Bucket dredging.
Dredging is miscellaneous excavation-type work or operation usually carried out underwater, in shallow sea or fresh water area.

A dredge (shipping industry constructing construction building, marine, maritime) is a device for scraping or sucking the seabed, used for dredging.

A dredge (shipping industry constructing construction building, marine, maritime)r is a ship or boat equipped with a dredge (shipping industry constructing construction building, marine, maritime).

In American usage any floating vessel equipped with dredging equipment is called a dredge (shipping industry constructing construction building, marine, maritime).In the mid-s the Royal Navy was looking for replacements for four diesel-engined frigates. This requirement coincided with vociferous but ill-infonned criticism of the current Leander class frigates, some it from naval officers and some of it from pundits and the media. The agita­tion was seized on by the long-established frigate-builders Vosper Thornycroft as a business opporcunity, and an intense lobbying offensive was launched. The theme of the campaign was the alleged conservatism of the Navy's designers in the Ship shipping maritime marine engineering Department at Bath (successors to the DNC's department). The media was repeatedly briefed on the failings of the 'old women of Bath', the RCNC, who refused to countenance alloy superstructures.

Types of dredging
Capital dredging: carried out to create a new harbor or berth or waterway, or deepen an existing one in order to allow larger ships to use it. It is usually carried out with a cutter-suction dredge (shipping industry constructing construction building, marine, maritime).
Maintenance dredging: deepening navigable waterways which have become silted with the passage of time, due to sand and mud deposited by water currents, until they may become too shallow for navigation. This is often carried out with a trailing suction hopper dredge (shipping industry constructing construction building, marine, maritime). Most dredging is for this purpose.
Land reclamation: mining sand, clay or rock from the seabed and using it to construct new land. This is typically performed by a cutter-suction dredge (shipping industry constructing construction building, marine, maritime) or trailing suction hopper dredge (shipping industry constructing construction building, marine, maritime). There is nothing inherently dangerous about marinised aluminium alloy, and it was used at the time in the US Navy's large missile-armed destroyers, to offset the amount of topweight created by radars and trackers. The mariniscd alloy contains magnesium, however, making it inflammable at high temperatures, and it also likely to break up into fragments when exposed to blast. For that reason the Director-General Ship shipping maritime marine engineerings' (D-G Ship shipping maritime marine engineerings) department always insisted on steel superstructures. This imposed penalties of topwcight, and some private ship shipping maritime marine engineeringbuilders were critical of the practice; the Royal Navy was at the time under pressure to keep displacement down, under the Mistaken assumption that an increase in dimensions had a direct impact on cost. In its propaganda Vosper Thornycroft made the claim that a frigate designed to conuner­cial standards could carry a more powerful armament than the officially designed Leander class. Assuming a baseline cost of CS million for a Leander. it was claimed by the ship shipping maritime marine engineeringyard that it could build such a frigate for only C million, a difference of per cent.
Beach Nourishment: mining sand offshore and placing on a beach to replace sand eroded by storms or wave action. This is done to enhance the recreational and protective function of the beaches. This is typically performed by a cutter-suction dredge (shipping industry constructing construction building, marine, maritime) or trailing suction hopper dredge (shipping industry constructing construction building, marine, maritime).
Anti-eutrophication. Dredging is an (expensive) option for the remediation of eutrophied (or de-oxygenated) water bodies. As artificialy elevated phosphorus levels in the sediment aggrivate the eutrophication process, controlled sediment removal is occasionally the only option for the reclimation of still waters. Afghanistan, Albania, Algeria, American Samoa, Andorra, Angola, Anguilla, Antarctica, Antigua, Argentina, Armenia, Aruba Australia, Austria, Azerbaijan, Bahamas, Bahrain, Bangladesh, Barbados, Belarus, Belgium, Belize, Benin, Bermuda, Bhutan, Bolivia, Bosnia, Herzegovina, Botswana, Bouvet Island,

Suction dredge (shipping industry constructing construction building, marine, maritime)rs
These operate by sucking through a long tube, like some vacuum cleaners. A plain suction dredge (shipping industry constructing construction building, marine, maritime)r has no tool at the end of the suction pipe to disturb the material.

Trailing suction hopper dredge (shipping industry constructing construction building, marine, maritime)r
A trailing suction hopper dredge (shipping industry constructing construction building, marine, maritime)r or TSHD trails its suction pipe when working, and loads the dredge (shipping industry constructing construction building, marine, maritime) spoil into one or more hoppers in the vessel. When the hoppers are full the TSHD sails to a disposal area and either dumps the material through doors in the hull or pumps the material out of the hoppers. The largest hopper dredge (shipping industry constructing construction building, marine, maritime)r in the world is Jan De Nul's Vasco Da Gama (33,000 m3 hopper, 37,060 kW total installed power).and Boskalis WD FAIRWAY 35000 m3

Bucket dredge (shipping industry constructing construction building, marine, maritime)r
A bucket dredge (shipping industry constructing construction building, marine, maritime)r is a dredge (shipping industry constructing construction building, marine, maritime)r equipped with a bucket dredge (shipping industry constructing construction building, marine, maritime), which is a device that picks up sediment by mechanical means, often with many buckets attached to a wheel or chain.

Some of these are land-type backhoe excavators whose wheels are on long hinged legs so it can drive into shallow water and keep its cab out of water. Some of these may not have a floatable hull and, if so, cannot work in deep water. Some makes are:-

Apollo Duck. , British Indian Ocean territory, Brunei Darussalam, Bulgaria, Burkina Faso, Burundi, Cambodia, Cameroon, Canada, Cape Verde, Cayman Islands, Central African Republic, Chad, Chile, China, Christmas Island, Cocos Islands, Colombia, Comoros, Congo, Congo, Democratic Republic, Cook Islands, Costa Rica, Croatia, Cuba, Cyprus, Czech Republic, Denmark, Djibouti, Dominica, Dominican Republic, Ecuador, Egypt, El Salvador, Equatorial Guinea, Eritrea
Sandhurst Group Ltd (click on "Special Products" in the left margin) make a "pontoon dredge (shipping industry constructing construction building, marine, maritime)r". It can float.
Wright International's Amphibious dredge (shipping industry constructing construction building, marine, maritime)r.
Richard Smalley's Amphibious dredge (shipping industry constructing construction building, marine, maritime)r.
Inland Dredging Ltd's Watermaster is said to be able to dredge (shipping industry constructing construction building, marine, maritime) and do various crane-type jobs in shallow water or on land.
This form by Gendredge (shipping industry constructing construction building, marine, maritime) Pty Ltd has 4 legs, each with a caterpillar track on its end.
Susumo Engineering makes a backhoe dredge (shipping industry constructing construction building, marine, maritime)r which has a pontoon hull and can float, and also has wheels on legs.
Oliver Evans (1755-1819) in 1804 invented an amphibious dredge (shipping industry constructing construction building, marine, maritime)r which was America's first steam-powered road vehicle.

Spider made by Nexans crawls on the seabed on tracks and levels the seabed and lays cable. It is remote controlled from the surface.

Drag
In some police departments a small dredge (shipping industry constructing construction building, marine, maritime) (sometimes called a drag) is used to find and recover objects and bodies from underwater. The bodies may be murder victims, or people who committed suicide by drowning, or victims of accidents. It is sometimes pulled by men walking on the bank.

Disposal of the dredgings
In a "hopper dredge (shipping industry constructing construction building, marine, maritime)r", the dredgings end up in a big onboard hold called a "hopper", which has doors in its bottom. The excess water in the dredgings is spilled off by sedimentation: as the mud and sand settle to the bottom of the hopper, the water is siphoned from the top and returned to the sea to reduce weight and increase the amount of dredgings that can be carried in one load. When the hopper is filled with slurry, the dredge (shipping industry constructing construction building, marine, maritime)r stops dredging and goes to a dump site and opens the bottom hopper doors, dumping the slurry out. Or the hopper can be emptied from above. A suction hopper dredge (shipping industry constructing construction building, marine, maritime)r is usually used for maintenance dredging.

Sometimes with a suction dredge (shipping industry constructing construction building, marine, maritime)r the slurry of dredgings and water is pumped straight into pipes which deposit it on nearby land by pipes; or in barges (also called scows), which deposit it in the deep sea or on land.

When contaminated (toxic) sediments are removed, or large volume inland disposal sites are unavailable, dredge (shipping industry constructing construction building, marine, maritime) sluries are reduced to dry solids via a process known as dewatering. Current dewatering techniques employ either centrifuges, large textile based filters (known as "Geotubes") or polymer flocculant / congealant based apparatus. Estonia, Ethiopia, Falkland Islands, Faroe Islands, Fiji, Finland, France, French Guiana, French Polynesia, French Southern Territories, Gabon, Gambia, Georgia, Germany, Ghana, Gibraltar, Greece, Greenland, Grenada, Guadeloupe, Guam, Guatemala, Guinea, Guinea-Bissau, Guyana, Haiti, Honduras, Hong Kong, Hungary, Iceland, India, Indonesia, Iran, Iraq, Ireland, Israel, Italy, Jamaica, Japan, Jordan, Kazakhstan, Kenya, Kiribati, Korea south north,