Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 189
A Risk-Management Strategy for PCB-Contaminated Sediments 7 Assessing Management Options The preceding stages in the framework for environmental risk management lead to the formulation of risk management goals, the identification of the chemicals, sources, affected media, and potential risks of contaminated sediments. Only after the risk-management goals have been defined and the risks assessed should management options be examined. A range of technologies are applicable to the management of contaminated sediments, and these technologies must be identified and analyzed, and their benefits, effectiveness, costs, feasibility, and adverse consequences compared. All technologies might be appropriate under some site and contaminant conditions, but no technology exists that is generally applicable or preferred for the management of all contaminated sediments. Even at a single site, the application of multiple technologies is likely to be required to achieve risk-management goals. The lack of a single generally applicable and effective option means that site-specific analyses are needed to determine which combination of technologies best meet the identified goals (as determined in stage 1) at the least cost and with the most benefit to the environment and the community. The identification and selection of a risk-management strategy and its component management options should be based on a range of considerations, including effectiveness, permanence, implementability, risks associated with implementation, costs, and state and community acceptance. These factors must be evaluated relative to the identified goals and based on site-specific
OCR for page 190
A Risk-Management Strategy for PCB-Contaminated Sediments Assessing Options Identifying Options Analyzing Options for Benefits Effectiveness Costs Feasibility Adverse Consequences conditions. The affected parties should be included in the identification, selection, and evaluation processes. Without a clear statement of goals, it is not possible to evaluate and compare the effectiveness of any management option at meeting those goals. Without adequate consideration of site-specific conditions, the comparison is incomplete. The primary purpose of this chapter is to outline the process of identifying and evaluating contaminated-sediment management options and identify the characteristics of specific technologies that influence their selection at a particular site. IDENTIFYING OPTIONS Among the many different regulatory and nonregulatory approaches to reducing and managing risks of contaminated sediments are Socioeconomic options. Institutional controls. Offsets. Source control. Natural attenuation and recovery. Biodegradation. Sedimentation. In situ treatment. Enhanced natural attenuation. Capping. Multicomponent removal and ex situ treatment. Dredging technologies. Pretreatment technologies. Ex situ treatment, storage, and disposal technologies. Technologies for management of residual contaminants. Often the identification of potential management options occurs simultaneously with the identification and analysis of risks and potential risks. Input from all affected parties, including the public, industry, local community-based organizations, and government, is critical to the identification of an
OCR for page 191
A Risk-Management Strategy for PCB-Contaminated Sediments appropriate range of possible options. In the identification of options, the initial emphasis should be on completeness. Possible options should not be arbitrarily eliminated prior to a systematic and thoughtful evaluation by all participants. The participation of concerned groups at this stage can also help to identify potential beneficial outcomes of some options that might not be readily apparent to others. Options that incorporate beneficial outcomes beyond that achieved simply by reducing the risks of contaminated sediments generally have a greater chance of acceptance and success, because they may be seen as win-win options. Examples of such beneficial outcomes include creation of green space, habitat, and wetlands or the use of dredged material for fill. Many of the potential technologies for management of contaminated sediments were initially developed to manage contaminated soils. Unfortunately, many of these technologies are difficult to apply to contaminated sediments, and they might impose potentially unacceptable risks. Sites with contaminated sediments are often poorly controlled, dynamic systems containing large volumes of moderately contaminated material. An analysis of the Superfund Record of Decisions from 1982 to 19971 showed that the average contaminated-soil site considered for ex situ treatment contained 38,000 cubic yards of contaminated material and that the average site considered for in situ treatment contained approximately 105,000 cubic yards of contaminated material. Sites at which contaminated sediments occur, however, often contain in excess of 1,000,000 cubic yards of contaminated material and generally are not directly accessible. Soils can be removed in a relatively dry state for further processing, and sediments are removed as slurries with a high proportion of water that must be processed. The control of releases of contaminants is much more difficult during removal of submerged sediments than during removal of soil for ex situ treatment. The difficulty is due to limited control of the subaqueous environment as well as the sometimes profound chemical and physical changes that the sediment undergoes during removal (e.g., anaerobic to aerobic and wet to dry). Identifying management options for contaminated sediment is also complicated by the multiple technologies often involved. The application of ex situ treatment or disposal of sediments, for example, typically introduces a complete train of technologies, including removal by dredging, temporary storage or pretreatment to reduce water content or volume, final dredged material treatment or disposal, and management of any residually contaminated materi- 1 Treatment Technologies for Site Cleanup: Annual Status Report, 9th Ed. U.S. Environmental Protection Agency 542-R99–001, April 1999.
OCR for page 192
A Risk-Management Strategy for PCB-Contaminated Sediments als. In situ treatments, such as capping, are normally coupled with source control and often require long-term monitoring and maintenance. Natural-attenuation processes (i.e., biodegradation and sedimentation) are also a component of all contaminated-sediment management options, because these processes are expected to have an impact on any residuals left after application of other management approaches. Generally, large contaminated-sediment sites also require the application of different options at different portions of the site, each containing multiple technologies. The identification of sediment management options must recognize the entire train of technologies that constitute each option so that a fair evaluation and comparison of these options can be accomplished. EVALUATING MANAGEMENT OPTIONS The evaluation of management options requires definition of The goals and objectives of the management actions (see Chapter 5). A valid conceptual model of the sediment system to be managed (see Chapter 6). Without definition of the management goals and objectives, it is not possible to measure the effectiveness of a management option. Without a valid conceptual model of the site, it is not possible to define how a management option can successfully meet the risk-reduction goals and objectives. The conceptual model must be based on site-specific conditions, and experience at other sites must be used to aid our understanding and not simply be presumed to represent default conditions at the site. Although a valid conceptual model of a site is a minimal requirement for success, it is recognized that many sites require much more. Large, complicated sites posing substantial risks and potentially large cleanup costs generally require development of an extensive database and sophisticated prognostic models to compare management options adequately and evaluate the risk reduction they can achieve. The primary purpose of evaluating options at this stage is to develop the information and data necessary to compare and select a viable alternative from among the options. The evaluation is not designed to make that selection. The evaluation of options is often conducted by technical personnel who might not fully recognize or consider such factors as acceptability to the community. For this reason, the process of evaluating options is separated from making decisions, the next stage in the decision-making framework (see Chapter 8). Although options may be eliminated from further consideration during evalua-
OCR for page 193
A Risk-Management Strategy for PCB-Contaminated Sediments tion due to technical infeasibility or other factors, elimination must be done cautiously to avoid prematurely eliminating options that might ultimately prove effective. For this reason, affected parties should participate in the development of the evaluation criteria and have input into the evaluation process. The options for managing contaminated sediments vary greatly with respect to the site-specific factors that must be evaluated: Feasibility. Expected benefits and effectiveness. Expected costs. Potential adverse consequences. Distribution of benefits, risks, and costs among various potentially affected groups. All technologies have advantages and disadvantages when applied at a particular site, and it is critical to the evaluation that these be identified as completely as possible. For example, reducing risks from contaminated sediment in the aqueous environment might create other risks in the terrestrial environment. These risks might be to the same community affected by the in situ sediments or to other communities faced with transportation, treatment, or disposal of contaminated dredged material. The evaluation of sediment management options must take into account the entire train of technologies that constitute an option and the costs and potential risks throughout the life cycle of the options. Evaluation, screening, and ultimately, selection of an option depends on recognition of the full environmental, human, social, and economic costs of implementing that option. Incomplete evaluation, particularly neglect of required components of a management option or their environmental and economic costs, biases the evaluation. Even if all components of a management option are considered, costs are difficult to estimate and compare. Management costs that are routinely available often use different bases and assumptions and can be influenced dramatically by site-specific conditions, such as the debris or the physical characteristics of the sediments. The existing database of costs is inadequate to provide anything more than a crude estimate of the costs of the application of a particular management option at a particular site. (See Table 5–1a,b for costs associated with management options, primarily dredging, at several PCB-contaminated-sediment sites.) Standardization of costing approaches has been advocated by such groups as the American Society of Testing and Materials; a proposed standard is under development by that organization. Such standardization, when combined with a detailed evaluation of site-specific conditions
OCR for page 194
A Risk-Management Strategy for PCB-Contaminated Sediments that might affect costs, should improve the ability to predict management costs accurately and allow comparison of costs of various management options and remediation technologies. The evaluation of options also requires assessment of their effectiveness. The primary goal of contaminated-sediment management is the protection of resources at risk, such as human or ecological health, commercial or recreational fishing stocks, or a particular endangered species. Ultimately, it would be preferable to choose management options that best protect affected resources or lead to their recovery. That takes time, however, and interim indicators of effectiveness, such as contaminant loss or exposure and risk to sensitive populations during and immediately after implementation of the option, are generally necessary. Assessing or predicting even short-term human health and ecological risks directly for all options at this stage can be exceedingly difficult. An alternative for the evaluation and comparison of management options is to use contaminant mass flows as a surrogate measure of exposure and, ultimately, risk—that is, a technology may generally be assumed to result in reduced exposure and risk if it leaves less residual contamination in the sediment and puts fewer contaminants into the air and water than an alternative technology. Evaluation of contaminant mass flows for each management option can be most useful in the comparative rather than the absolute evaluation of potentially applicable management options by providing a systematic screening tool. A comparative analysis of mass flows can also help identify those components of an overall management strategy that largely control the overall exposure or risk and, therefore, should receive the most resources and effort for detailed evaluation. Although contaminant mass flows can be useful, exposure and risk to human and ecological health ultimately drives the need for risk management and the success or failure of any management option. In particular, absolute rather than comparative analyses are needed to balance short-term acute risks, for example, from removal options with long-term risks, such as from in situ containment options. The actual magnitude of the resulting exposure and risk must be assessed for decision-makers to make these tradeoffs in the next stage of the framework. Mass release or flow analysis can also be used to estimate concentrations in surficial sediment or overlying water. Ultimately, it is these quantities that are most closely related to risk. The long-term behavior of the concentration can then be used to define exposure and risk as a function of time. For example, if dredging and onshore treatment or disposal are used, the water concentrations increase during the dredging action but, if effective, decrease rapidly beyond that expected of natural-attenuation processes. Finally, if in situ capping is used, the concentrations in water and the risk might be reduced dramat-
OCR for page 195
A Risk-Management Strategy for PCB-Contaminated Sediments ically over the short-term, but there is a possibility of cap failure at some later time, resulting in increased exposure and risk unless maintenance and repair are performed. The relative importance of the exposure and risk is dependent upon the magnitude of the concentrations and the type of adverse effects caused by the contaminant. Long-term cancer risk in humans, for example, is usually assumed to be related to average exposure or dose, whereas noncarcinogenic risk is usually assumed to be significant only if a certain threshold is exceeded. Thus, the cancer risks associated with various management options can be compared by evaluating the cumulative exposure over time, and the noncarcinogenic risks can be compared by evaluating the maximum exposure or the period exceeding the threshold. Other more complicated risk factors must be evaluated by more sophisticated analyses. There are at least two reasons why current risk might be of more concern than deferral of risks into the future. First, it is common practice to discount future gains and losses in recognition of rates of time preference and productivity of capital assets (e.g., Cropper and Portney 1990; Portney and Weyant 1999). So a given risk today is commonly viewed as more of a concern than an equivalent risk at some future date. Second, changing technology might make PCB-related risks less of an issue in the future. For example, if PCB-contaminated sediments are capped beneath clean sediments and if that cap is expected to last for a long enough time (say one century), it is possible that new technologies can be developed in the mean time to alleviate the risk. On the other hand, some might question whether it is morally acceptable to take actions that benefit society today, if those actions push risks off onto future generations (Kadak 2000). Component Technologies of Sediment Management Options A wide variety of management options exist for addressing contaminated-sediment problems. Socioeconomic options might provide offsets that improve human or ecological health or quality of life. Institutional controls attempt to reduce exposure to contaminants associated with sediments, for example, by restricting fishery usage or by providing alternative sources of fish. Source control, often by treatment, removal, or containment, seeks to eliminate the causes of the contamination to ensure the permanence of management actions. Natural-attenuation processes are likely to affect the risk of the contaminants in the sediments. These processes combined with institutional controls are expected to limit exposure to the contaminated sediments. The primary natural process likely to reduce risk to PCBs at contaminated-sediment sites is stable burial by deposition of clean sediment, a process that
OCR for page 196
A Risk-Management Strategy for PCB-Contaminated Sediments physically separates contaminants from organisms in the biologically active region near the sediment-water interface. A variety of more active in situ and ex situ options also exist for contaminated sediments. The application of ex situ treatment or disposal typically introduces a complete train of component technologies, including removal by dredging, temporary storage or pretreatment to reduce water content or volume, final dredged material treatment or disposal, and management of any residually contaminated materials, including air and water waste streams. All of these options pose varying degrees of effectiveness for any particular PCB-contaminated site. As indicated previously, the identification and comparative evaluation of these options as to effectiveness, cost, and contaminant losses and residuals must take into account all components of the individual options. These general approaches to sediment management are addressed below. Excellent reviews of the remediation technologies including a description of their design, application, and effectiveness are already available (see Averett et al. 1990; EPA 1994a; NRC 1997). As a result, only outlines of the various approaches and the potential advantages, disadvantages, limitations, and applications are discussed here. The primary goal is to indicate the risks associated with the various options or their components and the conditions under which those risks might be problematic. An important consideration in the selection of a management option is balancing effectiveness with costs. Unfortunately, costs are very site-specific and highly variable and are often estimated on different bases, making generalizations on costs difficult. As a result, the costs of various management options are not discussed here except in general terms. To be useful, project-costing information must be reported much more completely with identification of major cost factors at a particular site. Socioeconomic Options Options for reducing exposure to PCBs include approaches that do not directly address the contaminated sediments in which they reside. Two types of approaches in this area include the use of institutional or administrative controls to limit exposure and access by groups at risk and the use of offsets to meet environmental goals by reducing risks from sources other than the contaminated sediments. Institutional Controls In the parlance of a previous report by the NRC (1997), institutional controls are “interim controls” implemented to minimize exposure to contami-
OCR for page 197
A Risk-Management Strategy for PCB-Contaminated Sediments BOX 7–1 Administrative or Institutional Controls Are nonengineered instruments, such as administrative and legal controls, that minimize the potential for exposure to contamination by limiting land or resource use. Are generally to be used in conjunction with other risk-management options, such as treatment or containment. Can be used during all stages of the cleanup process to accomplish various cleanup-related objectives. Should be “layered” (i.e., use of multiple mechanisms) or implemented in a series to provide overlapping assurances of protection from contamination. nants and reduce risk to humans and the environment until long-term management reduces risks to acceptable levels (see Box 7-1). There are several general categories of institutional controls: government controls; informational devices; proprietary controls; and enforcement tools with institutional control components. Institutional controls involving PCB-contaminated sediments often take the form of government controls, such as fishing bans or fishing catch-and-release requirements, or informational devices, such as fishing advisories. These controls can also include physical measures, such as fences and signs, to limit activities that might result in exposure to contamination at a site. For example, in an effort to prevent or minimize exposure to fish with PCB contamination above a target risk level, signs warning against eating fish have been posted at most public boat-launch areas and recreational areas at Lake Hartwell in South Carolina since 1987 (Hahnenberg 1995, as cited in NRC 1997). As noted in the 1997 NRC report, in some cases fishing restrictions have been in place for so long that they have become de facto permanent solutions. For instance, PCB-contaminated fish and sediments were found in the upper Hudson River in the early 1970s. Health advisories against fish consumption from the lower river and a complete ban on fishing in the upper river have been in effect since the mid-1970s (Harkness et al. 1993). The effectiveness of fishing controls is an open question. The committee responsible for the 1997 NRC report was unable to find enough information to document or analyze the risk reduction of either fishing bans or advisories. The committee summarized a study by Belton et al. (1985) that illustrates the compliance problems involved. This study addressed a potential 60-fold increase in the risk of human cancer associated with the lifetime consumption
OCR for page 198
A Risk-Management Strategy for PCB-Contaminated Sediments of PCB-contaminated fish from the Hudson-Raritan estuary area. The effectiveness of public-health advisories as risk-reduction measures was evaluated by a careful, multidisciplinary study of recreational fishers. Approximately 59% of those surveyed fished for the purpose of catching food. More than 50% of the respondents were aware of the warnings, and those who did not consume the fish were generally persuaded by a perception of unacceptable risks. But 31% of those who ate their catch did so despite believing it was contaminated. The researchers concluded that the broad-scale rejection of the health advisories was due to a combination of factors: the way the media were used, the nature and delivery of the health advisory, and personal predispositions that tended to reduce the credibility or usefulness of the communication. In a more recent study (NYSDOH 2000), approximately half of the Hudson River anglers surveyed remained unaware of fish advisories, and approximately one-third ate the fish from the river. Of the anglers surveyed, however, only 6–7% indicated that their primary reason for fishing was for food, and 90% indicated that they were fishing primarily for recreation. Those that did eat the fish often shared the fish with women and children despite NYSDOH recommendations that these portions of the population eat no fish from the Hudson River. Fishing controls might have more impact if fish advisories are available in multiple languages, are handed out with fish licenses, or are readily accessible on the Internet. For example, the state of Indiana maintains an updated fish consumption advisory on its official website. Also, local health or environmental management personnel should be encouraged to visit local fishing holes and advise people about the risks of eating the fish they catch (i.e., enforce catch-and-release laws associated with a fish advisory). Institutional controls involving PCB-contaminated sediments may also take the form of legal restrictions on the use of aquatic or adjacent upland property (proprietary controls). These legal restrictions are often described in a restrictive covenant on the property that runs with the land executed by the property owner and recorded with the register of deeds for the county in which the site is located. The restrictive covenant may contain measures prohibiting uses (e.g., residential) or activities (e.g., recreational fishing) more likely to result in exposure to residual contamination on the property. The restrictive covenant may also provide for continued access to the site by appropriate agencies. The restrictive covenant may be removed, upon notice to and approval by the appropriate federal or state agency, if and when residual contamination on the site finally achieves acceptable risk levels. Like fishing bans, proprietary controls are only as effective as the willingness of local, state, or federal authorities to monitor and enforce such restrictions. Given that restrictive covenants may allow for residual contamination
OCR for page 199
A Risk-Management Strategy for PCB-Contaminated Sediments on the site, questions remain whether such measures truly reduce risks from exposure over the long term (see Chapter 4 for more discussion of community concerns regarding institutional controls). In summary, institutional controls “may be advisable when sediment contamination poses an imminent danger and immediate risk reduction is required” (NRC 1997). The committee finds that institutional controls might also be advisable as a supplement to long-term controls and technologies when management actions that would reduce contaminant risks to acceptable levels are impracticable and long-term solutions necessarily involve natural-attenuation processes. Although few data are available concerning the effectiveness of institutional controls, the measures identified above appear to be practical and are likely to reduce risk to some (albeit unknown) degree. Other advantages include low costs and ease of implementation. When institutional controls form part of the management strategy, they should be negotiated at the same time as the remainder of the strategy rather than after the strategy has proved to be ineffective. Negotiating institutional controls as part of the management strategy will allow maximal flexibility in achieving a solution acceptable to directly affected parties. To be effective, however, the controls must be understandable, monitored, and enforced. Offsets Offsets can be an effective way to attain environmental goals in a technically feasible and cost-effective manner and can facilitate negotiations among affected parties. Offsets trade off an increase in environmental harm by certain actions against an equivalent or greater reduction in harm by other actions. For example, suppose there is a goal to reduce aggregate pollution emissions from all sources by 50%. An offset might reduce overall emissions by 50% or more by reducing emissions by more than 50% at sites that are inexpensive to control and simultaneously allowing current levels of emission at sources where pollution control is very expensive. The goal is to think creatively to identify and pursue win-win solutions that are preferred by all parties. Typically, offsets focus on controlling pollution emissions. However, such control is not likely to be effective for a pollutant like PCBs, where zero emission is the environmental goal. Instead, offsets might focus directly on impacts to humans and the environment. For example, the community might agree to bear some risk from PCB-contaminated sediments if the responsible party agree to offset that risk by reducing other risks to human health. In such a case, a community might opt to have a catch-and-release program for its contaminated fish, if the responsible party restores a contaminated river bank
OCR for page 231
A Risk-Management Strategy for PCB-Contaminated Sediments examples, product streams from a soil washing system can still contain high contamination, and the disposal or subsequent treatment of these streams must be included in the identification, analysis, and screening of sediment management options. Other extractive technologies, such as thermal desorption and solvent extraction, are generally more effective than simple sediment washing. As with any extraction process, however, product streams and residuals contain the contaminants, and these streams generally require further treatment before disposal. Generally, the product streams are more concentrated in contaminants than the original sediment, since the desire is to reduce the volume of material for subsequent treatment or disposal. If the product stream is a fluid, either air or water, subsequent treatment might be more easily accomplished than treatment of the original sediment. If the product stream is a solid, subsequent treatment options might be identical to those available for the original contaminated sediment, but the reduction in volume might result in reduced overall costs. Because of the cost and complexity, solvent extraction has seen limited application to either sediment or soil remediation and is unlikely to be used except for specialized, small-volume applications. Thermal desorption has received somewhat wider usage and has been used in sediment management programs. Box 7-9 illustrates two examples of the effectiveness of thermal desorption and the residuals that might be produced. One example is low-temperature desorption, which has relatively low-energy requirements when applied to wet sediment but is limited in effectiveness. The second example is high-temperature desorption, which exhibits high effectiveness with correspondingly greater energy costs and process complexity. Both processes illustrate a key feature of extractive technologies: the products and residuals require further treatment or disposal. Stabilization technologies involve introduction of additives to the dredged material to prevent mobility of contaminants, providing a more secure material for disposal, or a reusable product, such as flowable or solid fill for construction. The contaminant levels are normally unchanged except for dilution due to mixing with the various additives required to prepare the product. Stabilization is expected to significantly reduce the potential for leaching of the contaminants. An important barrier, however, is the lack of regulatory standards for use of the product. Fill standards based on total contaminant levels are not suitable for stabilized materials, while fill standards based on leachate tests, such as EPA’s toxicity characteristic leaching procedure (TCLP), may not be sufficiently protective or acceptable to the community. Examples of solidification and stabilization processes that are being applied to contaminated sediments are the flowable fill technology marketed by Pohlman Materials Recovery and the solidification process of OENJ Cherokee. In the flowable fill process, partially dewatered sediment is blended, after debris removal, with
OCR for page 232
A Risk-Management Strategy for PCB-Contaminated Sediments BOX 7–9 Effectiveness of Thermal Desorption Thermal desorption enhances the evaporation of contaminants from soils and sediments. The resulting air stream can be treated for removal and destruction of contaminants prior to release to the atmosphere. Low-temperature thermal desorption has lower energy requirements, and high-temperature thermal desorption has the advantage of a high removal and destruction efficiency, which is typical of high-temperature processes. High-temperature processes, however, also involve high-energy costs associated with treatment of wet sediments and might result in the formation of dioxins and furans. The effectiveness of the process is illustrated with a pilot-scale demonstration on sediment dredged from Ashtabula, Ohio (EPA 1994b) and a full-scale management effort in Waukegon, Illinois (EPA 1995). Ashtabula River, Ohio: The Remediation Technologies (RETEC) Inc., process was evaluated in a pilot-scale demonstration on 36–55 gallon drums of sediment from Ashtabula, Ohio, in 1992 (EPA 1994b). This is a low-temperature (190–250°C) desorption process that collects particulate matter carried by exhaust gases with a cyclone separator and collects the vapors with a multistage condenser system. Average PCB concentrations in the sediments were 2.2 mg/kg before treatment and 0.4–0.8 mg/kg after treatment. The average removal efficiency was 82.8%, although efficiencies as high as 95.1% were observed. With low-temperature desorption, the PCBs are not destroyed. The bulk of the desorbed PCBs (as much as 55%) were collected in the condensate system. An activated carbon-polishing step collected as much as 6% of the desorbed PCBs. The remainder of the desorbed PCBs were not accounted for. Waukegon, Illinois: High-temperature (up to 1207°F) thermal desorption was used for the full-scale remediation of the Outboard Marine Corporation site in Waukegan, Illinois, during 1992 (EPA 1995). The process, developed by Soiltech ATP, involves a rotary kiln desorption under anaerobic conditions and with a mean solids residence time of 30–40 minutes followed by exhaust gas and water treatment. A total of 12,755 tons of soil and sediment containing an average of 10,484 mg/kg PCBs were treated, and 255 tons of soils and sediments containing extractable organic halides at 1,900 mg/kg were processed during a site process evaluation at the same site during June 1992. The treated soil contained an average of 2.2 mg/kg for greater than a 99.98% treatment efficiency. Because desorption was conducted under anaerobic conditions, PCBs in the effluent gases were removed with particulate collection devices and with an oil absorption system. Approximately 50,000 gallons of PCB-contaminated oil was produced that required subsequent disposal. PCBs released to the atmosphere met destruction and removal efficiency (DRE) targets (99.9999%), but meeting dioxin and furan emission targets required process modification.
OCR for page 233
A Risk-Management Strategy for PCB-Contaminated Sediments proprietary silicate binders and fine aggregate. Contaminants are not destroyed but are stabilized by incorporation into the physical matrix of the product. Reduction in mobility by 2–3 orders of magnitude is expected. Conventional stabilization of the New York/New Jersey Harbor sediments with Portland cement was conducted by OENJ Cherokee and used as a cap on a municipal landfill in Elizabeth, New Jersey. A similar project plan was to use 4.5 million yd3 of dredged harbor sediment as a cap on a 38-acre municipal landfill and a 97-acre industrial site in Bayonne, New Jersey. Because of the lack of quality standards for either the stabilized material or the leachate that it might produce, these processes are likely to be applied only to relatively clean sediments and only for use as fill in industrial or landfill applications. As indicated previously, destruction processes are primarily thermally based. Conventional incineration has a high cost, results in the formation of dioxins and furans, and is subject to considerable community resistance. Alternative destructive processes might include the production of a reusable product, such as blended cement, lightweight aggregate, or glass from the dredged material. The blended-cement process includes the use of dredged material along with other components to produce cement. It would be necessary, however, to develop regulatory standards that establish the safety of these products. Thermal destruction in cement kilns to make cement, however, can raise air-emission permit and community-acceptance issues similar to those that arise for a conventional incinerator. The production of lightweight aggregate also uses rotary kiln technology for the destruction of contaminants and production of the aggregate. The production of glassy products from dredged material using a plasma torch has been proposed. Very high temperatures (in excess of 5,000°C) are achieved in the plasma torch, causing vaporization and degradation of organic materials in the dredged material. The final product is of high quality and essentially contaminant free. In situ vitrification is a similar process in which very high temperatures are achieved in situ with the accompanying potential for contaminant vaporization and degradation. High-temperature degradation processes can also be conducted under reducing (oxygen-free) conditions. Under these conditions, the generation of dioxins and furans might be minimized. The Eco Logic process (Eco Logic 1998) is a high-temperature (more than 850°C) desorption process followed by a gas-phase reduction reaction using hydrogen. The process can achieve high destruction efficiencies with minimal production of dioxins, furans, and other products of incomplete reaction (Eco Logic 1998). The high temperatures, associated energy costs, and complexity of the process, however, have limited its application to contaminated-sediment treatment. The various nonthermal and thermal technologies, while providing permanence, are costly and not likely to compete on a cost basis with direct disposal of the dredged material in a landfill. The useful products that some of the
OCR for page 234
A Risk-Management Strategy for PCB-Contaminated Sediments above processes produce have the opportunity to offset part of the cost of treatment if their introduction to the marketplace in large volume will not overly disrupt the market. The costs of these processes are also likely to be large except when large volumes are dredged because of economies of scale. It has been estimated, but not demonstrated, that many of these technologies can be implemented for $20–$60 per cubic yard of dredged material if amounts greater than 100,000 yd3 per year for 10–20 years can be guaranteed (PIANC 2000). The success of the various technologies and the products they produce currently depends on community and regulatory acceptance of their operation and the proposed usefulness of the products. The factor common to all treatment technologies for dredged material is that 100% effectiveness cannot be realized and that residual and effluent streams containing significant contamination might require further treatment or disposal or both. The contaminant losses, treatment and disposal of the residuals, and the risks involved need to be considered when identifying, evaluating, and selecting sediment management options. Inadequate consideration of such problems can give rise to inaccurate and misleading comparisons between removal and nonremoval sediment management options. CONCLUSIONS AND RECOMMENDATIONS A summary of the various risk-management options and the areas of potential risks that must be assessed is given in Table 7–3. Ultimately, the ability to make decisions, the next step in the management framework, requires that the process of identifying and evaluating options collects the information necessary to complete such a table. It should be emphasized that the table is a conceptual framework in which to consider the various options. The information needed to make decisions requires far more information and data about the individual options than can be presented in a simple table. On the basis of the discussion in this chapter, a number of considerations should be kept in mind when identifying and evaluating options. The current ability to reduce health and environmental risks from PCB-contaminated sediments through technical options alone is limited. Successful contaminated-sediment management and risk reduction requires a combination of technical and institutional options as well as natural attenuation. There should be no preferred or default PCB-contaminated-sediment management option. The optimal option for a particular site is dependent upon site-specific factors and conditions and should be selected as a result of active participation by all affected by the decision.
OCR for page 235
A Risk-Management Strategy for PCB-Contaminated Sediments TABLE 7–3 Sediment Management Options and Associated Risks Option Component Goal Feasibility Cost Risk of Implementing Short-Term Risk Long-Term Risk Socioeconomic Institutional controls Sever exposure pathways Source control Eliminate source In situ management Natural attenuation Containment and degradation Thin-layer capping Containment Thick-layer capping Containment Ex situ management Mechanical dredging Removal Hydraulic dredging Removal Dry excavation Removal Pretreatment Dewatering, size separation Treatment and disposal Separation or destruction The first goal of any management activity for PCB-contaminated sediments should be to identify and, where possible, control the point and nonpoint sources that have caused and will continue to cause the contamination problem. The sources include, but are not limited to, run-off from contaminated soils, combined sewer overflows, and atmospheric inputs. Effectively responding to the contaminated sediment at a site generally requires using options that involve multiple technological and institutional components, and the evaluation, screening, and selection of these options must consider all the components, their interrelationships, and their impacts. Seven broad rules govern the analysis of management options: All sites require a conceptual model of the system, and the interaction of the management options with the sediments and contaminants is required. The use of mass flows can assist in developing and testing the
OCR for page 236
A Risk-Management Strategy for PCB-Contaminated Sediments conceptual model and can identify components of the management option that require additional review and analysis Evaluation of options at large, complicated sites requires the development of a sophisticated understanding of the specific system dynamics and the ability to predict future contaminant behavior and risks that are likely to result from the application of each of the various management options. The reduction of risks to human health and the environment at one location can often result in the creation of additional risks at other locations. The impact of these transferred risks and their acceptability to all concerned should be identified and fully explored. Natural attenuation is a component of all contaminated-sediment management options. No remediation technology is effective in removing all sediment contaminants from a site, and all remediation technologies result in the production of contaminated residuals and effluents that cannot be eliminated by known or likely technology. Such contaminated residuals and effluents left in place must ultimately be subjected to natural-attenuation processes. Removal options might produce short-term risks and, due to residual contamination from resuspension losses or leftover contaminated sediment, long-term risks that must be managed. Nonremoval options might produce long-term risks due to the potential of exposure to the remaining contaminants, and provisions for long-term monitoring and maintenance is required. The committee recommends that opportunities to restore or create critical habitats not be overlooked in the development and implementation of PCB-contaminated sediment risk-management strategies. Cleanup projects, such as the St. Paul Waterway Area Remedial Action and Habitat Restoration Project, demonstrate how sediment risk management can be successfully coupled with natural-resource restoration. Research should be directed toward improving understanding of the acute and chronic exposure and risk associated with the various management options. Because the appropriateness and effectiveness of the various options are dependent upon site-specific characteristics, such research should be directed toward defining models that can be used to project mass flows for a particular management option as a function of site conditions. A particular area of uncertainty is the long-term stability of sediments and sediment caps and the mode of failure if destabilized. Specifically, an ability is needed to quantitatively predict the extent of failure and the resulting exposure and risk in a low-probability storm or flow event.
OCR for page 237
A Risk-Management Strategy for PCB-Contaminated Sediments Due to the inability to target or capture all contaminated sediments, a second particular area of uncertainty is the assessment of residual contamination mass and concentrations. Under what conditions will dredging be unlikely to reduce risk? A third particular area of uncertainty is the assessment of the financial costs of a management alternative. Part of this uncertainty is due to the inability to adequately describe site conditions that influence the effectiveness and cost of management options. Part of this uncertainty is also due to the lack of a standard approach to accounting for present and future costs and inadequate representation of the entire life-cycle of management options. REFERENCES Alcoa. 1999. Analysis of Alternatives Report. Grasse River Study Area, Massena, New York. December. Averett, D.E., B.D.Perry, E.J.Torrey, and J.A.Miller. 1990. Review of Removal, Containment and Treatment Technologies for Remediation of Contaminated Sediment in the Great Lakes, Final Report. Paper EL-90–25, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS. Belton, T., B.Ruppel, K.Lockwood, S.Shiboski, G.Bukowski, R.Roundy, N. Weinstein, D.Wilson, and H.Wholan. 1985. A Study of Toxic Hazards to Urban Recreational Fisherman and Crabbers. Trenton, NJ: New York Department of Environmental Protection, Office of Science and Research. September 15 . BBL (Blasland, Bouck & Lee). 1996. St. Lawrence River Sediment Removal Project Remedial Action Completion Report. Prepared for General Motors Powertrain, Massena, New York. Blasland, Bouck & Lee, Syracuse, New York. June. Brown, M.P, and J.P.Doody. 2000. A Dredging Effectiveness Review—Case Studies and Lessons Learned. 16th Annual International Conference on Contaminated Soils, Sediments and Water, University of Massachusetts, Amherst, MA. October 16–19. Cropper, M.L., and P.R.Portney. 1990. Discounting and the evaluation of lifesaving programs. J. Risk Uncertainty 3(4):369–379. DiGiano, F.A., C.T.Miller, and J.Yoon. 1993. Predicting release of PCBs at the point of dredging. J. Environ. Eng. 119(1):72–89. Eco Logic. 1998. PCB-Contaminated Soil and Sediment Treatment Using Eco Logic’s Gas-Phase Chemical Reduction Process. Rockwood, Ontario: ELI Eco Logic International Inc. July 18. EPA (U.S. Environmental Protection Agency). 1994a. Assessment and Remediation of Contaminated Sediments (ARCS) Program: Remediation Guidance Document. EPA 905-R-94–003. Great Lakes National Program Office, Chicago, IL. October.
OCR for page 238
A Risk-Management Strategy for PCB-Contaminated Sediments EPA (U.S. Environmental Protection Agency). 1994b. Assessment and Remediation of Contaminated Sediments (ARCS) Program: Pilot Scale Demonstration of Thermal Desorption for the Treatment of Ashtabula River Sediments. EPA 905-R-94–021. Great Lakes National Program Office, Chicago, IL. EPA (U.S. Environmental Protection Agency). 1994c. Assessment and Remediation of Contaminated Sediments (ARCS) Program: Pilot Scale Demonstration of Sediment Washing for the Treatment of Saginaw River Sediments. EPA 905-R94–019. Great Lakes National Program Office, Chicago, IL. EPA (U.S. Environmental Protection Agency). 1995. Remediation Case Studies: Thermal Desorption, Soil Washing, and In Situ Vitrification. EPA 542/R-95/005. Federal Remediation Technologies Roundtable, U.S. Environmental Protection Agency, Washington, DC. EPA (U.S. Environmental Protection Agency). 1996. Assessment and Remediation of Contaminated Sediments (ARCS) Program: Estimating Contaminant Losses from Components of Remediation Alternatives for Contaminated Sediments. EPA-905-R-96–001. Great Lakes National Program Office, Chicago, IL. EPA (U.S. Environmental Protection Agency). 1998. EPA’s Contaminated Sediment Management Strategy. EPA-823-R-98–001. Office of Water, U.S. Environmental Protection Agency, Washington, DC. April. EPA (U.S. Environmental Protection Agency). 1999a. Treatment Technologies for Site Cleanup: Annual Status Report, 9th Ed. EPA 542-R-99–001. [Online]. Available: http://clu-in.org/products/asr/index2.html. [May 26, 1999]. EPA (U.S. Environmental Protection Agency). 1999b. Use of Monitored Natural Attenuation at Superfund, RCRA Corrective Action, and Underground Storage Tank Sites. OSWER Directive 9200.4–17P. Office of Solid Waste and Emergency Response, U.S. Environmental Protection Agency, Washington, DC. April 1999. [Online]. Available: http://www.epa.gov/OUST/directiv/d9200417.htm [June 16, 1999]. EPRI (Electric Power Research Institute). 1999. Review of Sediment Removal and Remediation Technologies at MGP and Other Contaminated Sites. Report No. TR-113106. Electric Power Research Institute, Palo Alto, CA. September. Farley, K.J., R.V.Thomann, T.F.Cooney, D.R.Damiani, and J.R.Wands. 1999. An Integrated Model of Organic Chemical Fate and Bioaccumulation in the Hudson River Estuary, Manhattan College, Riverdale, NY. Final Report to the Hudson River Foundation. [Online]. Available: http://www.hudsonriver.org/ Foster Wheeler (Foster Wheeler Environmental Corporation). 1999. New Bedford Harbor Cleanup Dredge Technology Review, Final Report. Prepared for U.S. Army Corps of Engineers, New England District. March. General Electric Company. 1999. Major Contaminated Sediment Site Database. [Online]. Available: http://www.hudsonwatch.com/mess/. Giesy, J.P. and K.Kannan. 1998. Dioxin-like and non-dioxin-like toxic effects of polychlorinated biphenyls (PCBs): implications for risk assessment. Crit. Rev. Toxicol. 28(6):511–569. Hahnenberg, J. 1995. Presentation at the Workshop on Interim Controls held July 31, 1995. Committee on Contaminated Sediments, National Research Council. EPA Headquarters, Chicago.
OCR for page 239
A Risk-Management Strategy for PCB-Contaminated Sediments Harkness, M.R., J.B.McDermott, D.A.Abramowicz, J.J.Salvo, W.P.Flanagan, M.L. Stephens, F.J.Mondello, R.J.May, and J.H.Lobos. 1993. In situ stimulation of aerobic PCB biodegradation in Hudson River sediments. Science 259:503–507. Hayes, D.F., T.Borrowman, and T.Welp. 2000a. Near field turbidity observations during Boston Harbor Bucket comparison study. Pp. 357–370 in Proceedings of the Western Dredging Association 20th Technical Conference and 32nd Annual Texas A&M Dredging Seminar, R.E.Randall, ed. CDC Report 372. Center for Dredging Studies, Texas A&M University. Hayes, D.F., T.R.Crockett, T.J.Ward, and D.Averett. 2000b. Sediment resuspension during cutterhead dredging operations. J. Waterw. Port Coastal Ocean Eng. 126(3):153–161. Herbich, J.B., and S.B.Brahme. 1991. Literature Review and Technical Evaluation of Sediment Resuspension During Dredging. Contract Report HL-91–1. Vicksburg, MS: U.S. Army Engineer Waterways Experiment Station. January. Jones, R.H., R.R.Williams, and T.K.Moore. 1978. Development and Application of Design and Operation Procedures for Coagulation of Dredged Material Slurry and Containment Area Effluent. Technical Report D-78–54. Vicksburg, MS: U.S. Army Engineer Waterways Experiment Station. Kadak, A.C. 2000. Intergenerational risk decision making: a practical example. Risk Anal. 20(6):883–894. Kauss, P.B., and P.C.Nettleton. 1999. Impact of 1996 Cole Drain Area Contaminated Sediment Cleanup on St. Clair River Water Quality. Technical report. Ministry of the Environment, Toronto, Ontario. NTIS MIC-99–07256INZ. King County. 2000. King County’s Combined Sewer Overflow (CSO) Control Program. Department of Natural Resources, Wastewater Treatment Division, Seattle, WA. [Online]. Available: http://dnr.metrokc.gov/WTD/cso/. [August 17, 2000]. Koenigsberg, S.S., and R.D.Norris, eds. 1999. Accelerated Bioremediation Using Slow Release Compounds: Selected Battelle Conference Papers: 1993–1999. San Clemente, CA: Regenesis Bioremediation Products. McLellan, T.N., and R.J.Hopman. 2000. Innovations in Dredging Technology: Equipment, Operations, and Management. ERDCTR-DOER-5. Vicksburg, MS: U.S. Army Corps of Engineers, Engineer Research and Development Center. McLellan, T.N., R.N.Havis, D.F.Hayes, and G.L.Raymond. 1989. Field Studies of Sediment Resuspension Characteristics of Selected Dredges. Technical Report HL-89–9. Vicksburg, MS: U.S. Army Engineer Waterways Experiment Station. Nakai, O. 1978. Turbidity generated by dredging projects. Pp. 31–47 in Management of Bottom Sediments Containing Toxic Substances: Proceedings of the Third U.S./Japan Experts Meeting. EPA-600/3–78–084. NRC (National Research Council). 1997. Contaminated Sediments in Ports and Waterways: Cleanup Strategies and Technologies. Washington, DC: National Academy Press. NRC (National Research Council). 2000. Natural Attenuation for Groundwater Remediation. Washington, DC: National Academy Press. NYSDOH (New York State Department of Health). 2000. Health Consultation 1996 Survey of Hudson River Anglers: Hudson Falls to Tappan Zee Bridge at Tarry-
OCR for page 240
A Risk-Management Strategy for PCB-Contaminated Sediments town, NY. Final Report. CERCLIS No. NYD980763841. Troy, NY: New York State Department of Health, The Center for Environmental Health. Palermo, M.R., J.Homziak, and A.M.Teeter. 1990. Evaluation of Clamshell Dredging and Barge Overflow, Military Ocean Terminal, Sunny Point, NC. Technical Report D-90–6. Vicksburg, MS: U.S. Army Engineer Waterways Experiment Station. Palermo, M.R., S.Maynord, J.Miller, and D.D.Reible. 1998. Assessment and Remedation of Contaminated Sediments (ARCS) Program: Guidance for In situ Subaqueous Capping of Contaminated Sediments. EPA 905-B96–004. Great Lakes National Program Office, Chicago, IL. [Online]. Available: http://www.epa.gov/glnpo/sediment/iscmain/index.html [December 09, 1998]. Parametrix. 1999. St. Paul Waterway Area Remedial Action and Habitat Restoration Project. Final 1998 Monitoring Report. Prepared for Simpson Tacoma Kraft Company, Tacoma, WA, and Champion International, Stanford, CT, by Parametrix, Inc., Kirkland, WA. February. Parker, J.H. and R.Valente. 1988. Long-Term Sand Cap Stability: New York Dredged Material Disposal Site. Contract Report CERC-88–2. Vicksburg, MS: US Army Engineer Waterways Experiment Station. PIANC (Permanent International Association of Navigation Congress). 2000. Innovative Dredged Sediment Decontamination and Treatment Technologies, U.S. Section PIANC Specialty Workshop, May 2, 2000, Waterfront Plaza Hotel, Oakland, CA. [Online]. Available: http://www.wes.army.mil/el/dots/training/pianc.html [March 2000]. Portney, P.R., and J.P.Weyant, eds. 1999. Discounting and Intergenerational Equity. Washington, DC: Resources for the Future Press. Scenic Hudson. 1997. Advances in Dredging Contaminated Sediments, New Technologies and Experience Relevant to The Hudson River PCBs Site. Prepared by J. Cleland for Scenic Hudson, Poughkeepsie, NY. April. Sloan, R.J. 1999. Hudson River Fish and the PCB Perspective. Paper presented to the National Research Council Committee on Remediation of PCB-Contaminated Sediments November 8. Smith, J.R. 1999. Non-time-critical removal action (NTCRA) pilot dredging in Grasse River. Pittsburgh, PA: Alcoa Inc. November 8. St. Lawrence Centre. 1993. Selecting and Operating Dredging Equipment: a Guide to Sound Environmental Practices. Prepared in collaboration with Public Works Canada and the Ministere de l’Environement du Quebec, and written by Les Consultants Jaques Berube Inc. Cat No En 40–438/1993E. Sumeri, A. 1989. Confined Aquatic Disposal and Capping of Contaminated Bottom Sediments in Puget Sound. Proceedings of the WODCON XII, Dredging: Technology, Environmental, Mining, World Dredging Congress, Orlando, FL, May 2–5, 1989. Sumeri, A., T.J.Fredette, P.G.Kullberg, J.D.Geermano, D.A.Carey and P.Pechko. 1994. Sediment Chemistry Profiles of Capped Dredged Sediment Deposits Taken 3 to 11 Years After Capping. Dredging Research Technical Note. DRP-5–09. Vicksburg, MS: U.S. Army Engineer Waterways Experiment Station. May. Thibodeaux, L.J., D.D.Reible, and K.T.Valsaraj. 1999. Effectiveness of Environ-
OCR for page 241
A Risk-Management Strategy for PCB-Contaminated Sediments mental Dredging. Final Report to Alcoa, Massena, NY. Hazardous Substance Research Center/South and Southwest, Louisiana State University, Baton Rouge, LA. Thoms, S.R., G.Matisoff, P.L.McCall, and X.Wang. 1995. Models for Alteration of Sediments by Benthic Organisms. Project 92-NPS-2. Alexandria VA: Water Environment Research Foundation. Valsaraj, K.T., L.J.Thibodeaux, and D.D.Reible. 1995. Modeling air emissions from contaminated sediment dredged materials. Pp. 227–238 in Dredging, Remediation, and Containment of Contaminated Sediments, K.R.Demars, G.N. Richardson, R.N.Young, and R.C.Chaney, eds. Philadelphia: American Society for Testing and Materials. Verbrugge, D.A., J.P.Giesy. M.A.Mora, L.L.Williams, R.Rossmann, R.A.Moll, and M.Tuchman. 1995. Concentrations of dissolved and particulate polychlorinated biphenyls in water from the Saginaw River, Michigan. J. Great Lakes Res. 21(2):219–233. WDNR (Wisconsin Department of Natural Resources). 1995. A Deterministic PCB Transport Model for the Lower Fox River Between Lake Winnebago and De Pere, Wisconsin. Prepared by J.Steuer, S.Jaeger, and D.Patterson. Publication WR 389–95. Wisconsin Department of Natural Resources. Weiner, K.S. 1991. Commencement Bay Nearshore/Tideflats Superfund Completion Report for St. Paul Waterway Sediment Remedial Action. Submitted to the U.S. Environmental Protection Agency for Simpson Tacoma Kraft Company and Champion International Corporation. January. Zeman, A.J., and T.S.Patterson. 1997. Results of in situ capping demonstration project in Hamilton Harbour, Lake Ontario. Pp. 2289–2295 in Engineering Geology and the Environment: Proceedings: International Symposium on Engineering Geology and the Environment, Athens, Greece, June 23–27, 1997, P.G. Marinos, ed. Rotterdam, Brookfield: A.A.Balkema.
Representative terms from entire chapter: