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3 Effectiveness of Environmental Dredging in Reducing Risk: Framework for Evaluation A wide variety of metrics can be used to evaluate the effectiveness of environmental-dredging projects in reducing risks to human health and the environment. The committee reviewed a number of them and developed a framework to facilitate the evaluation of the effectiveness of environmental-dredging projects at contaminated sediment sites. The framework is based on the effectiveness criteria used by the U.S. Envi- ronmental Protection Agency (EPA) Superfund program to select reme- dies (40 CFR Â§ 300.430[e][i]). In conducting its evaluation, the committee defined dredging effec- tiveness as the achievement of cleanup goals defined for each site, which take the form of remedial-action objectives, remediation goals, and cleanup levels.1 For CERCLA remedial actions, these goals are typically 1Remedial-action objectives âare intended to provide a general description of what remediation is expected to accomplishâ (EPA 2005a, p. 2-15). For example, a remedial-action objective might be to reduce to acceptable levels the risks to people who ingest contaminated fish. Remediation goals are paired contaminant- specific and media-specific concentrations intended to protect human and ecolo- gic health that incorporate site-specific information about exposure patterns and toxicity. âAt most CERCLA [Comprehensive Environmental Response, Compen- sation, and Liability Act] sites, [remediation goals] for human health and ecologic 70
Effectiveness of Environmental Dredging in Reducing Risk 71 documented in the record of decision (ROD). However, this definition is appropriate for evaluating the effectiveness of the project in reducing risk only when cleanup goals are derived from sound, site-specific risk modeling. An ideal evaluation of effectiveness at Superfund sites would be based on the site conceptual model, data from a baseline assessment, and a long-term monitoring program that permits sound statistical compari- son of the spatial scale of contamination and the magnitude of risk be- fore, during, and after dredging. At the outset of its work, the committee hoped to obtain that kind of information for a number of large contami- nated sediment sites to inform its deliberations. However, we found that such careful and prolonged monitoring either has not been conducted, has not been completed at large-contaminated sediment sites, or simply was not available to the committee. (The committee noted that some sites where remediation had not yet occurred or been completed have elec- tronic databases and long-term monitoring plans that would facilitate future attempts to evaluate remedy effectiveness, for example, Hudson River and New Bedford Harbor). In some cases, it is recognized that ad- ditional information, for example, raw data and consulting reports, may have been held by responsible parties, federal agencies, or their consult- ants. However, this information may not have been available in the pub- lic domain or to the committee, or the committeeâs time and resource constraints precluded a thorough compilation, analysis, and interpreta- tion (see further discussion in Chapter 4). In some cases a review of all site data was not necessary to determine whether cleanup goals had been met. This chapter details the committeeâs process for evaluating the ef- fectiveness of environmental dredging within the constraints imposed by the available data. The framework for this review is outlined in Box 3-1. receptors are developed into final, chemical-specific, sediment cleanup levels by weighing a number of factors, including site-specific uncertainty factors and the criteria for remedy selection found in the NCP [National Contingency Plan]â (EPA 2005a, p. 2-16). The ROD for each site generally should include chemical- specific cleanup levels, indicating how these values are related to risk and how their attainment will be measured (EPA 2005a).
72 Sediment Dredging at Superfund Megasites BOX 3-1 Framework for Evaluating the Effectiveness of Environmental Dredging Projects 1. Identify Superfund megasites and other large environmental-dredging projects. 2. Define criteria for selecting projects for committee evaluation from the list of environmental-dredging projects. 3. Select projects that represent a variety of site conditions. 4. Evaluate each project with respect to measures of short-term and long- term effectiveness. 5. Make recommendations for improved design, implementation, and monitoring of future environmental-dredging projects. SOURCES OF INFORMATION ABOUT ENVIRONMENTAL- DREDGING PROJECTS The statement of task (see Appendix A) indicates that the sources of information âwould include megasites for which dredging has been completed; megasites for which plans have been developed, partially implemented, and operations are ongoing; and smaller sites that exhibit lessons relevant to megasites.â The committeeâs evaluation focused on environmental-dredging projects at Superfund megasites, but, because remediation has not been completed at many of these sites, the commit- tee also reviewed other environmental-dredging projects on which data relevant to the committeeâs charge were available. As described in Chapter 2, numerous environmental-dredging projects have been conducted, and many other contaminated sediment sites will require decision-making soon. At the first committee meeting, EPA outlined sites from its database of tier 1 sediment sites where dredging had been completed. From those dredging sites, EPA provided the committee with a list of sites on which there were pre-remediation and post-remediation monitoring data. To identify other dredging projects for possible evaluation, the committee reviewed information from additional government, industry, and private consulting sources that summarize remedial activities at contaminated sediment sites (see Box 3-2). Collectively, those dredging project compilations and reviews
Effectiveness of Environmental Dredging in Reducing Risk 73 BOX 3-2 Compilations and Reviews of Sediment Remediation Projects EPAâs Great Lakes National Program Office summarized (EPA 1998) and updated (EPA 2000) information on contaminated sediment sites in the Great Lakes Basin that had been remediated with a variety of techniques. The reports provide some details about remedies but few details on post-remedial monitor- ing or on whether remediation achieved expected benefits. In 1999, the Great Lakes Water Quality Board summarized 20 sediment remediation projects in the Great Lakes areas of concern (Zarull et al. 1999). The report stated that of the projects implemented so far, only two (Waukegan Harbor, IL and Black River, OH) had adequate data on long-term ecologic health. The Great Lakes binational strategy progress reports (e.g., EPA and Environment Canada 2005) provide annual updates summarizing sediment remediation activities at Great Lakes sites in the United States and Canada. The Major Contaminated Sediment Sites (MCSS) Database (GE et al. 2004) is the largest compendium of information on such sites. It contains information on 123 major projects representing 103 sites. EPA maintains, although not publicly, a database on the 60 tier 1 sediment sites where remedies include dredging or excavation of at least 10,000 cy or capping or monitored natural recovery of at least 5 acres (EPA 2005a). Before this committeeâs deliberations, several other groups reviewed data on completed projects to examine whether remediation had been successful and to draw conclusions about the likely effects of dredging at other sites in the fu- ture. The General Electric Company (GE 2000) evaluated sediment remediation case studies involving 25 sites (including sites that used removal techniques other than dredging) and attempted to determine whether data indicated the ability to reduce risks to human health and the environment. Its report con- cluded that the success of the projects had not been demonstrated and that tech- nical limitations restricted the effectiveness of dredging in reducing surface sediment-contaminant concentrations. Cleland (2000) updated an earlier report prepared by Scenic Hudson (2000) and outlined experience at 15 sediment reme- diation sites, including many evaluated by GE (2000). Cleland presented sedi- ment and biota concentration data and concluded that post-dredging monitoring data consistently show beneficial results, including reductions in contaminant mass and in concentrations in sediment and fish. Many of the same case studies were also reviewed by EPA (Hahnenberg 1999), and EPA presented the results of its analysis to the National Research Councilâs Committee on Remediation of PCB-Contaminated Sediments (NRC 2001). EPAâs analysis indicated that dredg- ing resulted in reduced sediment and fish-tissue concentrations. An alternative analysis was also provided to that National Research Council committee by the (Continued on next page)
74 Sediment Dredging at Superfund Megasites BOX 3-2 Continued Fox River Group (1999, Appendix C in GE 2000), which refuted the connection between remedial actions and fish-tissue concentration declines on the basis of a paucity of data and flawed method in EPAâs linking of remediation to observed changes. During its deliberations, the previous National Research Council com- mittee (NRC 2001) reviewed the documents produced by GE (2000), Scenic Hud- son (2000), EPA (Hahnenberg 1999; Pastor 1999), and the Fox River Group (1999) to ascertain how groups reviewing the same documents could come to such dis- parate conclusions. It concluded: âFirst, in some instances, there is disagreement about the remediation goals and the measures by which achievement of the goals can be assessed. Second, in some cases, the available post-remediation monitoring data are sparse and incomplete compared with pre-remediation data and control data. Third, in some cases, it is the intention of reviewers, agencies, and industries to support their preferences, and that might lead to more con- flict.â Since the previous committee issued its report (2001), additional groups have sought to analyze the link between sediment remediation and reduced risk. Baker et al. (2001) sought to address the question âCan active remediation be implemented in such a way that it provides a net benefit to the Hudson River?â and commented on the biologic effects of sediment remediation at five sites. Thibodeaux and Duckworth (2001) evaluated measurements of environmental- dredging effectiveness in detail at three sites. Malcolm Pirnie (Malcolm Pirnie and TAMS Consultants, Inc. 2004), in an appendix to the engineering perform- ance standards developed for the Hudson River Superfund site, briefly reviewed data on 25 remediation projects (some had not initiated remediation) and pro- vided information on monitoring and remediation results. As part of its feasibil- ity study for the Kalamazoo River in Michigan, BBL (2000) compiled profiles of 20 environmental-dredging projects conducted nationwide and discussed their ability to meet project-specific objectives and their overall effectiveness. Several of those profiles were presented in an earlier analysis (GE 2000). In addition, the Great Lakes Dredging Team, a partnership of federal and state agencies, pro- vided a series of dredging project case studies (Great Lakes Dredging Team 2006). The U.S. Army Corps of Engineers Center for Contaminated Sediments also provided information on a series of environmental-dredging projects (USACE 2006). were extremely useful in forming the short list of dredging projects on which pre-dredging and post-dredging monitoring data were likely to be suitable for evaluation.
Effectiveness of Environmental Dredging in Reducing Risk 75 CRITERIA USED TO SELECT ENVIRONMENTAL-DREDGING PROJECTS FOR EFFECTIVENESS EVALUATION The committee used the criteria listed in Box 3-3 to select environ- mental-dredging projects for evaluation. Therefore, the committee pre- ferred projects that involved only dredging but did not limit its analysis to them. The committee did not select projects that involved dry excava- tion, because they are conducted under different conditions from con- ventional dredging. Pilot studies, although limited in scope and purpose, were also considered because they are often heavily monitored with sub- stantial information regarding the effect of dredging under specified conditions. The committee preferred projects with removal of at least 10,000 cy of sediment because of their similarity to megasites with respect to the spatial scale of ecologic and human health exposures. Some smaller pilot studies designed to inform decisions on larger sites were also included. This size threshold matches the threshold used by EPA to define tier 1 sediment sites (EPA 2005a). Any evaluation of dredging effectiveness depends on sufficient high-quality pre-dredging and post-dredging monitoring data. There- fore, another criterion used by the committee to select dredging projects was whether they had pre-dredging and post-dredging monitoring data. Environmental-dredging projects occur in a wide variety of aquatic environments, such as rivers, estuaries, bays, lakes, ponds, canals, and wetlands; and the effectiveness of dredging can be influenced by many BOX 3-3 Criteria Used to Select Environmental-Dredging Projects for Evaluation 1. The remedy consists of dredging only or a combined remedy that in- cludes dredging. 2. The remedy preferably includes removal of at least 10,000 yds3 of sedi- ment. 3. The project has some amount of pre-dredging and post-dredging data. 4. The projects collectively represent a wide variety of project types (for example, environmental settings, chemicals of concern, and dredging design and implementation).
76 Sediment Dredging at Superfund Megasites site-specific factors. Therefore, the committee endeavored to conduct a broad review of projects that represented a variety of site-specific condi- tions, including the type of water body, the form of chemical contamina- tion, and the type of dredging technology. SELECTION OF ENVIRONMENTAL-DREDGING PROJECTS The committee chose the 26 dredging projects listed in Table 3-1 for detailed evaluation (see Figure 3-1 for the location of the projects). Selected projects involved remedies with dredging only or dredging combined with backfilling or capping. Chemicals of concern included polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), pesticides, and metals detected in sediments in a variety of aquatic environments across the United States and one in Sweden. PCBs were the primary chemicals of concern in 19 of the 26 projects. Table 3-1 contains general information on the site and the remedy; further detail on several of the sites is provided in Chapter 4 and the associated references. In addition, summaries of many of these sites and their remediation have been compiled elsewhere (e.g., GE 2004; Malcolm Pirnie, Inc. and TAMS Consultants, Inc. 2004). The selected projects include all 12 sites (although not all the oper- able units at each site) on which there were pre-dredging and post- dredging data as reported by EPA at the first committee meeting (Ells 2006). The committee also chose three demonstration projects (two in the Lower Fox River, WI, and one in the Grasse River, NY) and one state- lead site (Cumberland Bay, NY) recommended for review by the Sedi- ment Management Work Group during the committeeâs second meeting (Nadeau 2006). Scenic Hudson (Cleland 2000), an advocacy group that promotes cleanup of the Hudson River in New York, also included those demon- stration projects and Cumberland Bay in its review of dredging effec- tiveness. In addition, Scenic Hudson identified Lake Jarnsjon in Sweden and the Black River, OH, as examples of successful dredging operations (as did Green and Savitz [unpublished] and Zarull et al. 1999), and the committee selected these two sites for evaluation. During the commit- teeâs second meeting, remediation consultants presented results of two recently completed large-scale dredging operations: in the Lower Fox
TABLE 3-1 Summary of 26 Environmental-Dredging Projects Selected for Evaluationa Primary Chemicals of Scale of Dates of Volume of Dredged Project Concern Water- Body Type Remedy Type Effort Dredging Sediment (cy) Bayou Bonfouca, PAHs Bayou Dredging followed by Full-scale 1994-1995 170,000 LA backfilling Lavaca Bay, TX Hg Estuary Dredging Pilot 1998 80,000 Black River, OH PAHs River Dredging Full-scale 1989-1990 45,000-60,000 Outboard PCBs Harbor Dredging Full-scale 1991-1992 38,000 Marine Corp., Waukegan Harbor, IL Commencement PCBs, As, Estuary Dredging Full-scale 2003-2006b 419,000c BayâHead of PAHs Hylebos, Tacoma, WA Commencement As, Cu Estuary Dredging Full-scale 1993-1994 428,000d BayâSitcum, Tacoma, WA Duwamish PCBs Tidally influenced Dredging followed by Full-scale 2003-2004 66,000 Diagonal, river capping Seattle, WA (Continued on next page) 77
78 TABLE 3-1 Continued Primary Chemicals of Scale of Dates of Volume of Dredged Project Concern Water- Body Type Remedy Type Effort Dredging Sediment (cy) Puget Sound PCBs Estuary Dredging Full-scale 2000-2004 225,000e Naval Shipyard, Bremerton, WA Harbor Islandâ PCBs, PAHs, Estuary Dredging in open-water Full-scale 2003-2004f 70,000 Lockheed, Hg, Pb, As, Cu, area, dredging and Seattle, WA Zn, tributyltin capping in nearshore area Harbor Islandâ As, Pb, Zn, Cu, Estuary Dredging, capping, and Full-scale 2004-2005 220,000 Todd, Seattle, PAHs, PCBs, habitat restoration in WA tributyltin, Hg selected areas Cumberland PCBs Inland lake Dredging Full-scale 1999-2000 195,000 Bay, NY Dupont, Zn, Pb, Cd River Dredging and backfilling Full-scale 1999 11,000 Christina River, DE Lower Fox River PCBs River Dredging Full-scale 2004-present Incomplete (OU-1), WI Lower Fox River PCBs River Dredging Pilot 1998-1999 8,200 (Deposit N), WI
Lower Fox River PCBs River Dredging and backfilling Pilot 1999-2000 82,000 (SMU 56/57), WI Ketchikan Pulp 4-methyl Fjord Dredging and backfilling Full-scale 2000-2001 8,700 Company, Ward phenol; (thin-layer) Cove, AK ammonia Newport Naval PAHs, PCBs Bay Dredging and backfilling Full-scale 2001 34,000 Complexâ McCallister Landfill, RI GM Central PCBs River Dredging (backfilling in Full-scale 1995 14,000 Foundry, St. one area) Lawrence River, NY Grasse River, PCBs River Dredging Pilot 1995 3,000 NY (non-time- critical removal action) Grasse River, PCBs River Dredging and backfilling Pilot 2005 30,000 NY remedial options pilot study (ROPS) Lake Jarnsjon, PCBs Lake Dredging Full-scale 1993-1994 196,000g Sweden (Continued on next page) 79
80 TABLE 3-1 Continued Primary Chemicals of Scale of Dates of Volume of Dredged Project Concern Water- Body Type Remedy Type Effort Dredging Sediment (cy) Manistique PCBs Harbor Dredging Full-scale 1995-2000 190,000h Harbor, MI Reynolds PCBs, PAHs, River Dredging Full-scale 2001 86,000 Metals, St. total (backfilling in one area) Lawrence River, dibenzofuran NY Marathon Cd River Dredging Full-scale 1993-1995 71,000 Battery, Hudson River, Cold Spring, NY New Bedford PCBs Estuary Dredging Full-scale 1994-1995 14,000 Harbor, MA (hot (hot spot spot) removal) United DDT, dieldrin Estuarine channel Dredging and backfilling Full-scale 1996-1997 110,000 Heckathorn, Richmond, CA aIn the review and collection of data on dredging sites it was determined that various sources will often provide inconsistent information. For example, the committee found several different estimates for the volume of sediment removed from the Black River: 49,700 cy (Zarull et al. 1999; Cleland et al. 2000); 45,000 cy (Malcolm Pirnie and TAMS Consultants, Inc. 2004); 50,000 cy (EPA 2000); 60,000 cy (GE 2000; GE 2004; Fox R. Group 1999). bFrom Dalton, Olmsted & Fuglevand, Inc. 2006.
c15,000 cy removed with upland-based equipment and 404,000 removed with marine-based equipment. dFrom EPA summary (EPA 2006 [Commencement BayâSitcum Waterway, April 26, 2006]): âApproximately 396,000 cy of sediment were dredged from Area A using hydraulic and clamshell dredges and approximately 32,300 cy were removed from Area B using a small hydraulic dredge.â eFrom EPA summary (EPA 2006 [Puget Sound Naval Shipyard, May 15, 2006]). fFrom EPA summary (EPA 2006 [Harbor Island Lockheed Shipyard Sediment Operable Unit, May 11, 2006]): âRemediation dates: These dates refer to dredging activities, not other remedial activities such as capping. November 22, 2003 to March 10, 2004 and from October 22, 2004 to November 22, 2004.â gBremle et al. 1998. hEPA 2006 (Manistique River and Harbor Site, May 10, 2006). Sources: Data are also unpublished data from EPA, NAS Completed Dredging Summary, March 22, 2006; Malcolm Pirnie, Inc., and TAMS Consultants, Inc. 2004. 81
82 Sediment Dredging at Superfund Megasites FIGURE 3-1 Locations of environmental-dredging projects selected for evalua- tion. Several locations comprise more than one site, including Commencement Bay, Grasse River, Lower Fox River, and Harbor Island. River Operable Unit 1 and the Grasse River Remedial Options Pilot Study (Connolly et al. 2006; Fox et al. 2006). Those two projects were se- lected for evaluation because extensive monitoring data on them were made available to the committee. The committee selected a pilot dredg- ing study in Lavaca Bay, TX, and a hot spot removal in New Bedford Harbor, MA, because they were the subject of extensive monitoring ef- forts. The Reynolds Metals Superfund site in the St. Lawrence River was selected because it has undergone monitoring for several years after ini- tial dredging (EPA 2005b). Of the 26 dredging projects, five have been identified by EPA as contaminated sediment megasites, that is, sites where the dredging por- tion of the remedy will cost at least $50 million (see âSediment Contami- nation at Superfund Sitesâ in Chapter 2).
Effectiveness of Environmental Dredging in Reducing Risk 83 APPROACH TO EVALUATING DREDGING PROJECTS The committee evaluated the effectiveness of the 26 dredging pro- jects, where data permitted such an evaluation, by determining whether cleanup levels and remedial action objectives were achieved. The com- mittee used lessons learned from the projects to identify means for im- proving future decisions about remediation at Superfund megasites. The lessons learned involved: âª Factors that contributed to the success of dredging operations. âª Factors that adversely affected dredging operations. âª Methods for improving the monitoring of dredging effective- ness. The committee did not attempt to substitute its own judgment about what remedial action objectives and cleanup levels should be, in- cluding the site-specific risk modeling on which they were based, but simply tried to determine whether the stated goals were achieved and why or why not. The committee chose to review sites where dredging was the only remedy (or at least the main remedy) to evaluate the effec- tiveness of only dredging. However, the committee acknowledges that the effects of dredging may be difficult or impossible to distinguish from other ongoing processes including additional source control and natural recovery. The committee recognizes the importance of quantifying the net risk reduction associated with dredging, which involves consideration of possible increases in risk to the spectrum of human and environmental receptors that might be caused by dredging and the treatment, storage, transport, and disposal of dredged sediment as well as risk reduction from removal of contaminated sediments from aquatic systems. The need for considering net risk reduction and incorporating the analysis into decision-making at Superfund sites has been noted in previous Na- tional Research Council reports (NRC 2001; NRC 2005), recognized by EPA (EPA 2005a), and examined in the scientific literature (Wenning et al. 2006). However, such analysis was not possible in this case. It was difficult (in some cases impossible) to obtain requisite data on the dredg- ing component of each project, much less some of the other measures relevant to a net risk reduction analysis (for example, number of acci-
84 Sediment Dredging at Superfund Megasites dents during transportation of dredged material) that are often not com- piled. These limitations combined with time and resource constraints prevented the committee from conducting net risk reduction evaluations for each dredging project. As a result, the committee chose to focus its time and resources on the dredging component of projects rather than treatment, storage, transport, and disposal. Methods Used to Evaluate Dredging Projects Each project review began with the identification of the remedial action objectives and cleanup levels for the project. That was followed by review of project data to judge whether the remedial action objectives and cleanup levels had been met. Those data could include chemical concentrations in sediment, surface water, the biota, and other environ- mental media; indicators of exposure (such as bioaccumulation testing and human biomonitoring data); and measures of risk (such as toxicity testing). The measures have inherent natural heterogeneity and are sub- ject to uncertainty. When, despite the variability and uncertainty, suffi- cient data were available to compare pre-dredging and post-dredging conditions, the committee attempted to answer the effectiveness ques- tions listed in Box 3-4. Ideally, the evaluation should be performed in the context of a comparison of all available remedial alternatives (EPA 2005a; Bridges et al. 2006), but the committee reviewed only dredging projects in accordance with the statement of task. Cleanup levels and remedial action objectives are not always risk- based, and some projects have no cleanup levels or other quantitative means to judge effectiveness at all. Therefore, the committee looked be- yond remedial action objectives and cleanup levels to identify dredging successes and failures in reducing exposure or risk, as well as the site, the remedy, or the contaminant conditions that led to the successes and failures. In its evaluation of project data, the committee distinguished between changes in environmental-media concentration, exposure, and risk. The committee evaluated whether baseline assessment data were available to define conditions before dredging for comparison with monitoring data collected during and after dredging. Optimally, those
Effectiveness of Environmental Dredging in Reducing Risk 85 BOX 3-4 Measures of Sediment-Remedy Effectiveness in the Superfund Program Dredging effectiveness is the achievement of cleanup goals (remedial action objectives and cleanup levels that are derived from appropriate site-specific risk modeling) in the predicted time frame with a reasonable degree of confidence that the achievement will be maintained. Interim Measures 1. Short-term remedy performance. For example, have sediment cleanup levels been achieved after dredging? 2. Long-term remedy performance. For example, have sediment cleanup levels been maintained for at least 5 years, and thereafter as appropriate? 3. Short-term risk reduction. For example, have remedial action objectives been achieved? Do data demonstrate or at least suggest a reduction in fish tissue concentrations, a decrease in benthic toxicity, or an increase in species diversity or other community indexes after 5 years? Key Measure 4. Long-term risk reduction. For example, have remedial action objectives been maintained for at least 5 years, and thereafter as appropriate? 5. Has the predicted magnitude and timing of risk reduction been achieved or are they likely to be achieved? Source: Adapted from EPA 2005a. assessment data would suffice to quantify exposures and risks and allow comparison with during-dredging and post-dredging monitoring data. Human and ecologic exposure and risk might increase during dredging, and these increases should also be weighed against exposure and risk reductions following dredging. Monitoring data and information col- lected during dredging were reviewed to identify changes in human and ecologic exposure and risk that occurred during this period. Dredging of contaminated sediment disrupts the bottom substrate, thereby destroy- ing the existing benthic community, and can increase exposure of hu- mans and the biota, depending on the degree of resuspension, residual generation, and release of sediment-bound, dissolved, or airborne con-
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