cost-effectiveness analysis may suffice in smaller projects. There is also room for improvement in federal guidelines for the computation and use of benefit and cost data For example, the guidelines do not take into account the economic effects of shifts in transportation patterns or changes in the prices of navigation services. Decision analysis offers a way to balance the consideration of risks, costs, and benefits of various strategies for managing contaminated sediments. Decision analysis could be particularly valuable because it can accommodate more variables (including uncertainty) and different perspectives than other techniques, such as cost-benefit analysis, that measure single outcomes. Decision analysis also can serve as a consensus-building tool by enabling stakeholders to explore the subjective elements of problems and, perhaps, find common ground. However, because it is technical in design and involves complex, albeit logical, computations, decision analysis is probably worth the effort only in exceptionally complicated and contentious situations in which stakeholders are willing to devote the time to gain confidence in the approach
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--> REFERENCES Brannon, J.M. , and V.A. McFarland 1996. Technical Considerations for Sediment Quality Criteria. Paper presented at Water Quality '96 Environmental Engineering and Ecosystem Management, U S Army Corps of Engineers, 11th Seminar on Water Quality held February 26, 1996-March 1, 1996, in Seattle, Washington. Dillon, T.M., D.W. Moore, and D.J. Relsh 1995. A 28 day sediment bioassay with the marine polychaete, Nereis (Neanthes) Arenaceodentata. Pp. 201-215 in Environmental Toxicology and Risk Assessment, vol. 3. J. S. Hughes, G.R. Biddinger, and E. Mones, eds ASTM STP 1218. Philadelphia: American Society for Testing and Materials. DiToro, D.M., C.S. Zarba, D.J. Hansen, W.J. Berry, R.C. Swartz. C.E. Cowan, S.P. Pavlou. H.E. Allen, N.A. Thomas, and P.R. Paquin 1991. Technical basis for establishing sediment quality criteria for nonionic chemicals using equilibrium partitioning Environmental Toxicology and Chemistry 10: 1541-1583. Emery, V.L., and D.W. Moore 1996. Preliminary protocol for conducting 28-day chronic sublethal sediment bioassays under the estuanne amphipod Leptocheirus plumulosus (Shoemaker). In Environmental Effects of Dredging. Technical Note EEDP-01-36. Vicksburg, Mississippi: U.S. Army Engineer Waterways Experiment Station. Environmental Protection Agency (EPA). 1992. An SAB Report Review of Sediment Quality Critena Development Methodology for Non-ionic Organic Contaminants. EPA-SAB-EPEC-93-002. Washington D.C.: EPA. EPA. 1994. Assessment and Remediation of Contaminated Sediments (ARCS) Program, Remediation Guidance Document. Great Lakes National Program Office. EPA 905-R94-003. Chicago: EPA. EPA. 1996. Draft Proposed Guidelines for Ecological Risk. Assessment Risk Assessment Forum. Washington, D.C.: EPA. Liber, K., D.J. Call, T.D. Dawson, F.W. Whiteman, and T.M. Dillon 1996. Effects of Churonomus tentans larval growth retardation on adult emergence and ovipositing success: Implications for interpreting freshwater sediment bioassays, Hydrobiologia 323: 1-13. National Research Council (NRC). 1989. Contaminated Marine Sediments: Assessment and Remediation Marine Board, Washington, D.C.: National Academy Press. NRC. 1996. Understanding Risk Informing Decision in a Democratic Society. Washington, D.C.: National Academy Press. U.S. Army Corps of Engineers (USACE). 1991. Risk Assessment An Overview of the Process. Environmental Effects of Dredging. Technical Notes EEDP-06-15. Vicksburg, Mississippi: U.S. Army Engineer Waterways Experiment Station. Water Resources Council. 1983. Economic and Environmental Principles and Guidelines for Water and Related Land Resources Implementation Studies. Washington, D.C.: U.S. Government Printing Office.
Representative terms from entire chapter: