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Timely and effective remediation of contaminated sediments is essential for protecting human health and the environment and restoring beneficial uses to waterways. A number of site operational conditions influence the effect of environmental dredging of contaminated sediment on aquatic systems. Site experience shows that resuspension of contaminated sediment and release of contaminants occur during dredging and that contaminated sediment residuals will remain after operations. It is also understood that these processes affect the magnitude, distribution, and bioavailability of the contaminants, and hence the exposure and risk to receptors of concern. However, even after decades of sediment remediation project experience, substantial uncertainties still exist in our understanding of the cause-effect relationships relating dredging processes to risk. During the past few years, contaminated sediment site managers, researchers, and practitioners have recognized the need to better define and understand dredging-related processes. In this article, we present information and research needs on these processes as synthesized from recent symposia, reports, and remediation efforts. Although predictions about the effect of environmental dredging continue to improve, a clear need remains to better understand the effect that sediment remediation processes have on contaminant exposures and receptors of concern. Collecting, learning from, and incorporating new information into practice is the only avenue to improving the effectiveness of remedial operations., (© 2010 SETAC.)

Sediments dredged from navigational waterways have historically been disposed in confined disposal facilities (CDFs) or in open water. When sediments are contaminated, open water disposal is typically not an alternative, and sediments are placed in CDFs. Many CDFs are nearing capacity, and siting and constructing new facilities is both difficult and expensive. In many cases, CDFs contain both clean and contaminated dredged material. Removal of materials suitable for beneficial use (BU) is one alternative under consideration to extend the life of existing CDFs, as is separation of recoverable materials at the time of disposal. Several technologies for recovery of clean materials or treatment of contaminated materials for beneficial use are presently under evaluation. Physical separation technologies have been demonstrated to have potential in reducing the volume of sediment that must be managed with confined disposal, but there are several technical issues that remain to be addressed. Determination of beneficial use specifications, physical and chemical characterization of dredged material, overall site characterization, selection of suitable unit operations, management of liquid and solid residuals, and cost/benefit analysis, are all important aspects to successful implementation of separation processes. Several of these elements are presently being evaluated in research conducted by the US Army Corps of Engineers, at the ERDC Waterways Experiment Station (WES).