By Tom Peters
The size of the vessels carrying containerized cargo calling along the East Coast of North America continues to increase. Earlier this year, the Port of Halifax received its largest Ultra-Class vessel so far, the 364-metre CMA CGM Libra, with TEU (twenty foot equivalent units) capacity of 11,400. As the only Canadian East Coast port capable of handling the ultra-class vessels, the Halifax Port Authority is taking the necessary steps to ensure these giants continue to have the space they need when they come calling.
The Halifax Port Authority (HPA) is moving forward, on schedule, with the construction of an extension to its South End container terminal operated by Halterm. The $35-million project will extend 134 metres and boast a working width of 57 metres. The goal of the extension to the existing terminal is to bring the total berth length to a continuous 800 metres, which will allow the Port of Halifax to accommodate two ultra-class container vessels simultaneously.
Greg Baker, Associate Vice-President, Engineering and Infrastructure for the Halifax Port Authority, said recently that the dredging aspect of the project had been completed with approximately 70,000 cubic metres of dredged organic silt and sand from the site deposited on the bottom of a HPA water lot at Fairview Cove. He said the material was perfectly clean but too soft to build on.
The extension will be anchored by eight, reusable caissons (concrete cribs) which are built at Richmond Terminals and then towed by tug to the site. At the time of the interview, three caissons were on site, “sitting on a prepared rock mattress, which is level,” Baker said.
The larger caissons are 21 metres high, 17 metres wide and 33 metres long. Five caissons are of this larger size while the other three vary in size but are all 11 metres wide. Construction of these caissons is being done by McNally Construction Inc., the lead contractor for the project.
Building, moving and positioning these caissons at the project site is an interesting process.
The wooden forms for the caissons were built inside Shed 9B at Richmond Terminals this past spring.
Each caisson begins with the casting of a reinforced concrete base slab on a semi submersible barge. The prepared form work, which totally defines all external and internal walls of the caisson, is placed on this slab. These forms are approximately 1.5 metres high and have an integral working platform, lights and hydraulic jacks. Once casting begins this formwork is continuously filled with concrete and reinforcing steel, as the concrete sets all forms for the entire caisson are uniformly jacked upwards.
The caissons are built high enough on the barge so when they are taken off, they float with no possibility of overturning. While floating, construction continues upwards and water is used as ballast to prevent them becoming top heavy. When a crib reaches the required height of 21 metres with proper ballast, it will draw about 14 metres of water, and that’s when it is ready to be towed to the South End container terminal for placement.
“On site, they get ballasted further but are kept level,” said Baker. “What you want to do is let the tide put them on the bottom, because if you try to do that with ballasting and they touch one corner first, they are difficult to control and can spin out of position. You want the tide to go down level, the crib to go down level with it. You want the caisson to uniformly touch the mattress.”
Once they are placed in position and the surveyor agrees they are within tolerance, the built-in valves are opened to allow water to flow in to the caisson, ensuring it doesn’t float again. “When they are fully flooded, they won’t move, regardless of the weather,” Baker explained. “They then get ballasted to the top with rock.” When filled, they will weigh approximately 26,000 metric tonnes.
Once the final caisson is in place, the entire extension will then be infilled with rock, which may result in additional caisson movement. “We will survey them, and when we are confident movement has stopped, we will build a cope wall around them which will be the portion everyone sees and the ships dock against,” said Baker. “The whole structure will then look straight.”
After the cope wall is completed, work will continue for supporting infrastructure such as lighting, asphalt and installation of 100-foot gauge crane rail for a new super post-Panamax crane which has been ordered by terminal operator Halterm. The new crane will reach across 24-containers.
“Halterm is working with the Halifax Port Authority to ensure dynamic demand-led capacity development,” said Kim Holtermand, Halterm’s CEO and Managing Director. “For example, the new berth extension will allow Halterm to handle two, Ultra-Class vessels while recent container yard expansion and inland rail initiatives with CN provide highly efficient low impact through-port container movements. The cranes and support equipment are key to the terminal’s unique position as Eastern Canada’s ‘Ultra-vessel’ container gateway,” he said.
The extension and crane are expected to be operational in 2020.