Offshore wetlands developments

Offshore wetlands developments are usually located in sheltered marine locations and serve as habitats for local and migrating birds. Fig. 20.29(a) shows a cross section of a typical offshore wetlands development area in which dredged spoil has been used as the hydraulic fill to construct the wetlands habitat. The wetlands development is contained within geotextile tube containment dykes which also can be filled with the dredged spoil material, which thus makes full use of the dredged spoil. If the... 

Figure 20.29 Offshore wetlands development, (a) Cross section through typical offshore wetlands development area and (b) construction of combined spoil containment and wetlands development area utilising geotextile tube containment dykes.

Fig. 20.29(b) shows the constmction of an offshore wetlands habitat area using spoil excavated from a nearby mnnel construction. The spoil, which consisted of fine, uniform sand, was also used to fill the geotextile tube containment dyke surrounding the wetlands development area. For permanent protection, a rock armour layer was placed over the outer surface of the geotextile mbe containment dyke. 

The disposal of dredged spoil in an environmentally friendly manner poses difficulties from the perspective of the normally large volumes of spoil involved and the modern requirements of environmental sustainability of such spoil disposal facilities. These driving forces have led to offshore spoil containment facilities being developed for wetlands habitats. 

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