Dredged material

Managing dredged material

Dredging has to be carried out to maintain the maritime access routes to the Belgian coastal ports and the depth of the coastal ports and is the responsibility of the Flemish Region. The large quantities of dredged material resulting from these activities, which may be polluted to varying degrees, are dumped back in the sea. This procedure is the responsibility of the federal environment department. It can have an impact on the marine ecosystem.

Consequently, managing dredged material is a shared responsibility. On 12 June 1990 a cooperation agreement was signed in this respect between the Belgian Sate and the Flemish Region to safeguard the North Sea from the adverse environmental effects of dumping dredged material in the waters covered by the Oslo Convention (Belgian Official Journal 22.08.90) as modified by a cooperation agreement signed on September 6, 2000 (Belgian Official Journal 21.09.00).

In accordance with the law of January 20, 1999, authorisation is required to dump dredging material at sea. The procedure to obtain authorisation for dumping dredged material from activities undertaken by the Flemish Region at sea is laid down in the Royal Decree of March 12, 2000 defining the procedure for authorising the dumping of certain substances and materials in the North Sea.

Permits for dumping dredged material at sea

At the moment there are five authorisations for dumping dredged material at sea in force. The maximum authorised quantity per year and per dredging area is given in Table 1. The period of validity is also given in the table. Maintenance dredging work is understood to mean 'maintaining at the required level' and deepening dredging work is understood to mean 'deepening or broadening ports and channels'.

Various dumping sites are used to dump dredged material.

The dredged material to be dumped at sea has to fulfil the sediment quality criteria (SQC) given in Table 2.

If the analysis results exceed the limit set for three of the criteria at the same time, the dredged material may not be dumped at sea. If the result lies between the target value and the limit, the number of samples has to be increased by five and new analyses have to be carried out. If the new analysis results confirm the previous ones, then bioassays prescribed at international level have to be conducted. Negative results from these bioassays may lead to a ban on dumping dredged material from these delimited areas at sea.

Every ten years or so, the quality of the dredged material is assessed on the basis of a large-scale monitoring programme in which samples are taken from all areas in which dredging takes place. Table 3 provides a survey of the average analysis results of the 1990 and 2000 measuring programmes.

Table 4 provides a survey over time of the quantities of dredged material dumped at sea. In the context of the permits, MUMM also carries out research programmes. A sediment transport model has been developed in several phases in order to ensure the selection of highly efficient dumping sites. These models have been improved, calibrated and validated in further programmes.

Managing dredged material at international level

The way in which dredged material is managed in Belgium is fully in line with the international obligations resulting from the (regional) OSPAR Convention and the (world) London Convention. (The London Convention on the prevention of marine pollution as a result of dumping waste. This treaty is the equivalent at worldwide level of the OSPAR Convention. It was signed in 1972 and there are currently 78 member states. A review of the Convention began in 1993 and this review was completed in 1996 with the acceptance of the 1996 Protocol to the London Convention. The 1996 Protocol is has not yet come into force as it has not yet been ratified by a sufficient number of countries).

In the context of OSPAR, the '1998 Guidelines for the Management of Dredged Material' are followed. In the context of the London Convention, the 'Waste-specific Guidelines for Dredged Material' are followed.