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A grab dredge. Dredging is the excavation of material from a water environment. Possible reasons for dredging include improving existing water features; reshaping land and water features to alter drainage, navigability, and commercial use; constructing dams, dikes, and other controls for streams and shorelines; and recovering valuable mineral deposits or marine life having commercial value.
Canal dredged in a wetland area. Wetlands are dynamic systems that undergo a variety of chemical reactions depending greatly on the specific physicochemical properties of the area, such as temperature, pressure, dissolved organic matter, pH, salinity, and dissolved gases (CO 2 and O 2).
Nearly all of the ocean dumping that takes place today is dredged materials at the hands of the Corps of Engineers and due to the fact that they are the entity primarily responsible for the dredging, they issue permits for ocean dumping of such materials. [3] [10] The dredged materials are sediments removed from the bottom of water bodies, but ...
Bottom trawling can both resuspend and bury biologically recyclable organic material, changing the flow of nutrients and carbon through the food web and thereby alter geomorphological landscapes. [15] Ocean sediments are the sink for many persistent organic pollutants, usually lipophilic pollutants like DDT, PCB and PAH. [24]
Studies have shown that fine-grained materials and sandy materials can be effective in the construction of an in-situ cap. [6] Furthermore, fine grain materials have been shown to act as better chemical barriers than sand caps. [7] Thus a fine grain material is a better capping component than factory-washed sand.
In relation to shipping channels, it is often necessary to dredge bay bottoms and barge the excavated material to an alternate location. In this case, chemical analyses are usually performed on the bay mud to determine whether there are elevated levels of heavy metals, PCBs or other toxic substances known to accumulate in a benthic environment.
The substances on the reverse list include dredged material; sewage sludge; industrial fish processing waste; vessels and offshore platforms or other man-made structures at sea; inert, inorganic geological material; organic material of natural origin; and bulky items including iron, steel, concrete and similar materials for which the concern is ...
Amends the Water Resources Development Act of 1990 to add environmental remediation in the removal of dredged material under a navigation project; and (2) increase funding for the removal of contaminated sediments from navigable waters. Lists specified projects to be given priority in such sediment removal.