FACTOID # 30: If Alaska were its own country, it would be the 26th largest in total area, slightly larger than Iran.
 
 Home   Encyclopedia   Statistics   States A-Z   Flags   Maps   FAQ   About 
   
 
WHAT'S NEW
RELATED ARTICLES
People who viewed "Dredging" also viewed:
 

SEARCH ALL

FACTS & STATISTICS    Advanced view

Search encyclopedia, statistics and forums:

 

 

(* = Graphable)

 

 


Encyclopedia > Dredging
For other uses, see Dredge (disambiguation).
The 'business end' (excavator) of a Yukon dredge.
The 'business end' (excavator) of a Yukon dredge.
Profile view of above dredge tied up to a quay, note the size. The dredge conveys the spoils to the rear (left side) into a receiving vessel such as a barge.
Profile view of above dredge tied up to a quay, note the size. The dredge conveys the spoils to the rear (left side) into a receiving vessel such as a barge.

Dredging is an excavation activity or operation usually carried out at least partly underwater, in shallow seas or fresh water areas with the purpose of gathering up bottom sediments and disposing of them at a different location, mostly to keep waterways navigable. A dredge is a device for scraping or sucking the seabed, used for dredging. A dredger is a ship or boat equipped with a dredge (though in American usage, there is no added letter). Dredge or dredging may refer to: Dredge, underwater excavation work. ... Image File history File links Metadata Size of this preview: 794 × 599 pixelsFull resolution (1632 × 1232 pixel, file size: 390 KB, MIME type: image/jpeg) Dredge_No-4, Bonanza Creek, Dawson, Yukon, Canada Picture taken August 10th, 2005 by Janothird File history Legend: (cur) = this is the current file, (del) = delete... Image File history File links Metadata Size of this preview: 794 × 599 pixelsFull resolution (1632 × 1232 pixel, file size: 390 KB, MIME type: image/jpeg) Dredge_No-4, Bonanza Creek, Dawson, Yukon, Canada Picture taken August 10th, 2005 by Janothird File history Legend: (cur) = this is the current file, (del) = delete... This article or section is in need of attention from an expert on the subject. ... Image File history File linksMetadata Size of this preview: 794 × 599 pixel Image in higher resolution (1632 × 1232 pixel, file size: 375 KB, MIME type: image/jpeg) Dredge_No-4, Bonanza Creek, Dawson, Yukon, Canada Picture taken August 10th, 2005 by Janothird File links The following pages on the English Wikipedia... Image File history File linksMetadata Size of this preview: 794 × 599 pixel Image in higher resolution (1632 × 1232 pixel, file size: 375 KB, MIME type: image/jpeg) Dredge_No-4, Bonanza Creek, Dawson, Yukon, Canada Picture taken August 10th, 2005 by Janothird File links The following pages on the English Wikipedia... A quay, pronounced key, kay, is a wharf or bank where ships and other vessels are loaded. ... Self propelled barge carrying bulk crushed stone A barge is a flat-bottomed boat, built mainly for river and canal transport of heavy goods. ... The term archaeological excavation has a double meaning. ... For the village on the Isle of Wight, see Freshwater, Isle of Wight. ... This article or section cites very few or no references or sources. ...


The process of dredging creates spoils (excess material), which are conveyed to a location different from the dredged area. Dredging can produce materials for land reclamation or other purposes (usually construction-related), and has also historically played a significant role in gold mining. Dredging can create disturbance in aquatic ecosystems, often with adverse impacts. Gold mining consists of the processes and techniques employed in the removal of gold from the ground. ...

Contents

Uses

Usage

  • Capital: dredging carried out to create a new harbour, berth or waterway, or to deepen existing facilities in order to allow larger ships access. This process is usually carried out with a cutter-suction dredge.
  • Maintenance: dredging to deepen or maintain navigable waterways or channels which are threatened to become silted with the passage of time, due to sedimented sand and mud, possibly making them too shallow for navigation. This is often carried out with a trailing suction hopper dredge. Most dredging is for this purpose, and it may also be done to maintain the holding capacity of reservoirs or lakes.
  • Land reclamation: dredging to mine sand, clay or rock from the seabed and using it to construct new land elsewhere. This is typically performed by a cutter-suction dredge or trailing suction hopper dredge. The material may also be used for flood or erosion control.
  • 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, which can be eroded by human activity or by storms. This is typically performed by a cutter-suction dredge or trailing suction hopper dredge.
  • Harvesting materials: dredging sediment for elements like gold or other valuable trace substances.
  • Seabed mining: a possible future use, recovering natural metal ore nodules from the sea's abyssal plains.
  • Anti-eutrophication: Dredging is an expensive option for the remediation of eutrophied (or de-oxygenated) water bodies. However, as artificially elevated phosphorus levels in the sediment aggravate the eutrophication process, controlled sediment removal is occasionally the only option for the reclamation of still waters.
  • Contaminant remediation: to reclaim areas affected by chemical spills, storm water surges (with urban runoff), and other soil contaminations. Disposal becomes a proportionally large factor in these operations.
  • Removing trash and debris: often done in combination with maintenance dredging, this process removes non-natural matter from the bottoms of rivers and canals and harbors.

A harbor (or harbour) or haven is a place where ships may shelter from the weather or are stored. ... Look up berth in Wiktionary, the free dictionary. ... volcanic rock. ... For the type of foundation, see Deep foundation. ... Dock can refer to several things: Places for the transfer of people and materials to, from, or between different forms of transport or working with transport: A maritime dock. ... Metung Wharf on Bancroft Bay, Gippsland Lakes, Victoria, Australia A wharf is a fixed platform, commonly on pilings, roughly parallel to and alongside navigable water, where ships are loaded and unloaded. ... A foundation is a structure that transmits loads from a building or road to the underlying ground. ... Look up Channel on Wiktionary, the free dictionary In general, channel refers to the path between two endpoints. ... This article or section cites very few or no references or sources. ... ... Land reclamation is either of two distinct practices. ... Flooding in Amphoe Sena, Ayutthaya Province, Thailand. ... Severe soil erosion in a wheat field near Washington State University, USA. For erosion as an operation of Mathematical morphology, see Erosion (morphology) Erosion is displacement of solids (soil, mud, rock and other particles) by the agents of ocean currents, wind, water, or ice by downward or down-slope movement... Before and after photos of beach restoration efforts, Florida coastline, USA. Beach nourishment is a process by which sediment (usually sand) lost through longshore drift or erosion is replaced on a beach. ... This article or section cites very few or no references or sources. ... General Name, Symbol, Number gold, Au, 79 Chemical series transition metals Group, Period, Block 11, 6, d Appearance metallic yellow Standard atomic weight 196. ... Iron ore (Banded iron formation) Manganese ore Lead ore Gold ore An ore is a volume of rock containing components or minerals in a mode of occurrence which renders it valuable for mining. ... Abyssal plains are flat or very gently sloping areas of the deep ocean basin floor. ... Eutrophication refers to an increase in the primary productivity of any ecosystem. ... Excavation of leaking underground storage tank causing soil contamination Soil contamination is the presence of man-made chemicals or other alteration of the natural soil environment. ... Generally, remediation means giving a remedy. ...

Relevance

Without the many and almost non-stop dredging operations world wide, much of the world's commerce would be impaired, often within a few months, since much of world's goods travel by ship, and need to access harbours or seas via channels. Recreational boating also would be constrained to the smallest vessels. The majority of marine dredging operations (and the disposal of the dredged material) will require that appropriate licences are obtained from the relevant regulatory authorities, and dredging is usually carried out by (or for) harbour companies or corresponding government agencies. Italian Full rigged ship Amerigo Vespucci in New York Harbor, 1976 A ship is a large watercraft capable of offshore navigation. ... A harbor (or harbour) or haven is a place where ships may shelter from the weather or are stored. ... // Boating, the leisurely activity of traveling by boat typically refers to the recreational use of boats whether power boats, sail boats, or yachts (large vessels), focused on the travel itself, as well as sports activities, such as fishing or waterskiing. ... Italian Full rigged ship Amerigo Vespucci in New York Harbor, 1976 A ship is a large watercraft capable of offshore navigation. ... Marine is an umbrella term for things relating to the ocean, as with marine biology, marine geology, and as a term for a navy, etc. ... In the context of government and public services regulation (as a process) is the control of something by rules, as opposed to its prohibition. ...


Types

Example of a trailing suction dredger: the Orisant in the port of Ijmuiden, Netherland.
Example of a trailing suction dredger: the Orisant in the port of Ijmuiden, Netherland.

Image File history File links Metadata Size of this preview: 800 × 532 pixelsFull resolution (3008 × 2000 pixel, file size: 2. ... Image File history File links Metadata Size of this preview: 800 × 532 pixelsFull resolution (3008 × 2000 pixel, file size: 2. ... Velsen (population: 67,642 in 2004) is a municipality in the north-western Netherlands, in the province of North Holland, on both sides of the North Sea Canal. ...

Suction

These operate by sucking through a long tube, like some vacuum cleaners. A plain suction dredger has no tool at the end of the suction pipe to disturb the material. This is often the most commonly used form of dredging.[citation needed] Regular vacuum cleaner for home use. ...

Trailing suction

A trailing suction hopper dredger (TSHD) trails its suction pipe when working, and loads the dredge 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. Some dredges also self-offload using drag buckets and conveyors. The largest trailing suction hopper dredger in the world is currently Vasco da Gama (Jan De Nul) with its 33,000 cu.m. hopper and a maximum dredging depth of 135m. The next mega trailing suction hopper dredgers Cristobal Colon and Leiv Eriksson are actually under construction in Spain and should be delivered in 2008. Main design specs are the 46,000 cu.m. hopper and a design dredging depth of 155m. [1]

Cutter suction

A cutter-suction dredger's (CSD) suction tube has a cutter head at the suction inlet, to loosen the earth and transport it to the suction mouth. The cutter can also be used for hard surface materials like gravel or rock. The dredged soil is usually sucked up by a wear resistant centrifugal pump and discharged through a pipe line or to a barge. In recent years dredgers with more powerful cutters have been built in order to excavate harder and harder rock without blasting. The two largest cutter suction dredgers in the world are Deme's D'Artagnan (28,200 kW total installed power), and Jan De Nul's J.F.J. DeNul (27,240 kW).

Auger suction

This process functions like a cutter suction dredger, but the cutting tool is a rotating Archimedean screw set at right angles to the suction pipe. Archimedess screw (also the Archimedean screw) is one of several inventions and discoveries reputed to have been made by Archimedes. ...

Jet-lift

This uses the Venturi effect of a concentrated high-speed stream of water to pull the nearby water, together with bed material, into a pipe. A Venturi meter is shown in a diagram, the pressure in 1 conditions is higher than 2, and the relationship between the fluid speed in 2 and 1 respectively, is the same as for pressure. ...

Air-lift

An airlift is a type of small suction dredge. It is sometimes used like other dredges. At other times, often an airlift is used handheld underwater by a diver. It works by blowing air into the pipe, and dragging water with it. An Airlift is device based on a pipe, used in nautical archaeology to suck small objects, sand and mud from the sea bed and to transport the resulting debris upwards and away from its source. ... It has been suggested that this article or section be merged with Professional diving. ...


Bucket

A bucket dredger is a dredger equipped with a bucket dredge, which is a device that picks up sediment by mechanical means, often with many circulating buckets attached to a wheel or chain. Some bucket dredgers and grab dredgers are powerful enough to work through coral reefs to make a shipping channel. This article or section cites very few or no references or sources. ... The force bearing on the axle has an eccentricity e with the point of contact to the rolling surface and exerts a moment about the contact point. ... Some of the biodiversity of a coral reef, in this case the Great Barrier Reef, Australia. ...


Grab

A grab dredger picks up seabed material with a clam shell grab, which hangs from an onboard crane, or is carried by a hydraulic arm, or is mounted like on a dragline. This technique is often used in excavation of bay mud. Most of these dredges are crane barges with spuds. Huge Manitowok 4600 Heavy lift Dragline at the SNS Project, 2005. ... Richardson Bay mudflats of are exposed layers of bay mud Bay mud consists of thick deposits of soft, unconsolidated silty clay, which is saturated with water; these soil layers are situated at the bottom of certain estuaries, which are normally in temperate regions that have experienced cyclical glacial cycles. ...


Backhoe/dipper

A backhoe/dipper dredge has a backhoe like on some excavators. A crude but usable backhoe dredger can be made by mounting a land-type backhoe excavator on a pontoon. The two largest backhoe dredgers in the world were Tauracavor (Great Lakes), New York (Great Lakes) and Il Principe (Jan De Nul).[citation needed] Both feature a barge mounted excavator. In 2007, the new generation of backhoe dredgers has arrived. The backhoe dredge of the ‘Backacter’ type 1100 is a new and revolutionary designed type of dredging excavator mounted on a pontoon with enhanced capabilities in respect of penetration force, production and maintenance. Featuring double the power of the ‘Il Principe’ backhoe dredge of the Jan De Nul’s fleet, these ‘Backacters’ are by far the biggest backhoe dredges in the world. [2] It has been suggested that Backhoe fade be merged into this article or section. ... A tracked excavator by Daewoo. ... It has been suggested that Backhoe fade be merged into this article or section. ... A tracked excavator by Daewoo. ... For the car body style, see Ponton (automobile). ... Self propelled barge carrying bulk crushed stone A barge is a flat-bottomed boat, built mainly for river and canal transport of heavy goods. ...


Water injection

A water injection dredger injects water in a small jet under low pressure (low pressure because the sediment should not explode into the surrounding waters, rather it is carefully moved to another location) into the seabed to bring the sediment in suspension, which then becomes a turbidity current, which flows away down slope, is moved by a second burst of water from the WID or is carried away in natural currents. Opposition claims that Water Injection Dredging is not a natural way of dredging while the side of the WID claims otherwise. A turbidity current or density current is a current of of rapidly moving, sediment-laden water moving down a slope through air, water, or another fluid. ...


As a side note: Water injection results in a lot of sediment in the water which makes measurement with most hydrographic equipment (for instance: singlebeam echosounder) difficult and should make use of filtering to produce better results.


Pneumatic

These dredgers use a chamber with inlets, out of which the water is pumped with the inlets closed. It is usually suspended from a crane on land or from a small pontoon or barge. Its effectiveness depends on depth pressure.


Bed leveler

This is a bar or blade which is pulled over the seabed behind any suitable ship or boat. It has an effect similar to that of a bulldozer on land. A Caterpillar D10N bulldozer at work A bulldozer is a very powerful crawler (caterpillar tracked tractor) equipped with a blade. ...


Krabbelaar

This is an early type of dredger which was formerly used in shallow water in the Netherlands. It was a flat-bottomed boat with spikes sticking out of its bottom. As tide current pulled the boat, the spikes scraped seabed material loose, and the tide current washed the material away, hopefully to deeper water. Krabbelaar is Dutch for "scratcher".


Other types

Amphibious

Some of these are any of the above types of dredger, which can operate normally, or by extending legs, also known as spuds, so it stands on the seabed with its hull out of the water. Some forms can go on land.


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. It has been suggested that Backhoe fade be merged into this article or section. ... A tracked excavator by Daewoo. ...

  • Oliver Evans (1755-1819) in 1804 invented an amphibious dredger which was America's first steam-powered road vehicle.

Oliver Evans Oliver Evans (13 September 1755 – 15 April 1819) was a United States inventor. ... Oliver Evans Oliver Evans (13 September 1755 – 15 April 1819) was a United States inventor. ...

Submersible

These are usually used to recover useful materials from the seabed. Many of them travel on caterpillar tracks. Caterpillar tracks are large (modular) tracks used on tanks, construction equipment and certain other off-road vehicles. ...


This link describes a type intended to walk on legs on the seabed. It is a summary of the article "Concept of a mathematical model for prediction of major design parameters of a submersible dredger/miner" by Sritama Sarkar, Neil Bose, Mridul Sarkar, and Dan Walker, in "3rd Indian National Conference on Harbour and Ocean Engineering, National Institute of Oceanography", Dona Paula, Goa 403 004 India, 7 - 9 December 2004: see http://www.nio.org for more information about publisher etc. , Goa   (Konkani: गोंय goṃya; Marathi: govā; Portuguese: ) is Indias smallest state in terms of area and the fourth smallest in terms of population. ... A publisher is a person or entity which engages in the act of publishing. ...


Fishing

There are types of dredges used for collecting scallops or oysters from the seabed. They tend to have the form of a scoop made of chain mesh. They are towed by a fishing boat. Scallop dredging is very destructive to the seabed, and nowadays is often replaced by scuba diving to collect the scallops. Genera See text. ... Crassostrea gigas, Marennes-Oléron Crassostrea gigas, Marennes-Oléron Crassostrea gigas, Marennes-Oléron, opened The name oyster is used for a number of different groups of mollusks which grow for the most part in marine or brackish water. ... A fishing boat can range from two-person pleasure fishing boats up to 7-8 ton commercial fishers that can haul in over a billion fish at one time. ... Scuba diving is swimming underwater while using self-contained breathing equipment. ...


Police drag

In some police departments a small dredge (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. Mayor of Leipzig, Germany, committed suicide along with his wife and daughter on April 20, 1945. ...


Disposal of materials

In a "hopper dredger", 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 dredger 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 dredger is usually used for maintenance dredging. A slurry is in general a thick suspension of solids in a liquid and may be: Look up slurry in Wiktionary, the free dictionary. ...


Sometimes with a suction dredger 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. Self propelled barge carrying bulk crushed stone A barge is a flat-bottomed boat, built mainly for river and canal transport of heavy goods. ... A scow, in the original sense, is a flat bottomed boat with a blunt bow, often used to haul garbage or similar bulk freight; cf. ...


When contaminated (toxic) sediments are removed, or large volume inland disposal sites are unavailable, dredge slurries are reduced to dry solids via a process known as dewatering. Current dewatering techniques employ either centrifuges, large textile based filters or polymer flocculant/congealant based apparatus. A flocculant is a chemical which causes the particles in a colloidal dispersal to clump together and form flocs. Flocculants are commonly used to facilitate the removal by filtration of particles of impurity from a liquid which would otherwise be too fine to be caught by a filter. ...


In many projects, slurry dewatering is performed in large inland settling pits, although this is becoming less and less common as mechanical dewatering techniques continue to improve.


Similarly, many groups (most notable in east Asia) are performing research towards utilizing dewatered sediments for the production of concretes and construction block, although the high organic content (in many cases) of this material is a hindrance toward such ends.


Environmental impacts

Dredging can create disturbance to aquatic ecosystems, often with adverse impacts. In addition, dredge spoils may contain toxic chemicals that may have an adverse effect on the disposal area; furthermore, the process of dredging often dislodges chemicals residing in benthic substrates and injects them into the water column. Toxic redirects here, but this is also the name of a song by Britney Spears; see Toxic (song) Look up toxic and toxicity in Wiktionary, the free dictionary. ... In marine geology and biology, benthos are the organisms and habitats of the sea floor; in freshwater biology they are the organisms and habitats of the bottoms of lakes, rivers, and creeks. ... A water column is a conceptual column of water from surface to bottom sediments. ...


The activity of dredging can create the following principal impacts to the environment:

  • Release of toxic chemicals (including heavy metals and PCB) from bottom sediments into the water column.
  • Short term increases in turbidity, which can affect aquatic species metabolism and interfere with spawning.
  • Secondary effects from water column contamination of uptake of heavy metals, DDT and other persistent organic toxins, via food chain uptake and subsequent concentrations of these toxins in higher organisms including humans.
  • Secondary impacts to marsh productivity from sedimentation
  • Tertiary impacts to avafauna which may prey upon contaminated aquatic organisms
  • Secondary impacts to aquatic and benthic organisms' metabolism and mortality
  • Possible contamination of dredge spoils sites

A heavy metal is any of a number of higher atomic weight elements, which has the properties of a metallic substance at room temperature. ... Labelling transformers containing PCBs Polychlorinated biphenyls (PCBs) are a class of organic compounds with 1 to 10 chlorine atoms are attached to biphenyl and a general structure of C12H10-xClx. ... This article or section cites very few or no references or sources. ... A water column is a conceptual column of water from surface to bottom sediments. ... Turbidity standards of 5, 50, and 500 NTU Turbidity is a cloudiness or haziness of water (or other fluid) caused by individual particles (suspended solids) that are generally invisible to the naked eye, thus being much like smoke in air. ... The hierarchy of scientific classification. ... A few of the metabolic pathways in a cell. ... Frog spawn Spawning is the production or depositing of eggs in large numbers by aquatic animals. ... DDT or Dichloro-Diphenyl-Trichloroethane is the first modern pesticide and is one of the best known synthetic pesticides. ... This article or section does not cite any references or sources. ... This article or section does not cite any references or sources. ... This article needs additional references or sources for verification. ... Freshwater marsh in Florida In geography, a marsh is a type of wetland, featuring grasses, rushes, reeds, typhas, sedges, cat tails, and other herbaceous plants (possibly with low-growing woody plants) in a context of shallow water. ... Sedimentation describes the motion of particles in solutions or suspensions in response to an external force such as gravity, centrifugal force or electric force. ... “Aves” redirects here. ... Prey can refer to: Look up Prey in Wiktionary, the free dictionary A prey animal eaten by a predator in an act called predation. ... A few of the metabolic pathways in a cell. ...

Gallery

See also

The W.T. Preston is a specialized paddle steamer that operated as a river dredger, otherwise known as a snagboat, removing log jams and natural debris that prevented river navigation on several Puget Sound-area rivers, including the Skagit, Stillaguamish, and Snohomish rivers. ...

External links

Nautical Portal
Wikimedia Commons has media related to:
Dredge ships

  Results from FactBites:
 
Albums by Dredg - Rate Your Music (556 words)
Dredg formed in Los Gatos, CA in or around 1993 as a metal cover band which was then went by the name of bi-standard and featured now vocalist Gavin Hayes as a guitar player along with guitarist Mark Engles, bassist Drew Roulette, drummer Dino Campanella, and a different vocalist.
Gavin took over on vocals and Dredg began to start playing more of a "rapcore" style and became local favorites in their hometown of Los Gatos.
Around this time Dredg got one of their big breaks opening for friends Alien Ant Farm on a full US tour.
Dredg – Music at Last.fm (936 words)
dredg is a progressive alternative band from Los Gatos, California.
El Cielo, dredg's proper Interscope debut, arrived in autumn 2002, and Deftones producer Terry Date was at the helm for their 2005 effort Catch Without Arms.
Industry Demos is a collection of four songs from 2001 that dredg recorded before they were signed to impress record labels.
  More results at FactBites »

 
 

COMMENTARY     


Share your thoughts, questions and commentary here
Your name
Your comments

Want to know more?
Search encyclopedia, statistics and forums:

 


Press Releases |  Feeds | Contact
The Wikipedia article included on this page is licensed under the GFDL.
Images may be subject to relevant owners' copyright.
All other elements are (c) copyright NationMaster.com 2003-5. All Rights Reserved.
Usage implies agreement with terms, 1022, m