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Towards a Cleaner Marine Environment 9. Harbours as recycling centresDanish harbours play a vital part in our efforts to secure a clean marine environment. Good waste reception facilities are decisive, if we are to prevent ships from illegally dumping their waste in the sea. According to Danish regulations, all harbours must establish a scheme for receiving oil residues, sewage and other waste. Payment for ships' use of these facilities is based on the "no special fee" system. In other words, payment for depositing operational waste brought in by ships since the last time they called at a harbour is included in the harbour charges. This system encourages all ships to take advantage of the scheme. In addition, compulsory depositing of waste before ships leave harbour has been introduced throughout the Baltic area. Depositing of sea-bed waste can harm the environment Harbours and channels occasionally need dredging, because sandbars gradually build up. About five million tonnes of sea-bed waste is dredged up annually in Danish harbours. This waste is then transported to selected neighbouring areas and dumped. If the waste contains environmentally hazardous substances, such dumping can damage the marine environment. For this reason, dumping is only permitted for waste that contains insignificant quantities of hazardous substances, such as the heavy metals, oil residues and PCBs. These are substances that can accumulate in sediment - not least in harbours. The risk is that the substances will be picked up by turbulence in the water column and be absorbed into the marine food chains or by organisms in the sea-bed. TBT is especially problematical. Concentrations of up to 20,000 times greater than are found in the sea-bed of the open sea have been found in sea-bed waste from harbours and channels. Instead of dumping in the selected areas, therefore, it could become necessary in the future to decontaminate and deposit much greater quantities of sea-bed waste than is the case today.
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