It consists of a flexible pipe connected at one end to a powerful centrifugal pump. At the other, open end there is usually a device designed to break up the material to be dredged. The open end of the pipe is lowered to the bottom, where the material to be dredged is mixed with water, pumped up, and then discharged into hopper barges. There the heavy material settles, and the surplus water is allowed to overflow. Material from these dredges is sometimes pumped through pipes for long distances and used to build up low-lying ground.
Hopper barges made to carry away and sink the material brought up by dredges are of a special type.
In the space where the material is carried are hinged doors, or flaps, held closed by chains and opening downward. Around the space are watertight compartments to give the barge buoyancy. Licensed from Columbia University Press. All rights reserved.