Maintenance dredging

Maintenance dredging is the routine periodic removal of material in approach channels to port and harbour basins to maintain widths and depths in previously dredged areas to ensure the safe access for vessels. Maintenance dredgings are generally composed of sands and silts that have been recently deposited by siltation and must be removed in order to keep a channel or berth open for navigation at the defined design profile.

Maintenance dredging may vary from an almost continuous activity throughout the year to an infrequent activity occurring only once every few years. For the purpose of disposal licensing a general rule of thumb is applied, that if a period of over five years has lapsed between a new and previous dredge, the material will be treated as capital dredgings for disposal purposes due to its characteristics. However, this will be considered on a case-by-case basis.

In ports and harbours dredging may be required to deal with unforeseen circumstances, such as the movement of a sandbank across an entrance channel to a port which must be removed as a matter of emergency. From a disposal viewpoint this is considered as maintenance dredging.

Definitions are based on those provided by the following dredging specialists and organisations:

  • Bray, Bates & Land 1997.
  • Institute of Civil Engineers 1995.
  • ABP Research, R462 1994.
  • IADC & CEDA 1996.
  • Bowles, MAFF personal communication 1999.

Next section