As container ships become larger, shipping channels and harbour basins need to be made bigger and wider. The sea around the port of Helsinki in Finland is being dredged so that the harbour can be expanded; in some areas this means that toxic waste which was previously lying on the sea bed is being disturbed and there is a possibility that it will upset the eco-systems. Other tracts of land which were part of the harbour area of Helsinki are being converted to residential use – this is happening in Jaetkaesaari and Sompasaari.