Once a dredging project is completed, the need to care for the works that have been constructed should not be underestimated. Construction and extension of a port and access channels is not the end of the process.
Following the deposition of sediments, access channels and harbour basins may become silted up quite rapidly. It is of vital importance to ports that the depth of waterways is at all times maintained so that they always remain accessible to shipping traffic. Therefore, large-scale maintenance contracts are often put out to tender, and this sometimes will result in long-term contracts.
As sedimentation and siltation are natural phenomena, they are always a threat to navigation and accessibility of ports, even when the ports have been dredged to a navigable depth during port expansion.
Cost of maintenance
For that reason, maintenance should not be overlooked, especially as the costs for maintenance can be high and the need is not always obvious. A plan for maintenance dredging should be part of a management plan and the costs of recurring operations should be budgeted in the total project plan.
Amongst issues that may arise that require maintenance are:
- siltation of channels that need to be deepened;
- breakwaters and groynes needing repair; and
- the addition of navigational aids.
Maintenance dredging will require clear knowledge about the dynamics of an estuary, and even more experience on how to deal with tides, currents, flood channels, bars, bends, and the various nature of suspended material. A contractor who has executed the original capital dredging will possess detailed knowledge of these elements and so creating a plan for maintenance of the works is a logical extension of a capital dredging project.
Maintenance dredging projects may also aim at improving the water quality, where contaminated sediments are removed and decontaminated or disposed in a safe manner.
As with all dredging work, maintenance dredging must be carried out with respect for the environment, reducing overflow and limiting turbidity
. Maintenance dredging when executed properly and in a timely fashion will support the natural processes and uses the river dynamics for keeping the gateways open.