Bottlenecks along a 30km stretch of one of Belgium's busy inland waterways will be removed in a five year deepening and straightening project being carried out by a joint venture of Dredging International and Jan de Nul. Client is the Direction of the Upstream Schelde, the Flemish government department responsible for inland waterways.
The canal which runs between Ghent and Bruges was built to accommodate 1,350t class vessels but a combination of sedimentation and relatively tight curves in its course is presenting navigation difficulties and delays at busy times.
The project team is based at St Joris, a village near Beernem, 12km south east of Bruges where a 65ha island has been formed by an earlier canal straightening scheme.
The joint venture began work on the island in April 1999. First step was an earthmoving exercise to create eight discharge and sedimentation basins; six for sand and two for silt. Capacities ranged between 60,000m3 and 120,000m3.
Excavation of an underwater pit for the secure storage of silt deposits began in last June. Conventional methods of dry excavation were used until the water table was reached when Dredging International's cutter suction dredger Concorde was brought in to remove the final 500,000m3.
Preparation of the island base also includes the setting up of sand commercialisation plant and stock areas. Once this is completed - scheduled date is April - work on the canal can begin.
Maintenance dredging will remove up to 500mm depth of sediment along the 30km stretch and capital dredging will then take off a further 500mm to a new design depth of 3.7m. A number of small dipper dredgers will be involved in this work. It is anticipated that they will remove 1M.m3 of material, half of it silt destined for the underwater disposal pit.
Material dredged from the canal and its new straight reaches will first be deposited in the discharge and sedimentation basins. Sand and silt fractions will then separate under gravity.
Subject to sample testing the sand will be sold for use in civil engineering applications. Sand from the silt pit is already being used in a major road scheme near Bruges.
After being drained in the basins the silt fraction will be moved into the pit for final storage.
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