The Ngqura industrial Port has been a major new initiative for South Africa and PRDW were involved with all aspects of the marine work. This includes port planning and layout, onshore and offshore geotechnical investigations, environmental data collection, hydraulic and numerical model studies and the detailed designs of breakwaters, quay walls and a sand bypassing system.
The Ngqura Port is constructed on the open coast (i.e. seaward of the original natural coastline). The port’s breakwaters intercept the natural nett northward sediment drift of approximately 200,000m3 per year.
A sand bypass facility has been provided to control accretion of the beach profile updrift of the port, to prevent sedimentation of the port entrance channel to ensure continuity of sediment transport along the coast and to prevent downdrift erosion.
The detailed design of the sand bypassing system included detailed mathematical modelling of the wave conditions and sediment dynamics of the beaches up and downdrift of the port.
The sand bypass scheme comprises a row of 6 jet pumps embedded in the seabed below a 225m piled jetty to support connecting pipework and facititate deployment and maintenance of the pumps. The structure extends across the surf zone creating a trap on the updrift beach. The discharge is north of the port, a distance of 3,4km from the sand trap. Three booster stations are included in the discharge route. The typical pumping capacity is 400tph of solids and is generally operated automatically by means of a PLC system.
Construction commenced in September 2002 and the system was commissioned in February 2007.