Port of Cotonou

Following completion of the installation of the Diaphragm Wall forming the quay face to the new container berth in the port of Cotonou, Benin West Africa, the contractor, Soletanche Bachy, was asked by the client to increase the final depth of the berth by 2m and install scour protection to enable larger vessels to use the berth.

The installation of a rock armour scour protection system required that a 2m thick layer of riprap rock be placed. Due to the toe level of the Diaphragm wall excavation to the required depth for the rock layer could not be undertaken was out weakening the walls structure.

In order to achieve the clients requirements, a fabric formwork concrete scour mattress system was developed which only required a increase of 240mm of dredge depth over and above the 2m increase in berth depth asked for by the client. This was within the capabilities of the wall design and Norfolk Marine Ltd was tasked with the installation of the mattress system.

 The required equipment was despatched to site by air and sea freight and an advanced team sent to site to establish methods for the installation and filling of the mattress. Despite set backs due to the long length of the supply chain to Benin the team manage to stream line the installation works and once up and running the two dive teams on site installed and filled over 750m2of scour mattress per day. This more than doubled the expected installation rate.

The works were completed in late September of 2011 and the equipment shipped back to Norfolk Marine’s base in Ireland.