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. Most of the committee’s earlier recommendations focus on these issues at the site-specific level, but this chapter focuses on the national level.
With the establishment of Superfund in 1980, we now have the opportunity for retrospective analysis at dozens of sediment sites to evaluate decision-making, field experience, and remedial effectiveness where dredging has been selected for sediment cleanup. In the past, a rigorous evaluation of whether site remediation achieved risk reduction goals and what factors contributed to or limited the achievement of those goals was often just not done. Although information is available from various sites with respect to volume of bulk material removed or sediment concentration achieved, that information does not permit determination of the degree to which remedial objectives for risk-reduction were achieved. Thus, it is not easy to determine which approaches resulted in risk reduction under various site conditions. The difficulty stems partly from the lack of comprehensive post-dredging monitoring data and from the fact that followup assessments typically do not quantify uncertainty in both risk measurements and predictions.
In hindsight, it is clear that there are limitations to dredging effectiveness. With this historical perspective comes the opportunity to learn and improve how we think about and implement environmental dredging. Perhaps nothing is more important than to step back and derive common lessons from experience, as was done in Chapter 4. This type of review needs to be continuous and needs to part of a shared experience among regulators, practitioners, and the public.
As described in Chapter 2, sediment megasites are among the most challenging and costly sites on the National Priorities List (NPL). Megasites are conventionally defined as sites with remedial activities costing at least $50 million; the U.S. Environmental Protection Agency (EPA) has defined contaminated sediment megasites as sites for which the sediment component of remedial activities will cost at least $50 million.