Underwater placement of fill is usually performed by trailing suction hopper dredgers and barges by opening their bottom doors or by split hull vessels.
Release of the material
Upon arrival at the reclamation site, this vessels drop their loads through the water column down onto the seabed. After the release of the material the entrainment of surrounding water will dilute the mixture, reducing its concentration and increasing the seabed area that will be covered by the material.
Fill may also be placed underwater through the discharge pipeline of a cutter suction dredger equipped with a diffuser to control the soil mixture flow.
Optimal filling control and management of placement
For optimal filling control and management of placement, the placement area is usually divided into grids, which are generally slightly larger than the size of the vessel’s hopper. Combined with global positioning systems and computer aided methods, the filling of the grids can be controlled with precision.
To allow the vessels access to the reclamation site in order to execute placement this way, the reclamation area should not be fully closed by bunds.
related
Facts About
Cutter Suction Dredgers
“Facts About Cutter Suction Dredgers” describes a type of hydraulic dredger that can dredge nearly all kinds of soils, especially hard ground and rock.
Trailing Suction Hopper Dredgers
“Facts About Trailing Suction Hopper Dredgers” describes self-propelled hydraulic dredgers with drag heads that suction up loose materials like sand.
Publications
Hydraulic Fill Manual
This manual, a first of its kind, is an ideal reference for all involved in the development of such infrastructure projects.
Management of Aquatic Disposal of Dredged Material
Good practice regarding the management of aquatic disposal of dredged material based on the Dredged Material Assessment Framework of the London Convention.