1

Dredging Phases

• 4 phases– excavation– lifting– transportation– disposal

Guide 4: Machines, Methods and Mitigation;

Chapter 2: Phases of a Dredging Project;

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Dredging Phases

• Excavation of the in-situ material by– cutter head– draghead– cutting edge of a bucket

• Main environmental aspects– Increase of suspended sediments– Mixing of soil layers– Dilution (in case of hydraulic dredging)

Guide 4: Machines, Methods and Mitigation;

Chapter 2: Phases of a Dredging Project;

Page 15

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Dredging Phases

• Raising the material– mechanically backhoe, dipper, bucket ladder

dredger– hydraulically cutter suction, trailing suction

hopper, disc bottom, auger and sweep dredgers• Main environmental aspects

– Release of suspended sediments– Loose and mobile spill layers– Density of material– Overflow during loading of hopper or barges

Guide 4: Machines, Methods and Mitigation;

Chapter 2: Phases of a Dredging Project;

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Dredging Phases• Horizontal transport by

– hydraulic pipeline– hopper dredgers– barges– also: trucks or

conveyor belts

• Main environmental aspects– safety– dilution– spillage– noise and air pollution

Guide 4: Machines, Methods and Mitigation;

Chapter 2: Phases of a Dredging Project;

Page 16

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Dredging Phases

• Placement or further treatment– reclamation of a site– beach nourishment– wetland creation– relocation on land, in a pit or at sea (underwater)

• Main environmental aspects– Occupation of space and surface– Dispersion of the deposited material– Noise and air pollution– Groundwater quality

Guide 4: Machines, Methods and Mitigation;

Chapter 2: Phases of a Dredging Project;

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Environmental Dredging• Often with normal equipment• Sometimes with adapted procedures• When required, with special tools

• Always resulting in lower output, higher costGuide 4: Machines, Methods and Mitigation

Chapter 3: Dredging Equipment

Page 19

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Suction Dredger (SD)

Guide 4: Machines, Methods and Mitigation

Chapter 3: Dredging Equipment

Page 19