Dredging of material can be done either hydraulically or mechanically. Hydraulic dredges use hydraulic pumps to produce a slurry of the dredged material, are typically used when there is much material to remove and it can be easily transported long distances via a pipeline attached to the dredge. Sometimes a cutterhead is attached to the dredge intake to loosen hardened material. Mechanical dredges remove the sediments via mechanical methods which can include grab dredges (clamshells & buckets), backhoes or bucket ladder dredges. Most common mechanical dredges used on Great Lakes projects are the grab or bucket type dredge. The removed material is then typically placed into a barge which transports the material to its final destination.
Dredged material is sometimes placed into specific engineering designed areas designed to contain the material called confined disposal facilities (CDF’s). These structures are usually very large and very costly to construct. Nowadays, port and harbor facility managers try to place only contaminated material into CDF’s while beneficially using the uncontaminated material for other types of projects such as construction projects, habitat creation or restoration, landfill and landfill cover material, soil amendments, and many other re-use applications. This saves not only valuable space in the CDF’s for only the contaminated material but also benefits the port and harbor region economically and environmentally by realizing dredged material can be a valuable resource and not just a waste material.
Other Web Sites with Dredging Information
The Great Lakes Commission has a web site for the Great Lakes Dredging Team; a partnership of federal and state agencies to assure that dredging is done in a manner that meets environmental protection, restoration and enhancement goals. The website: http://www.glc.org/dredging/lakes/lakes.html
The U.S. Army Corps of Engineers Waterways Experiment Station has a Dredging Research Program, a Dredging Operations Technical Support Program and a Dredging Operations and Environmental Research Program. Numerous publications are available. Check out the following website: http://el.erdc.usace.army.mil/dots/