Views: 0 Author: iTECH Dredger Publish Time: 2026-11-13 Origin: Site
Land reclamation turns water into usable ground by pumping or placing fill, and the dredger is the production unit of that process. The engineering question is not only how much material can be moved but how it must be delivered so that the reclaimed area settles predictably and reaches the required density. This article explains how reclamation dredgers are specified, how the pipeline network is planned, and what determines the cost of a cubic metre of fill.
Reclamation starts with the target: the finished level, the allowable settlement and the required bearing capacity. Fill volume is the product of area and thickness plus an allowance for consolidation and for losses, and that allowance is often twenty to thirty percent above the nominal volume.
A dredger selected only on nominal volume will be short of capacity once settlement and losses are counted. The specification should always use the bulked volume, not the neat figure.
Hydraulic fill is the standard method for large reclamation: the dredger pumps a sand slurry through a pipeline into the reclamation area, where the solids settle and the water returns through weirs or overflow structures. The method is fast and continuous, and the resulting fill is usually well compacted by the water flow, provided the placement is managed.
The alternative is mechanical placement by barge and excavator, which is slower and more expensive at scale but allows better control of grading and of contamination.
The table sets out how discharge distance scales with equipment.
| Distance | Configuration | Notes |
| up to 300 m | single pump, steel line | simplest and cheapest |
| 300-800 m | one booster station | adds fuel and a failure point |
| 800-2,000 m | two to three boosters | line pressure and wear increase |
| above 2,000 m | multiple boosters or rehandling | consider barge transfer |
The bund, or perimeter embankment, must be built before filling starts, and it must be high enough to contain the slurry and strong enough to resist the internal water pressure. Weirs or overflow pipes control the water level and the return water quality.
Return water quality is a permit condition on most projects. A settlement arrangement, sometimes with coagulant dosing, is needed where the fill contains fines, and the outlet must be monitored.
Capacity, depth and discharge pressure are the three governing parameters. Reclamation work usually involves large volumes, so a 500 mm or 650 mm class machine is typical, with a pump selected for the head required by the pipeline rather than for maximum flow at low head.
The cutter head should suit the borrow area material. Sand borrow areas need a basket head, while borrow areas with clay lenses need a clay head and a slower swing to avoid blocking the line.
Placement management decides whether the fill consolidates well or leaves soft pockets. Discharging at a single point creates a beach that slopes into the pond, with coarse material settling near the outlet and fines carried to the far end. Moving the discharge point during filling produces a more uniform deposit.
Where the fill must meet a density requirement, the programme should include staged filling, settlement periods and possibly vibro-compaction or surcharging after reclamation. Those operations have a cost and a schedule effect that belong in the feasibility study.
Reclamation requires environmental approval covering the borrow area, the filling operation, turbidity at the bund overflow and the effect on adjacent shoreline. In coastal areas, the approval may also cover the impact on currents and on sediment transport.
Borrow area selection is part of the approval. Taking sand from a sensitive seabed or riverbed can be refused, and the approved borrow area may be further from the site, which increases the pipeline distance and the booster requirement.
Reclamation cost per cubic metre includes dredging, pumping, bund construction, weir and outlet works, settlement allowance, compaction and the eventual surface preparation. Pumping cost rises sharply with distance, which is why the borrow area location is a commercial decision as much as an engineering one.
Fuel, wear parts and booster maintenance dominate the pumping cost. On long lines, the difference between one and three boosters can change the project economics, so pipeline routing and borrow area selection should be optimised together.
Reclamation is usually schedule-critical because the finished ground unlocks the next phase of development. Production planning should be based on placed fill per week after settlement allowance, with a realistic allowance for weather, pipeline moves and bund raising.
A programme that assumes continuous pumping for the whole period will not survive a monsoon or a winter storm season. Seasonal windows belong in the schedule from the start.
Specify the bulked fill volume, the borrow area distance and depth, the material gradation, the required finished level and the density requirement. Then ask for a machine whose pump curve matches the pipeline and whose cutter suits the borrow material, with a production test that demonstrates placed fill rather than slurry flow.
