1 Dredging Phases 4 phases –excavation –lifting –transportation –disposal Guide 4: Machines, Methods and Mitigation; Chapter 2: Phases of a Dredging Project; Page 15 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 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 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 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 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 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 Guide 4: Machines, Methods and Mitigation Chapter 3: Dredging Equipment Page 19