Project 5: Dewatering, Remediation, and Evaluation of Dredged Sediments

Principal Investigators: Paul Schwab, Lee Newman, Krishnakumar Nedunuri, and Kathy Banks (Purdue University, University of South Carolina, and Central State University)

Collaborator: Department of Defense

Dredging operations remove large quantities of sediments from the rivers and lakes of the United States to keep the waters navigable. Some of the sediments cannot be disposed on land due to concentrations of regulated contaminants that exceed allowable levels. These contaminated sediments are stored in confined placement facilities, but these facilities are nearing their capacity and new sites are becoming difficult to obtain. A need exists to remediate these sediments to make them suitable for beneficial use such as industrial fill or construction. This proposal describes a research project in which plants (primarily grasses and trees) are used to accelerate the removal of water from the sediments and degradation/extraction of the contaminants. The plant-based technology will be tested in the field on sediments currently stored near Milwaukee and Green Bay, Wisconsin. In the dewatering phase of the project, small trees will be densely planted in the confined placement facility and allowed to grow for at least one year. The plantings will be in a statistical valid design to compare the effects of species and management practices. In situ monitors will provide real-time data relevant to the progress of the project (e.g., moisture content and dissolve oxygen in the sediments). At the end of the growth period, we will make recommendations concerning choices of species for dewatering sediments and proceed to the remediation phase of the project. At the conclusion of the dewatering phase, the trees will be removed, and grasses and legumes will be planted in their place. As with the trees, these species will be planted in a statistically valid design, with plant species and N and P fertilization rates as experimental variables. The success of the project will be gauged by the final concentrations of the contaminants (compared to the regulated concentrations) and the residual toxicity, which will be assessed with a suite of receptor organisms including seedlings, soil microorganisms, and earthworms.