Design of a greenfield port on a remote island

This paper discusses some of challenges faced in the design of ports on remote islands. The paper is based on a project that has involved design development of a greenfield port on one of the most remote islands in the world in an environment with multiple natural obstructions to the construction of a sea port. The volcanic island is an atoll with no lagoon and a 200 m wide fringing reef that is exposed at spring low tide. Beyond the reef edge the seabed grades down at a 45 degree angle. The reef itself comprises mostly hard limestone rock with SPT 'N' values around 50. There is no natural inlet or inner lagoon on the island that might form a natural inlet for vessel as is the case for many atolls. Traditional enclosed harbours are very expensive to construct due to the need for deep water breakwaters or significant excavation in hard rock. The existing Port operations have been in place for over 50 years. Vessels are held out at sea with a set of deep water moorings in 500 m depth of water. The nearest tugs are hundreds of nautical miles away from the remote island. Containers are transferred to shore one-by-one via lightering. In rough weather the transfer from vessel to barge is a dangerous operation which is often suspended until seas abate. Consequently the unloading of a container vessel can take several weeks to complete and as a result, the cost of cargo on the island is unsustainably expensive. The project's aim was to provide an alternative berthing system for the country's container trade and fuel transfer that was more efficient, safe and sustainable. Due to the lack of ability to construct an enclosed harbour the option study was driven primarily by which option offered the best overall solution considering navigability, berth availability (operability) and lifecycle cost. This paper discusses how these criteria and the impact each criterion had on the final layout chosen.