What’s dredging

Port is a social infrastructure comprising our
living and economical and industrial activities by
handling 99.7% of export and import cargo.
We contribute to affluent living by "dredging" that
secures water depth and area necessary for a large
vessel's navigation by excavating soil on seabed.

Dredging secures necessary water area and depth of channel, basin and berth by excavating seabed.

Sediment in seabed blocks navigation of large vessel.

Dredge channel and basin.

Dredging expands and deepens channel.

Recently container ships are getting larger. Especially International strategic ports and hub ports are required to expand channel for larger vessel's safe navigation. That increases the importance level of "dredging". In dredging, operation has to be done without suspending any port's function. Because of KOJIMAGUMI's unique technology and know-how, no suspension is necessary in navigation.

Dredging helps to maintain the water

depth by removing sediments that

accumulates gradually.

Inflowing soil from the river becomes sediment in channel and basin in port. When it is left as, seabed level becomes shallower and port's function will be lost by hindering the vessel from navigation and mooring. We remove the sediment by dredging to secure and maintain the water depth in port. Dredging is indispensable to secure the safe navigation in port.

©Nagoya port authority

Dredging can remove the debris and

help to restore port's function

soonest after disaster.

Dredging can restore and rebuild the port suffered from natural disaster such as typhoon, earthquake, tsunami and torrential rain. The port loses the function due to sediment, driftwood, debris, containers, cars, home-appliances and wastes. Dredging has a vital role to regain port's function as soon as possible.

Before sand capping sludge.

Sludge sediment deteriorates the environment.

Cover it with good dredged sand.

Improved environment provides better environment for the living.

Closed area where inflow sea water is little tends to have poor water quality or seabed condition, and later causes red or blue tide. Those area is treated with sand capping (=scattering sand on sludge surface and cover with sand) for environmental improvement using the good quality sand dredged from channel or basin. Creating the tidal flat or sandy beach with the good sand is another environmental improvement we engage in. Our work vessel (barge unloader vessel, sand scatter vessel, etc.) are engaged in there, too.

We send sediment to reclamation

site for recycle with environmentally-


Dredged material is used for reclamation that converts the sea into land.Our work vessel can send soil to reclamation site by pipeline.This reduces the burden on environment, and is also efficient and economical method.We have two unloading technology.One is "Air pressure vessel". That can send soil through pipeline with the help of pressured air to reclamation site.The other is "Barge unloader vessel". That can make the mixture of soil and sea water on the barge, sucks it with pump and send it through pipeline to reclamation site. Our technology is high evaluated as environmentally-friendly-methods among the marine concerned.

Air pressure vessel AP 1660 RYOSEI MARU

Barge unloader vessel P8160 RYOSEI MARU