Sediment Dredging at Superfund Megasites Assessing the Effectiveness (2007) / Chapter Skim
Currently Skimming:
6 Dredging at Superfund Megasites: Improving Future Decision-Making
6 Dredging at Superfund Megasites: Improving Future Decision-Making
Pages 240-263
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 240... ...
6 Dredging at Superfund Megasites: Improving Future Decision-Making INTRODUCTION The preceding chapters discussed sediment management and dredging at Superfund megasites and included sections on assessing the effectiveness of dredging for removing contaminated sediment to attain remedial-action objectives and achieve specified cleanup levels. The assessment included the review of 26 projects from which general conclusions were developed with respect to the appropriate use and limitations of dredging in meeting risk-based goals.
|
From page 241... ...
Improving Future Decision-Making 241 tices and management of contaminated sediment at megasites. This includes the expected role of dredging in the future and the issues and factors that need to be addressed to ensure the effective use of dredging as a component of contaminated sediment remediation.
|
From page 242... ...
242 Sediment Dredging at Superfund Megasites The charge to this committee focused on megasites, but the dearth of such sites with completed dredging remedies and with good predredging and post-dredging data has meant that the committee reviewed smaller sites, or individual projects at megasites. The projects evaluated did not include any of the magnitude (that is, tens of miles of river stretches and thousands of hectares)
|
From page 243... ...
Improving Future Decision-Making 243 ment contamination at any site must be viewed in a larger framework to permit valid predictions about cleanup and risk reduction. Sediment megasites can span an entire waterbody (such as the Lower Fox River in Wisconsin)
|
From page 244... ...
244 Sediment Dredging at Superfund Megasites A related issue is the lack of essential tools for understanding how reductions in sediment toxicity or biologic exposure will enhance ecosystem response and benefit ecosystem recovery. Much of our understanding of these topics is wholly observational or is derived from ancillary measures (such as sediment chemistry)
|
From page 245... ...
Improving Future Decision-Making 245 and stakeholders." NRC (2005) recommends an adaptive-management approach at Superfund megasites where it is unlikely that final remedies can be identified and implemented.
|
From page 246... ...
246 Sediment Dredging at Superfund Megasites BOX 6-1 Six-Step Adaptive-management Process 1. Assessing the problem, including establishing measurable management objectives, key indicators of those objectives, quantitative or conceptual models to predict effects of remedial alternatives on the indicators, and forecasts of responses of indicators to remedial actions.
|
From page 247... ...
Improving Future Decision-Making 247 There are also examples of sites where adaptive-management principles, if not an explicit, rigorous adaptive-management process, have been applied in remediating contaminated sediment sites (see Box 6-2)
|
From page 248... ...
248 Sediment Dredging at Superfund Megasites The Future of Dredging While some improvements have been made to dredge design and operation (for example, precision positioning systems or dredge head or bucket modifications to reduce resuspension) , in many respects dredging as a technology has not changed dramatically in the last few decades.
|
From page 249... ...
Improving Future Decision-Making 249 achieve desired risk reduction, both in the short term and in the long term, is needed. The challenge to this committee was twofold: to make pertinent technical recommendations (contained in Chapters 4 and 5)
|
From page 250... ...
250 Sediment Dredging at Superfund Megasites ommendations add more specificity than past efforts regarding the effective remediation and management of contaminated sediment. The three recommendations, which are described in more detail below, will in some cases require additional resources and, equally challenging in large organizations, new ways of doing business.
|
From page 251... ...
Improving Future Decision-Making 251 The typical Superfund remedy-selection approach, in which site studies in the remedial investigation and feasibility study establish a single path to remediation in the record of decision, is not the best approach to remedy selection and implementation at these sites owing to the inherent uncertainties in remedy effectiveness. At the largest sites, the time frames and scales are in many ways unprecedented.
|
From page 252... ...
252 Sediment Dredging at Superfund Megasites Baseline risk is quantified in the remedial investigation for all NPL sites, but the feasibility study may or may not include a quantitative estimate of the risks posed by alternative remedies.
|
From page 253... ...
Improving Future Decision-Making 253 Tier 3 Advanced PRA 2-D MCA Probabilistic Sensitivity Analysis (Microexposure Modeling, Bayesian Statistics, Geostatistics) a Characterization of Variability and/or Uncertainty Increasing Complexity/Resource Requirements Complete RI/FS Process Tier 2 PRA 1-D MCA Probabilistic Sensitivity Analysis Tier 1 Point Estimate Risk Assessment Point Estimate Sensitivity Analysis Problem Formulation/Scoping/Work Planning/Data Collection = Decision Making Cycle: Evaluation, Deliberation, Data Collection, Work Planning, Communication At each tier, a decision may be to exit the tiered process aExamples of advanced methods for quantifying temporal variability, spatial variability, and uncertainty.
|
From page 254... ...
254 Sediment Dredging at Superfund Megasites little consideration in EPA's feasibility studies at Superfund sites (Wenning et al.
|
From page 255... ...
Improving Future Decision-Making 255 3. There is a great need for centralized EPA resources, responsibility, and authority at the national level to ensure that necessary improvements are made so that contaminated sediment megasites are remediated as effectively as possible.
|
From page 256... ...
256 Sediment Dredging at Superfund Megasites Years of experience suggests that to garner the needed resources, focus, and management attention for a problem of this magnitude, it is necessary not only to create a "critical mass" of personnel and expertise but to clearly identify those responsible and accountable for implementing needed changes and policies. The committee strongly recommends that this gap be addressed.
|
From page 257... ...
Improving Future Decision-Making 257 sediment sites, including the development and testing of new technologies. • Serve as a focal point for coordination and communication among the many EPA programs and federal agencies who are involved in the cleanup of contaminated sediment sites.
|
From page 258... ...
258 Sediment Dredging at Superfund Megasites and, as described in Chapter 2, there is no current list of contaminated sediment sites, nor does the Agency evaluate new NPL sites when they are listed to develop a "watch list" of those sites that are likely to be future megasites. In this regard, conclusions of one of EPA's earliest reports on the subject (EPA 1987)
|
From page 259... ...
Improving Future Decision-Making 259 portant tasks to accomplish the goal of improving the scientific basis of selecting the most effective remedies for contaminated sediment sites. EPA should ensure that adequate monitoring strategies are implemented.
|
From page 260... ...
260 Sediment Dredging at Superfund Megasites The objective of the research and evaluation program should be to answer key questions as to what risk reduction will be achieved by different technical approaches, under what site conditions, and with what certainty. The agency needs to answer those questions through pilot studies and data collection efforts that monitor baseline to long-term conditions and that stress robust sampling and statistical analysis.
|
From page 261... ...
Improving Future Decision-Making 261 Efforts to understand and promote those practices and operations that improve remediation effectiveness, and the training of decision makers and practitioners in those operations, is also critical to advance the field and improve the performance of remedial operations. In sum, EPA's efforts should focus on moving forward with remedies at sites and, at the same time on investing the effort needed to make sure that each new pilot test or remedy implemented increases our collective knowledge of what works and what does not work and why.
|
From page 262... ...
262 Sediment Dredging at Superfund Megasites EPA (U.S. Environmental Protection Agency)
|
From page 263... ...
Improving Future Decision-Making 263 [online]
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.