Volume 8 – Mechanical and Electrical Services - Malaysia Geoportal

Chapter 8 DREDGER
Table 8.3 - Disposal Systems
Dredge type Disposal Method Comments
Hopper dredger
(THD)
Hopper dredger
(THD)
Cutter suction
pipeline dredger
(CSD)
Cutter suction
pipeline dredger
(CSD)
Mechanical clam
shell dredger
Desiltation and
water jetting plants
Excavators, grab
dredgers and
bucket suction
dredgers
Sea dumping, shore pumping,
rain bowing, booster station,
submerged pipeline
Hopper dredger combined with
cutter suction – double
handling, submerged pipelines
Spider barge, hopper barge,
hydraulic unloading and
dredge pipelines
Hopper barge and second
cutter suction pipeline dredger
with submerged pipelines
Hopper barge and hydraulic
unloader with submerged
pipelines
Displacement of silt through
pipelines or travel through tidal
waves
Barge/truck loading, beach and
sea walls nourishment
Maintenance/capital dredging of widening and
deepening of port channels, beach/sea wall
nourishment and land reclamation
Maintenance/capital dredging of widening and
deepening of port channels, beach/sea wall
nourishment and land reclamation
Capital dredging of port channels, harbour berths,
land reclamation, beach and coastal restoration
New port projects under capital dredging
Offshore location operations
Environmantal effects and siltation near the harbour
berths
Construction of jetty, bunds, roads/buildings and
other earth works on shore
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.
The activity of dredging can create the following principal impacts to the environment:
• Release of toxic chemicals (including heavy metals and PCB{polychlorinated biphenyls}) 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{Dichloro-Diphenyl-Trichloroethane} 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 avifauna which may prey upon contaminated aquatic organisms.
• Secondary impacts to aquatic and benthic organisms' metabolism and mortality.
• Possible contamination of dredge spoils sites.
8-10 March 2009