Dredging has evolved into a highly sophisticated process drawing from some of the latest technology. The methods of navigational dredging range from clamshell buckets to sophisticated hydraulic dredges. More recently, these techniques have evolved into the processes used for environmental dredging applications. High concentrations of certain contaminants in sediments pose human heath and ecological risks. Dredging of contaminated sediment provides a method of removal of these contaminants of concern (COC). One of the most obvious benefits of environmental dredging is the fact the contaminated sediments are permanently removed from the water body. These sediments are typically disposed of in an upland containment facility or landfill. In some cases disposal of contaminates may not be permitted or the costs to transport them to a permitted facility may be very high. Alternate uses for the contaminated sediments may be considered and may help to reduce or eliminate risks. The cost of these alternate treatment and use methods must be evaluated against other permit-able disposal options. Of paramount concern when dredging is the ability of the process to remove the COCs to a level that is below the regulated concentration. Although dredging techniques have been demonstrated to reduce sediment contaminant concentrations, it appears that these techniques can result in residual contamination. This residual contamination may be the result of re-suspension of contaminates into the water column or sloughing of adjacent materials into the dredged areas. Concern over these residual concentrations may lead to subsequent passes or other means to minimize risk from the residuals. The impacts of the cleanup activity to the surrounding area need to be evaluated regarding the impact of the operation or long-term disturbance of an area. A dredging operation will typically require some sort of sediment dewatering process. After removal of the solids, the associated water may have to be treated before it can be discharged back into the waterway. Because of these facts a dredging operation typically requires onshore support facilities. Construction of these facilities will likely impact the area surrounding the dredged area.
Olsta, James T. and Darlington, Jerald W.
"Innovative Systems For Dredging, Dewatering Or For In-Situ Capping Of Contaminated Sediments,"
Proceedings of the Annual International Conference on Soils, Sediments, Water and Energy:
Vol. 11, Article 20.
Available at: http://scholarworks.umass.edu/soilsproceedings/vol11/iss1/20