1
The Challenge

Sediment particles of mineral and organic matter accumulate in coastal waters as the result of physical, chemical, and biological processes, both natural and anthropogenic. Human activities can affect marine sediments by accelerating the rate of accumulation and introducing contamination. Many chemical contaminants have an affinity for fine-grained sediment particles. Contaminated sediments are widespread in U.S. coastal waters and have potentially far-reaching consequences to both public health and the environment (National Research Council [NRC], 1989a).

Industries located in or upstream of urban ports or industries that discharge wastes into waterways can be direct sources of contamination. Dense populations also contribute contaminants through sewage discharges, automobile emissions, and other waste-generating activities. Sediments can be contaminated by remote sources, such as stormwater runoff and suburban or agricultural effluents containing heavy metals, oil, pesticides, and fertilizers. Because estuaries have a natural tendency to trap sediment, contaminants from distant sources can be concentrated in already-stressed industrial harbors. Contaminants deposited from the atmosphere can be carried from sources even further afield. Recent studies have shown that about half of the metal contamination in the sediments of Long Island Sound may have come from atmospheric fallout (Cochran et al., 1993). Contamination sometimes concentrates in "hot spots" but is often diffuse, with low to moderate levels of chemicals less than a meter deep but covering wide areas.

Chemical contaminants associated with sediments can be considered toxic when they adversely affect living organisms. Submerged contaminated sediments may be in intimate contact with aquatic biota that may be affected adversely by, or serve as carriers of, contamination. In this way, contaminants pose a potential



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--> 1 The Challenge Sediment particles of mineral and organic matter accumulate in coastal waters as the result of physical, chemical, and biological processes, both natural and anthropogenic. Human activities can affect marine sediments by accelerating the rate of accumulation and introducing contamination. Many chemical contaminants have an affinity for fine-grained sediment particles. Contaminated sediments are widespread in U.S. coastal waters and have potentially far-reaching consequences to both public health and the environment (National Research Council [NRC], 1989a). Industries located in or upstream of urban ports or industries that discharge wastes into waterways can be direct sources of contamination. Dense populations also contribute contaminants through sewage discharges, automobile emissions, and other waste-generating activities. Sediments can be contaminated by remote sources, such as stormwater runoff and suburban or agricultural effluents containing heavy metals, oil, pesticides, and fertilizers. Because estuaries have a natural tendency to trap sediment, contaminants from distant sources can be concentrated in already-stressed industrial harbors. Contaminants deposited from the atmosphere can be carried from sources even further afield. Recent studies have shown that about half of the metal contamination in the sediments of Long Island Sound may have come from atmospheric fallout (Cochran et al., 1993). Contamination sometimes concentrates in "hot spots" but is often diffuse, with low to moderate levels of chemicals less than a meter deep but covering wide areas. Chemical contaminants associated with sediments can be considered toxic when they adversely affect living organisms. Submerged contaminated sediments may be in intimate contact with aquatic biota that may be affected adversely by, or serve as carriers of, contamination. In this way, contaminants pose a potential

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--> risk to coastal ecosystems and, primarily through consumption of fish and shellfish, to human health. Management of contaminated sediments is a complicated problem.1 At the technical level, controlling input is difficult because of the multiplicity of sources, and the wide dispersion of sediments by hydrodynamic and biological processes tends to expand the scope of cleanup operations. At the legal level, ports that may have no causal role in the contamination of sediments but must still dredge channels are faced with a number of hurdles, including identifying and paying for space for the placement of dredged material and many chemical, regulatory, political, and technological challenges.2 Proper management of contaminated sediments is becoming more complicated because environmental concerns increasingly hinder the removal of sediments from economically critical shipping lanes and because growing numbers of contaminated sites are being identified for remediation. DRIVING FORCES FOR REMEDIATION Contaminated sediment becomes an issue when an environmental or human health risk is identified or when navigational needs require that contaminated sediment be dredged from shipping channels. Environmental risks may lead to the identification of human health risks and to limits on fishing or recreational uses of marine resources. The presence of contamination can make removing sediments that obstruct navigation in and around important ports very expensive. The choice of a remediation strategy is determined in large part by whether the driving force is environmental cleanup or navigational needs. In addition to influencing the choice of remediation strategies, the driving force also affects which laws and regulations apply. At least seven federal agencies and six comprehensive Acts of the U.S. Congress influence remediation or dredging operations for managing contaminated sediments in settings that range from the open ocean to the inland and freshwater reaches of estuaries and wetlands (see Figure 1-1). If environmental cleanup is the driving force, applicable laws include the Comprehensive Environmental Response, Cleanup, and 1   For purposes of this report, sediment management is a broad term encompassing remediation technologies as well as nontechnical strategies. Remediation refers generally to technologies and controls designed to limit or reduce sediment contamination or its effects. Controls are practices, such as health advisories, that limit the exposure of contaminants to specific receptors. Technologies include containment, removal, and treatment approaches. Treatment refers to advanced technologies that remove a large percentage of contamination from sediments. 2   When referring to the final placement sites for dredged material, this report uses the terms of art established by applicable laws. Sediments are "dumped" in the open ocean (where the Marine Protection. Research and Sanctuaries Act applies) but "discharged" or "disposed of' in near-shore or inland waters (where the Clean Water Act applies). "Placement" is a generic term referring to all sites, both in the water and on land.

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--> FIGURE 1-1 Regulation of contaminated sediments The complexity of contaminated sediment regulation is depicted in this schematic diagram, which shows the locations to which various regulations apply, the interactions between regulations, and the responsible government agencies Note: USACE, U.S. Army Corps of Engineers; CWA, Clean Water Act; CZMA, Coastal Zone Management Act; DOI, Department of the Interior; EPA, Environmental Protection Agency; ESA, Endangered Species Act; MPRSA, Marine Protection, Research and Sanctuaries Act; NOAA, National Oceanic and Atmospheric Administration; RCRA/CERCLA, Resource Conservation and Recovery Act/Comprehensive Environmental Response, Cleanup, and Liability Act; RHA, Rivers and Harbors Act, state, any state government.

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--> Liability Act (CERCLA), commonly known as Superfund (P.L. 96-510); the Resource Conservation and Recovery Act (RCRA) (P L. 94-580); and Section 115 of the Clean Water Act (CWA) (originally called the Federal Water Pollution Control Act [P.L. 80-845 (1948)]). If navigation dredging is the issue, the applicable statutes are likely to be the CWA; the Rivers and Harbors Act of 1899 (P.L. 55-525); the Marine Protection, Research and Sanctuaries Act (MPRSA, also known as the Ocean Dumping Act) (P.L. 92-532); and the Coastal Zone Management Act (CZMA) (P.L. 92-583). Three federal agencies are most active in contaminated sediment issues. The Environmental Protection Agency (EPA) is responsible for implementing Superfund and has major responsibilities and veto power for site designation and regulation development under the CWA and MPRSA. The National Oceanic and Atmospheric Administration is responsible for assessing the potential threat of Superfund sites to coastal resources, has significant research responsibilities under MPRSA, and has review obligations under both the CWA and MPRSA. The U.S. Army Corps of Engineers (USACE) assists in the design and implementation of remedial actions under Superfund and exercises primary responsibilities for permitting dredged material under the CWA, MPRSA, and Rivers and Harbors Act. The federal navigation dredging program is the responsibility of the EPA and USACE; the EPA addresses issues pertaining to disposal, and the USACE handles the dredging. Other federal, state, and local agencies have a hand in these matters as well. States are authorized to establish water quality standards within their jurisdictions and can block actions, such as sediment dredging or disposal, if they violate these standards. States also have the authority to review plans for consistency with coastal zone management plans. (Appendix B provides additional details on the regulatory framework.) The overlapping jurisdictions of federal, state, and local authorities further complicate the situation, which is discussed further in the forthcoming section, Regulatory and Legal Challenges. The federal laws and regulations that apply to the handling and disposal of contaminated sediments are reviewed in detail in Appendix B. Management of Natural Resources Environmental cleanup, almost by definition, involves small volumes of highly contaminated sediment usually emanating from a known historical source and confined to well-defined areas. In environmental cleanup projects, the remediation strategy can be either in situ (i.e., in-place containment or treatment of the sediment) or ex situ (i.e., removal and disposal or treatment elsewhere). The removal of contaminated sediment for the sole purpose of cleanup as part of navigation projects has been permitted only in recent years in the United States. The USACE was given specific authorization under Section 312 of the Water Resources Development Act (WRDA) of 1990 (P.L. 101-640) to remove

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--> contaminated sediment outside the bounds of, but adjacent to, navigation channels. However, this apparently broad authority to clean up contaminated sediment in conjunction with federal navigation projects has not been used to date by the USACE for specific cleanup projects because of the inability to locate financially viable project sponsors and because of concerns about liability. When sediment removal is not required for navigation, contaminated sediment may go unrecognized and the problem remain undefined until some event (e.g., routine water quality analysis) triggers recognition that the sediment may pose a risk to human health or the environment. Actual risk can be identified through a formal assessment (a process described in Chapter 2). Sometimes the response to this risk has an obvious and direct impact and economic consequences, such as restrictions on particular fisheries. In other cases, the response may be less visible but still significant in terms of impact, as when a site is designated in a Superfund "hazard ranking." Economic impact, as well as a high degree of risk, may make cleanup necessary. The full extent of the need for environmental cleanup has not been quantified, but it is substantial. Approximately 100 marine sites 3 have been listed or proposed for inclusion on the National Priorities List (NPL) for long-term remedial action under Superfund, which addresses inactive or abandoned facilities that threaten public health or the environment. A national inventory4 of contaminated sediment sites mandated by Congress in WRDA 1992 (P.L 102-580) is under way. The EPA has designed the database and compiled the data and is expected to submit the first report to Congress in 1997. Navigation Needs Contaminated sediments usually accumulate slowly over large areas of the seafloor, but they can also accumulate very rapidly, especially in artificially deepened and confined areas, such as navigational channels and anchorages. Sediments in these areas must be dredged to maintain navigable waters. Navigation dredging typically involves the removal of large volumes of material over a large area that contains many different types of contaminants, albeit in low concentrations, from multiple, unidentifiable sources. In situ remediation strategies, such as leaving the contaminated sediment in place (i.e., allowing natural recovery to occur), may not be feasible in navigation channels. When navigation is the driving force, usually only ex situ techniques can be considered because the sediment must be relocated so the channel or harbor can be deepened or widened. In isolated instances, however, overdredging and capping the contaminated fraction of the dredged sediment within the navigation channel can be considered. 3   This estimate includes Superfund sites adjacent to oceans and bays (L. Zaragosa, EPA, personal communication to Marine Board staff, October 1995). 4   The inventory as released by the EPA for external review in July 1996.

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--> FIGURE 1-2 Volume and costs of dredging by the USACE and industry, 1963 to 1994. Estimates do not include disposal costs and are current, not constant, dollars. Dredging is commonplace in the United States and is essential to many of the routine activities and services Americans have come to expect and demand (Maritime Administration, 1994). Figure 1-2 summarizes the volume (in millions of cubic yards [MCY]) and costs of dredging by the USACE and industry from 1963 to 1994 (USACE, 1995) Approximately 283 MCY of material, on the average, has been dredged annually in recent years from U.S. coastal and inland waters (1987 to 1994). Dredging and associated sediment disposal are expensive. The actual costs vary dramatically depending primarily on the nature (including contamination status) of the material to be dredged, the distance it must be transported for disposal, the number and nature of the required handling steps, the extent to which pre-disposal treatment is necessary, and the need for post-disposal monitoring. For major projects, environmental regulators require that all alternatives be explored before a decision to dredge is made, to ensure that a less costly or more environmentally acceptable alternative has not been overlooked. Although the economic impact of not dredging sediment is difficult to quantify, there is no doubt that well maintained channels, ports, and harbors are essential if the United States is to continue to attract and retain commercial shipping (Interagency Working Group on the Dredging Process, 1994). Ports and harbors

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--> are essential to the nation's competitiveness in world markets. Approximately 95 percent of all U.S. foreign trade is waterborne and passes through U.S. ports (Maritime Administration, 1994). In 1992 the volume of waterborne foreign trade reached 897 million metric tons (MT) and was valued at $488 billion. It is expected that the value of imports and exports will increase from $488 billion in 1992 to $1.6 trillion in 2010, while increasing in volume from 897 million MT to 1.5 billion MT (U.S. Department of Transportation, 1994). There are two types of navigation dredging: maintenance dredging and new-work (or new-construction) dredging. Maintenance dredging is carried out to maintain existing navigation services, whereas new-work dredging is intended to expand existing navigation channels or make them accessible to ships of deeper draft or to create new ones. Maintenance dredging is the more common of the two types. From 1987 to 1994, maintenance dredging in the United States moved, on average, approximately 238 MCY per year. This total includes dredging by the USACE on the inland waterway system and in federal channels of deep-draft ports, as well as dredging in other ports and by private parties. The amount of new-work dredging varies from year to year, depending on the commercial need for extended navigation facilities and the level of congressional appropriations. From 1987 through 1994, a total of 359 MCY was dredged for new construction Most new-work dredging is associated with large federal projects. To qualify as a federal project—approved by U.S. Congress and/or under the management of the USACE—the benefits must be greater than the costs Federal cost-sharing policies make a distinction between new-work dredging, for which the local sponsor must share the cost, and maintenance dredging, which is financed fully by the federal government through the Harbor Maintenance Trust Fund.5 New-construction dredging is motivated primarily by economics—that is, regional development pressures as well as the competitive position of a local port in relation to neighboring ports. Port upgrades also benefit the nation as a whole by supporting trade, an important element of the U.S. economy. Foreign trade now accounts for 20 percent of the gross domestic product (GDP), and this percentage is expected to grow in the future (Interagency Working Group on the Dredging Process, 1994). The combined economic impact of U.S. ports, port users, and public port capital expenditures is substantial. The demand for waterborne cargo initiates a chain of activity that contributes to the national economy. In 1992 U.S ports handled approximately 2.9 billion MT of cargo, supported the employment of 15 million Americans, added $780 billion to the GDP and $523 billion to personal income, and contributed $210 billion in taxes to all levels of government (Maritime Administration, 1994). 5   The trust fund is supplied by a tax levied on cargo passing through U.S. ports. The status of the fund was unclear as of late 1996; the U.S. Court of International Trade has ruled that the tax on exports is unconstitutional. The government, which claims the tax is actually a user fee, was expected to appeal the decision.

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--> In summary, sustained U.S. economic growth is expected to depend increasingly on foreign trade and international commerce, most of which currently moves through the nation's ports. But ports cannot support economic growth without corresponding improvements in their capacity to accommodate an increase in commercial shipping as well as new classes of ships, some of which may have greater beam and deeper drafts than those found on today's vessels. Contaminated sediments and associated management difficulties can impede the expansion of navigational capacity and impose economic penalties. RISK MANAGEMENT PROCESS Contaminated marine sediments can pose risks to public health and the environment, and sound decisions about health and ecological risks must be based on formal assessments of those risks. The most elemental form of risk assessment is intended to determine whether the concentrations likely to be encountered by organisms are higher or lower than the level identified as causing an unacceptable effect. In this context, an effects assessment is a determination of the toxic concentration and the duration of exposure necessary to cause an effect of concern in a given species. Risk assessment as a decision-making tool is widely accepted in the scientific and engineering communities (NRC, 1983) and has been endorsed by the USACE for dredging operations (USACE, 1991). Risk is discussed in other reports of the NRC (1989b, 1993a,b, 1994a,b,c, 1995, and 1996), which address broad issues linking risk, science, and policy. Risk management is the evaluation, selection, and implementation of alternative methods of risk control. Contaminated sediments are considered a problem only if they pose a risk above a toxicological benchmark, or acceptable level, which can be identified through a risk assessment.6 Once the ''acceptable risk" has been identified and quantified, a series of challenges in risk management become apparent. These challenges are outlined here to lay the groundwork for the analysis in forthcoming chapters First, management strategies must be identified that reduce risk to the benchmark value. The values currently used as benchmarks are imperfect in that they are based on inconsistent or incomplete applications of risk assessment principles (as discussed in chapters 2 and 3). Second, remediation technologies must be identified that can reduce the risk associated with contaminants to acceptable levels (sometimes known as "environmentally acceptable end-points"7) within 6   The application of the risk assessment process to environmental or cleanup dredging has been summarized by the USACE (1991). 7   An environmentally acceptable end-point is defined for soils as "a concentration of chemical(s) or test response(s) that is judged acceptable by a regulatory agency or other appropriate entity either by a standard or guideline, or which is derived using site-specific information" (Nakles and Linz, in

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--> the constraints of applicable laws and regulations. Imminent health or environmental risks may call for prompt interim action and, later, more complete remediation. Where initial risk levels warrant some action but are not critically high, slower remediation tactics, such as natural recovery, may be appropriate. The capabilities of the various remediation technologies for reducing risk can only be estimated (see Chapter 5). Third, promising alternatives must be evaluated within the context of making trade-offs among risks, costs, and benefits. This is a difficult process, due in part to the uncertainties of risk and cost estimates. Fourth, the trade-offs must be communicated effectively to the stakeholders who have a say in the allocation of resources and an interest in ensuring that the decision-making process results in the successful resolution of the problem. UNIQUE CHALLENGES POSED BY CONTAMINATED SEDIMENTS Chemical Challenges Marine sediments are contaminated by chemicals that tend to sorb to fine-grained particles, which offer a greater combined surface area for contaminant sorption than coarser particles (Gibbs, 1973; Moore et al., 1989). The contaminants of concern include trace metals and hydrophobic organics, such as dioxins, polychlorinated biphenyls (PCBs), and polyaromatic hydrocarbons. Metals bind to mineral surfaces or are present as sulfide precipitates. Because of the physiochemical state of the hydrophobic organics, they tend either to sorb to natural organic matter and fine clays or to be partitioned into a separate liquid phase, such as oil or coal tar. As a result, most highly contaminated sediments, regardless of the source of the contamination, tend to be fine-grained materials deposited in low-energy areas, which serve as sinks. The strong binding of contaminants with sediment, and their correspondingly slow release, suggest that risks to humans and the ecosystem, both lethal and sublethal, are linked to long-term rather than transitory exposure. The accumulation of mixed contaminants complicates the selection of management strategies and treatment technologies for three reasons. First, opportunities for controlling the sources of contamination are limited, given that many different sources, some of them remote, may have contributed to the problem. Second, different types of contaminants must sometimes be treated in different ways. Third, a mixture of contaminants virtually guarantees that any treatment will leave behind untreated components. However, one particular contaminant is     press). As an example, it has been postulated that effective bioremediation can reduce hydrocarbon concentrations in soil to a level where they no longer pose an unacceptable risk to the environment or human health. It is believed that the remaining levels of hydrocarbons in the treated soil are no longer available to the environment or ecological and human receptors and represent an environmentally acceptable end-point.

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--> usually the primary concern at a specific site, and the nature of this contaminant dictates the choice of remedial techniques. Typical fine-grained contaminated sediments tend to have a relatively high water content and poor engineering qualities. Moreover, improper handling can remobilize the contaminants. Pore water containing dissolved contaminants may escape during dredging or transport.8 In addition, small particles released into the water during handling have low settling rates and remain suspended in the water column where they are subject to wide dispersion. Special measures, such as silt curtains or water-tight bucket dredges, may be needed to limit the spread of resuspended contaminated sediments in some settings. Low settling rates can also complicate containment in a confined disposal facility (CDF); coagulating agents may be necessary to speed settling and reduce turbidity. But a percentage of fine-grained material and associated contaminants may remain suspended. Regulatory and Legal Challenges The regulations affecting contaminated sediments management are complicated. They were developed to implement a range of unrelated federal and state statutes dealing with issues, such as water quality and hazardous waste cleanup. As a result, the framework is inconsistent in its approach to contaminated sediments. Few aspects of sediment handling, treatment, or containment have been left unregulated, but most applicable laws and rules were not written explicitly to deal with contaminated sediments. As a result, related decisions may not be fully risk-based, and some technically sound management strategies may be foreclosed (a situation that is discussed further in Chapter 3). The mechanisms of the regulatory process in a given situation depend on where the sediments are located; where they will be placed; the nature and extent of the contamination; and whether the purpose of removing or manipulating the sediment is navigation dredging, environmental cleanup, site development, or waste management (see Appendix B, Table B-1). For example, the dredging of sediment in navigable waters requires a Section 10 permit from the USACE under the Rivers and Harbors Act (RHA). Excavation of sediment from nonnavigable waters, or from containment structures, may not be regulated under federal law but could be affected by a variety of state laws. The erection of structures in navigable waters or the emplacement of materials that may obstruct navigation or alter the course, condition, location, or capacity of the waterway may also require a Section 10 permit. This could be the case, for example, where a CDF is constructed to contain dredged material, where dredged material is used to construct an offshore island, or where a clean sand or clay "cap" is used to isolate and contain in situ or deposited sediments. 8   Not all contaminants are dissolved in pore water. PCBs, for example, can be present in the pore space as an organic liquid phase.

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--> Transport for the purpose of dumping dredged sediment in ocean waters (defined as waters beyond the baseline from which the territorial seas are measured) is regulated by the USACE under Section 103 of the MPRSA. Similar discharges in inland or coastal waters on the other side (inland) of the ocean baseline are regulated by the USACE under Section 404 of the CWA, as are discharges of fill material into both inland and ocean waters out to the three-mile limit (the territorial sea). In both cases, affected states may veto or attach conditions to a discharge if it contravenes the state's water quality standards or approved coastal zone management plan. If sediments proposed for ocean disposal are deemed to contain mercury or cadmium compounds, organohalogens, or petroleum hydrocarbons (as other than "trace contaminants") based on prescribed bioassay and bioaccumulation testing procedures, then ocean dumping may be prohibited, although discharge into inland waters may be acceptable as long as the sediments satisfy applicable regulations and guidelines under Section 404 of the CWA. Placement on land is also acceptable, unless the sediments exhibit hazardous waste characteristics (i.e., exceed RCRA regulatory limits, in which case disposal is permitted only at approved RCRA facilities). However, since 1988 the USACE has maintained that dredged materials are not subject to regulation under RCRA, and rule making is pending to clarify this point. Finally, if contaminated sediments are excavated as part of a remedial response under CERCLA, then they must be treated, contained, or disposed of in a way consistent with applicable or appropriate and relevant regulatory requirements under federal or state law and must meet other Superfund standards. These requirements may impede the cost-effective management of contaminated sediments. Section 121(b) of CERCLA, for example, gives preference to treatments that "permanently" reduce contamination, thereby possibly constraining a site manager's ability to use capping (an issue discussed further in Chapter 5). A further constraint is imposed on the management of contaminated sediments by the lack of regulatory adherence to the "polluter pays" principle typically followed in other cases of waste management. All too often, point and nonpoint sources of contamination, often far upstream, are not held accountable. As a result, downstream ports seeking to proceed with critical navigation dredging are burdened with extra costs and delays. A situation of this type arose in Newark Bay, a highly industrialized area beset for more than a century by contamination from multiple sources. When the Port Authority of New York and New Jersey applied for dredging permits in 1990, it was required for the first time ever to test for dioxin, which was found to be present at low, part-per-trillion levels. Despite the upstream origin of the contamination, the port had to undertake a series of studies, and, because of interagency disputes over the permit and a lawsuit, the dredging was delayed until 1993 (Weis, 1994). The fragmented nature of the combined federal and state regulatory framework demands that many parties be involved in decision making, a situation that sometimes results in confusion over who is in charge. Because each regulatory

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--> TABLE 1-1 Time Lapse between Identification of a Problem and Implementation of a Solution: Examples from Six Case Historiesa Case Study Problem Identified Solution Implemented Boston Harbor Problem seen in late 1960s, litigation in early 1980s forced action 1996 or later Hart and Miller Islands Permit obtained 1976 Legal challenge resolved 1980, containment structure completed 1984 James River Fisheries closed 1975 Decision made after 1978 Marathon Battery Problem seen in early 1970s, NPL listing 1981 1993 Port of Tacoma Problem seen in 1983 1994 Waukegan Harbor Problem seen in mid-1970s 1991 a These case histories are summarized in Appendix C program emphasizes different issues, the lead decision maker may be unsure how to address the related but separate concerns of other agencies and the public, in which case the decision maker may simply request more and more information and analysis or even defer action. The problem is compounded if there is no strong, knowledgeable project proponent who can maintain pressure on the decision maker and keep the regulatory process moving. Even under the best of circumstances, solutions may not be implemented for years. In the committee's six case histories (summarized in Appendix C), the delay between discovery of a problem and implementation of a solution ranged from approximately 3 to 15 years (see Table 1-1). The problem is not the involvement of many stakeholders but the often adversarial nature of their relationships and the convoluted regulatory path they must follow. The diverse areas of expertise and interests of multiple agencies can be accommodated as long as they are applied in a constructive way to accomplish a logical, risk-based objective. Political Challenges The risk posed by contaminated marine sediment is neither easily measured nor highly visible-characteristics that may foster disagreements among stakeholders about how to manage the problem. On land, where contamination may occur in direct proximity to people and food sources or in groundwater that people drink, exposure pathways are clear, and there is a reasonable basis for

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--> anticipating sufficient risks to justify a major effort. In the aquatic environment, even when the risk of contaminating the food chain is a real concern, the contamination and exposure pathways are hidden under water and may be difficult to define. In addition, the extent of the threat may be altered by physical and biochemical sequestration mechanisms, which may reduce the bioavailability of a contaminant and thereby limit ecosystem effects, including biodegradation. Regardless of these factors, members of the public and their elected representatives tend to equate the physical presence of contaminants with risk and to insist on more intensive removal and treatment of underwater sediments than of terrestrial contaminants. At the same time, in an era of shrinking federal budgets and dwindling disposal space, it is becoming more important than ever to ensure that management efforts are cost effective. Sometimes conflicts arise between minimizing or eliminating risk and controlling costs. Striking a balance can be a formidable political challenge. Failure to strike a balance among stakeholder interests can delay or stall a project, which was apparent in the committee's case histories (Appendix C). Techniques for meeting the political challenge are discussed in Chapter 3. Whether motivated by technically sound arguments or emotional self-interest, many stakeholders have common concerns in decisions about managing contaminated sediments. Port communities have powerful economic reasons for dredging. Government regulators are responsible for protecting natural resources and enforcing a complex web of laws and regulations Environmental groups and community residents who are concerned about public health and natural resource quality are just as committed. They may want remedial action but oppose the deposition of dredged sediment on nearby land or in the ocean. Management Challenges Many strategies for managing contaminated sediments are available, some of them very sophisticated. However (as discussed in Chapter 5), many advanced remediation technologies have not been tested extensively at marine sites, and costs can be very high. Superfund cleanup costs can be as high as $1 million per acre (NRC, 1989a). The cost of an entire management plan—dredging, transportation, treatment or containment, and long-term monitoring—must be considered. Costs of these steps vary widely. Dredging is relatively inexpensive per unit volume. At the other end of the spectrum, some treatment technologies have such high unit costs that their use is effectively precluded for treating large volumes of sediment. Trade-offs often must be made between technology effectiveness and cost The challenge is to identify the most cost-effective9 solution for the project at 9   Cost effectiveness is defined here as a measure of tangible benefits for the money spent.

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--> hand and then optimize it by the using systems engineering approaches. When contamination is concentrated in hot spots, effective but expensive treatment options may be feasible. In some instances, it may be cost effective to identify the most highly contaminated sediment and treat the smallest possible volume. In other cases, in order to be acceptable economically and to the public and environmental authorities, large volumes of sediment must be handled, necessitating the use of less costly containment methods. The beneficial reuse of clean or contaminated dredged material can improve prospects for success. Although there is clearly room to increase the effectiveness and reduce the costs of contaminated sediment management, there is also a built-in bias against innovation. Funding and executing most dredging projects is the responsibility of public agencies, which are subject to the historical constraints on custodians of public funds. These constraints, by design, narrowly focus the contracting process and do not encourage innovative approaches or technologies. In fact, the term "innovative" in this context is often interpreted to mean high risk, an uncertain outcome, and an invitation to post-project censure. Creative management is required to overcome the institutional barriers to innovation. All participants must recognize that an innovative approach may end in failure, and they must agree up front to share the bureaucratic and financial risk. SUMMARY The management of contaminated sediments is a difficult problem. The combination of high public expectations, confusing and overlapping jurisdictions, generally low contamination levels, large quantities of affected sediments, risk management challenges, and handling and treatment difficulties may result in large sums of money being spent on partial solutions for low-risk situations. As economic and environmental interests converge and conflict, improved management approaches and technologies need to be developed. Progress in science and engineering have advanced the nation's capability of detecting contaminants; the challenge now is to foster similar advances in decision making and remediation. There is a conceptual need to balance the risks, costs, and benefits in the face of uncertainties and disagreements about decisions (NRC, 1989b). There is also a practical need to comply with relevant regulations, consider the concerns of all stakeholders, address site-specific considerations, and identify appropriate technologies. Recognizing the multifaceted nature of the problem, the present report is an attempt to set out a risk-based strategy for making management decisions and for selecting remediation technologies. Chapter 2 describes the committee's conceptual management approach, which takes into account the challenges outlined in this chapter.

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