ABSTRACT
Dredging is the excavation of materials (sediments) from the bottom of the water column for a number of different purposes, as follows.
1. Navigation: to maintain navigation depths 2. Construction and reclamation: to excavate the bottom for foundations of
structures, such as breakwaters, bridges, pipe lines, etc. 3. Purication of surface water: to clean up the bottom of rivers, lakes, ports,
and harbors to purify the surface water 4. Environmental: to remove contaminated sediments to protect aquatic life
and preserve the safety of seafood 5. Mining: to obtain coarse materials for construction materials
The objective sites for dredging are seas, canals, rivers, ponds, lakes, etc. To maintain navigable waterways, approximately 306 million cubic meters of material are dredged in the United States every year. Of this amount, about 46 million cubic meters are placed in ocean waters at more than 100 Environmental Protect Agency approved sites (https://www.globalsecurity.org/military/systems/ship/dredges.htm). It is also estimated that another 260 million cubic meters are dredged in coastal and inland waters and placed in a variety of locations, including uplands, beach sites, wetlands construction sites, and riverine sandbars, etc. Dredged material in the United States cannot be dumped at sea if it is toxic according to laboratory tests or if, in separate tests, certain chemicals have accumulated in the tissues of exposed organisms (USEPA/USACE, 1991).
