Platform supply vessels used in TOTAL’s Brulpadda gas exploration project, as well as other ships with a specific under-keel clearance, will be better able to berth without hassle in the Port of Mossel Bay. This is thanks to a maintenance dredging campaign currently underway at the port, including the first quayside dredging there in 20 years.
Dredging is a critical aspect of port maintenance and refers to underwater excavation that helps to ensure safe navigational channels and maintain port depths. Transnet National Ports Authority (TNPA)’s Dredging Services division carries out dredging in all of South Africa’s commercial ports using a fleet of special craft built for this purpose.
Two dredgers will be working in the Port of Mossel Bay – the 4500m3 Italeni grab hopper which arrived in November and the Isandlwana trailing suction hopper dredger (TSHD) which will arrive in January.
The smaller Italeni will focus on the quaysides picking up seabed material with a clam shell bucket attached to an onboard crane or hydraulic arm, while the larger Isandlwana will focus on the entrance channel, sand trap and the turning basin of the port, using its propulsion equipment to proceed over the track and a suction arm that works as vacuum cleaner on the seabed.
The two dredgers complement each other in that the TSHD Isandlwana is built for high speed sailing to the offshore disposal site while the Italeni improves the accuracy of the final dredged depths.
Mossel Bay Port Manager Shadrack Tshikalange said TNPA was mandated by the National Ports Act (Act 12 of 2005) to provide or arrange marine related activities and to provide aids such as tugs, pilot boats and other facilities and services for navigation of vessels within port limits and along the coast.
“The Platform supply vessels (PSV) used by TOTAL require a specific under-keel clearance. The clearance is a vertical distance between the deepest underwater point of the ship’s hull and the water area bottom or ground,” he said. “That clearance should be sufficient to allow ship’s floatability in most unfavourable hydrological and meteorological conditions. Therefore, the quaysides that will be used to berth the PSV must be dredged to its maximum dredge depth to allow berthing of such vessels in any condition.”
TNPA’s fleet renewal programme has boosted the dredging division’s capacity to aid the removal of approximately four million cubic meters of excess material from the seabed every year at South Africa’s ports.
With the most modern equipment available in the specialised service industry, Dredging Services is able to not only meet the needs of the South African port system, but the needs of Southern Africa, helping other African countries grow their economies.