IV. Retreating Shorelines
257
3.1.7.4.3 Use of a rehandle pit
This approach can be used when high pumping power is required and when sea
conditions are rather rough and a sheltered area available not too far from the
beach area.
Or.
Conditions
The dimensions of the rehandle pit will have to be large enough to
accommodate the rehandle pit dredger with sufficient room to achieve
optimal production. At the same time, in the other part of the rehandle pit,
sufficient room is to be given to the trailing suction hopper dredger to
discharge its load safely without any danger of collision. With this working
method, the rehandle pit is divided into two parts, thus avoiding a situation
in which the hopper dredger dumps just upstream of the stationary dredger.
Another advantage of this system is that a certain buffer capacity is
introduced so that only the matching of weekly production levels remains
necessary.
Execution
The layer height dumped by the trailing suction hopper dredgers should be
at least 3 to 4 m (+ 10 to 13 ft) in order to maintain a continuous high
output with cutter dredgers.
During the dredging operation with the cutter dredger a certain amount of
spillage will occur, which influences the buffer capacity of the rehandle pit.
Usually, after rehandling operations are finished, these pits are filled by the
trailing suction hopper dredgers to the original sea bed level.
An additional advantage of this system is that the fill material is washed out
twice, resulting in clean beach sand with almost no particles smaller than
63 #m. However, more pumping horsepower is required and more wear and
tear will result.
3.1.7.4.4 Use of barges and a barge unloading dredger
0/.
Conditions
A barge unloading dredger can only be used when calm weather conditions
are envisaged, allowing barges to travel safety from the borrow area to the
rehandle pit and permitting the sand winning dredger to work, without any
hazards, for a long stretch of time.
257
3.1.7.4.3 Use of a rehandle pit
This approach can be used when high pumping power is required and when sea
conditions are rather rough and a sheltered area available not too far from the
beach area.
Or.
Conditions
The dimensions of the rehandle pit will have to be large enough to
accommodate the rehandle pit dredger with sufficient room to achieve
optimal production. At the same time, in the other part of the rehandle pit,
sufficient room is to be given to the trailing suction hopper dredger to
discharge its load safely without any danger of collision. With this working
method, the rehandle pit is divided into two parts, thus avoiding a situation
in which the hopper dredger dumps just upstream of the stationary dredger.
Another advantage of this system is that a certain buffer capacity is
introduced so that only the matching of weekly production levels remains
necessary.
Execution
The layer height dumped by the trailing suction hopper dredgers should be
at least 3 to 4 m (+ 10 to 13 ft) in order to maintain a continuous high
output with cutter dredgers.
During the dredging operation with the cutter dredger a certain amount of
spillage will occur, which influences the buffer capacity of the rehandle pit.
Usually, after rehandling operations are finished, these pits are filled by the
trailing suction hopper dredgers to the original sea bed level.
An additional advantage of this system is that the fill material is washed out
twice, resulting in clean beach sand with almost no particles smaller than
63 #m. However, more pumping horsepower is required and more wear and
tear will result.
3.1.7.4.4 Use of barges and a barge unloading dredger
0/.
Conditions
A barge unloading dredger can only be used when calm weather conditions
are envisaged, allowing barges to travel safety from the borrow area to the
rehandle pit and permitting the sand winning dredger to work, without any
hazards, for a long stretch of time.