Dredging Phases

1
Dredging Phases

• 4 phases
• excavation
• lifting
• transportation
• disposal

Guide 4 Machines, Methods and Mitigation Chapter
2 Phases of a Dredging Project Page 15
2
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
3
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 Page 16
4
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
5
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 Page 17
6
Environmental Dredging

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

• Always resulting in lower output, higher cost

Guide 4 Machines, Methods and Mitigation Chapter
3 Dredging Equipment Page 19
7
Suction Dredger (SD)
Guide 4 Machines, Methods and Mitigation Chapter
3 Dredging Equipment Page 19