Selection of disposal options

Under guidance from MAFF, CEFAS, SOAEFD and DOE(NI), ports and harbours throughout the UK select the Best Practical Environmental Option for a sea disposal site which is considered carefully so as to avoid adverse effects on marine organisms from occurring. If the sediment is going to be disposed of on land, an equal amount of consideration should be given to the sediment type and the location and status of the site under guidance of the environment agencies.

The benefits of returning dredged sediments back to the estuary system are becoming increasingly recognised. Disposal of fine sediments at suitable locations within the estuary allows the dynamics of the system to be maintained and the morphological and ecological development of the estuary to be conserved. Examples of the application of this disposal option are given below. Disposal of dredged sediments within the estuary or coastal cell system has the additional benefit of reducing the costs incurred transporting materials to deep-sea disposal sites.

Examples of the disposal of dredged sediments within the estuary system

In the Humber the dredged channel is maintained in such a way, feeding the whole estuary as dredged material is disposed and redistributed within the estuary. As much as 8 million tonnes of fine sediments are disposed in this way each year with little physical or biological effect as the sediments are redistributed within the estuary (Murray 1994b).

A similar approach is being proposed in the Stour/Orwell Estuaries by Harwich Harbour Authority to address the problems of intertidal erosion caused by capital dredge operations, which are being sustained by current disposal practices (HR Wallingford & Posford Duvivier Environment 1998).

Fine dredged sediments have been disposed and retained within the Medway Estuary system in a manner that is not harmful to the environment (Pethick & Burd 1996).

Next section