Iconic Port Maintains Deep Water Access for Mega Vessels Whilst Planning to Fight Drought

SOUTH AFRICA – Deep water ports are now an important facility considering the new generation of mega container and other vessels, but they need regular maintenance as the actions of tides and ships tend to silt up the waters, making the depths shown unreliable. One of the world's iconic ports, Cape Town, is about to embark on a dredging programme whilst also taking a look at one of the region's most serious issues, drought.

A maintenance campaign is underway and scheduled for completion by the end of May to restore the design depths at certain berths inside the Port’s Duncan Dock. Transnet National Ports Authority (TNPA)’s Dredging Services division intends to prioritise the removal of high spots that had been detected within the dock which contains the multi-purpose cargo and fruit terminals as well as the Sturrock Dry Dock, repair quay and tanker basin.

Two dredging vessels, the Isandlwana, a Trailing Suction Hopper Dredger (TSHD) and the Italeni, a Grab Hopper Dredger will be mobilised and the two dredgers will complement each other in that the TSHD is built for high speed sailing to the offshore disposal site while the Italeni improves the accuracy of the final dredged depths. Multi-beam bathymetric surveys will be conducted at regular intervals throughout the campaign to ensure that all areas within Duncan Dock are restored to their original design depths.

The Isandlwana, which has a 4200 m³ hopper capacity, will remove approximately 60,000 to 70,000 m³ of material from the harbour sea bed. Dredged material is pumped into the hopper and can be offloaded by discharging through the vessel's conical bottom valves.

TNPA’s fleet renewal programme has boosted the dredging division’s capacity to aid the removal of approximately four million cubic metres of excess material from the seabed every year at South Africa’s ports. The dredge material within Duncan Dock will be disposed of at an offshore disposal site which has been approved by Department Environmental Affairs.

Elsewhere in the Port, Transnet SOC Ltd has given approval for further studies to be conducted into a Sea Water Reverse Osmosis (SWRO) plant to convert seawater into drinking water. The proposed location for the plant is the Quay 700 area in the port. If it proves viable it is expected to provide in the order of 1 million to 3 million litres a day.

Cape Town remains a water scarce region and has just emerged from the worst drought since 1904. The good rainfall in 2018 and the substantial reduction in usage has allowed for municipal restrictions to be reduced from level 6 to level 3 in 2019. While this is positive, the region’s dependence on dam water could result in similar shortfalls in future.

TNPA previously implemented measures to manage water usage at the port after the City imposed widespread restrictions on using municipal drinking quality water for non-essential purposes. These water conservation steps included suspending the sale and supply of potable fresh water to vessels calling at the Port of Cape Town, with exceptions considered on merit. Ship repairers were also informed to make use of mobile water supply.

TNPA’s Cape Town acting Port Manager, Captain Alex Miya, said the next steps would be to appoint consultants to conduct studies that could be concluded by September 2019. If the SWRO plant is found to be a viable option, it could be introduced by the end of 2020. In the meantime, Alex Miya said the port would continue to coordinate its approach with the City of Cape Town’s initiatives to supply extra water, explaining:

“The port is confident that the municipality will ensure a water resilient region through a mix of water sources. In the meantime, we have considered a few options to ensure economic sustainability. One of these options is a Sea Water Reverse Osmosis (SWRO) plant for port use. This is currently being explored in conjunction with various regulatory authorities and has received support from Transnet to proceed with further studies.”

Photo: The Italeni